merge-ort: drop unused parameters from detect_and_process_renames()

[alt-git.git] / grep.c

#include "git-compat-util.h"
#include "config.h"
#include "gettext.h"
#include "grep.h"
#include "hex.h"
#include "object-store-ll.h"
#include "pretty.h"
#include "userdiff.h"
#include "xdiff-interface.h"
#include "diff.h"
#include "diffcore.h"
#include "commit.h"
#include "quote.h"
#include "help.h"

static int grep_source_load(struct grep_source *gs);
static int grep_source_is_binary(struct grep_source *gs,
                                 struct index_state *istate);

static void std_output(struct grep_opt *opt UNUSED, const void *buf, size_t size)
{
        fwrite(buf, size, 1, stdout);
}

static const char *color_grep_slots[] = {
        [GREP_COLOR_CONTEXT]        = "context",
        [GREP_COLOR_FILENAME]       = "filename",
        [GREP_COLOR_FUNCTION]       = "function",
        [GREP_COLOR_LINENO]         = "lineNumber",
        [GREP_COLOR_COLUMNNO]       = "column",
        [GREP_COLOR_MATCH_CONTEXT]  = "matchContext",
        [GREP_COLOR_MATCH_SELECTED] = "matchSelected",
        [GREP_COLOR_SELECTED]       = "selected",
        [GREP_COLOR_SEP]            = "separator",
};

static int parse_pattern_type_arg(const char *opt, const char *arg)
{
        if (!strcmp(arg, "default"))
                return GREP_PATTERN_TYPE_UNSPECIFIED;
        else if (!strcmp(arg, "basic"))
                return GREP_PATTERN_TYPE_BRE;
        else if (!strcmp(arg, "extended"))
                return GREP_PATTERN_TYPE_ERE;
        else if (!strcmp(arg, "fixed"))
                return GREP_PATTERN_TYPE_FIXED;
        else if (!strcmp(arg, "perl"))
                return GREP_PATTERN_TYPE_PCRE;
        die("bad %s argument: %s", opt, arg);
}

define_list_config_array_extra(color_grep_slots, {"match"});

/*
 * Read the configuration file once and store it in
 * the grep_defaults template.
 */
int grep_config(const char *var, const char *value,
                const struct config_context *ctx, void *cb)
{
        struct grep_opt *opt = cb;
        const char *slot;

        if (userdiff_config(var, value) < 0)
                return -1;

        if (!strcmp(var, "grep.extendedregexp")) {
                opt->extended_regexp_option = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "grep.patterntype")) {
                opt->pattern_type_option = parse_pattern_type_arg(var, value);
                return 0;
        }

        if (!strcmp(var, "grep.linenumber")) {
                opt->linenum = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "grep.column")) {
                opt->columnnum = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "grep.fullname")) {
                opt->relative = !git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "color.grep"))
                opt->color = git_config_colorbool(var, value);
        if (!strcmp(var, "color.grep.match")) {
                if (grep_config("color.grep.matchcontext", value, ctx, cb) < 0)
                        return -1;
                if (grep_config("color.grep.matchselected", value, ctx, cb) < 0)
                        return -1;
        } else if (skip_prefix(var, "color.grep.", &slot)) {
                int i = LOOKUP_CONFIG(color_grep_slots, slot);
                char *color;

                if (i < 0)
                        return -1;
                color = opt->colors[i];
                if (!value)
                        return config_error_nonbool(var);
                return color_parse(value, color);
        }
        return 0;
}

void grep_init(struct grep_opt *opt, struct repository *repo)
{
        struct grep_opt blank = GREP_OPT_INIT;
        memcpy(opt, &blank, sizeof(*opt));

        opt->repo = repo;
        opt->pattern_tail = &opt->pattern_list;
        opt->header_tail = &opt->header_list;
}

static struct grep_pat *create_grep_pat(const char *pat, size_t patlen,
                                        const char *origin, int no,
                                        enum grep_pat_token t,
                                        enum grep_header_field field)
{
        struct grep_pat *p = xcalloc(1, sizeof(*p));
        p->pattern = xmemdupz(pat, patlen);
        p->patternlen = patlen;
        p->origin = origin;
        p->no = no;
        p->token = t;
        p->field = field;
        return p;
}

static void do_append_grep_pat(struct grep_pat ***tail, struct grep_pat *p)
{
        **tail = p;
        *tail = &p->next;
        p->next = NULL;

        switch (p->token) {
        case GREP_PATTERN: /* atom */
        case GREP_PATTERN_HEAD:
        case GREP_PATTERN_BODY:
                for (;;) {
                        struct grep_pat *new_pat;
                        size_t len = 0;
                        char *cp = p->pattern + p->patternlen, *nl = NULL;
                        while (++len <= p->patternlen) {
                                if (*(--cp) == '\n') {
                                        nl = cp;
                                        break;
                                }
                        }
                        if (!nl)
                                break;
                        new_pat = create_grep_pat(nl + 1, len - 1, p->origin,
                                                  p->no, p->token, p->field);
                        new_pat->next = p->next;
                        if (!p->next)
                                *tail = &new_pat->next;
                        p->next = new_pat;
                        *nl = '\0';
                        p->patternlen -= len;
                }
                break;
        default:
                break;
        }
}

void append_header_grep_pattern(struct grep_opt *opt,
                                enum grep_header_field field, const char *pat)
{
        struct grep_pat *p = create_grep_pat(pat, strlen(pat), "header", 0,
                                             GREP_PATTERN_HEAD, field);
        if (field == GREP_HEADER_REFLOG)
                opt->use_reflog_filter = 1;
        do_append_grep_pat(&opt->header_tail, p);
}

void append_grep_pattern(struct grep_opt *opt, const char *pat,
                         const char *origin, int no, enum grep_pat_token t)
{
        append_grep_pat(opt, pat, strlen(pat), origin, no, t);
}

void append_grep_pat(struct grep_opt *opt, const char *pat, size_t patlen,
                     const char *origin, int no, enum grep_pat_token t)
{
        struct grep_pat *p = create_grep_pat(pat, patlen, origin, no, t, 0);
        do_append_grep_pat(&opt->pattern_tail, p);
}

struct grep_opt *grep_opt_dup(const struct grep_opt *opt)
{
        struct grep_pat *pat;
        struct grep_opt *ret = xmalloc(sizeof(struct grep_opt));
        *ret = *opt;

        ret->pattern_list = NULL;
        ret->pattern_tail = &ret->pattern_list;

        for(pat = opt->pattern_list; pat != NULL; pat = pat->next)
        {
                if(pat->token == GREP_PATTERN_HEAD)
                        append_header_grep_pattern(ret, pat->field,
                                                   pat->pattern);
                else
                        append_grep_pat(ret, pat->pattern, pat->patternlen,
                                        pat->origin, pat->no, pat->token);
        }

        return ret;
}

static NORETURN void compile_regexp_failed(const struct grep_pat *p,
                const char *error)
{
        char where[1024];

        if (p->no)
                xsnprintf(where, sizeof(where), "In '%s' at %d, ", p->origin, p->no);
        else if (p->origin)
                xsnprintf(where, sizeof(where), "%s, ", p->origin);
        else
                where[0] = 0;

        die("%s'%s': %s", where, p->pattern, error);
}

static int is_fixed(const char *s, size_t len)
{
        size_t i;

        for (i = 0; i < len; i++) {
                if (is_regex_special(s[i]))
                        return 0;
        }

        return 1;
}

#ifdef USE_LIBPCRE2
#define GREP_PCRE2_DEBUG_MALLOC 0

static void *pcre2_malloc(PCRE2_SIZE size, MAYBE_UNUSED void *memory_data)
{
        void *pointer = malloc(size);
#if GREP_PCRE2_DEBUG_MALLOC
        static int count = 1;
        fprintf(stderr, "PCRE2:%p -> #%02d: alloc(%lu)\n", pointer, count++, size);
#endif
        return pointer;
}

static void pcre2_free(void *pointer, MAYBE_UNUSED void *memory_data)
{
#if GREP_PCRE2_DEBUG_MALLOC
        static int count = 1;
        if (pointer)
                fprintf(stderr, "PCRE2:%p -> #%02d: free()\n", pointer, count++);
#endif
        free(pointer);
}

static int pcre2_jit_functional(void)
{
        static int jit_working = -1;
        pcre2_code *code;
        size_t off;
        int err;

        if (jit_working != -1)
                return jit_working;

        /*
         * Try to JIT compile a simple pattern to probe if the JIT is
         * working in general. It might fail for systems where creating
         * memory mappings for runtime code generation is restricted.
         */
        code = pcre2_compile((PCRE2_SPTR)".", 1, 0, &err, &off, NULL);
        if (!code)
                return 0;

        jit_working = pcre2_jit_compile(code, PCRE2_JIT_COMPLETE) == 0;
        pcre2_code_free(code);

        return jit_working;
}

static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt)
{
        int error;
        PCRE2_UCHAR errbuf[256];
        PCRE2_SIZE erroffset;
        int options = PCRE2_MULTILINE;
        int jitret;
        int patinforet;
        size_t jitsizearg;
        int literal = !opt->ignore_case && (p->fixed || p->is_fixed);

        /*
         * Call pcre2_general_context_create() before calling any
         * other pcre2_*(). It sets up our malloc()/free() functions
         * with which everything else is allocated.
         */
        p->pcre2_general_context = pcre2_general_context_create(
                pcre2_malloc, pcre2_free, NULL);
        if (!p->pcre2_general_context)
                die("Couldn't allocate PCRE2 general context");

        if (opt->ignore_case) {
                if (!opt->ignore_locale && has_non_ascii(p->pattern)) {
                        p->pcre2_tables = pcre2_maketables(p->pcre2_general_context);
                        p->pcre2_compile_context = pcre2_compile_context_create(p->pcre2_general_context);
                        pcre2_set_character_tables(p->pcre2_compile_context,
                                                        p->pcre2_tables);
                }
                options |= PCRE2_CASELESS;
        }
        if (!opt->ignore_locale && is_utf8_locale() && !literal)
                options |= (PCRE2_UTF | PCRE2_UCP | PCRE2_MATCH_INVALID_UTF);

#ifndef GIT_PCRE2_VERSION_10_35_OR_HIGHER
        /*
         * Work around a JIT bug related to invalid Unicode character handling
         * fixed in 10.35:
         * https://github.com/PCRE2Project/pcre2/commit/c21bd977547d
         */
        options &= ~PCRE2_UCP;
#endif

#ifndef GIT_PCRE2_VERSION_10_36_OR_HIGHER
        /* Work around https://bugs.exim.org/show_bug.cgi?id=2642 fixed in 10.36 */
        if (PCRE2_MATCH_INVALID_UTF && options & (PCRE2_UTF | PCRE2_CASELESS))
                options |= PCRE2_NO_START_OPTIMIZE;
#endif

        p->pcre2_pattern = pcre2_compile((PCRE2_SPTR)p->pattern,
                                         p->patternlen, options, &error, &erroffset,
                                         p->pcre2_compile_context);

        if (p->pcre2_pattern) {
                p->pcre2_match_data = pcre2_match_data_create_from_pattern(p->pcre2_pattern, p->pcre2_general_context);
                if (!p->pcre2_match_data)
                        die("Couldn't allocate PCRE2 match data");
        } else {
                pcre2_get_error_message(error, errbuf, sizeof(errbuf));
                compile_regexp_failed(p, (const char *)&errbuf);
        }

        pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
        if (p->pcre2_jit_on) {
                jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
                if (jitret == PCRE2_ERROR_NOMEMORY && !pcre2_jit_functional()) {
                        /*
                         * Even though pcre2_config(PCRE2_CONFIG_JIT, ...)
                         * indicated JIT support, the library might still
                         * fail to generate JIT code for various reasons,
                         * e.g. when SELinux's 'deny_execmem' or PaX's
                         * MPROTECT prevent creating W|X memory mappings.
                         *
                         * Instead of faling hard, fall back to interpreter
                         * mode, just as if the pattern was prefixed with
                         * '(*NO_JIT)'.
                         */
                        p->pcre2_jit_on = 0;
                        return;
                } else if (jitret) {
                        int need_clip = p->patternlen > 64;
                        int clip_len = need_clip ? 64 : p->patternlen;
                        die("Couldn't JIT the PCRE2 pattern '%.*s'%s, got '%d'%s",
                            clip_len, p->pattern, need_clip ? "..." : "", jitret,
                            pcre2_jit_functional()
                            ? "\nPerhaps prefix (*NO_JIT) to your pattern?"
                            : "");
                }

                /*
                 * The pcre2_config(PCRE2_CONFIG_JIT, ...) call just
                 * tells us whether the library itself supports JIT,
                 * but to see whether we're going to be actually using
                 * JIT we need to extract PCRE2_INFO_JITSIZE from the
                 * pattern *after* we do pcre2_jit_compile() above.
                 *
                 * This is because if the pattern contains the
                 * (*NO_JIT) verb (see pcre2syntax(3))
                 * pcre2_jit_compile() will exit early with 0. If we
                 * then proceed to call pcre2_jit_match() further down
                 * the line instead of pcre2_match() we'll either
                 * segfault (pre PCRE 10.31) or run into a fatal error
                 * (post PCRE2 10.31)
                 */
                patinforet = pcre2_pattern_info(p->pcre2_pattern, PCRE2_INFO_JITSIZE, &jitsizearg);
                if (patinforet)
                        BUG("pcre2_pattern_info() failed: %d", patinforet);
                if (jitsizearg == 0) {
                        p->pcre2_jit_on = 0;
                        return;
                }
        }
}

static int pcre2match(struct grep_pat *p, const char *line, const char *eol,
                regmatch_t *match, int eflags)
{
        int ret, flags = 0;
        PCRE2_SIZE *ovector;
        PCRE2_UCHAR errbuf[256];

        if (eflags & REG_NOTBOL)
                flags |= PCRE2_NOTBOL;

        if (p->pcre2_jit_on)
                ret = pcre2_jit_match(p->pcre2_pattern, (unsigned char *)line,
                                      eol - line, 0, flags, p->pcre2_match_data,
                                      NULL);
        else
                ret = pcre2_match(p->pcre2_pattern, (unsigned char *)line,
                                  eol - line, 0, flags, p->pcre2_match_data,
                                  NULL);

        if (ret < 0 && ret != PCRE2_ERROR_NOMATCH) {
                pcre2_get_error_message(ret, errbuf, sizeof(errbuf));
                die("%s failed with error code %d: %s",
                    (p->pcre2_jit_on ? "pcre2_jit_match" : "pcre2_match"), ret,
                    errbuf);
        }
        if (ret > 0) {
                ovector = pcre2_get_ovector_pointer(p->pcre2_match_data);
                ret = 0;
                match->rm_so = (int)ovector[0];
                match->rm_eo = (int)ovector[1];
        }

        return ret;
}

static void free_pcre2_pattern(struct grep_pat *p)
{
        pcre2_compile_context_free(p->pcre2_compile_context);
        pcre2_code_free(p->pcre2_pattern);
        pcre2_match_data_free(p->pcre2_match_data);
#ifdef GIT_PCRE2_VERSION_10_34_OR_HIGHER
        pcre2_maketables_free(p->pcre2_general_context, p->pcre2_tables);
#else
        free((void *)p->pcre2_tables);
#endif
        pcre2_general_context_free(p->pcre2_general_context);
}
#else /* !USE_LIBPCRE2 */
static void compile_pcre2_pattern(struct grep_pat *p UNUSED,
                                  const struct grep_opt *opt UNUSED)
{
        die("cannot use Perl-compatible regexes when not compiled with USE_LIBPCRE");
}

static int pcre2match(struct grep_pat *p UNUSED, const char *line UNUSED,
                      const char *eol UNUSED, regmatch_t *match UNUSED,
                      int eflags UNUSED)
{
        return 1;
}

static void free_pcre2_pattern(struct grep_pat *p UNUSED)
{
}

static void compile_fixed_regexp(struct grep_pat *p, struct grep_opt *opt)
{
        struct strbuf sb = STRBUF_INIT;
        int err;
        int regflags = 0;

        basic_regex_quote_buf(&sb, p->pattern);
        if (opt->ignore_case)
                regflags |= REG_ICASE;
        err = regcomp(&p->regexp, sb.buf, regflags);
        strbuf_release(&sb);
        if (err) {
                char errbuf[1024];
                regerror(err, &p->regexp, errbuf, sizeof(errbuf));
                compile_regexp_failed(p, errbuf);
        }
}
#endif /* !USE_LIBPCRE2 */

static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
{
        int err;
        int regflags = REG_NEWLINE;

        if (opt->pattern_type_option == GREP_PATTERN_TYPE_UNSPECIFIED)
                opt->pattern_type_option = (opt->extended_regexp_option
                                            ? GREP_PATTERN_TYPE_ERE
                                            : GREP_PATTERN_TYPE_BRE);

        p->word_regexp = opt->word_regexp;
        p->ignore_case = opt->ignore_case;
        p->fixed = opt->pattern_type_option == GREP_PATTERN_TYPE_FIXED;

        if (opt->pattern_type_option != GREP_PATTERN_TYPE_PCRE &&
            memchr(p->pattern, 0, p->patternlen))
                die(_("given pattern contains NULL byte (via -f <file>). This is only supported with -P under PCRE v2"));

        p->is_fixed = is_fixed(p->pattern, p->patternlen);
#ifdef USE_LIBPCRE2
       if (!p->fixed && !p->is_fixed) {
               const char *no_jit = "(*NO_JIT)";
               const int no_jit_len = strlen(no_jit);
               if (starts_with(p->pattern, no_jit) &&
                   is_fixed(p->pattern + no_jit_len,
                            p->patternlen - no_jit_len))
                       p->is_fixed = 1;
       }
#endif
        if (p->fixed || p->is_fixed) {
#ifdef USE_LIBPCRE2
                if (p->is_fixed) {
                        compile_pcre2_pattern(p, opt);
                } else {
                        /*
                         * E.g. t7811-grep-open.sh relies on the
                         * pattern being restored.
                         */
                        char *old_pattern = p->pattern;
                        size_t old_patternlen = p->patternlen;
                        struct strbuf sb = STRBUF_INIT;

                        /*
                         * There is the PCRE2_LITERAL flag, but it's
                         * only in PCRE v2 10.30 and later. Needing to
                         * ifdef our way around that and dealing with
                         * it + PCRE2_MULTILINE being an error is more
                         * complex than just quoting this ourselves.
                        */
                        strbuf_add(&sb, "\\Q", 2);
                        strbuf_add(&sb, p->pattern, p->patternlen);
                        strbuf_add(&sb, "\\E", 2);

                        p->pattern = sb.buf;
                        p->patternlen = sb.len;
                        compile_pcre2_pattern(p, opt);
                        p->pattern = old_pattern;
                        p->patternlen = old_patternlen;
                        strbuf_release(&sb);
                }
#else /* !USE_LIBPCRE2 */
                compile_fixed_regexp(p, opt);
#endif /* !USE_LIBPCRE2 */
                return;
        }

        if (opt->pattern_type_option == GREP_PATTERN_TYPE_PCRE) {
                compile_pcre2_pattern(p, opt);
                return;
        }

        if (p->ignore_case)
                regflags |= REG_ICASE;
        if (opt->pattern_type_option == GREP_PATTERN_TYPE_ERE)
                regflags |= REG_EXTENDED;
        err = regcomp(&p->regexp, p->pattern, regflags);
        if (err) {
                char errbuf[1024];
                regerror(err, &p->regexp, errbuf, 1024);
                compile_regexp_failed(p, errbuf);
        }
}

static struct grep_expr *grep_not_expr(struct grep_expr *expr)
{
        struct grep_expr *z = xcalloc(1, sizeof(*z));
        z->node = GREP_NODE_NOT;
        z->u.unary = expr;
        return z;
}

static struct grep_expr *grep_binexp(enum grep_expr_node kind,
                                     struct grep_expr *left,
                                     struct grep_expr *right)
{
        struct grep_expr *z = xcalloc(1, sizeof(*z));
        z->node = kind;
        z->u.binary.left = left;
        z->u.binary.right = right;
        return z;
}

static struct grep_expr *grep_or_expr(struct grep_expr *left, struct grep_expr *right)
{
        return grep_binexp(GREP_NODE_OR, left, right);
}

static struct grep_expr *grep_and_expr(struct grep_expr *left, struct grep_expr *right)
{
        return grep_binexp(GREP_NODE_AND, left, right);
}

static struct grep_expr *compile_pattern_or(struct grep_pat **);
static struct grep_expr *compile_pattern_atom(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x;

        p = *list;
        if (!p)
                return NULL;
        switch (p->token) {
        case GREP_PATTERN: /* atom */
        case GREP_PATTERN_HEAD:
        case GREP_PATTERN_BODY:
                CALLOC_ARRAY(x, 1);
                x->node = GREP_NODE_ATOM;
                x->u.atom = p;
                *list = p->next;
                return x;
        case GREP_OPEN_PAREN:
                *list = p->next;
                x = compile_pattern_or(list);
                if (!*list || (*list)->token != GREP_CLOSE_PAREN)
                        die("unmatched parenthesis");
                *list = (*list)->next;
                return x;
        default:
                return NULL;
        }
}

static struct grep_expr *compile_pattern_not(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x;

        p = *list;
        if (!p)
                return NULL;
        switch (p->token) {
        case GREP_NOT:
                if (!p->next)
                        die("--not not followed by pattern expression");
                *list = p->next;
                x = compile_pattern_not(list);
                if (!x)
                        die("--not followed by non pattern expression");
                return grep_not_expr(x);
        default:
                return compile_pattern_atom(list);
        }
}

static struct grep_expr *compile_pattern_and(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x, *y;

        x = compile_pattern_not(list);
        p = *list;
        if (p && p->token == GREP_AND) {
                if (!x)
                        die("--and not preceded by pattern expression");
                if (!p->next)
                        die("--and not followed by pattern expression");
                *list = p->next;
                y = compile_pattern_and(list);
                if (!y)
                        die("--and not followed by pattern expression");
                return grep_and_expr(x, y);
        }
        return x;
}

static struct grep_expr *compile_pattern_or(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x, *y;

        x = compile_pattern_and(list);
        p = *list;
        if (x && p && p->token != GREP_CLOSE_PAREN) {
                y = compile_pattern_or(list);
                if (!y)
                        die("not a pattern expression %s", p->pattern);
                return grep_or_expr(x, y);
        }
        return x;
}

static struct grep_expr *compile_pattern_expr(struct grep_pat **list)
{
        return compile_pattern_or(list);
}

static struct grep_expr *grep_true_expr(void)
{
        struct grep_expr *z = xcalloc(1, sizeof(*z));
        z->node = GREP_NODE_TRUE;
        return z;
}

static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
{
        struct grep_pat *p;
        struct grep_expr *header_expr;
        struct grep_expr *(header_group[GREP_HEADER_FIELD_MAX]);
        enum grep_header_field fld;

        if (!opt->header_list)
                return NULL;

        for (p = opt->header_list; p; p = p->next) {
                if (p->token != GREP_PATTERN_HEAD)
                        BUG("a non-header pattern in grep header list.");
                if (p->field < GREP_HEADER_FIELD_MIN ||
                    GREP_HEADER_FIELD_MAX <= p->field)
                        BUG("unknown header field %d", p->field);
                compile_regexp(p, opt);
        }

        for (fld = 0; fld < GREP_HEADER_FIELD_MAX; fld++)
                header_group[fld] = NULL;

        for (p = opt->header_list; p; p = p->next) {
                struct grep_expr *h;
                struct grep_pat *pp = p;

                h = compile_pattern_atom(&pp);
                if (!h || pp != p->next)
                        BUG("malformed header expr");
                if (!header_group[p->field]) {
                        header_group[p->field] = h;
                        continue;
                }
                header_group[p->field] = grep_or_expr(h, header_group[p->field]);
        }

        header_expr = NULL;

        for (fld = 0; fld < GREP_HEADER_FIELD_MAX; fld++) {
                if (!header_group[fld])
                        continue;
                if (!header_expr)
                        header_expr = grep_true_expr();
                header_expr = grep_or_expr(header_group[fld], header_expr);
        }
        return header_expr;
}

static struct grep_expr *grep_splice_or(struct grep_expr *x, struct grep_expr *y)
{
        struct grep_expr *z = x;

        while (x) {
                assert(x->node == GREP_NODE_OR);
                if (x->u.binary.right &&
                    x->u.binary.right->node == GREP_NODE_TRUE) {
                        x->u.binary.right = y;
                        break;
                }
                x = x->u.binary.right;
        }
        return z;
}

void compile_grep_patterns(struct grep_opt *opt)
{
        struct grep_pat *p;
        struct grep_expr *header_expr = prep_header_patterns(opt);
        int extended = 0;

        for (p = opt->pattern_list; p; p = p->next) {
                switch (p->token) {
                case GREP_PATTERN: /* atom */
                case GREP_PATTERN_HEAD:
                case GREP_PATTERN_BODY:
                        compile_regexp(p, opt);
                        break;
                default:
                        extended = 1;
                        break;
                }
        }

        if (opt->all_match || opt->no_body_match || header_expr)
                extended = 1;
        else if (!extended)
                return;

        p = opt->pattern_list;
        if (p)
                opt->pattern_expression = compile_pattern_expr(&p);
        if (p)
                die("incomplete pattern expression: %s", p->pattern);

        if (opt->no_body_match && opt->pattern_expression)
                opt->pattern_expression = grep_not_expr(opt->pattern_expression);

        if (!header_expr)
                return;

        if (!opt->pattern_expression)
                opt->pattern_expression = header_expr;
        else if (opt->all_match)
                opt->pattern_expression = grep_splice_or(header_expr,
                                                         opt->pattern_expression);
        else
                opt->pattern_expression = grep_or_expr(opt->pattern_expression,
                                                       header_expr);
        opt->all_match = 1;
}

static void free_pattern_expr(struct grep_expr *x)
{
        switch (x->node) {
        case GREP_NODE_TRUE:
        case GREP_NODE_ATOM:
                break;
        case GREP_NODE_NOT:
                free_pattern_expr(x->u.unary);
                break;
        case GREP_NODE_AND:
        case GREP_NODE_OR:
                free_pattern_expr(x->u.binary.left);
                free_pattern_expr(x->u.binary.right);
                break;
        }
        free(x);
}

static void free_grep_pat(struct grep_pat *pattern)
{
        struct grep_pat *p, *n;

        for (p = pattern; p; p = n) {
                n = p->next;
                switch (p->token) {
                case GREP_PATTERN: /* atom */
                case GREP_PATTERN_HEAD:
                case GREP_PATTERN_BODY:
                        if (p->pcre2_pattern)
                                free_pcre2_pattern(p);
                        else
                                regfree(&p->regexp);
                        free(p->pattern);
                        break;
                default:
                        break;
                }
                free(p);
        }
}

void free_grep_patterns(struct grep_opt *opt)
{
        free_grep_pat(opt->pattern_list);
        free_grep_pat(opt->header_list);

        if (opt->pattern_expression)
                free_pattern_expr(opt->pattern_expression);
}

static const char *end_of_line(const char *cp, unsigned long *left)
{
        unsigned long l = *left;
        while (l && *cp != '\n') {
                l--;
                cp++;
        }
        *left = l;
        return cp;
}

static int word_char(char ch)
{
        return isalnum(ch) || ch == '_';
}

static void output_color(struct grep_opt *opt, const void *data, size_t size,
                         const char *color)
{
        if (want_color(opt->color) && color && color[0]) {
                opt->output(opt, color, strlen(color));
                opt->output(opt, data, size);
                opt->output(opt, GIT_COLOR_RESET, strlen(GIT_COLOR_RESET));
        } else
                opt->output(opt, data, size);
}

static void output_sep(struct grep_opt *opt, char sign)
{
        if (opt->null_following_name)
                opt->output(opt, "\0", 1);
        else
                output_color(opt, &sign, 1, opt->colors[GREP_COLOR_SEP]);
}

static void show_name(struct grep_opt *opt, const char *name)
{
        output_color(opt, name, strlen(name), opt->colors[GREP_COLOR_FILENAME]);
        opt->output(opt, opt->null_following_name ? "\0" : "\n", 1);
}

static int patmatch(struct grep_pat *p,
                    const char *line, const char *eol,
                    regmatch_t *match, int eflags)
{
        int hit;

        if (p->pcre2_pattern)
                hit = !pcre2match(p, line, eol, match, eflags);
        else
                hit = !regexec_buf(&p->regexp, line, eol - line, 1, match,
                                   eflags);

        return hit;
}

static void strip_timestamp(const char *bol, const char **eol_p)
{
        const char *eol = *eol_p;

        while (bol < --eol) {
                if (*eol != '>')
                        continue;
                *eol_p = ++eol;
                break;
        }
}

static struct {
        const char *field;
        size_t len;
} header_field[] = {
        { "author ", 7 },
        { "committer ", 10 },
        { "reflog ", 7 },
};

static int headerless_match_one_pattern(struct grep_pat *p,
                                        const char *bol, const char *eol,
                                        enum grep_context ctx,
                                        regmatch_t *pmatch, int eflags)
{
        int hit = 0;
        const char *start = bol;

        if ((p->token != GREP_PATTERN) &&
            ((p->token == GREP_PATTERN_HEAD) != (ctx == GREP_CONTEXT_HEAD)))
                return 0;

 again:
        hit = patmatch(p, bol, eol, pmatch, eflags);

        if (hit && p->word_regexp) {
                if ((pmatch[0].rm_so < 0) ||
                    (eol - bol) < pmatch[0].rm_so ||
                    (pmatch[0].rm_eo < 0) ||
                    (eol - bol) < pmatch[0].rm_eo)
                        die("regexp returned nonsense");

                /* Match beginning must be either beginning of the
                 * line, or at word boundary (i.e. the last char must
                 * not be a word char).  Similarly, match end must be
                 * either end of the line, or at word boundary
                 * (i.e. the next char must not be a word char).
                 */
                if ( ((pmatch[0].rm_so == 0) ||
                      !word_char(bol[pmatch[0].rm_so-1])) &&
                     ((pmatch[0].rm_eo == (eol-bol)) ||
                      !word_char(bol[pmatch[0].rm_eo])) )
                        ;
                else
                        hit = 0;

                /* Words consist of at least one character. */
                if (pmatch->rm_so == pmatch->rm_eo)
                        hit = 0;

                if (!hit && pmatch[0].rm_so + bol + 1 < eol) {
                        /* There could be more than one match on the
                         * line, and the first match might not be
                         * strict word match.  But later ones could be!
                         * Forward to the next possible start, i.e. the
                         * next position following a non-word char.
                         */
                        bol = pmatch[0].rm_so + bol + 1;
                        while (word_char(bol[-1]) && bol < eol)
                                bol++;
                        eflags |= REG_NOTBOL;
                        if (bol < eol)
                                goto again;
                }
        }
        if (hit) {
                pmatch[0].rm_so += bol - start;
                pmatch[0].rm_eo += bol - start;
        }
        return hit;
}

static int match_one_pattern(struct grep_pat *p,
                             const char *bol, const char *eol,
                             enum grep_context ctx, regmatch_t *pmatch,
                             int eflags)
{
        const char *field;
        size_t len;

        if (p->token == GREP_PATTERN_HEAD) {
                assert(p->field < ARRAY_SIZE(header_field));
                field = header_field[p->field].field;
                len = header_field[p->field].len;
                if (strncmp(bol, field, len))
                        return 0;
                bol += len;

                switch (p->field) {
                case GREP_HEADER_AUTHOR:
                case GREP_HEADER_COMMITTER:
                        strip_timestamp(bol, &eol);
                        break;
                default:
                        break;
                }
        }

        return headerless_match_one_pattern(p, bol, eol, ctx, pmatch, eflags);
}


static int match_expr_eval(struct grep_opt *opt, struct grep_expr *x,
                           const char *bol, const char *eol,
                           enum grep_context ctx, ssize_t *col,
                           ssize_t *icol, int collect_hits)
{
        int h = 0;

        switch (x->node) {
        case GREP_NODE_TRUE:
                h = 1;
                break;
        case GREP_NODE_ATOM:
                {
                        regmatch_t tmp;
                        h = match_one_pattern(x->u.atom, bol, eol, ctx,
                                              &tmp, 0);
                        if (h && (*col < 0 || tmp.rm_so < *col))
                                *col = tmp.rm_so;
                }
                if (x->u.atom->token == GREP_PATTERN_BODY)
                        opt->body_hit |= h;
                break;
        case GREP_NODE_NOT:
                /*
                 * Upon visiting a GREP_NODE_NOT, col and icol become swapped.
                 */
                h = !match_expr_eval(opt, x->u.unary, bol, eol, ctx, icol, col,
                                     0);
                break;
        case GREP_NODE_AND:
                h = match_expr_eval(opt, x->u.binary.left, bol, eol, ctx, col,
                                    icol, 0);
                if (h || opt->columnnum) {
                        /*
                         * Don't short-circuit AND when given --column, since a
                         * NOT earlier in the tree may turn this into an OR. In
                         * this case, see the below comment.
                         */
                        h &= match_expr_eval(opt, x->u.binary.right, bol, eol,
                                             ctx, col, icol, 0);
                }
                break;
        case GREP_NODE_OR:
                if (!(collect_hits || opt->columnnum)) {
                        /*
                         * Don't short-circuit OR when given --column (or
                         * collecting hits) to ensure we don't skip a later
                         * child that would produce an earlier match.
                         */
                        return (match_expr_eval(opt, x->u.binary.left, bol, eol,
                                                ctx, col, icol, 0) ||
                                match_expr_eval(opt, x->u.binary.right, bol,
                                                eol, ctx, col, icol, 0));
                }
                h = match_expr_eval(opt, x->u.binary.left, bol, eol, ctx, col,
                                    icol, 0);
                if (collect_hits)
                        x->u.binary.left->hit |= h;
                h |= match_expr_eval(opt, x->u.binary.right, bol, eol, ctx, col,
                                     icol, collect_hits);
                break;
        default:
                die("Unexpected node type (internal error) %d", x->node);
        }
        if (collect_hits)
                x->hit |= h;
        return h;
}

static int match_expr(struct grep_opt *opt,
                      const char *bol, const char *eol,
                      enum grep_context ctx, ssize_t *col,
                      ssize_t *icol, int collect_hits)
{
        struct grep_expr *x = opt->pattern_expression;
        return match_expr_eval(opt, x, bol, eol, ctx, col, icol, collect_hits);
}

static int match_line(struct grep_opt *opt,
                      const char *bol, const char *eol,
                      ssize_t *col, ssize_t *icol,
                      enum grep_context ctx, int collect_hits)
{
        struct grep_pat *p;
        int hit = 0;

        if (opt->pattern_expression)
                return match_expr(opt, bol, eol, ctx, col, icol,
                                  collect_hits);

        /* we do not call with collect_hits without being extended */
        for (p = opt->pattern_list; p; p = p->next) {
                regmatch_t tmp;
                if (match_one_pattern(p, bol, eol, ctx, &tmp, 0)) {
                        hit |= 1;
                        if (!opt->columnnum) {
                                /*
                                 * Without --column, any single match on a line
                                 * is enough to know that it needs to be
                                 * printed. With --column, scan _all_ patterns
                                 * to find the earliest.
                                 */
                                break;
                        }
                        if (*col < 0 || tmp.rm_so < *col)
                                *col = tmp.rm_so;
                }
        }
        return hit;
}

static int match_next_pattern(struct grep_pat *p,
                              const char *bol, const char *eol,
                              enum grep_context ctx,
                              regmatch_t *pmatch, int eflags)
{
        regmatch_t match;

        if (!headerless_match_one_pattern(p, bol, eol, ctx, &match, eflags))
                return 0;
        if (match.rm_so < 0 || match.rm_eo < 0)
                return 0;
        if (pmatch->rm_so >= 0 && pmatch->rm_eo >= 0) {
                if (match.rm_so > pmatch->rm_so)
                        return 1;
                if (match.rm_so == pmatch->rm_so && match.rm_eo < pmatch->rm_eo)
                        return 1;
        }
        pmatch->rm_so = match.rm_so;
        pmatch->rm_eo = match.rm_eo;
        return 1;
}

int grep_next_match(struct grep_opt *opt,
                    const char *bol, const char *eol,
                    enum grep_context ctx, regmatch_t *pmatch,
                    enum grep_header_field field, int eflags)
{
        struct grep_pat *p;
        int hit = 0;

        pmatch->rm_so = pmatch->rm_eo = -1;
        if (bol < eol) {
                for (p = ((ctx == GREP_CONTEXT_HEAD)
                           ? opt->header_list : opt->pattern_list);
                          p; p = p->next) {
                        switch (p->token) {
                        case GREP_PATTERN_HEAD:
                                if ((field != GREP_HEADER_FIELD_MAX) &&
                                    (p->field != field))
                                        continue;
                                /* fall thru */
                        case GREP_PATTERN: /* atom */
                        case GREP_PATTERN_BODY:
                                hit |= match_next_pattern(p, bol, eol, ctx,
                                                          pmatch, eflags);
                                break;
                        default:
                                break;
                        }
                }
        }
        return hit;
}

static void show_line_header(struct grep_opt *opt, const char *name,
                             unsigned lno, ssize_t cno, char sign)
{
        if (opt->heading && opt->last_shown == 0) {
                output_color(opt, name, strlen(name), opt->colors[GREP_COLOR_FILENAME]);
                opt->output(opt, "\n", 1);
        }
        opt->last_shown = lno;

        if (!opt->heading && opt->pathname) {
                output_color(opt, name, strlen(name), opt->colors[GREP_COLOR_FILENAME]);
                output_sep(opt, sign);
        }
        if (opt->linenum) {
                char buf[32];
                xsnprintf(buf, sizeof(buf), "%d", lno);
                output_color(opt, buf, strlen(buf), opt->colors[GREP_COLOR_LINENO]);
                output_sep(opt, sign);
        }
        /*
         * Treat 'cno' as the 1-indexed offset from the start of a non-context
         * line to its first match. Otherwise, 'cno' is 0 indicating that we are
         * being called with a context line.
         */
        if (opt->columnnum && cno) {
                char buf[32];
                xsnprintf(buf, sizeof(buf), "%"PRIuMAX, (uintmax_t)cno);
                output_color(opt, buf, strlen(buf), opt->colors[GREP_COLOR_COLUMNNO]);
                output_sep(opt, sign);
        }
}

static void show_line(struct grep_opt *opt,
                      const char *bol, const char *eol,
                      const char *name, unsigned lno, ssize_t cno, char sign)
{
        int rest = eol - bol;
        const char *match_color = NULL;
        const char *line_color = NULL;

        if (opt->file_break && opt->last_shown == 0) {
                if (opt->show_hunk_mark)
                        opt->output(opt, "\n", 1);
        } else if (opt->pre_context || opt->post_context || opt->funcbody) {
                if (opt->last_shown == 0) {
                        if (opt->show_hunk_mark) {
                                output_color(opt, "--", 2, opt->colors[GREP_COLOR_SEP]);
                                opt->output(opt, "\n", 1);
                        }
                } else if (lno > opt->last_shown + 1) {
                        output_color(opt, "--", 2, opt->colors[GREP_COLOR_SEP]);
                        opt->output(opt, "\n", 1);
                }
        }
        if (!opt->only_matching) {
                /*
                 * In case the line we're being called with contains more than
                 * one match, leave printing each header to the loop below.
                 */
                show_line_header(opt, name, lno, cno, sign);
        }
        if (opt->color || opt->only_matching) {
                regmatch_t match;
                enum grep_context ctx = GREP_CONTEXT_BODY;
                int eflags = 0;

                if (opt->color) {
                        if (sign == ':')
                                match_color = opt->colors[GREP_COLOR_MATCH_SELECTED];
                        else
                                match_color = opt->colors[GREP_COLOR_MATCH_CONTEXT];
                        if (sign == ':')
                                line_color = opt->colors[GREP_COLOR_SELECTED];
                        else if (sign == '-')
                                line_color = opt->colors[GREP_COLOR_CONTEXT];
                        else if (sign == '=')
                                line_color = opt->colors[GREP_COLOR_FUNCTION];
                }
                while (grep_next_match(opt, bol, eol, ctx, &match,
                                       GREP_HEADER_FIELD_MAX, eflags)) {
                        if (match.rm_so == match.rm_eo)
                                break;

                        if (opt->only_matching)
                                show_line_header(opt, name, lno, cno, sign);
                        else
                                output_color(opt, bol, match.rm_so, line_color);
                        output_color(opt, bol + match.rm_so,
                                     match.rm_eo - match.rm_so, match_color);
                        if (opt->only_matching)
                                opt->output(opt, "\n", 1);
                        bol += match.rm_eo;
                        cno += match.rm_eo;
                        rest -= match.rm_eo;
                        eflags = REG_NOTBOL;
                }
        }
        if (!opt->only_matching) {
                output_color(opt, bol, rest, line_color);
                opt->output(opt, "\n", 1);
        }
}

int grep_use_locks;

/*
 * This lock protects access to the gitattributes machinery, which is
 * not thread-safe.
 */
pthread_mutex_t grep_attr_mutex;

static inline void grep_attr_lock(void)
{
        if (grep_use_locks)
                pthread_mutex_lock(&grep_attr_mutex);
}

static inline void grep_attr_unlock(void)
{
        if (grep_use_locks)
                pthread_mutex_unlock(&grep_attr_mutex);
}

static int match_funcname(struct grep_opt *opt, struct grep_source *gs,
                          const char *bol, const char *eol)
{
        xdemitconf_t *xecfg = opt->priv;
        if (xecfg && !xecfg->find_func) {
                grep_source_load_driver(gs, opt->repo->index);
                if (gs->driver->funcname.pattern) {
                        const struct userdiff_funcname *pe = &gs->driver->funcname;
                        xdiff_set_find_func(xecfg, pe->pattern, pe->cflags);
                } else {
                        xecfg = opt->priv = NULL;
                }
        }

        if (xecfg) {
                char buf[1];
                return xecfg->find_func(bol, eol - bol, buf, 1,
                                        xecfg->find_func_priv) >= 0;
        }

        if (bol == eol)
                return 0;
        if (isalpha(*bol) || *bol == '_' || *bol == '$')
                return 1;
        return 0;
}

static void show_funcname_line(struct grep_opt *opt, struct grep_source *gs,
                               const char *bol, unsigned lno)
{
        while (bol > gs->buf) {
                const char *eol = --bol;

                while (bol > gs->buf && bol[-1] != '\n')
                        bol--;
                lno--;

                if (lno <= opt->last_shown)
                        break;

                if (match_funcname(opt, gs, bol, eol)) {
                        show_line(opt, bol, eol, gs->name, lno, 0, '=');
                        break;
                }
        }
}

static int is_empty_line(const char *bol, const char *eol);

static void show_pre_context(struct grep_opt *opt, struct grep_source *gs,
                             const char *bol, const char *end, unsigned lno)
{
        unsigned cur = lno, from = 1, funcname_lno = 0, orig_from;
        int funcname_needed = !!opt->funcname, comment_needed = 0;

        if (opt->pre_context < lno)
                from = lno - opt->pre_context;
        if (from <= opt->last_shown)
                from = opt->last_shown + 1;
        orig_from = from;
        if (opt->funcbody) {
                if (match_funcname(opt, gs, bol, end))
                        comment_needed = 1;
                else
                        funcname_needed = 1;
                from = opt->last_shown + 1;
        }

        /* Rewind. */
        while (bol > gs->buf && cur > from) {
                const char *next_bol = bol;
                const char *eol = --bol;

                while (bol > gs->buf && bol[-1] != '\n')
                        bol--;
                cur--;
                if (comment_needed && (is_empty_line(bol, eol) ||
                                       match_funcname(opt, gs, bol, eol))) {
                        comment_needed = 0;
                        from = orig_from;
                        if (cur < from) {
                                cur++;
                                bol = next_bol;
                                break;
                        }
                }
                if (funcname_needed && match_funcname(opt, gs, bol, eol)) {
                        funcname_lno = cur;
                        funcname_needed = 0;
                        if (opt->funcbody)
                                comment_needed = 1;
                        else
                                from = orig_from;
                }
        }

        /* We need to look even further back to find a function signature. */
        if (opt->funcname && funcname_needed)
                show_funcname_line(opt, gs, bol, cur);

        /* Back forward. */
        while (cur < lno) {
                const char *eol = bol, sign = (cur == funcname_lno) ? '=' : '-';

                while (*eol != '\n')
                        eol++;
                show_line(opt, bol, eol, gs->name, cur, 0, sign);
                bol = eol + 1;
                cur++;
        }
}

static int should_lookahead(struct grep_opt *opt)
{
        struct grep_pat *p;

        if (opt->pattern_expression)
                return 0; /* punt for too complex stuff */
        if (opt->invert)
                return 0;
        for (p = opt->pattern_list; p; p = p->next) {
                if (p->token != GREP_PATTERN)
                        return 0; /* punt for "header only" and stuff */
        }
        return 1;
}

static int look_ahead(struct grep_opt *opt,
                      unsigned long *left_p,
                      unsigned *lno_p,
                      const char **bol_p)
{
        unsigned lno = *lno_p;
        const char *bol = *bol_p;
        struct grep_pat *p;
        const char *sp, *last_bol;
        regoff_t earliest = -1;

        for (p = opt->pattern_list; p; p = p->next) {
                int hit;
                regmatch_t m;

                hit = patmatch(p, bol, bol + *left_p, &m, 0);
                if (!hit || m.rm_so < 0 || m.rm_eo < 0)
                        continue;
                if (earliest < 0 || m.rm_so < earliest)
                        earliest = m.rm_so;
        }

        if (earliest < 0) {
                *bol_p = bol + *left_p;
                *left_p = 0;
                return 1;
        }
        for (sp = bol + earliest; bol < sp && sp[-1] != '\n'; sp--)
                ; /* find the beginning of the line */
        last_bol = sp;

        for (sp = bol; sp < last_bol; sp++) {
                if (*sp == '\n')
                        lno++;
        }
        *left_p -= last_bol - bol;
        *bol_p = last_bol;
        *lno_p = lno;
        return 0;
}

static int fill_textconv_grep(struct repository *r,
                              struct userdiff_driver *driver,
                              struct grep_source *gs)
{
        struct diff_filespec *df;
        char *buf;
        size_t size;

        if (!driver || !driver->textconv)
                return grep_source_load(gs);

        /*
         * The textconv interface is intimately tied to diff_filespecs, so we
         * have to pretend to be one. If we could unify the grep_source
         * and diff_filespec structs, this mess could just go away.
         */
        df = alloc_filespec(gs->path);
        switch (gs->type) {
        case GREP_SOURCE_OID:
                fill_filespec(df, gs->identifier, 1, 0100644);
                break;
        case GREP_SOURCE_FILE:
                fill_filespec(df, null_oid(), 0, 0100644);
                break;
        default:
                BUG("attempt to textconv something without a path?");
        }

        /*
         * fill_textconv is not remotely thread-safe; it modifies the global
         * diff tempfile structure, writes to the_repo's odb and might
         * internally call thread-unsafe functions such as the
         * prepare_packed_git() lazy-initializator. Because of the last two, we
         * must ensure mutual exclusion between this call and the object reading
         * API, thus we use obj_read_lock() here.
         *
         * TODO: allowing text conversion to run in parallel with object
         * reading operations might increase performance in the multithreaded
         * non-worktreee git-grep with --textconv.
         */
        obj_read_lock();
        size = fill_textconv(r, driver, df, &buf);
        obj_read_unlock();
        free_filespec(df);

        /*
         * The normal fill_textconv usage by the diff machinery would just keep
         * the textconv'd buf separate from the diff_filespec. But much of the
         * grep code passes around a grep_source and assumes that its "buf"
         * pointer is the beginning of the thing we are searching. So let's
         * install our textconv'd version into the grep_source, taking care not
         * to leak any existing buffer.
         */
        grep_source_clear_data(gs);
        gs->buf = buf;
        gs->size = size;

        return 0;
}

static int is_empty_line(const char *bol, const char *eol)
{
        while (bol < eol && isspace(*bol))
                bol++;
        return bol == eol;
}

static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int collect_hits)
{
        const char *bol;
        const char *peek_bol = NULL;
        unsigned long left;
        unsigned lno = 1;
        unsigned last_hit = 0;
        int binary_match_only = 0;
        unsigned count = 0;
        int try_lookahead = 0;
        int show_function = 0;
        struct userdiff_driver *textconv = NULL;
        enum grep_context ctx = GREP_CONTEXT_HEAD;
        xdemitconf_t xecfg;

        if (!opt->status_only && gs->name == NULL)
                BUG("grep call which could print a name requires "
                    "grep_source.name be non-NULL");

        if (!opt->output)
                opt->output = std_output;

        if (opt->pre_context || opt->post_context || opt->file_break ||
            opt->funcbody) {
                /* Show hunk marks, except for the first file. */
                if (opt->last_shown)
                        opt->show_hunk_mark = 1;
                /*
                 * If we're using threads then we can't easily identify
                 * the first file.  Always put hunk marks in that case
                 * and skip the very first one later in work_done().
                 */
                if (opt->output != std_output)
                        opt->show_hunk_mark = 1;
        }
        opt->last_shown = 0;

        if (opt->allow_textconv) {
                grep_source_load_driver(gs, opt->repo->index);
                /*
                 * We might set up the shared textconv cache data here, which
                 * is not thread-safe. Also, get_oid_with_context() and
                 * parse_object() might be internally called. As they are not
                 * currently thread-safe and might be racy with object reading,
                 * obj_read_lock() must be called.
                 */
                grep_attr_lock();
                obj_read_lock();
                textconv = userdiff_get_textconv(opt->repo, gs->driver);
                obj_read_unlock();
                grep_attr_unlock();
        }

        /*
         * We know the result of a textconv is text, so we only have to care
         * about binary handling if we are not using it.
         */
        if (!textconv) {
                switch (opt->binary) {
                case GREP_BINARY_DEFAULT:
                        if (grep_source_is_binary(gs, opt->repo->index))
                                binary_match_only = 1;
                        break;
                case GREP_BINARY_NOMATCH:
                        if (grep_source_is_binary(gs, opt->repo->index))
                                return 0; /* Assume unmatch */
                        break;
                case GREP_BINARY_TEXT:
                        break;
                default:
                        BUG("unknown binary handling mode");
                }
        }

        memset(&xecfg, 0, sizeof(xecfg));
        opt->priv = &xecfg;

        try_lookahead = should_lookahead(opt);

        if (fill_textconv_grep(opt->repo, textconv, gs) < 0)
                return 0;

        bol = gs->buf;
        left = gs->size;
        while (left) {
                const char *eol;
                int hit;
                ssize_t cno;
                ssize_t col = -1, icol = -1;

                /*
                 * look_ahead() skips quickly to the line that possibly
                 * has the next hit; don't call it if we need to do
                 * something more than just skipping the current line
                 * in response to an unmatch for the current line.  E.g.
                 * inside a post-context window, we will show the current
                 * line as a context around the previous hit when it
                 * doesn't hit.
                 */
                if (try_lookahead
                    && !(last_hit
                         && (show_function ||
                             lno <= last_hit + opt->post_context))
                    && look_ahead(opt, &left, &lno, &bol))
                        break;
                eol = end_of_line(bol, &left);

                if ((ctx == GREP_CONTEXT_HEAD) && (eol == bol))
                        ctx = GREP_CONTEXT_BODY;

                hit = match_line(opt, bol, eol, &col, &icol, ctx, collect_hits);

                if (collect_hits)
                        goto next_line;

                /* "grep -v -e foo -e bla" should list lines
                 * that do not have either, so inversion should
                 * be done outside.
                 */
                if (opt->invert)
                        hit = !hit;
                if (opt->unmatch_name_only) {
                        if (hit)
                                return 0;
                        goto next_line;
                }
                if (hit && (opt->max_count < 0 || count < opt->max_count)) {
                        count++;
                        if (opt->status_only)
                                return 1;
                        if (opt->name_only) {
                                show_name(opt, gs->name);
                                return 1;
                        }
                        if (opt->count)
                                goto next_line;
                        if (binary_match_only) {
                                opt->output(opt, "Binary file ", 12);
                                output_color(opt, gs->name, strlen(gs->name),
                                             opt->colors[GREP_COLOR_FILENAME]);
                                opt->output(opt, " matches\n", 9);
                                return 1;
                        }
                        /* Hit at this line.  If we haven't shown the
                         * pre-context lines, we would need to show them.
                         */
                        if (opt->pre_context || opt->funcbody)
                                show_pre_context(opt, gs, bol, eol, lno);
                        else if (opt->funcname)
                                show_funcname_line(opt, gs, bol, lno);
                        cno = opt->invert ? icol : col;
                        if (cno < 0) {
                                /*
                                 * A negative cno indicates that there was no
                                 * match on the line. We are thus inverted and
                                 * being asked to show all lines that _don't_
                                 * match a given expression. Therefore, set cno
                                 * to 0 to suggest the whole line matches.
                                 */
                                cno = 0;
                        }
                        show_line(opt, bol, eol, gs->name, lno, cno + 1, ':');
                        last_hit = lno;
                        if (opt->funcbody)
                                show_function = 1;
                        goto next_line;
                }
                if (show_function && (!peek_bol || peek_bol < bol)) {
                        unsigned long peek_left = left;
                        const char *peek_eol = eol;

                        /*
                         * Trailing empty lines are not interesting.
                         * Peek past them to see if they belong to the
                         * body of the current function.
                         */
                        peek_bol = bol;
                        while (is_empty_line(peek_bol, peek_eol)) {
                                peek_bol = peek_eol + 1;
                                peek_eol = end_of_line(peek_bol, &peek_left);
                        }

                        if (match_funcname(opt, gs, peek_bol, peek_eol))
                                show_function = 0;
                }
                if (show_function ||
                    (last_hit && lno <= last_hit + opt->post_context)) {
                        /* If the last hit is within the post context,
                         * we need to show this line.
                         */
                        show_line(opt, bol, eol, gs->name, lno, col + 1, '-');
                }

        next_line:
                bol = eol + 1;
                if (!left)
                        break;
                left--;
                lno++;
        }

        if (collect_hits)
                return 0;

        if (opt->status_only)
                return opt->unmatch_name_only;
        if (opt->unmatch_name_only) {
                /* We did not see any hit, so we want to show this */
                show_name(opt, gs->name);
                return 1;
        }

        xdiff_clear_find_func(&xecfg);
        opt->priv = NULL;

        /* NEEDSWORK:
         * The real "grep -c foo *.c" gives many "bar.c:0" lines,
         * which feels mostly useless but sometimes useful.  Maybe
         * make it another option?  For now suppress them.
         */
        if (opt->count && count) {
                char buf[32];
                if (opt->pathname) {
                        output_color(opt, gs->name, strlen(gs->name),
                                     opt->colors[GREP_COLOR_FILENAME]);
                        output_sep(opt, ':');
                }
                xsnprintf(buf, sizeof(buf), "%u\n", count);
                opt->output(opt, buf, strlen(buf));
                return 1;
        }
        return !!last_hit;
}

static void clr_hit_marker(struct grep_expr *x)
{
        /* All-hit markers are meaningful only at the very top level
         * OR node.
         */
        while (1) {
                x->hit = 0;
                if (x->node != GREP_NODE_OR)
                        return;
                x->u.binary.left->hit = 0;
                x = x->u.binary.right;
        }
}

static int chk_hit_marker(struct grep_expr *x)
{
        /* Top level nodes have hit markers.  See if they all are hits */
        while (1) {
                if (x->node != GREP_NODE_OR)
                        return x->hit;
                if (!x->u.binary.left->hit)
                        return 0;
                x = x->u.binary.right;
        }
}

int grep_source(struct grep_opt *opt, struct grep_source *gs)
{
        /*
         * we do not have to do the two-pass grep when we do not check
         * buffer-wide "all-match".
         */
        if (!opt->all_match && !opt->no_body_match)
                return grep_source_1(opt, gs, 0);

        /* Otherwise the toplevel "or" terms hit a bit differently.
         * We first clear hit markers from them.
         */
        clr_hit_marker(opt->pattern_expression);
        opt->body_hit = 0;
        grep_source_1(opt, gs, 1);

        if (opt->all_match && !chk_hit_marker(opt->pattern_expression))
                return 0;
        if (opt->no_body_match && opt->body_hit)
                return 0;

        return grep_source_1(opt, gs, 0);
}

static void grep_source_init_buf(struct grep_source *gs,
                                 const char *buf,
                                 unsigned long size)
{
        gs->type = GREP_SOURCE_BUF;
        gs->name = NULL;
        gs->path = NULL;
        gs->buf = buf;
        gs->size = size;
        gs->driver = NULL;
        gs->identifier = NULL;
}

int grep_buffer(struct grep_opt *opt, const char *buf, unsigned long size)
{
        struct grep_source gs;
        int r;

        grep_source_init_buf(&gs, buf, size);

        r = grep_source(opt, &gs);

        grep_source_clear(&gs);
        return r;
}

void grep_source_init_file(struct grep_source *gs, const char *name,
                           const char *path)
{
        gs->type = GREP_SOURCE_FILE;
        gs->name = xstrdup_or_null(name);
        gs->path = xstrdup_or_null(path);
        gs->buf = NULL;
        gs->size = 0;
        gs->driver = NULL;
        gs->identifier = xstrdup(path);
}

void grep_source_init_oid(struct grep_source *gs, const char *name,
                          const char *path, const struct object_id *oid,
                          struct repository *repo)
{
        gs->type = GREP_SOURCE_OID;
        gs->name = xstrdup_or_null(name);
        gs->path = xstrdup_or_null(path);
        gs->buf = NULL;
        gs->size = 0;
        gs->driver = NULL;
        gs->identifier = oiddup(oid);
        gs->repo = repo;
}

void grep_source_clear(struct grep_source *gs)
{
        FREE_AND_NULL(gs->name);
        FREE_AND_NULL(gs->path);
        FREE_AND_NULL(gs->identifier);
        grep_source_clear_data(gs);
}

void grep_source_clear_data(struct grep_source *gs)
{
        switch (gs->type) {
        case GREP_SOURCE_FILE:
        case GREP_SOURCE_OID:
                /* these types own the buffer */
                free((char *)gs->buf);
                gs->buf = NULL;
                gs->size = 0;
                break;
        case GREP_SOURCE_BUF:
                /* leave user-provided buf intact */
                break;
        }
}

static int grep_source_load_oid(struct grep_source *gs)
{
        enum object_type type;

        gs->buf = repo_read_object_file(gs->repo, gs->identifier, &type,
                                        &gs->size);
        if (!gs->buf)
                return error(_("'%s': unable to read %s"),
                             gs->name,
                             oid_to_hex(gs->identifier));
        return 0;
}

static int grep_source_load_file(struct grep_source *gs)
{
        const char *filename = gs->identifier;
        struct stat st;
        char *data;
        size_t size;
        int i;

        if (lstat(filename, &st) < 0) {
        err_ret:
                if (errno != ENOENT)
                        error_errno(_("failed to stat '%s'"), filename);
                return -1;
        }
        if (!S_ISREG(st.st_mode))
                return -1;
        size = xsize_t(st.st_size);
        i = open(filename, O_RDONLY);
        if (i < 0)
                goto err_ret;
        data = xmallocz(size);
        if (st.st_size != read_in_full(i, data, size)) {
                error_errno(_("'%s': short read"), filename);
                close(i);
                free(data);
                return -1;
        }
        close(i);

        gs->buf = data;
        gs->size = size;
        return 0;
}

static int grep_source_load(struct grep_source *gs)
{
        if (gs->buf)
                return 0;

        switch (gs->type) {
        case GREP_SOURCE_FILE:
                return grep_source_load_file(gs);
        case GREP_SOURCE_OID:
                return grep_source_load_oid(gs);
        case GREP_SOURCE_BUF:
                return gs->buf ? 0 : -1;
        }
        BUG("invalid grep_source type to load");
}

void grep_source_load_driver(struct grep_source *gs,
                             struct index_state *istate)
{
        if (gs->driver)
                return;

        grep_attr_lock();
        if (gs->path)
                gs->driver = userdiff_find_by_path(istate, gs->path);
        if (!gs->driver)
                gs->driver = userdiff_find_by_name("default");
        grep_attr_unlock();
}

static int grep_source_is_binary(struct grep_source *gs,
                                 struct index_state *istate)
{
        grep_source_load_driver(gs, istate);
        if (gs->driver->binary != -1)
                return gs->driver->binary;

        if (!grep_source_load(gs))
                return buffer_is_binary(gs->buf, gs->size);

        return 0;
}