Changes for kernel and Busybox

[tomato.git] / release / src / router / busybox / editors / sed.c

/* vi: set sw=4 ts=4: */
/*
 * sed.c - very minimalist version of sed
 *
 * Copyright (C) 1999,2000,2001 by Lineo, inc. and Mark Whitley
 * Copyright (C) 1999,2000,2001 by Mark Whitley <markw@codepoet.org>
 * Copyright (C) 2002  Matt Kraai
 * Copyright (C) 2003 by Glenn McGrath
 * Copyright (C) 2003,2004 by Rob Landley <rob@landley.net>
 *
 * MAINTAINER: Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

/* Code overview.
 *
 * Files are laid out to avoid unnecessary function declarations.  So for
 * example, every function add_cmd calls occurs before add_cmd in this file.
 *
 * add_cmd() is called on each line of sed command text (from a file or from
 * the command line).  It calls get_address() and parse_cmd_args().  The
 * resulting sed_cmd_t structures are appended to a linked list
 * (G.sed_cmd_head/G.sed_cmd_tail).
 *
 * add_input_file() adds a FILE* to the list of input files.  We need to
 * know all input sources ahead of time to find the last line for the $ match.
 *
 * process_files() does actual sedding, reading data lines from each input FILE*
 * (which could be stdin) and applying the sed command list (sed_cmd_head) to
 * each of the resulting lines.
 *
 * sed_main() is where external code calls into this, with a command line.
 */

/* Supported features and commands in this version of sed:
 *
 * - comments ('#')
 * - address matching: num|/matchstr/[,num|/matchstr/|$]command
 * - commands: (p)rint, (d)elete, (s)ubstitue (with g & I flags)
 * - edit commands: (a)ppend, (i)nsert, (c)hange
 * - file commands: (r)ead
 * - backreferences in substitution expressions (\0, \1, \2...\9)
 * - grouped commands: {cmd1;cmd2}
 * - transliteration (y/source-chars/dest-chars/)
 * - pattern space hold space storing / swapping (g, h, x)
 * - labels / branching (: label, b, t, T)
 *
 * (Note: Specifying an address (range) to match is *optional*; commands
 * default to the whole pattern space if no specific address match was
 * requested.)
 *
 * Todo:
 * - Create a wrapper around regex to make libc's regex conform with sed
 *
 * Reference http://www.opengroup.org/onlinepubs/007904975/utilities/sed.html
 */

//usage:#define sed_trivial_usage
//usage:       "[-inr] [-f FILE]... [-e CMD]... [FILE]...\n"
//usage:       "or: sed [-inr] CMD [FILE]..."
//usage:#define sed_full_usage "\n\n"
//usage:       "        -e CMD  Add CMD to sed commands to be executed"
//usage:     "\n        -f FILE Add FILE contents to sed commands to be executed"
//usage:     "\n        -i      Edit files in-place (else sends result to stdout)"
//usage:     "\n        -n      Suppress automatic printing of pattern space"
//usage:     "\n        -r      Use extended regex syntax"
//usage:     "\n"
//usage:     "\nIf no -e or -f, the first non-option argument is the sed command string."
//usage:     "\nRemaining arguments are input files (stdin if none)."
//usage:
//usage:#define sed_example_usage
//usage:       "$ echo \"foo\" | sed -e 's/f[a-zA-Z]o/bar/g'\n"
//usage:       "bar\n"

#include "libbb.h"
#include "xregex.h"

#if 0
# define dbg(...) bb_error_msg(__VA_ARGS__)
#else
# define dbg(...) ((void)0)
#endif


enum {
        OPT_in_place = 1 << 0,
};

/* Each sed command turns into one of these structures. */
typedef struct sed_cmd_s {
        /* Ordered by alignment requirements: currently 36 bytes on x86 */
        struct sed_cmd_s *next; /* Next command (linked list, NULL terminated) */

        /* address storage */
        regex_t *beg_match;     /* sed -e '/match/cmd' */
        regex_t *end_match;     /* sed -e '/match/,/end_match/cmd' */
        regex_t *sub_match;     /* For 's/sub_match/string/' */
        int beg_line;           /* 'sed 1p'   0 == apply commands to all lines */
        int beg_line_orig;      /* copy of the above, needed for -i */
        int end_line;           /* 'sed 1,3p' 0 == one line only. -1 = last line ($) */

        FILE *sw_file;          /* File (sw) command writes to, -1 for none. */
        char *string;           /* Data string for (saicytb) commands. */

        unsigned which_match;   /* (s) Which match to replace (0 for all) */

        /* Bitfields (gcc won't group them if we don't) */
        unsigned invert:1;      /* the '!' after the address */
        unsigned in_match:1;    /* Next line also included in match? */
        unsigned sub_p:1;       /* (s) print option */

        char sw_last_char;      /* Last line written by (sw) had no '\n' */

        /* GENERAL FIELDS */
        char cmd;               /* The command char: abcdDgGhHilnNpPqrstwxy:={} */
} sed_cmd_t;

static const char semicolon_whitespace[] ALIGN1 = "; \n\r\t\v";

struct globals {
        /* options */
        int be_quiet, regex_type;
        FILE *nonstdout;
        char *outname, *hold_space;

        /* List of input files */
        int input_file_count, current_input_file;
        FILE **input_file_list;

        regmatch_t regmatch[10];
        regex_t *previous_regex_ptr;

        /* linked list of sed commands */
        sed_cmd_t *sed_cmd_head, **sed_cmd_tail;

        /* Linked list of append lines */
        llist_t *append_head;

        char *add_cmd_line;

        struct pipeline {
                char *buf;  /* Space to hold string */
                int idx;    /* Space used */
                int len;    /* Space allocated */
        } pipeline;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
struct BUG_G_too_big {
        char BUG_G_too_big[sizeof(G) <= COMMON_BUFSIZE ? 1 : -1];
};
#define INIT_G() do { \
        G.sed_cmd_tail = &G.sed_cmd_head; \
} while (0)


#if ENABLE_FEATURE_CLEAN_UP
static void sed_free_and_close_stuff(void)
{
        sed_cmd_t *sed_cmd = G.sed_cmd_head;

        llist_free(G.append_head, free);

        while (sed_cmd) {
                sed_cmd_t *sed_cmd_next = sed_cmd->next;

                if (sed_cmd->sw_file)
                        xprint_and_close_file(sed_cmd->sw_file);

                if (sed_cmd->beg_match) {
                        regfree(sed_cmd->beg_match);
                        free(sed_cmd->beg_match);
                }
                if (sed_cmd->end_match) {
                        regfree(sed_cmd->end_match);
                        free(sed_cmd->end_match);
                }
                if (sed_cmd->sub_match) {
                        regfree(sed_cmd->sub_match);
                        free(sed_cmd->sub_match);
                }
                free(sed_cmd->string);
                free(sed_cmd);
                sed_cmd = sed_cmd_next;
        }

        free(G.hold_space);

        while (G.current_input_file < G.input_file_count)
                fclose(G.input_file_list[G.current_input_file++]);
}
#else
void sed_free_and_close_stuff(void);
#endif

/* If something bad happens during -i operation, delete temp file */

static void cleanup_outname(void)
{
        if (G.outname) unlink(G.outname);
}

/* strcpy, replacing "\from" with 'to'. If to is NUL, replacing "\any" with 'any' */

static void parse_escapes(char *dest, const char *string, int len, char from, char to)
{
        int i = 0;

        while (i < len) {
                if (string[i] == '\\') {
                        if (!to || string[i+1] == from) {
                                *dest++ = to ? to : string[i+1];
                                i += 2;
                                continue;
                        }
                        *dest++ = string[i++];
                }
                /* TODO: is it safe wrt a string with trailing '\\' ? */
                *dest++ = string[i++];
        }
        *dest = '\0';
}

static char *copy_parsing_escapes(const char *string, int len)
{
        const char *s;
        char *dest = xmalloc(len + 1);

        /* sed recognizes \n */
        /* GNU sed also recognizes \t and \r */
        for (s = "\nn\tt\rr"; *s; s += 2) {
                parse_escapes(dest, string, len, s[1], s[0]);
                string = dest;
                len = strlen(dest);
        }
        return dest;
}


/*
 * index_of_next_unescaped_regexp_delim - walks left to right through a string
 * beginning at a specified index and returns the index of the next regular
 * expression delimiter (typically a forward slash ('/')) not preceded by
 * a backslash ('\').  A negative delimiter disables square bracket checking.
 */
static int index_of_next_unescaped_regexp_delim(int delimiter, const char *str)
{
        int bracket = -1;
        int escaped = 0;
        int idx = 0;
        char ch;

        if (delimiter < 0) {
                bracket--;
                delimiter = -delimiter;
        }

        for (; (ch = str[idx]) != '\0'; idx++) {
                if (bracket >= 0) {
                        if (ch == ']'
                         && !(bracket == idx - 1 || (bracket == idx - 2 && str[idx - 1] == '^'))
                        ) {
                                bracket = -1;
                        }
                } else if (escaped)
                        escaped = 0;
                else if (ch == '\\')
                        escaped = 1;
                else if (bracket == -1 && ch == '[')
                        bracket = idx;
                else if (ch == delimiter)
                        return idx;
        }

        /* if we make it to here, we've hit the end of the string */
        bb_error_msg_and_die("unmatched '%c'", delimiter);
}

/*
 *  Returns the index of the third delimiter
 */
static int parse_regex_delim(const char *cmdstr, char **match, char **replace)
{
        const char *cmdstr_ptr = cmdstr;
        unsigned char delimiter;
        int idx = 0;

        /* verify that the 's' or 'y' is followed by something.  That something
         * (typically a 'slash') is now our regexp delimiter... */
        if (*cmdstr == '\0')
                bb_error_msg_and_die("bad format in substitution expression");
        delimiter = *cmdstr_ptr++;

        /* save the match string */
        idx = index_of_next_unescaped_regexp_delim(delimiter, cmdstr_ptr);
        *match = copy_parsing_escapes(cmdstr_ptr, idx);

        /* save the replacement string */
        cmdstr_ptr += idx + 1;
        idx = index_of_next_unescaped_regexp_delim(- (int)delimiter, cmdstr_ptr);
        *replace = copy_parsing_escapes(cmdstr_ptr, idx);

        return ((cmdstr_ptr - cmdstr) + idx);
}

/*
 * returns the index in the string just past where the address ends.
 */
static int get_address(const char *my_str, int *linenum, regex_t ** regex)
{
        const char *pos = my_str;

        if (isdigit(*my_str)) {
                *linenum = strtol(my_str, (char**)&pos, 10);
                /* endstr shouldnt ever equal NULL */
        } else if (*my_str == '$') {
                *linenum = -1;
                pos++;
        } else if (*my_str == '/' || *my_str == '\\') {
                int next;
                char delimiter;
                char *temp;

                delimiter = '/';
                if (*my_str == '\\')
                        delimiter = *++pos;
                next = index_of_next_unescaped_regexp_delim(delimiter, ++pos);
                temp = copy_parsing_escapes(pos, next);
                *regex = xzalloc(sizeof(regex_t));
                xregcomp(*regex, temp, G.regex_type|REG_NEWLINE);
                free(temp);
                /* Move position to next character after last delimiter */
                pos += (next+1);
        }
        return pos - my_str;
}

/* Grab a filename.  Whitespace at start is skipped, then goes to EOL. */
static int parse_file_cmd(/*sed_cmd_t *sed_cmd,*/ const char *filecmdstr, char **retval)
{
        int start = 0, idx, hack = 0;

        /* Skip whitespace, then grab filename to end of line */
        while (isspace(filecmdstr[start]))
                start++;
        idx = start;
        while (filecmdstr[idx] && filecmdstr[idx] != '\n')
                idx++;

        /* If lines glued together, put backslash back. */
        if (filecmdstr[idx] == '\n')
                hack = 1;
        if (idx == start)
                bb_error_msg_and_die("empty filename");
        *retval = xstrndup(filecmdstr+start, idx-start+hack+1);
        if (hack)
                (*retval)[idx] = '\\';

        return idx;
}

static int parse_subst_cmd(sed_cmd_t *sed_cmd, const char *substr)
{
        int cflags = G.regex_type;
        char *match;
        int idx;

        /*
         * A substitution command should look something like this:
         *    s/match/replace/ #gIpw
         *    ||     |        |||
         *    mandatory       optional
         */
        idx = parse_regex_delim(substr, &match, &sed_cmd->string);

        /* determine the number of back references in the match string */
        /* Note: we compute this here rather than in the do_subst_command()
         * function to save processor time, at the expense of a little more memory
         * (4 bits) per sed_cmd */

        /* process the flags */

        sed_cmd->which_match = 1;
        while (substr[++idx]) {
                /* Parse match number */
                if (isdigit(substr[idx])) {
                        if (match[0] != '^') {
                                /* Match 0 treated as all, multiple matches we take the last one. */
                                const char *pos = substr + idx;
/* FIXME: error check? */
                                sed_cmd->which_match = (unsigned)strtol(substr+idx, (char**) &pos, 10);
                                idx = pos - substr;
                        }
                        continue;
                }
                /* Skip spaces */
                if (isspace(substr[idx]))
                        continue;

                switch (substr[idx]) {
                /* Replace all occurrences */
                case 'g':
                        if (match[0] != '^')
                                sed_cmd->which_match = 0;
                        break;
                /* Print pattern space */
                case 'p':
                        sed_cmd->sub_p = 1;
                        break;
                /* Write to file */
                case 'w':
                {
                        char *temp;
                        idx += parse_file_cmd(/*sed_cmd,*/ substr+idx, &temp);
                        break;
                }
                /* Ignore case (gnu exension) */
                case 'I':
                        cflags |= REG_ICASE;
                        break;
                /* Comment */
                case '#':
                        // while (substr[++idx]) continue;
                        idx += strlen(substr + idx); // same
                        /* Fall through */
                /* End of command */
                case ';':
                case '}':
                        goto out;
                default:
                        bb_error_msg_and_die("bad option in substitution expression");
                }
        }
 out:
        /* compile the match string into a regex */
        if (*match != '\0') {
                /* If match is empty, we use last regex used at runtime */
                sed_cmd->sub_match = xzalloc(sizeof(regex_t));
                dbg("xregcomp('%s',%x)", match, cflags);
                xregcomp(sed_cmd->sub_match, match, cflags);
                dbg("regcomp ok");
        }
        free(match);

        return idx;
}

/*
 *  Process the commands arguments
 */
static const char *parse_cmd_args(sed_cmd_t *sed_cmd, const char *cmdstr)
{
        static const char cmd_letters[] = "saicrw:btTydDgGhHlnNpPqx={}";
        enum {
                IDX_s = 0,
                IDX_a,
                IDX_i,
                IDX_c,
                IDX_r,
                IDX_w,
                IDX_colon,
                IDX_b,
                IDX_t,
                IDX_T,
                IDX_y,
                IDX_d,
                IDX_D,
                IDX_g,
                IDX_G,
                IDX_h,
                IDX_H,
                IDX_l,
                IDX_n,
                IDX_N,
                IDX_p,
                IDX_P,
                IDX_q,
                IDX_x,
                IDX_equal,
                IDX_lbrace,
                IDX_rbrace,
                IDX_nul
        };
        struct chk { char chk[sizeof(cmd_letters)-1 == IDX_nul ? 1 : -1]; };

        unsigned idx = strchrnul(cmd_letters, sed_cmd->cmd) - cmd_letters;

        /* handle (s)ubstitution command */
        if (idx == IDX_s) {
                cmdstr += parse_subst_cmd(sed_cmd, cmdstr);
        }
        /* handle edit cmds: (a)ppend, (i)nsert, and (c)hange */
        else if (idx <= IDX_c) { /* a,i,c */
                if ((sed_cmd->end_line || sed_cmd->end_match) && sed_cmd->cmd != 'c')
                        bb_error_msg_and_die("only a beginning address can be specified for edit commands");
                for (;;) {
                        if (*cmdstr == '\n' || *cmdstr == '\\') {
                                cmdstr++;
                                break;
                        }
                        if (!isspace(*cmdstr))
                                break;
                        cmdstr++;
                }
                sed_cmd->string = xstrdup(cmdstr);
                /* "\anychar" -> "anychar" */
                parse_escapes(sed_cmd->string, sed_cmd->string, strlen(cmdstr), '\0', '\0');
                cmdstr += strlen(cmdstr);
        }
        /* handle file cmds: (r)ead */
        else if (idx <= IDX_w) { /* r,w */
                if (sed_cmd->end_line || sed_cmd->end_match)
                        bb_error_msg_and_die("command only uses one address");
                cmdstr += parse_file_cmd(/*sed_cmd,*/ cmdstr, &sed_cmd->string);
                if (sed_cmd->cmd == 'w') {
                        sed_cmd->sw_file = xfopen_for_write(sed_cmd->string);
                        sed_cmd->sw_last_char = '\n';
                }
        }
        /* handle branch commands */
        else if (idx <= IDX_T) { /* :,b,t,T */
                int length;

                cmdstr = skip_whitespace(cmdstr);
                length = strcspn(cmdstr, semicolon_whitespace);
                if (length) {
                        sed_cmd->string = xstrndup(cmdstr, length);
                        cmdstr += length;
                }
        }
        /* translation command */
        else if (idx == IDX_y) {
                char *match, *replace;
                int i = cmdstr[0];

                cmdstr += parse_regex_delim(cmdstr, &match, &replace)+1;
                /* \n already parsed, but \delimiter needs unescaping. */
                parse_escapes(match, match, strlen(match), i, i);
                parse_escapes(replace, replace, strlen(replace), i, i);

                sed_cmd->string = xzalloc((strlen(match) + 1) * 2);
                for (i = 0; match[i] && replace[i]; i++) {
                        sed_cmd->string[i*2] = match[i];
                        sed_cmd->string[i*2+1] = replace[i];
                }
                free(match);
                free(replace);
        }
        /* if it wasnt a single-letter command that takes no arguments
         * then it must be an invalid command.
         */
        else if (idx >= IDX_nul) { /* not d,D,g,G,h,H,l,n,N,p,P,q,x,=,{,} */
                bb_error_msg_and_die("unsupported command %c", sed_cmd->cmd);
        }

        /* give back whatever's left over */
        return cmdstr;
}


/* Parse address+command sets, skipping comment lines. */

static void add_cmd(const char *cmdstr)
{
        sed_cmd_t *sed_cmd;
        unsigned len, n;

        /* Append this line to any unfinished line from last time. */
        if (G.add_cmd_line) {
                char *tp = xasprintf("%s\n%s", G.add_cmd_line, cmdstr);
                free(G.add_cmd_line);
                cmdstr = G.add_cmd_line = tp;
        }

        /* If this line ends with unescaped backslash, request next line. */
        n = len = strlen(cmdstr);
        while (n && cmdstr[n-1] == '\\')
                n--;
        if ((len - n) & 1) { /* if odd number of trailing backslashes */
                if (!G.add_cmd_line)
                        G.add_cmd_line = xstrdup(cmdstr);
                G.add_cmd_line[len-1] = '\0';
                return;
        }

        /* Loop parsing all commands in this line. */
        while (*cmdstr) {
                /* Skip leading whitespace and semicolons */
                cmdstr += strspn(cmdstr, semicolon_whitespace);

                /* If no more commands, exit. */
                if (!*cmdstr) break;

                /* if this is a comment, jump past it and keep going */
                if (*cmdstr == '#') {
                        /* "#n" is the same as using -n on the command line */
                        if (cmdstr[1] == 'n')
                                G.be_quiet++;
                        cmdstr = strpbrk(cmdstr, "\n\r");
                        if (!cmdstr) break;
                        continue;
                }

                /* parse the command
                 * format is: [addr][,addr][!]cmd
                 *            |----||-----||-|
                 *            part1 part2  part3
                 */

                sed_cmd = xzalloc(sizeof(sed_cmd_t));

                /* first part (if present) is an address: either a '$', a number or a /regex/ */
                cmdstr += get_address(cmdstr, &sed_cmd->beg_line, &sed_cmd->beg_match);
                sed_cmd->beg_line_orig = sed_cmd->beg_line;

                /* second part (if present) will begin with a comma */
                if (*cmdstr == ',') {
                        int idx;

                        cmdstr++;
                        idx = get_address(cmdstr, &sed_cmd->end_line, &sed_cmd->end_match);
                        if (!idx)
                                bb_error_msg_and_die("no address after comma");
                        cmdstr += idx;
                }

                /* skip whitespace before the command */
                cmdstr = skip_whitespace(cmdstr);

                /* Check for inversion flag */
                if (*cmdstr == '!') {
                        sed_cmd->invert = 1;
                        cmdstr++;

                        /* skip whitespace before the command */
                        cmdstr = skip_whitespace(cmdstr);
                }

                /* last part (mandatory) will be a command */
                if (!*cmdstr)
                        bb_error_msg_and_die("missing command");
                sed_cmd->cmd = *cmdstr++;
                cmdstr = parse_cmd_args(sed_cmd, cmdstr);

                /* Add the command to the command array */
                *G.sed_cmd_tail = sed_cmd;
                G.sed_cmd_tail = &sed_cmd->next;
        }

        /* If we glued multiple lines together, free the memory. */
        free(G.add_cmd_line);
        G.add_cmd_line = NULL;
}

/* Append to a string, reallocating memory as necessary. */

#define PIPE_GROW 64

static void pipe_putc(char c)
{
        if (G.pipeline.idx == G.pipeline.len) {
                G.pipeline.buf = xrealloc(G.pipeline.buf,
                                G.pipeline.len + PIPE_GROW);
                G.pipeline.len += PIPE_GROW;
        }
        G.pipeline.buf[G.pipeline.idx++] = c;
}

static void do_subst_w_backrefs(char *line, char *replace)
{
        int i, j;

        /* go through the replacement string */
        for (i = 0; replace[i]; i++) {
                /* if we find a backreference (\1, \2, etc.) print the backref'ed * text */
                if (replace[i] == '\\') {
                        unsigned backref = replace[++i] - '0';
                        if (backref <= 9) {
                                /* print out the text held in G.regmatch[backref] */
                                if (G.regmatch[backref].rm_so != -1) {
                                        j = G.regmatch[backref].rm_so;
                                        while (j < G.regmatch[backref].rm_eo)
                                                pipe_putc(line[j++]);
                                }
                                continue;
                        }
                        /* I _think_ it is impossible to get '\' to be
                         * the last char in replace string. Thus we dont check
                         * for replace[i] == NUL. (counterexample anyone?) */
                        /* if we find a backslash escaped character, print the character */
                        pipe_putc(replace[i]);
                        continue;
                }
                /* if we find an unescaped '&' print out the whole matched text. */
                if (replace[i] == '&') {
                        j = G.regmatch[0].rm_so;
                        while (j < G.regmatch[0].rm_eo)
                                pipe_putc(line[j++]);
                        continue;
                }
                /* Otherwise just output the character. */
                pipe_putc(replace[i]);
        }
}

static int do_subst_command(sed_cmd_t *sed_cmd, char **line_p)
{
        char *line = *line_p;
        int altered = 0;
        unsigned match_count = 0;
        regex_t *current_regex;

        current_regex = sed_cmd->sub_match;
        /* Handle empty regex. */
        if (!current_regex) {
                current_regex = G.previous_regex_ptr;
                if (!current_regex)
                        bb_error_msg_and_die("no previous regexp");
        }
        G.previous_regex_ptr = current_regex;

        /* Find the first match */
        dbg("matching '%s'", line);
        if (REG_NOMATCH == regexec(current_regex, line, 10, G.regmatch, 0)) {
                dbg("no match");
                return 0;
        }
        dbg("match");

        /* Initialize temporary output buffer. */
        G.pipeline.buf = xmalloc(PIPE_GROW);
        G.pipeline.len = PIPE_GROW;
        G.pipeline.idx = 0;

        /* Now loop through, substituting for matches */
        do {
                int i;

                /* Work around bug in glibc regexec, demonstrated by:
                 * echo " a.b" | busybox sed 's [^ .]* x g'
                 * The match_count check is so not to break
                 * echo "hi" | busybox sed 's/^/!/g'
                 */
                if (!G.regmatch[0].rm_so && !G.regmatch[0].rm_eo && match_count) {
                        pipe_putc(*line++);
                        goto next;
                }

                match_count++;

                /* If we aren't interested in this match, output old line to
                   end of match and continue */
                if (sed_cmd->which_match
                 && (sed_cmd->which_match != match_count)
                ) {
                        for (i = 0; i < G.regmatch[0].rm_eo; i++)
                                pipe_putc(*line++);
                        goto next;
                }

                /* print everything before the match */
                for (i = 0; i < G.regmatch[0].rm_so; i++)
                        pipe_putc(line[i]);

                /* then print the substitution string */
                do_subst_w_backrefs(line, sed_cmd->string);

                /* advance past the match */
                line += G.regmatch[0].rm_eo;
                /* flag that something has changed */
                altered++;

                /* if we're not doing this globally, get out now */
                if (sed_cmd->which_match != 0)
                        break;
 next:
                if (*line == '\0')
                        break;

//maybe (G.regmatch[0].rm_eo ? REG_NOTBOL : 0) instead of unconditional REG_NOTBOL?
        } while (regexec(current_regex, line, 10, G.regmatch, REG_NOTBOL) != REG_NOMATCH);

        /* Copy rest of string into output pipeline */
        while (1) {
                char c = *line++;
                pipe_putc(c);
                if (c == '\0')
                        break;
        }

        free(*line_p);
        *line_p = G.pipeline.buf;
        return altered;
}

/* Set command pointer to point to this label.  (Does not handle null label.) */
static sed_cmd_t *branch_to(char *label)
{
        sed_cmd_t *sed_cmd;

        for (sed_cmd = G.sed_cmd_head; sed_cmd; sed_cmd = sed_cmd->next) {
                if (sed_cmd->cmd == ':' && sed_cmd->string && !strcmp(sed_cmd->string, label)) {
                        return sed_cmd;
                }
        }
        bb_error_msg_and_die("can't find label for jump to '%s'", label);
}

static void append(char *s)
{
        llist_add_to_end(&G.append_head, xstrdup(s));
}

static void flush_append(void)
{
        char *data;

        /* Output appended lines. */
        while ((data = (char *)llist_pop(&G.append_head))) {
                fprintf(G.nonstdout, "%s\n", data);
                free(data);
        }
}

static void add_input_file(FILE *file)
{
        G.input_file_list = xrealloc_vector(G.input_file_list, 2, G.input_file_count);
        G.input_file_list[G.input_file_count++] = file;
}

/* Get next line of input from G.input_file_list, flushing append buffer and
 * noting if we ran out of files without a newline on the last line we read.
 */
enum {
        NO_EOL_CHAR = 1,
        LAST_IS_NUL = 2,
};
static char *get_next_line(char *gets_char)
{
        char *temp = NULL;
        int len;
        char gc;

        flush_append();

        /* will be returned if last line in the file
         * doesn't end with either '\n' or '\0' */
        gc = NO_EOL_CHAR;
        while (G.current_input_file < G.input_file_count) {
                FILE *fp = G.input_file_list[G.current_input_file];
                /* Read line up to a newline or NUL byte, inclusive,
                 * return malloc'ed char[]. length of the chunk read
                 * is stored in len. NULL if EOF/error */
                temp = bb_get_chunk_from_file(fp, &len);
                if (temp) {
                        /* len > 0 here, it's ok to do temp[len-1] */
                        char c = temp[len-1];
                        if (c == '\n' || c == '\0') {
                                temp[len-1] = '\0';
                                gc = c;
                                if (c == '\0') {
                                        int ch = fgetc(fp);
                                        if (ch != EOF)
                                                ungetc(ch, fp);
                                        else
                                                gc = LAST_IS_NUL;
                                }
                        }
                        /* else we put NO_EOL_CHAR into *gets_char */
                        break;

                /* NB: I had the idea of peeking next file(s) and returning
                 * NO_EOL_CHAR only if it is the *last* non-empty
                 * input file. But there is a case where this won't work:
                 * file1: "a woo\nb woo"
                 * file2: "c no\nd no"
                 * sed -ne 's/woo/bang/p' input1 input2 => "a bang\nb bang"
                 * (note: *no* newline after "b bang"!) */
                }
                /* Close this file and advance to next one */
                fclose(fp);
                G.current_input_file++;
        }
        *gets_char = gc;
        return temp;
}

/* Output line of text. */
/* Note:
 * The tricks with NO_EOL_CHAR and last_puts_char are there to emulate gnu sed.
 * Without them, we had this:
 * echo -n thingy >z1
 * echo -n again >z2
 * >znull
 * sed "s/i/z/" z1 z2 znull | hexdump -vC
 * output:
 * gnu sed 4.1.5:
 * 00000000  74 68 7a 6e 67 79 0a 61  67 61 7a 6e              |thzngy.agazn|
 * bbox:
 * 00000000  74 68 7a 6e 67 79 61 67  61 7a 6e                 |thzngyagazn|
 */
static void puts_maybe_newline(char *s, FILE *file, char *last_puts_char, char last_gets_char)
{
        char lpc = *last_puts_char;

        /* Need to insert a '\n' between two files because first file's
         * last line wasn't terminated? */
        if (lpc != '\n' && lpc != '\0') {
                fputc('\n', file);
                lpc = '\n';
        }
        fputs(s, file);

        /* 'x' - just something which is not '\n', '\0' or NO_EOL_CHAR */
        if (s[0])
                lpc = 'x';

        /* had trailing '\0' and it was last char of file? */
        if (last_gets_char == LAST_IS_NUL) {
                fputc('\0', file);
                lpc = 'x'; /* */
        } else
        /* had trailing '\n' or '\0'? */
        if (last_gets_char != NO_EOL_CHAR) {
                fputc(last_gets_char, file);
                lpc = last_gets_char;
        }

        if (ferror(file)) {
                xfunc_error_retval = 4;  /* It's what gnu sed exits with... */
                bb_error_msg_and_die(bb_msg_write_error);
        }
        *last_puts_char = lpc;
}

#define sed_puts(s, n) (puts_maybe_newline(s, G.nonstdout, &last_puts_char, n))

static int beg_match(sed_cmd_t *sed_cmd, const char *pattern_space)
{
        int retval = sed_cmd->beg_match && !regexec(sed_cmd->beg_match, pattern_space, 0, NULL, 0);
        if (retval)
                G.previous_regex_ptr = sed_cmd->beg_match;
        return retval;
}

/* Process all the lines in all the files */

static void process_files(void)
{
        char *pattern_space, *next_line;
        int linenum = 0;
        char last_puts_char = '\n';
        char last_gets_char, next_gets_char;
        sed_cmd_t *sed_cmd;
        int substituted;

        /* Prime the pump */
        next_line = get_next_line(&next_gets_char);

        /* Go through every line in each file */
 again:
        substituted = 0;

        /* Advance to next line.  Stop if out of lines. */
        pattern_space = next_line;
        if (!pattern_space)
                return;
        last_gets_char = next_gets_char;

        /* Read one line in advance so we can act on the last line,
         * the '$' address */
        next_line = get_next_line(&next_gets_char);
        linenum++;

        /* For every line, go through all the commands */
 restart:
        for (sed_cmd = G.sed_cmd_head; sed_cmd; sed_cmd = sed_cmd->next) {
                int old_matched, matched;

                old_matched = sed_cmd->in_match;

                /* Determine if this command matches this line: */

                dbg("match1:%d", sed_cmd->in_match);
                dbg("match2:%d", (!sed_cmd->beg_line && !sed_cmd->end_line
                                && !sed_cmd->beg_match && !sed_cmd->end_match));
                dbg("match3:%d", (sed_cmd->beg_line > 0
                        && (sed_cmd->end_line || sed_cmd->end_match
                            ? (sed_cmd->beg_line <= linenum)
                            : (sed_cmd->beg_line == linenum)
                            )
                        ));
                dbg("match4:%d", (beg_match(sed_cmd, pattern_space)));
                dbg("match5:%d", (sed_cmd->beg_line == -1 && next_line == NULL));

                /* Are we continuing a previous multi-line match? */
                sed_cmd->in_match = sed_cmd->in_match
                        /* Or is no range necessary? */
                        || (!sed_cmd->beg_line && !sed_cmd->end_line
                                && !sed_cmd->beg_match && !sed_cmd->end_match)
                        /* Or did we match the start of a numerical range? */
                        || (sed_cmd->beg_line > 0
                            && (sed_cmd->end_line || sed_cmd->end_match
                                  /* note: even if end is numeric and is < linenum too,
                                   * GNU sed matches! We match too, therefore we don't
                                   * check here that linenum <= end.
                                   * Example:
                                   * printf '1\n2\n3\n4\n' | sed -n '1{N;N;d};1p;2,3p;3p;4p'
                                   * first three input lines are deleted;
                                   * 4th line is matched and printed
                                   * by "2,3" (!) and by "4" ranges
                                   */
                                ? (sed_cmd->beg_line <= linenum)    /* N,end */
                                : (sed_cmd->beg_line == linenum)    /* N */
                                )
                            )
                        /* Or does this line match our begin address regex? */
                        || (beg_match(sed_cmd, pattern_space))
                        /* Or did we match last line of input? */
                        || (sed_cmd->beg_line == -1 && next_line == NULL);

                /* Snapshot the value */
                matched = sed_cmd->in_match;

                dbg("cmd:'%c' matched:%d beg_line:%d end_line:%d linenum:%d",
                        sed_cmd->cmd, matched, sed_cmd->beg_line, sed_cmd->end_line, linenum);

                /* Is this line the end of the current match? */

                if (matched) {
                        /* once matched, "n,xxx" range is dead, disabling it */
                        if (sed_cmd->beg_line > 0) {
                                sed_cmd->beg_line = -2;
                        }
                        sed_cmd->in_match = !(
                                /* has the ending line come, or is this a single address command? */
                                (sed_cmd->end_line
                                        ? sed_cmd->end_line == -1
                                                ? !next_line
                                                : (sed_cmd->end_line <= linenum)
                                        : !sed_cmd->end_match
                                )
                                /* or does this line matches our last address regex */
                                || (sed_cmd->end_match && old_matched
                                     && (regexec(sed_cmd->end_match,
                                                 pattern_space, 0, NULL, 0) == 0)
                                )
                        );
                }

                /* Skip blocks of commands we didn't match */
                if (sed_cmd->cmd == '{') {
                        if (sed_cmd->invert ? matched : !matched) {
                                unsigned nest_cnt = 0;
                                while (1) {
                                        if (sed_cmd->cmd == '{')
                                                nest_cnt++;
                                        if (sed_cmd->cmd == '}') {
                                                nest_cnt--;
                                                if (nest_cnt == 0)
                                                        break;
                                        }
                                        sed_cmd = sed_cmd->next;
                                        if (!sed_cmd)
                                                bb_error_msg_and_die("unterminated {");
                                }
                        }
                        continue;
                }

                /* Okay, so did this line match? */
                if (sed_cmd->invert ? matched : !matched)
                        continue; /* no */

                /* Update last used regex in case a blank substitute BRE is found */
                if (sed_cmd->beg_match) {
                        G.previous_regex_ptr = sed_cmd->beg_match;
                }

                /* actual sedding */
                dbg("pattern_space:'%s' next_line:'%s' cmd:%c",
                                pattern_space, next_line, sed_cmd->cmd);
                switch (sed_cmd->cmd) {

                /* Print line number */
                case '=':
                        fprintf(G.nonstdout, "%d\n", linenum);
                        break;

                /* Write the current pattern space up to the first newline */
                case 'P':
                {
                        char *tmp = strchr(pattern_space, '\n');
                        if (tmp) {
                                *tmp = '\0';
                                /* TODO: explain why '\n' below */
                                sed_puts(pattern_space, '\n');
                                *tmp = '\n';
                                break;
                        }
                        /* Fall Through */
                }

                /* Write the current pattern space to output */
                case 'p':
                        /* NB: we print this _before_ the last line
                         * (of current file) is printed. Even if
                         * that line is nonterminated, we print
                         * '\n' here (gnu sed does the same) */
                        sed_puts(pattern_space, '\n');
                        break;
                /* Delete up through first newline */
                case 'D':
                {
                        char *tmp = strchr(pattern_space, '\n');
                        if (tmp) {
                                overlapping_strcpy(pattern_space, tmp + 1);
                                goto restart;
                        }
                }
                /* discard this line. */
                case 'd':
                        goto discard_line;

                /* Substitute with regex */
                case 's':
                        if (!do_subst_command(sed_cmd, &pattern_space))
                                break;
                        dbg("do_subst_command succeeeded:'%s'", pattern_space);
                        substituted |= 1;

                        /* handle p option */
                        if (sed_cmd->sub_p)
                                sed_puts(pattern_space, last_gets_char);
                        /* handle w option */
                        if (sed_cmd->sw_file)
                                puts_maybe_newline(
                                        pattern_space, sed_cmd->sw_file,
                                        &sed_cmd->sw_last_char, last_gets_char);
                        break;

                /* Append line to linked list to be printed later */
                case 'a':
                        append(sed_cmd->string);
                        break;

                /* Insert text before this line */
                case 'i':
                        sed_puts(sed_cmd->string, '\n');
                        break;

                /* Cut and paste text (replace) */
                case 'c':
                        /* Only triggers on last line of a matching range. */
                        if (!sed_cmd->in_match)
                                sed_puts(sed_cmd->string, '\n');
                        goto discard_line;

                /* Read file, append contents to output */
                case 'r':
                {
                        FILE *rfile;
                        rfile = fopen_for_read(sed_cmd->string);
                        if (rfile) {
                                char *line;

                                while ((line = xmalloc_fgetline(rfile))
                                                != NULL)
                                        append(line);
                                xprint_and_close_file(rfile);
                        }

                        break;
                }

                /* Write pattern space to file. */
                case 'w':
                        puts_maybe_newline(
                                pattern_space, sed_cmd->sw_file,
                                &sed_cmd->sw_last_char, last_gets_char);
                        break;

                /* Read next line from input */
                case 'n':
                        if (!G.be_quiet)
                                sed_puts(pattern_space, last_gets_char);
                        if (next_line) {
                                free(pattern_space);
                                pattern_space = next_line;
                                last_gets_char = next_gets_char;
                                next_line = get_next_line(&next_gets_char);
                                substituted = 0;
                                linenum++;
                                break;
                        }
                        /* fall through */

                /* Quit.  End of script, end of input. */
                case 'q':
                        /* Exit the outer while loop */
                        free(next_line);
                        next_line = NULL;
                        goto discard_commands;

                /* Append the next line to the current line */
                case 'N':
                {
                        int len;
                        /* If no next line, jump to end of script and exit. */
                        /* http://www.gnu.org/software/sed/manual/sed.html:
                         * "Most versions of sed exit without printing anything
                         * when the N command is issued on the last line of
                         * a file. GNU sed prints pattern space before exiting
                         * unless of course the -n command switch has been
                         * specified. This choice is by design."
                         */
                        if (next_line == NULL) {
                                //goto discard_line;
                                goto discard_commands; /* GNU behavior */
                        }
                        /* Append next_line, read new next_line. */
                        len = strlen(pattern_space);
                        pattern_space = xrealloc(pattern_space, len + strlen(next_line) + 2);
                        pattern_space[len] = '\n';
                        strcpy(pattern_space + len+1, next_line);
                        last_gets_char = next_gets_char;
                        next_line = get_next_line(&next_gets_char);
                        linenum++;
                        break;
                }

                /* Test/branch if substitution occurred */
                case 't':
                        if (!substituted) break;
                        substituted = 0;
                        /* Fall through */
                /* Test/branch if substitution didn't occur */
                case 'T':
                        if (substituted) break;
                        /* Fall through */
                /* Branch to label */
                case 'b':
                        if (!sed_cmd->string) goto discard_commands;
                        else sed_cmd = branch_to(sed_cmd->string);
                        break;
                /* Transliterate characters */
                case 'y':
                {
                        int i, j;
                        for (i = 0; pattern_space[i]; i++) {
                                for (j = 0; sed_cmd->string[j]; j += 2) {
                                        if (pattern_space[i] == sed_cmd->string[j]) {
                                                pattern_space[i] = sed_cmd->string[j + 1];
                                                break;
                                        }
                                }
                        }

                        break;
                }
                case 'g':       /* Replace pattern space with hold space */
                        free(pattern_space);
                        pattern_space = xstrdup(G.hold_space ? G.hold_space : "");
                        break;
                case 'G':       /* Append newline and hold space to pattern space */
                {
                        int pattern_space_size = 2;
                        int hold_space_size = 0;

                        if (pattern_space)
                                pattern_space_size += strlen(pattern_space);
                        if (G.hold_space)
                                hold_space_size = strlen(G.hold_space);
                        pattern_space = xrealloc(pattern_space,
                                        pattern_space_size + hold_space_size);
                        if (pattern_space_size == 2)
                                pattern_space[0] = 0;
                        strcat(pattern_space, "\n");
                        if (G.hold_space)
                                strcat(pattern_space, G.hold_space);
                        last_gets_char = '\n';

                        break;
                }
                case 'h':       /* Replace hold space with pattern space */
                        free(G.hold_space);
                        G.hold_space = xstrdup(pattern_space);
                        break;
                case 'H':       /* Append newline and pattern space to hold space */
                {
                        int hold_space_size = 2;
                        int pattern_space_size = 0;

                        if (G.hold_space)
                                hold_space_size += strlen(G.hold_space);
                        if (pattern_space)
                                pattern_space_size = strlen(pattern_space);
                        G.hold_space = xrealloc(G.hold_space,
                                        hold_space_size + pattern_space_size);

                        if (hold_space_size == 2)
                                *G.hold_space = 0;
                        strcat(G.hold_space, "\n");
                        if (pattern_space)
                                strcat(G.hold_space, pattern_space);

                        break;
                }
                case 'x': /* Exchange hold and pattern space */
                {
                        char *tmp = pattern_space;
                        pattern_space = G.hold_space ? G.hold_space : xzalloc(1);
                        last_gets_char = '\n';
                        G.hold_space = tmp;
                        break;
                }
                } /* switch */
        } /* for each cmd */

        /*
         * Exit point from sedding...
         */
 discard_commands:
        /* we will print the line unless we were told to be quiet ('-n')
           or if the line was suppressed (ala 'd'elete) */
        if (!G.be_quiet)
                sed_puts(pattern_space, last_gets_char);

        /* Delete and such jump here. */
 discard_line:
        flush_append();
        free(pattern_space);

        goto again;
}

/* It is possible to have a command line argument with embedded
 * newlines.  This counts as multiple command lines.
 * However, newline can be escaped: 's/e/z\<newline>z/'
 * We check for this.
 */

static void add_cmd_block(char *cmdstr)
{
        char *sv, *eol;

        cmdstr = sv = xstrdup(cmdstr);
        do {
                eol = strchr(cmdstr, '\n');
 next:
                if (eol) {
                        /* Count preceding slashes */
                        int slashes = 0;
                        char *sl = eol;

                        while (sl != cmdstr && *--sl == '\\')
                                slashes++;
                        /* Odd number of preceding slashes - newline is escaped */
                        if (slashes & 1) {
                                overlapping_strcpy(eol - 1, eol);
                                eol = strchr(eol, '\n');
                                goto next;
                        }
                        *eol = '\0';
                }
                add_cmd(cmdstr);
                cmdstr = eol + 1;
        } while (eol);
        free(sv);
}

int sed_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sed_main(int argc UNUSED_PARAM, char **argv)
{
        unsigned opt;
        llist_t *opt_e, *opt_f;
        int status = EXIT_SUCCESS;

        INIT_G();

        /* destroy command strings on exit */
        if (ENABLE_FEATURE_CLEAN_UP) atexit(sed_free_and_close_stuff);

        /* Lie to autoconf when it starts asking stupid questions. */
        if (argv[1] && !strcmp(argv[1], "--version")) {
                puts("This is not GNU sed version 4.0");
                return 0;
        }

        /* do normal option parsing */
        opt_e = opt_f = NULL;
        opt_complementary = "e::f::" /* can occur multiple times */
                            "nn"; /* count -n */
        /* -i must be first, to match OPT_in_place definition */
        opt = getopt32(argv, "irne:f:", &opt_e, &opt_f,
                            &G.be_quiet); /* counter for -n */
        //argc -= optind;
        argv += optind;
        if (opt & OPT_in_place) { // -i
                atexit(cleanup_outname);
        }
        if (opt & 0x2) G.regex_type |= REG_EXTENDED; // -r
        //if (opt & 0x4) G.be_quiet++; // -n
        while (opt_e) { // -e
                add_cmd_block(llist_pop(&opt_e));
        }
        while (opt_f) { // -f
                char *line;
                FILE *cmdfile;
                cmdfile = xfopen_for_read(llist_pop(&opt_f));
                while ((line = xmalloc_fgetline(cmdfile)) != NULL) {
                        add_cmd(line);
                        free(line);
                }
                fclose(cmdfile);
        }
        /* if we didn't get a pattern from -e or -f, use argv[0] */
        if (!(opt & 0x18)) {
                if (!*argv)
                        bb_show_usage();
                add_cmd_block(*argv++);
        }
        /* Flush any unfinished commands. */
        add_cmd("");

        /* By default, we write to stdout */
        G.nonstdout = stdout;

        /* argv[0..(argc-1)] should be names of file to process. If no
         * files were specified or '-' was specified, take input from stdin.
         * Otherwise, we process all the files specified. */
        if (argv[0] == NULL) {
                if (opt & OPT_in_place)
                        bb_error_msg_and_die(bb_msg_requires_arg, "-i");
                add_input_file(stdin);
        } else {
                int i;

                for (i = 0; argv[i]; i++) {
                        struct stat statbuf;
                        int nonstdoutfd;
                        FILE *file;
                        sed_cmd_t *sed_cmd;

                        if (LONE_DASH(argv[i]) && !(opt & OPT_in_place)) {
                                add_input_file(stdin);
                                process_files();
                                continue;
                        }
                        file = fopen_or_warn(argv[i], "r");
                        if (!file) {
                                status = EXIT_FAILURE;
                                continue;
                        }
                        add_input_file(file);
                        if (!(opt & OPT_in_place)) {
                                continue;
                        }

                        /* -i: process each FILE separately: */

                        G.outname = xasprintf("%sXXXXXX", argv[i]);
                        nonstdoutfd = xmkstemp(G.outname);
                        G.nonstdout = xfdopen_for_write(nonstdoutfd);

                        /* Set permissions/owner of output file */
                        fstat(fileno(file), &statbuf);
                        /* chmod'ing AFTER chown would preserve suid/sgid bits,
                         * but GNU sed 4.2.1 does not preserve them either */
                        fchmod(nonstdoutfd, statbuf.st_mode);
                        fchown(nonstdoutfd, statbuf.st_uid, statbuf.st_gid);

                        process_files();
                        fclose(G.nonstdout);
                        G.nonstdout = stdout;

                        /* unlink(argv[i]); */
                        xrename(G.outname, argv[i]);
                        free(G.outname);
                        G.outname = NULL;

                        /* Re-enable disabled range matches */
                        for (sed_cmd = G.sed_cmd_head; sed_cmd; sed_cmd = sed_cmd->next) {
                                sed_cmd->beg_line = sed_cmd->beg_line_orig;
                        }
                }
                /* Here, to handle "sed 'cmds' nonexistent_file" case we did:
                 * if (G.current_input_file >= G.input_file_count)
                 *      return status;
                 * but it's not needed since process_files() works correctly
                 * in this case too. */
        }
        process_files();

        return status;
}