Teach 'diff' about 'diff' attribute.

[git.git] / attr.c

#include "cache.h"
#include "attr.h"

/*
 * The basic design decision here is that we are not going to have
 * insanely large number of attributes.
 *
 * This is a randomly chosen prime.
 */
#define HASHSIZE 257

#ifndef DEBUG_ATTR
#define DEBUG_ATTR 0
#endif

struct git_attr {
        struct git_attr *next;
        unsigned h;
        char name[FLEX_ARRAY];
};

static struct git_attr *(git_attr_hash[HASHSIZE]);

static unsigned hash_name(const char *name, int namelen)
{
        unsigned val = 0;
        unsigned char c;

        while (namelen--) {
                c = *name++;
                val = ((val << 7) | (val >> 22)) ^ c;
        }
        return val;
}

struct git_attr *git_attr(const char *name, int len)
{
        unsigned hval = hash_name(name, len);
        unsigned pos = hval % HASHSIZE;
        struct git_attr *a;

        for (a = git_attr_hash[pos]; a; a = a->next) {
                if (a->h == hval &&
                    !memcmp(a->name, name, len) && !a->name[len])
                        return a;
        }

        a = xmalloc(sizeof(*a) + len + 1);
        memcpy(a->name, name, len);
        a->name[len] = 0;
        a->h = hval;
        a->next = git_attr_hash[pos];
        git_attr_hash[pos] = a;
        return a;
}

/*
 * .gitattributes file is one line per record, each of which is
 *
 * (1) glob pattern.
 * (2) whitespace
 * (3) whitespace separated list of attribute names, each of which
 *     could be prefixed with '!' to mean "not set".
 */

struct attr_state {
        int unset;
        struct git_attr *attr;
};

struct match_attr {
        char *pattern;
        unsigned num_attr;
        struct attr_state state[FLEX_ARRAY];
};

static const char blank[] = " \t\r\n";

static struct match_attr *parse_attr_line(const char *line)
{
        int namelen;
        int num_attr;
        const char *cp, *name;
        struct match_attr *res = res;
        int pass;

        cp = line + strspn(line, blank);
        if (!*cp || *cp == '#')
                return NULL;
        name = cp;
        namelen = strcspn(name, blank);

        for (pass = 0; pass < 2; pass++) {
                /* pass 0 counts and allocates, pass 1 fills */
                num_attr = 0;
                cp = name + namelen;
                cp = cp + strspn(cp, blank);
                while (*cp) {
                        const char *ep;
                        ep = cp + strcspn(cp, blank);
                        if (pass) {
                                struct attr_state *e;

                                e = &(res->state[num_attr]);
                                if (*cp == '!') {
                                        e->unset = 1;
                                        cp++;
                                }
                                e->attr = git_attr(cp, ep - cp);
                        }
                        num_attr++;
                        cp = ep + strspn(ep, blank);
                }
                if (pass)
                        break;
                res = xcalloc(1,
                              sizeof(*res) +
                              sizeof(struct attr_state) * num_attr +
                              namelen + 1);
                res->pattern = (char*)&(res->state[num_attr]);
                memcpy(res->pattern, name, namelen);
                res->pattern[namelen] = 0;
                res->num_attr = num_attr;
        }
        return res;
}

/*
 * Like info/exclude and .gitignore, the attribute information can
 * come from many places.
 *
 * (1) .gitattribute file of the same directory;
 * (2) .gitattribute file of the parent directory if (1) does not have any match;
 *     this goes recursively upwards, just like .gitignore
 * (3) perhaps $GIT_DIR/info/attributes, as the final fallback.
 *
 * In the same file, later entries override the earlier match, so in the
 * global list, we would have entries from info/attributes the earliest
 * (reading the file from top to bottom), .gitattribute of the root
 * directory (again, reading the file from top to bottom) down to the
 * current directory, and then scan the list backwards to find the first match.
 * This is exactly the same as what excluded() does in dir.c to deal with
 * .gitignore
 */

static struct attr_stack {
        struct attr_stack *prev;
        char *origin;
        unsigned num_matches;
        struct match_attr **attrs;
} *attr_stack;

static void free_attr_elem(struct attr_stack *e)
{
        int i;
        free(e->origin);
        for (i = 0; i < e->num_matches; i++)
                free(e->attrs[i]);
        free(e);
}

static const char *builtin_attr[] = {
        NULL,
};

static struct attr_stack *read_attr_from_array(const char **list)
{
        struct attr_stack *res;
        const char *line;

        res = xcalloc(1, sizeof(*res));
        while ((line = *(list++)) != NULL) {
                struct match_attr *a = parse_attr_line(line);
                if (!a)
                        continue;
                res->attrs = xrealloc(res->attrs, res->num_matches + 1);
                res->attrs[res->num_matches++] = a;
        }
        return res;
}

static struct attr_stack *read_attr_from_file(const char *path)
{
        FILE *fp;
        struct attr_stack *res;
        char buf[2048];

        res = xcalloc(1, sizeof(*res));
        fp = fopen(path, "r");
        if (!fp)
                return res;

        while (fgets(buf, sizeof(buf), fp)) {
                struct match_attr *a = parse_attr_line(buf);
                if (!a)
                        continue;
                res->attrs = xrealloc(res->attrs, res->num_matches + 1);
                res->attrs[res->num_matches++] = a;
        }
        fclose(fp);
        return res;
}

#if DEBUG_ATTR
static void debug_info(const char *what, struct attr_stack *elem)
{
        fprintf(stderr, "%s: %s\n", what, elem->origin ? elem->origin : "()");
}
#define debug_push(a) debug_info("push", (a))
#define debug_pop(a) debug_info("pop", (a))
#else
#define debug_push(a) do { ; } while (0)
#define debug_pop(a) do { ; } while (0)
#endif

static void prepare_attr_stack(const char *path, int dirlen)
{
        struct attr_stack *elem, *info;
        int len;
        char pathbuf[PATH_MAX];

        /*
         * At the bottom of the attribute stack is the built-in
         * set of attribute definitions.  Then, contents from
         * .gitattribute files from directories closer to the
         * root to the ones in deeper directories are pushed
         * to the stack.  Finally, at the very top of the stack
         * we always keep the contents of $GIT_DIR/info/attributes.
         *
         * When checking, we use entries from near the top of the
         * stack, preferring $GIT_DIR/info/attributes, then
         * .gitattributes in deeper directories to shallower ones,
         * and finally use the built-in set as the default.
         */
        if (!attr_stack) {
                elem = read_attr_from_array(builtin_attr);
                elem->origin = NULL;
                elem->prev = attr_stack;
                attr_stack = elem;

                elem = read_attr_from_file(GITATTRIBUTES_FILE);
                elem->origin = strdup("");
                elem->prev = attr_stack;
                attr_stack = elem;
                debug_push(elem);

                elem = read_attr_from_file(git_path(INFOATTRIBUTES_FILE));
                elem->origin = NULL;
                elem->prev = attr_stack;
                attr_stack = elem;
        }

        /*
         * Pop the "info" one that is always at the top of the stack.
         */
        info = attr_stack;
        attr_stack = info->prev;

        /*
         * Pop the ones from directories that are not the prefix of
         * the path we are checking.
         */
        while (attr_stack && attr_stack->origin) {
                int namelen = strlen(attr_stack->origin);

                elem = attr_stack;
                if (namelen <= dirlen &&
                    !strncmp(elem->origin, path, namelen))
                        break;

                debug_pop(elem);
                attr_stack = elem->prev;
                free_attr_elem(elem);
        }

        /*
         * Read from parent directories and push them down
         */
        while (1) {
                char *cp;

                len = strlen(attr_stack->origin);
                if (dirlen <= len)
                        break;
                memcpy(pathbuf, path, dirlen);
                memcpy(pathbuf + dirlen, "/", 2);
                cp = strchr(pathbuf + len + 1, '/');
                strcpy(cp + 1, GITATTRIBUTES_FILE);
                elem = read_attr_from_file(pathbuf);
                *cp = '\0';
                elem->origin = strdup(pathbuf);
                elem->prev = attr_stack;
                attr_stack = elem;
                debug_push(elem);
        }

        /*
         * Finally push the "info" one at the top of the stack.
         */
        info->prev = attr_stack;
        attr_stack = info;
}

static int path_matches(const char *pathname, int pathlen,
                        const char *pattern,
                        const char *base, int baselen)
{
        if (!strchr(pattern, '/')) {
                /* match basename */
                const char *basename = strrchr(pathname, '/');
                basename = basename ? basename + 1 : pathname;
                return (fnmatch(pattern, basename, 0) == 0);
        }
        /*
         * match with FNM_PATHNAME; the pattern has base implicitly
         * in front of it.
         */
        if (*pattern == '/')
                pattern++;
        if (pathlen < baselen ||
            (baselen && pathname[baselen - 1] != '/') ||
            strncmp(pathname, base, baselen))
                return 0;
        return fnmatch(pattern, pathname + baselen, FNM_PATHNAME) == 0;
}

/*
 * I do not like this at all.  Only because we allow individual
 * attribute to be set or unset incrementally by individual
 * lines in .gitattribute files, we need to do this triple
 * loop which looks quite wasteful.
 */
static int fill(const char *path, int pathlen,
                struct attr_stack *stk, struct git_attr_check *check,
                int num, int rem)
{
        int i, j, k;
        const char *base = stk->origin ? stk->origin : "";

        for (i = stk->num_matches - 1; 0 < rem && 0 <= i; i--) {
                struct match_attr *a = stk->attrs[i];
                if (path_matches(path, pathlen,
                                 a->pattern, base, strlen(base))) {
                        for (j = 0; j < a->num_attr; j++) {
                                struct git_attr *attr = a->state[j].attr;
                                int set = !a->state[j].unset;
                                for (k = 0; k < num; k++) {
                                        if (0 <= check[k].isset ||
                                            check[k].attr != attr)
                                                continue;
                                        check[k].isset = set;
                                        rem--;
                                }
                        }
                }
        }
        return rem;
}

int git_checkattr(const char *path, int num, struct git_attr_check *check)
{
        struct attr_stack *stk;
        const char *cp;
        int dirlen, pathlen, i, rem;

        for (i = 0; i < num; i++)
                check[i].isset = -1;

        pathlen = strlen(path);
        cp = strrchr(path, '/');
        if (!cp)
                dirlen = 0;
        else
                dirlen = cp - path;
        prepare_attr_stack(path, dirlen);
        rem = num;
        for (stk = attr_stack; 0 < rem && stk; stk = stk->prev)
                rem = fill(path, pathlen, stk, check, num, rem);
        return 0;
}