use skip_prefix to avoid repeating strings

It's a common idiom to match a prefix and then skip past it
with strlen, like:

if (starts_with(foo, "bar"))
foo += strlen("bar");

This avoids magic numbers, but means we have to repeat the
string (and there is no compiler check that we didn't make a
typo in one of the strings).

We can use skip_prefix to handle this case without repeating
ourselves.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f1dc56e55f7b2200412142b10517458ccfda2952..463cfeea5067fe02d8eb1414018c97ff9a757176 100644 (file)
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -776,8 +776,8 @@ static int switch_branches(const struct checkout_opts *opts,
        if (!(flag & REF_ISSYMREF))
                old.path = NULL;
 
-       if (old.path && starts_with(old.path, "refs/heads/"))
-               old.name = old.path + strlen("refs/heads/");
+       if (old.path)
+               skip_prefix(old.path, "refs/heads/", &old.name);
 
        if (!new->name) {
                new->name = "HEAD";

diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index 3c19241554da225423fb1f10eaaebb56db7e73fd..ad3bc58c74a2b6927d3604e458e01a14b9834946 100644 (file)
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -100,7 +100,8 @@ static int handle_line(char *line, struct merge_parents *merge_parents)
 {
        int i, len = strlen(line);
        struct origin_data *origin_data;
-       char *src, *origin;
+       char *src;
+       const char *origin;
        struct src_data *src_data;
        struct string_list_item *item;
        int pulling_head = 0;
@@ -164,8 +165,7 @@ static int handle_line(char *line, struct merge_parents *merge_parents)
                origin = line;
                string_list_append(&src_data->tag, origin + 4);
                src_data->head_status |= 2;
-       } else if (starts_with(line, "remote-tracking branch ")) {
-               origin = line + strlen("remote-tracking branch ");
+       } else if (skip_prefix(line, "remote-tracking branch ", &origin)) {
                string_list_append(&src_data->r_branch, origin);
                src_data->head_status |= 2;
        } else {

diff --git a/builtin/log.c b/builtin/log.c
index a7ba211731ecc02523c4509878679f050c151f0b..0f59c25d362d8238786a884f0a154f29bd97d767 100644 (file)
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -872,7 +872,7 @@ static char *find_branch_name(struct rev_info *rev)
        int i, positive = -1;
        unsigned char branch_sha1[20];
        const unsigned char *tip_sha1;
-       const char *ref;
+       const char *ref, *v;
        char *full_ref, *branch = NULL;
 
        for (i = 0; i < rev->cmdline.nr; i++) {
@@ -888,9 +888,9 @@ static char *find_branch_name(struct rev_info *rev)
        ref = rev->cmdline.rev[positive].name;
        tip_sha1 = rev->cmdline.rev[positive].item->sha1;
        if (dwim_ref(ref, strlen(ref), branch_sha1, &full_ref) &&
-           starts_with(full_ref, "refs/heads/") &&
+           skip_prefix(full_ref, "refs/heads/", &v) &&
            !hashcmp(tip_sha1, branch_sha1))
-               branch = xstrdup(full_ref + strlen("refs/heads/"));
+               branch = xstrdup(v);
        free(full_ref);
        return branch;
 }
@@ -1394,10 +1394,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 
                if (check_head) {
                        unsigned char sha1[20];
-                       const char *ref;
+                       const char *ref, *v;
                        ref = resolve_ref_unsafe("HEAD", sha1, 1, NULL);
-                       if (ref && starts_with(ref, "refs/heads/"))
-                               branch_name = xstrdup(ref + strlen("refs/heads/"));
+                       if (ref && skip_prefix(ref, "refs/heads/", &v))
+                               branch_name = xstrdup(v);
                        else
                                branch_name = xstrdup(""); /* no branch */
                }

diff --git a/diff.c b/diff.c
index 97db9323eeb7f6b6522b701da05a42ab92cb1140..2378ae49c6683789f82da64765e4be12d598c869 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -3395,12 +3395,10 @@ int parse_long_opt(const char *opt, const char **argv,
                   const char **optarg)
 {
        const char *arg = argv[0];
-       if (arg[0] != '-' || arg[1] != '-')
+       if (!skip_prefix(arg, "--", &arg))
                return 0;
-       arg += strlen("--");
-       if (!starts_with(arg, opt))
+       if (!skip_prefix(arg, opt, &arg))
                return 0;
-       arg += strlen(opt);
        if (*arg == '=') { /* stuck form: --option=value */
                *optarg = arg + 1;
                return 1;
@@ -3429,8 +3427,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 
        switch (*arg) {
        case '-':
-               if (starts_with(arg, "-width")) {
-                       arg += strlen("-width");
+               if (skip_prefix(arg, "-width", &arg)) {
                        if (*arg == '=')
                                width = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
@@ -3439,8 +3436,7 @@ static int stat_opt(struct diff_options *options, const char **av)
                                width = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
-               } else if (starts_with(arg, "-name-width")) {
-                       arg += strlen("-name-width");
+               } else if (skip_prefix(arg, "-name-width", &arg)) {
                        if (*arg == '=')
                                name_width = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
@@ -3449,8 +3445,7 @@ static int stat_opt(struct diff_options *options, const char **av)
                                name_width = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
-               } else if (starts_with(arg, "-graph-width")) {
-                       arg += strlen("-graph-width");
+               } else if (skip_prefix(arg, "-graph-width", &arg)) {
                        if (*arg == '=')
                                graph_width = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
@@ -3459,8 +3454,7 @@ static int stat_opt(struct diff_options *options, const char **av)
                                graph_width = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
-               } else if (starts_with(arg, "-count")) {
-                       arg += strlen("-count");
+               } else if (skip_prefix(arg, "-count", &arg)) {
                        if (*arg == '=')
                                count = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
@@ -3905,16 +3899,13 @@ static int diff_scoreopt_parse(const char *opt)
        cmd = *opt++;
        if (cmd == '-') {
                /* convert the long-form arguments into short-form versions */
-               if (starts_with(opt, "break-rewrites")) {
-                       opt += strlen("break-rewrites");
+               if (skip_prefix(opt, "break-rewrites", &opt)) {
                        if (*opt == 0 || *opt++ == '=')
                                cmd = 'B';
-               } else if (starts_with(opt, "find-copies")) {
-                       opt += strlen("find-copies");
+               } else if (skip_prefix(opt, "find-copies", &opt)) {
                        if (*opt == 0 || *opt++ == '=')
                                cmd = 'C';
-               } else if (starts_with(opt, "find-renames")) {
-                       opt += strlen("find-renames");
+               } else if (skip_prefix(opt, "find-renames", &opt)) {
                        if (*opt == 0 || *opt++ == '=')
                                cmd = 'M';
                }

diff --git a/help.c b/help.c
index b0f1a697216ded21bf7e1f9147be4dc611bd94de..79e800714780568009f66787aa25079ec6b81fac 100644 (file)
--- a/help.c
+++ b/help.c
@@ -414,11 +414,12 @@ static int append_similar_ref(const char *refname, const unsigned char *sha1,
 {
        struct similar_ref_cb *cb = (struct similar_ref_cb *)(cb_data);
        char *branch = strrchr(refname, '/') + 1;
+       const char *remote;
+
        /* A remote branch of the same name is deemed similar */
-       if (starts_with(refname, "refs/remotes/") &&
+       if (skip_prefix(refname, "refs/remotes/", &remote) &&
            !strcmp(branch, cb->base_ref))
-               string_list_append(cb->similar_refs,
-                                  refname + strlen("refs/remotes/"));
+               string_list_append(cb->similar_refs, remote);
        return 0;
 }
 

diff --git a/merge-recursive.c b/merge-recursive.c
index cab16fafb5c2b7792c78d3a7fbace1f43ab099cc..f8480018178c7eb8b88dcd3e1f166dc953bfbe11 100644 (file)
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -2063,6 +2063,8 @@ void init_merge_options(struct merge_options *o)
 
 int parse_merge_opt(struct merge_options *o, const char *s)
 {
+       const char *arg;
+
        if (!s || !*s)
                return -1;
        if (!strcmp(s, "ours"))
@@ -2071,14 +2073,14 @@ int parse_merge_opt(struct merge_options *o, const char *s)
                o->recursive_variant = MERGE_RECURSIVE_THEIRS;
        else if (!strcmp(s, "subtree"))
                o->subtree_shift = "";
-       else if (starts_with(s, "subtree="))
-               o->subtree_shift = s + strlen("subtree=");
+       else if (skip_prefix(s, "subtree=", &arg))
+               o->subtree_shift = arg;
        else if (!strcmp(s, "patience"))
                o->xdl_opts = DIFF_WITH_ALG(o, PATIENCE_DIFF);
        else if (!strcmp(s, "histogram"))
                o->xdl_opts = DIFF_WITH_ALG(o, HISTOGRAM_DIFF);
-       else if (starts_with(s, "diff-algorithm=")) {
-               long value = parse_algorithm_value(s + strlen("diff-algorithm="));
+       else if (skip_prefix(s, "diff-algorithm=", &arg)) {
+               long value = parse_algorithm_value(arg);
                if (value < 0)
                        return -1;
                /* clear out previous settings */
@@ -2096,9 +2098,8 @@ int parse_merge_opt(struct merge_options *o, const char *s)
                o->renormalize = 1;
        else if (!strcmp(s, "no-renormalize"))
                o->renormalize = 0;
-       else if (starts_with(s, "rename-threshold=")) {
-               const char *score = s + strlen("rename-threshold=");
-               if ((o->rename_score = parse_rename_score(&score)) == -1 || *score != 0)
+       else if (skip_prefix(s, "rename-threshold=", &arg)) {
+               if ((o->rename_score = parse_rename_score(&arg)) == -1 || *arg != 0)
                        return -1;
        }
        else

diff --git a/pretty.c b/pretty.c
index 4f512876ceb20f538256bac30dd98288abe2d682..f24752a85bc101c117d91b86a0526ca4c1eceee0 100644 (file)
--- a/pretty.c
+++ b/pretty.c
@@ -40,10 +40,9 @@ static int git_pretty_formats_config(const char *var, const char *value, void *c
        const char *fmt;
        int i;
 
-       if (!starts_with(var, "pretty."))
+       if (!skip_prefix(var, "pretty.", &name))
                return 0;
 
-       name = var + strlen("pretty.");
        for (i = 0; i < builtin_formats_len; i++) {
                if (!strcmp(commit_formats[i].name, name))
                        return 0;

diff --git a/remote-curl.c b/remote-curl.c
index 4493b389ded6a814bd8c40481f3d06855c963bd7..cdcca2903b100c775d4e004312086581f5839ad4 100644 (file)
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -791,9 +791,9 @@ static void parse_fetch(struct strbuf *buf)
        int alloc_heads = 0, nr_heads = 0;
 
        do {
-               if (starts_with(buf->buf, "fetch ")) {
-                       char *p = buf->buf + strlen("fetch ");
-                       char *name;
+               const char *p;
+               if (skip_prefix(buf->buf, "fetch ", &p)) {
+                       const char *name;
                        struct ref *ref;
                        unsigned char old_sha1[20];
 
@@ -968,6 +968,8 @@ int main(int argc, const char **argv)
        http_init(remote, url.buf, 0);
 
        do {
+               const char *arg;
+
                if (strbuf_getline(&buf, stdin, '\n') == EOF) {
                        if (ferror(stdin))
                                fprintf(stderr, "Error reading command stream\n");
@@ -989,9 +991,8 @@ int main(int argc, const char **argv)
                } else if (starts_with(buf.buf, "push ")) {
                        parse_push(&buf);
 
-               } else if (starts_with(buf.buf, "option ")) {
-                       char *name = buf.buf + strlen("option ");
-                       char *value = strchr(name, ' ');
+               } else if (skip_prefix(buf.buf, "option ", &arg)) {
+                       char *value = strchr(arg, ' ');
                        int result;
 
                        if (value)
@@ -999,7 +1000,7 @@ int main(int argc, const char **argv)
                        else
                                value = "true";
 
-                       result = set_option(name, value);
+                       result = set_option(arg, value);
                        if (!result)
                                printf("ok\n");
                        else if (result < 0)

diff --git a/remote.c b/remote.c
index 0e9459cc0675d2f232b1c1fda62080d04aa88ec5..30d2829c2b171f7af8891b5c07a0317c72de1871 100644 (file)
--- a/remote.c
+++ b/remote.c
@@ -488,9 +488,8 @@ static void read_config(void)
        current_branch = NULL;
        head_ref = resolve_ref_unsafe("HEAD", sha1, 0, &flag);
        if (head_ref && (flag & REF_ISSYMREF) &&
-           starts_with(head_ref, "refs/heads/")) {
-               current_branch =
-                       make_branch(head_ref + strlen("refs/heads/"), 0);
+           skip_prefix(head_ref, "refs/heads/", &head_ref)) {
+               current_branch = make_branch(head_ref, 0);
        }
        git_config(handle_config, NULL);
        if (branch_pushremote_name) {

diff --git a/sha1_name.c b/sha1_name.c
index 2b6322fad064845f4c782286fe9764f6b958f30d..72e6ac6a6e4f8573676084e443ce8fae038f4f56 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -911,10 +911,8 @@ static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
        const char *match = NULL, *target = NULL;
        size_t len;
 
-       if (starts_with(message, "checkout: moving from ")) {
-               match = message + strlen("checkout: moving from ");
+       if (skip_prefix(message, "checkout: moving from ", &match))
                target = strstr(match, " to ");
-       }
 
        if (!match || !target)
                return 0;