fast-import: use skip_prefix for parsing input

Fast-import does a lot of parsing of commands and
dispatching to sub-functions. For example, given "option
foo", we might recognize "option " using starts_with, and
then hand it off to parse_option() to do the rest.

However, we do not let parse_option know that we have parsed
the first part already. It gets the full buffer, and has to
skip past the uninteresting bits. Some functions simply add
a magic constant:

char *option = command_buf.buf + 7;

Others use strlen:

char *option = command_buf.buf + strlen("option ");

And others use strchr:

char *option = strchr(command_buf.buf, ' ') + 1;

All of these are brittle and easy to get wrong (especially
given that the starts_with call and the code that assumes
the presence of the prefix are far apart). Instead, we can
use skip_prefix, and just pass each handler a pointer to its
arguments.

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

diff --git a/fast-import.c b/fast-import.c
index a3ffe3063c3b89ad20af5d9e32903d3b76607e53..c608fc68a0fa3516f49d939994ca0c018c853692 100644 (file)
--- a/fast-import.c
+++ b/fast-import.c
@@ -371,8 +371,8 @@ static volatile sig_atomic_t checkpoint_requested;
 static int cat_blob_fd = STDOUT_FILENO;
 
 static void parse_argv(void);
-static void parse_cat_blob(void);
-static void parse_ls(struct branch *b);
+static void parse_cat_blob(const char *p);
+static void parse_ls(const char *p, struct branch *b);
 
 static void write_branch_report(FILE *rpt, struct branch *b)
 {
@@ -1861,6 +1861,8 @@ static int read_next_command(void)
        }
 
        for (;;) {
+               const char *p;
+
                if (unread_command_buf) {
                        unread_command_buf = 0;
                } else {
@@ -1893,8 +1895,8 @@ static int read_next_command(void)
                        rc->prev->next = rc;
                        cmd_tail = rc;
                }
-               if (starts_with(command_buf.buf, "cat-blob ")) {
-                       parse_cat_blob();
+               if (skip_prefix(command_buf.buf, "cat-blob ", &p)) {
+                       parse_cat_blob(p);
                        continue;
                }
                if (command_buf.buf[0] == '#')
@@ -2273,9 +2275,8 @@ static uintmax_t parse_mark_ref_space(const char **p)
        return mark;
 }
 
-static void file_change_m(struct branch *b)
+static void file_change_m(const char *p, struct branch *b)
 {
-       const char *p = command_buf.buf + 2;
        static struct strbuf uq = STRBUF_INIT;
        const char *endp;
        struct object_entry *oe;
@@ -2376,9 +2377,8 @@ static void file_change_m(struct branch *b)
        tree_content_set(&b->branch_tree, p, sha1, mode, NULL);
 }
 
-static void file_change_d(struct branch *b)
+static void file_change_d(const char *p, struct branch *b)
 {
-       const char *p = command_buf.buf + 2;
        static struct strbuf uq = STRBUF_INIT;
        const char *endp;
 
@@ -2391,15 +2391,14 @@ static void file_change_d(struct branch *b)
        tree_content_remove(&b->branch_tree, p, NULL, 1);
 }
 
-static void file_change_cr(struct branch *b, int rename)
+static void file_change_cr(const char *s, struct branch *b, int rename)
 {
-       const char *s, *d;
+       const char *d;
        static struct strbuf s_uq = STRBUF_INIT;
        static struct strbuf d_uq = STRBUF_INIT;
        const char *endp;
        struct tree_entry leaf;
 
-       s = command_buf.buf + 2;
        strbuf_reset(&s_uq);
        if (!unquote_c_style(&s_uq, s, &endp)) {
                if (*endp != ' ')
@@ -2444,9 +2443,8 @@ static void file_change_cr(struct branch *b, int rename)
                leaf.tree);
 }
 
-static void note_change_n(struct branch *b, unsigned char *old_fanout)
+static void note_change_n(const char *p, struct branch *b, unsigned char *old_fanout)
 {
-       const char *p = command_buf.buf + 2;
        static struct strbuf uq = STRBUF_INIT;
        struct object_entry *oe;
        struct branch *s;
@@ -2587,7 +2585,7 @@ static int parse_from(struct branch *b)
        const char *from;
        struct branch *s;
 
-       if (!starts_with(command_buf.buf, "from "))
+       if (!skip_prefix(command_buf.buf, "from ", &from))
                return 0;
 
        if (b->branch_tree.tree) {
@@ -2595,7 +2593,6 @@ static int parse_from(struct branch *b)
                b->branch_tree.tree = NULL;
        }
 
-       from = strchr(command_buf.buf, ' ') + 1;
        s = lookup_branch(from);
        if (b == s)
                die("Can't create a branch from itself: %s", b->name);
@@ -2636,8 +2633,7 @@ static struct hash_list *parse_merge(unsigned int *count)
        struct branch *s;
 
        *count = 0;
-       while (starts_with(command_buf.buf, "merge ")) {
-               from = strchr(command_buf.buf, ' ') + 1;
+       while (skip_prefix(command_buf.buf, "merge ", &from)) {
                n = xmalloc(sizeof(*n));
                s = lookup_branch(from);
                if (s)
@@ -2668,11 +2664,10 @@ static struct hash_list *parse_merge(unsigned int *count)
        return list;
 }
 
-static void parse_new_commit(void)
+static void parse_new_commit(const char *arg)
 {
        static struct strbuf msg = STRBUF_INIT;
        struct branch *b;
-       char *sp;
        char *author = NULL;
        char *committer = NULL;
        struct hash_list *merge_list = NULL;
@@ -2680,11 +2675,9 @@ static void parse_new_commit(void)
        unsigned char prev_fanout, new_fanout;
        const char *v;
 
-       /* Obtain the branch name from the rest of our command */
-       sp = strchr(command_buf.buf, ' ') + 1;
-       b = lookup_branch(sp);
+       b = lookup_branch(arg);
        if (!b)
-               b = new_branch(sp);
+               b = new_branch(arg);
 
        read_next_command();
        parse_mark();
@@ -2713,20 +2706,20 @@ static void parse_new_commit(void)
 
        /* file_change* */
        while (command_buf.len > 0) {
-               if (starts_with(command_buf.buf, "M "))
-                       file_change_m(b);
-               else if (starts_with(command_buf.buf, "D "))
-                       file_change_d(b);
-               else if (starts_with(command_buf.buf, "R "))
-                       file_change_cr(b, 1);
-               else if (starts_with(command_buf.buf, "C "))
-                       file_change_cr(b, 0);
-               else if (starts_with(command_buf.buf, "N "))
-                       note_change_n(b, &prev_fanout);
+               if (skip_prefix(command_buf.buf, "M ", &v))
+                       file_change_m(v, b);
+               else if (skip_prefix(command_buf.buf, "D ", &v))
+                       file_change_d(v, b);
+               else if (skip_prefix(command_buf.buf, "R ", &v))
+                       file_change_cr(v, b, 1);
+               else if (skip_prefix(command_buf.buf, "C ", &v))
+                       file_change_cr(v, b, 0);
+               else if (skip_prefix(command_buf.buf, "N ", &v))
+                       note_change_n(v, b, &prev_fanout);
                else if (!strcmp("deleteall", command_buf.buf))
                        file_change_deleteall(b);
-               else if (starts_with(command_buf.buf, "ls "))
-                       parse_ls(b);
+               else if (skip_prefix(command_buf.buf, "ls ", &v))
+                       parse_ls(v, b);
                else {
                        unread_command_buf = 1;
                        break;
@@ -2769,10 +2762,9 @@ static void parse_new_commit(void)
        b->last_commit = object_count_by_type[OBJ_COMMIT];
 }
 
-static void parse_new_tag(void)
+static void parse_new_tag(const char *arg)
 {
        static struct strbuf msg = STRBUF_INIT;
-       char *sp;
        const char *from;
        char *tagger;
        struct branch *s;
@@ -2782,11 +2774,9 @@ static void parse_new_tag(void)
        enum object_type type;
        const char *v;
 
-       /* Obtain the new tag name from the rest of our command */
-       sp = strchr(command_buf.buf, ' ') + 1;
        t = pool_alloc(sizeof(struct tag));
        memset(t, 0, sizeof(struct tag));
-       t->name = pool_strdup(sp);
+       t->name = pool_strdup(arg);
        if (last_tag)
                last_tag->next_tag = t;
        else
@@ -2795,9 +2785,8 @@ static void parse_new_tag(void)
        read_next_command();
 
        /* from ... */
-       if (!starts_with(command_buf.buf, "from "))
+       if (!skip_prefix(command_buf.buf, "from ", &from))
                die("Expected from command, got %s", command_buf.buf);
-       from = strchr(command_buf.buf, ' ') + 1;
        s = lookup_branch(from);
        if (s) {
                if (is_null_sha1(s->sha1))
@@ -2853,14 +2842,11 @@ static void parse_new_tag(void)
                t->pack_id = pack_id;
 }
 
-static void parse_reset_branch(void)
+static void parse_reset_branch(const char *arg)
 {
        struct branch *b;
-       char *sp;
 
-       /* Obtain the branch name from the rest of our command */
-       sp = strchr(command_buf.buf, ' ') + 1;
-       b = lookup_branch(sp);
+       b = lookup_branch(arg);
        if (b) {
                hashclr(b->sha1);
                hashclr(b->branch_tree.versions[0].sha1);
@@ -2871,7 +2857,7 @@ static void parse_reset_branch(void)
                }
        }
        else
-               b = new_branch(sp);
+               b = new_branch(arg);
        read_next_command();
        parse_from(b);
        if (command_buf.len > 0)
@@ -2929,14 +2915,12 @@ static void cat_blob(struct object_entry *oe, unsigned char sha1[20])
                free(buf);
 }
 
-static void parse_cat_blob(void)
+static void parse_cat_blob(const char *p)
 {
-       const char *p;
        struct object_entry *oe = oe;
        unsigned char sha1[20];
 
        /* cat-blob SP <object> LF */
-       p = command_buf.buf + strlen("cat-blob ");
        if (*p == ':') {
                oe = find_mark(parse_mark_ref_eol(p));
                if (!oe)
@@ -3053,14 +3037,12 @@ static void print_ls(int mode, const unsigned char *sha1, const char *path)
        cat_blob_write(line.buf, line.len);
 }
 
-static void parse_ls(struct branch *b)
+static void parse_ls(const char *p, struct branch *b)
 {
-       const char *p;
        struct tree_entry *root = NULL;
        struct tree_entry leaf = {NULL};
 
        /* ls SP (<tree-ish> SP)? <path> */
-       p = command_buf.buf + strlen("ls ");
        if (*p == '"') {
                if (!b)
                        die("Not in a commit: %s", command_buf.buf);
@@ -3276,10 +3258,8 @@ static int parse_one_feature(const char *feature, int from_stream)
        return 1;
 }
 
-static void parse_feature(void)
+static void parse_feature(const char *feature)
 {
-       char *feature = command_buf.buf + 8;
-
        if (seen_data_command)
                die("Got feature command '%s' after data command", feature);
 
@@ -3289,10 +3269,8 @@ static void parse_feature(void)
        die("This version of fast-import does not support feature %s.", feature);
 }
 
-static void parse_option(void)
+static void parse_option(const char *option)
 {
-       char *option = command_buf.buf + 11;
-
        if (seen_data_command)
                die("Got option command '%s' after data command", option);
 
@@ -3408,26 +3386,27 @@ int main(int argc, char **argv)
        set_die_routine(die_nicely);
        set_checkpoint_signal();
        while (read_next_command() != EOF) {
+               const char *v;
                if (!strcmp("blob", command_buf.buf))
                        parse_new_blob();
-               else if (starts_with(command_buf.buf, "ls "))
-                       parse_ls(NULL);
-               else if (starts_with(command_buf.buf, "commit "))
-                       parse_new_commit();
-               else if (starts_with(command_buf.buf, "tag "))
-                       parse_new_tag();
-               else if (starts_with(command_buf.buf, "reset "))
-                       parse_reset_branch();
+               else if (skip_prefix(command_buf.buf, "ls ", &v))
+                       parse_ls(v, NULL);
+               else if (skip_prefix(command_buf.buf, "commit ", &v))
+                       parse_new_commit(v);
+               else if (skip_prefix(command_buf.buf, "tag ", &v))
+                       parse_new_tag(v);
+               else if (skip_prefix(command_buf.buf, "reset ", &v))
+                       parse_reset_branch(v);
                else if (!strcmp("checkpoint", command_buf.buf))
                        parse_checkpoint();
                else if (!strcmp("done", command_buf.buf))
                        break;
                else if (starts_with(command_buf.buf, "progress "))
                        parse_progress();
-               else if (starts_with(command_buf.buf, "feature "))
-                       parse_feature();
-               else if (starts_with(command_buf.buf, "option git "))
-                       parse_option();
+               else if (skip_prefix(command_buf.buf, "feature ", &v))
+                       parse_feature(v);
+               else if (skip_prefix(command_buf.buf, "option git ", &v))
+                       parse_option(v);
                else if (starts_with(command_buf.buf, "option "))
                        /* ignore non-git options*/;
                else