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fast-import: use skip_prefix for parsing input
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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>
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Jeff King authored and Junio C Hamano committed Jun 20, 2014
1 parent 95b567c commit 97313be
Showing 1 changed file with 51 additions and 72 deletions.
123 changes: 51 additions & 72 deletions fast-import.c
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down Expand Up @@ -1861,6 +1861,8 @@ static int read_next_command(void)
}

for (;;) {
const char *p;

if (unread_command_buf) {
unread_command_buf = 0;
} else {
Expand Down Expand Up @@ -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] == '#')
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;

Expand All @@ -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 != ' ')
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -2587,15 +2585,14 @@ 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) {
release_tree_content_recursive(b->branch_tree.tree);
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);
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -2668,23 +2664,20 @@ 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;
unsigned int merge_count;
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();
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand All @@ -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
Expand All @@ -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))
Expand Down Expand Up @@ -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);
Expand All @@ -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)
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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);

Expand All @@ -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);

Expand Down Expand Up @@ -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
Expand Down

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