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strbuf: instate cleanup rule in case of non-memory errors

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Make all strbuf functions that can fail free() their memory on error if
they have allocated it.  They don't shrink buffers that have been grown,
though.

This allows for easier error handling, as callers only need to call
strbuf_release() if A) the command succeeded or B) if they would have had
to do so anyway because they added something to the strbuf themselves.

Bonus hunk: document strbuf_readlink.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe 2009-01-06 21:41:14 +01:00 committed by Junio C Hamano
parent 2d642a6f8a
commit 2fc647004a
2 changed files with 22 additions and 6 deletions
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11
Documentation/technical/api-strbuf.txt
View File

@ -133,8 +133,10 @@ Functions
* Adding data to the buffer
NOTE: All of these functions in this section will grow the buffer as
necessary.
NOTE: All of the functions in this section will grow the buffer as necessary.
If they fail for some reason other than memory shortage and the buffer hadn't
been allocated before (i.e. the `struct strbuf` was set to `STRBUF_INIT`),
then they will free() it.
`strbuf_addch`::
@ -235,6 +237,11 @@ same behaviour as well.
Read the contents of a file, specified by its path. The third argument
can be used to give a hint about the file size, to avoid reallocs.
`strbuf_readlink`::
Read the target of a symbolic link, specified by its path. The third
argument can be used to give a hint about the size, to avoid reallocs.
`strbuf_getline`::
Read a line from a FILE* pointer. The second argument specifies the line

17
strbuf.c
View File

@ -256,18 +256,21 @@ size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
{
size_t res;
size_t oldalloc = sb->alloc;
strbuf_grow(sb, size);
res = fread(sb->buf + sb->len, 1, size, f);
if (res > 0) {
if (res > 0)
strbuf_setlen(sb, sb->len + res);
}
else if (res < 0 && oldalloc == 0)
strbuf_release(sb);
return res;
}
ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
{
size_t oldlen = sb->len;
size_t oldalloc = sb->alloc;
strbuf_grow(sb, hint ? hint : 8192);
for (;;) {
@ -275,7 +278,10 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
cnt = xread(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
if (cnt < 0) {
strbuf_setlen(sb, oldlen);
if (oldalloc == 0)
strbuf_release(sb);
else
strbuf_setlen(sb, oldlen);
return -1;
}
if (!cnt)
@ -292,6 +298,8 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
{
size_t oldalloc = sb->alloc;
if (hint < 32)
hint = 32;
@ -311,7 +319,8 @@ int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
/* .. the buffer was too small - try again */
hint *= 2;
}
strbuf_release(sb);
if (oldalloc == 0)
strbuf_release(sb);
return -1;
}