[PATCH 15/18] fill_sha1_file: write into a strbuf
- From
Jeff King <peff@peff.net>
- Date
- Oct 3, 2016, 20:36 UTC
- Message-ID
- <20161003203609.4hig3e24lyvswdcf@sigill.intra.peff.net>
- In-Reply-To
- <20161003203321.rj5jepviwo57uhqw@sigill.intra.peff.net>
It's currently the responsibility of the caller to give fill_sha1_file() enough bytes to write into, leading them to manually compute the required lengths. Instead, let's just write into a strbuf so that it's impossible to get this wrong.
The alt_odb caller already has a strbuf, so this makes things strictly simpler. The other caller, sha1_file_name(), uses a static PATH_MAX buffer and dies when it would overflow. We can convert this to a static strbuf, which means our allocation cost is amortized (and as a bonus, we no longer have to worry about PATH_MAX being too short for normal use).
This does introduce some small overhead in fill_sha1_file(), as each strbuf_addchar() will check whether it needs to grow. However, between the optimization in fec501d (strbuf_addch: avoid calling strbuf_grow, 2015-04-16) and the fact that this is not generally called in a tight loop (after all, the next step is typically to access the file!) this probably doesn't matter. And even if it did, the right place to micro-optimize is inside fill_sha1_file(), by calling a single strbuf_grow() there.
Signed-off-by: Jeff King <peff@peff.net> --- sha1_file.c | 34 ++++++++++------------------------ 1 file changed, 10 insertions(+), 24 deletions(-)
diff --git a/sha1_file.c b/sha1_file.c index efc8cee..80a3333 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -172,36 +172,28 @@ enum scld_error safe_create_leading_directories_const(const char *path) return result; } -static void fill_sha1_path(char *pathbuf, const unsigned char *sha1) +static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1) { int i; for (i = 0; i < 20; i++) { static char hex[] = "0123456789abcdef"; unsigned int val = sha1[i]; - *pathbuf++ = hex[val >> 4]; - *pathbuf++ = hex[val & 0xf]; + strbuf_addch(buf, hex[val >> 4]); + strbuf_addch(buf, hex[val & 0xf]); if (!i) - *pathbuf++ = '/'; + strbuf_addch(buf, '/'); } - *pathbuf = '\0'; } const char *sha1_file_name(const unsigned char *sha1) { - static char buf[PATH_MAX]; - const char *objdir; - int len; + static struct strbuf buf = STRBUF_INIT; - objdir = get_object_directory(); - len = strlen(objdir); + strbuf_reset(&buf); + strbuf_addf(&buf, "%s/", get_object_directory()); - /* '/' + sha1(2) + '/' + sha1(38) + '\0' */ - if (len + 43 > PATH_MAX) - die("insanely long object directory %s", objdir); - memcpy(buf, objdir, len); - buf[len] = '/'; - fill_sha1_path(buf + len + 1, sha1); - return buf; + fill_sha1_path(&buf, sha1); + return buf.buf; } struct strbuf *alt_scratch_buf(struct alternate_object_database *alt) @@ -213,14 +205,8 @@ struct strbuf *alt_scratch_buf(struct alternate_object_database *alt) static const char *alt_sha1_path(struct alternate_object_database *alt, const unsigned char *sha1) { - /* hex sha1 plus internal "/" */ - size_t len = GIT_SHA1_HEXSZ + 1; struct strbuf *buf = alt_scratch_buf(alt); - - strbuf_grow(buf, len); - fill_sha1_path(buf->buf + buf->len, sha1); - strbuf_setlen(buf, buf->len + len); - + fill_sha1_path(buf, sha1); return buf->buf; }
-- 2.10.0.618.g82cc264