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avformat/dump: Avoid unnecessary implicit calculation of strlen

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av_strlcpy() returns the length of the src string to enable
the caller to check for truncation. It is currently used in
the following way in dump_metadata(): Every metadata value
is searched for \b, \n, \v, \f, \r and then the data up to
the first of these characters found is copied to a small
temporary buffer via av_strlcpy() (but of course not more
than fits into said buffer) and then printed; all characters up
to the character found earlier are then treated as consumed.

But this is bad performance-wise if the while string is big
and contains many of these characters, because av_strlcpy()
will unnecessarily calculate the length of the whole remaining string.
(dump_metadata() actually ignored the return value of av_strlcpy().)

Fix this by not copying the data to a temporary buffer at all.
Instead just use %.*s to bound the number of characters output.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2022-09-14 02:21:41 +02:00
parent 130483449e
commit 62af385b91
1 changed files with 1 additions and 3 deletions
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4
libavformat/dump.c
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@ -145,10 +145,8 @@ static void dump_metadata(void *ctx, const AVDictionary *m, const char *indent)
av_log(ctx, AV_LOG_INFO,
"%s %-16s: ", indent, tag->key);
while (*p) {
char tmp[256];
size_t len = strcspn(p, "\x8\xa\xb\xc\xd");
av_strlcpy(tmp, p, FFMIN(sizeof(tmp), len+1));
av_log(ctx, AV_LOG_INFO, "%s", tmp);
av_log(ctx, AV_LOG_INFO, "%.*s", (int)(FFMIN(255, len)), p);
p += len;
if (*p == 0xd) av_log(ctx, AV_LOG_INFO, " ");
if (*p == 0xa) av_log(ctx, AV_LOG_INFO, "\n%s %-16s: ", indent, "");