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avcodec/htmlsubtitles: Replace very slow redundant sscanf() calls by cleaner and faster code 

This reduces the worst case from O(n²) to O(n) time

Fixes Timeout
Fixes: 2127/clusterfuzz-testcase-minimized-6595787859427328

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2017-06-11 17:58:45 +02:00
parent 27c2006805
commit 4132218b87
1 changed files with 15 additions and 5 deletions
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20
libavcodec/htmlsubtitles.c
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@ -56,6 +56,7 @@ int ff_htmlmarkup_to_ass(void *log_ctx, AVBPrint *dst, const char *in)
char *param, buffer[128], tmp[128];
int len, tag_close, sptr = 1, line_start = 1, an = 0, end = 0;
SrtStack stack[16];
int closing_brace_missing = 0;
stack[0].tag[0] = 0;
strcpy(stack[0].param[PARAM_SIZE], "{\\fs}");
@ -83,11 +84,20 @@ int ff_htmlmarkup_to_ass(void *log_ctx, AVBPrint *dst, const char *in)
and all microdvd like styles such as {Y:xxx} */
len = 0;
an += sscanf(in, "{\\an%*1u}%n", &len) >= 0 && len > 0;
if ((an != 1 && (len = 0, sscanf(in, "{\\%*[^}]}%n", &len) >= 0 && len > 0)) ||
(len = 0, sscanf(in, "{%*1[CcFfoPSsYy]:%*[^}]}%n", &len) >= 0 && len > 0)) {
in += len - 1;
} else
av_bprint_chars(dst, *in, 1);
if (!closing_brace_missing) {
if ( (an != 1 && in[1] == '\\')
|| (in[1] && strchr("CcFfoPSsYy", in[1]) && in[2] == ':')) {
char *bracep = strchr(in+2, '}');
if (bracep) {
in = bracep;
break;
} else
closing_brace_missing = 1;
}
}
av_bprint_chars(dst, *in, 1);
break;
case '<':
tag_close = in[1] == '/';