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af_pan: Fix sscanf formats to work with buggy sscanf implementations

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Some implementations of sscanf do not handle a space before a trailing %n
properly.

As an example, MSVC's does this for the second insatnce in this patch, for
an input of "0x3:c0=c1:c1=c0":
    1) Match the final "c0" or "c1".
    2) Realize it's at the end of the string.
    3) Check for %n.
    4) There is no %n, but a space instead.
    5) Leave 'len' unitilialized.

So, move it out of the sscanf format strings, and call skip_spaces instead.

This bug does not affect skip_spaces since %n is the first and only formatting
string.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
This commit is contained in:
Hendrik Leppkes 2012-09-14 12:45:34 -04:00 committed by Derek Buitenhuis
parent d512e74dec
commit e3a1eb9edf
1 changed files with 5 additions and 4 deletions
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9
libavfilter/af_pan.c
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@ -60,7 +60,7 @@ static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
int64_t layout, layout0;
/* try to parse a channel name, e.g. "FL" */
if (sscanf(*arg, " %7[A-Z] %n", buf, &len)) {
if (sscanf(*arg, "%7[A-Z]%n", buf, &len)) {
layout0 = layout = av_get_channel_layout(buf);
/* channel_id <- first set bit in layout */
for (i = 32; i > 0; i >>= 1) {
@ -78,7 +78,7 @@ static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
return 0;
}
/* try to parse a channel number, e.g. "c2" */
if (sscanf(*arg, " c%d %n", &channel_id, &len) &&
if (sscanf(*arg, "c%d%n", &channel_id, &len) &&
channel_id >= 0 && channel_id < MAX_CHANNELS) {
*rchannel = channel_id;
*rnamed = 0;
@ -143,6 +143,7 @@ static av_cold int init(AVFilterContext *ctx, const char *args0)
"Invalid out channel name \"%.8s\"\n", arg0);
return AVERROR(EINVAL);
}
skip_spaces(&arg);
if (*arg == '=') {
arg++;
} else if (*arg == '<') {
@ -156,7 +157,7 @@ static av_cold int init(AVFilterContext *ctx, const char *args0)
/* gains */
while (1) {
gain = 1;
if (sscanf(arg, " %lf %n* %n", &gain, &len, &len))
if (sscanf(arg, "%lf%n *%n", &gain, &len, &len))
arg += len;
if (parse_channel_name(&arg, &in_ch_id, &named)){
av_log(ctx, AV_LOG_ERROR,
@ -170,6 +171,7 @@ static av_cold int init(AVFilterContext *ctx, const char *args0)
return AVERROR(EINVAL);
}
pan->gain[out_ch_id][in_ch_id] = gain;
skip_spaces(&arg);
if (!*arg)
break;
if (*arg != '+') {
@ -177,7 +179,6 @@ static av_cold int init(AVFilterContext *ctx, const char *args0)
return AVERROR(EINVAL);
}
arg++;
skip_spaces(&arg);
}
}
pan->need_renumber = !!nb_in_channels[1];