Re: [FFmpeg-devel] [PATCH] libavformat/img2dec: fix unable to find svg format when the svg resources start with "<svg"

From: wangyaqiang <1035567130@qq.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] libavformat/img2dec: fix unable to find svg format when the svg resources start with "<svg"
Date: Thu, 9 Mar 2023 17:12:39 +0800
Message-ID: <tencent_890821994385ECF1E429DB68C0558F8F6705@qq.com> (raw)
In-Reply-To: <482cee52-20e6-ce9d-e16d-ecee3040d433@passwd.hu>

> 2023年3月9日 07:37，Marton Balint <cus@passwd.hu> 写道：
> 
> 
> On Tue, 7 Mar 2023, 1035567130@qq.com <mailto:1035567130@qq.com> wrote:
> 
>> From: Wang Yaqiang <wangyaqiang03@kuaishou.com>
>> 
>> svg is xml, but <?xml is not required,
>> it can start with <svg and can have multiple empty lines.
>> 
>> Signed-off-by: Wang Yaqiang <wangyaqiang03@kuaishou.com>
>> ---
>> libavformat/img2dec.c | 10 ++++++----
>> 1 file changed, 6 insertions(+), 4 deletions(-)
>> 
>> diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
>> index 5a63d7c81d..448a574b59 100644
>> --- a/libavformat/img2dec.c
>> +++ b/libavformat/img2dec.c
>> @@ -25,6 +25,7 @@
>> #define _DEFAULT_SOURCE
>> #define _BSD_SOURCE
>> #include <sys/stat.h>
>> +#include <ctype.h>
> 
> Please no, use libavutil/avstring.h for av_isspace() instead.

Thanks，i will fix it

> 
>> #include "libavutil/avstring.h"
>> #include "libavutil/log.h"
>> #include "libavutil/opt.h"
>> @@ -964,18 +965,19 @@ static int svg_probe(const AVProbeData *p)
>> {
>>    const uint8_t *b = p->buf;
>>    const uint8_t *end = p->buf + p->buf_size;
>> -
>> -    if (memcmp(p->buf, "<?xml", 5))
>> +    while (b && b < end && isspace(*b)) b++;
> 
> av_isspace()

Thanks，i will fix it.

> 
>> +    if (b >= end - 5) return 0;
> 
> line break before return

Thanks，i will fix it.

> 
>> +    if (memcmp(p->buf, "<?xml", 5) && memcmp(b, "<svg", 4))
>>        return 0;
> 
> Why not simply return AVPROBE_SCORE_EXTENSION + 1 here for the <svg case? You don't have to change the rest that way which skips the first line which supposed to contain <?xml
> 

Thanks，i will fix it, and fix the case start with "<!—" 

> Regards,
> Marton
> 
>>    while (b < end) {
>>        int inc = ff_subtitles_next_line(b);
>>        if (!inc)
>>            break;
>> +        if (!memcmp(b, "<svg", 4))
>> +            return AVPROBE_SCORE_EXTENSION + 1;
>>        b += inc;
>>        if (b >= end - 4)
>>            return 0;
>> -        if (!memcmp(b, "<svg", 4))
>> -            return AVPROBE_SCORE_EXTENSION + 1;
>>    }
>>    return 0;
>> }
>> -- 
>> 2.39.2
>> 
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