[Spice-devel] [vdagent-win PATCH 3/4] png: re-allocate enough memory

[Uri Lublin]

On 07/14/2017 12:42 PM, Frediano Ziglio wrote:
>>
>> It can happen that new_size, although double the previous
>> io.size is still not big enough.
>>
>> Signed-off-by: Uri Lublin <uril at redhat.com>
>> ---
>>   vdagent/imagepng.cpp | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/vdagent/imagepng.cpp b/vdagent/imagepng.cpp
>> index 7108675..de0eb2f 100644
>> --- a/vdagent/imagepng.cpp
>> +++ b/vdagent/imagepng.cpp
>> @@ -61,6 +61,9 @@ static void write_to_bufio(png_structp png, png_bytep in,
>> png_size_t size)
>>       if (io.pos + size >= io.size) {
>>           io.allocated = true;
>>           uint32_t new_size = io.size ? io.size * 2 : 4096;
>> +        while (io.pos + size >= new_size) {
>> +            new_size *= 2;
>> +        }
>>           uint8_t *p = (uint8_t*) realloc(io.buf, new_size);
>>           if (!p)
>>               png_error(png, "out of memory");
> 
> As a fix to a not merged patch I think should be squashed in the other one.

OK.

> 
> Also I think the check should be "io.pos + size > new_size" (same change on the if
> above).

It should be safe.
Not sure how this change affects performance (probably negligible):
- removing '=' from outer loop can save a call to realloc
- removing '=' from inner loop -- next write will cause another realloc.
                on the other hand if there is no next write, it's better.

Uri.