Fix a bug that JPX images can't be shown

core/src/fxcodec/codec/fx_codec_jpx_opj.cpp

Index: core/src/fxcodec/codec/fx_codec_jpx_opj.cpp
diff --git a/core/src/fxcodec/codec/fx_codec_jpx_opj.cpp b/core/src/fxcodec/codec/fx_codec_jpx_opj.cpp
index c4a0f88201a81db97599ac9aea9b1d7385585cdd..393c56781bf066b736716e5288b4488f213bfc29 100644
--- a/core/src/fxcodec/codec/fx_codec_jpx_opj.cpp
+++ b/core/src/fxcodec/codec/fx_codec_jpx_opj.cpp
@@ -52,9 +52,12 @@ static OPJ_SIZE_T opj_write_from_memory (void * p_buffer, OPJ_SIZE_T p_nb_bytes,
 static OPJ_OFF_T opj_skip_from_memory (OPJ_OFF_T p_nb_bytes, void* p_user_data)
 {
     DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
-    if (srcData == NULL || srcData->src_size == 0 || srcData->src_data == NULL || srcData->offset >= srcData->src_size) {
+    if (srcData == NULL || srcData->src_size == 0 || srcData->src_data == NULL) {
         return -1;
     }
+    if (srcData->offset >= srcData->src_size) {
+        return p_nb_bytes;

[Tom Sepez, 2015/03/11 18:25:41]

I think we have to adjust the offset here, for example imagine a "file"
of size 1024 with a current offset of 1000, and we do a skip of 100. A
subsequent read should then return 0 bytes, but we'd give the remaining 24.

It gets worse should we allow negative seeks (is OPJ_OFF_T signed?), in which
case we'd have to handle seeking back into a valid portion of the "file" at the
correct offset even after seeking past EOF. This kind of implies that the
invariant that srcData->offset < srcData->src_size can't hold, which is
unfortunate because it feels safer that way. 

Let's assume that we don't have to handle negative seeks, and just set
srcData->offset to srcData->size here. 

[jun_fang, 2015/03/11 21:14:41]

Acknowledged.

+    }
     OPJ_SIZE_T bufferLength = srcData->src_size - srcData->offset;
     OPJ_SIZE_T skipLength = p_nb_bytes < bufferLength ? p_nb_bytes : bufferLength;
     srcData->offset += skipLength;
@@ -63,9 +66,12 @@ static OPJ_OFF_T opj_skip_from_memory (OPJ_OFF_T p_nb_bytes, void* p_user_data)
 static OPJ_BOOL opj_seek_from_memory (OPJ_OFF_T p_nb_bytes, void* p_user_data)
 {
     DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
-    if (srcData == NULL || srcData->src_size == 0 || srcData->src_data == NULL || srcData->offset >= srcData->src_size) {
+    if (srcData == NULL || srcData->src_size == 0 || srcData->src_data == NULL) {
         return OPJ_FALSE;
     }
+    if (srcData->offset >= srcData->src_size) {
+        return OPJ_TRUE;
+    }
     if (p_nb_bytes >= srcData->src_size) {
         return OPJ_FALSE;
     }
@@ -629,7 +635,7 @@ FX_BOOL CJPX_Decoder::Init(const unsigned char* src_data, int src_size)
             image = NULL;
             return FALSE;
         }
-        if (!(opj_decode(l_codec, l_stream, image) && opj_end_decompress(l_codec,	l_stream))) {
+        if (!(opj_decode(l_codec, l_stream, image) && opj_end_decompress(l_codec, l_stream))) {
             opj_image_destroy(image);
             image = NULL;
             return FALSE;