avcodec/codec_internal: Use union for FFCodec decode/encode callbacks

This is possible, because every given FFCodec has to implement
exactly one of these. Doing so decreases sizeof(FFCodec) and
therefore decreases the size of the binary.
Notice that in case of position-independent code the decrease
is in .data.rel.ro, so that this translates to decreased
memory consumption.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

1 files changed, 30 insertions, 12 deletions

diff --git a/libavcodec/tests/avcodec.c b/libavcodec/tests/avcodec.c
index 73c09d00a0..08b5fbede1 100644
--- a/libavcodec/tests/avcodec.c
+++ b/libavcodec/tests/avcodec.c
@@ -64,7 +64,7 @@ int main(void){
     while (codec = av_codec_iterate(&iter)) {
         const FFCodec *const codec2 = ffcodec(codec);
         const AVCodecDescriptor *desc;
-        int is_decoder, is_encoder;
+        int is_decoder = 0, is_encoder = 0;
 
         if (!codec->name) {
             AV_LOG("Codec for format %s has no name\n",
@@ -102,17 +102,38 @@ int main(void){
                                      AV_CODEC_CAP_OTHER_THREADS)))
             ERR("Codec %s has private-only threading support\n");
 
-        is_decoder = av_codec_is_decoder(codec);
-        is_encoder = av_codec_is_encoder(codec);
-        if (!!is_decoder + !!is_encoder != 1) {
-            ERR("Codec %s is decoder and encoder or neither.\n");
+        switch (codec2->cb_type) {
+        case FF_CODEC_CB_TYPE_DECODE:
+        case FF_CODEC_CB_TYPE_DECODE_SUB:
+        case FF_CODEC_CB_TYPE_RECEIVE_FRAME:
+            is_decoder = 1;
+            break;
+        case FF_CODEC_CB_TYPE_ENCODE:
+        case FF_CODEC_CB_TYPE_ENCODE_SUB:
+        case FF_CODEC_CB_TYPE_RECEIVE_PACKET:
+            is_encoder = 1;
+            break;
+        default:
+            ERR("Codec %s has unknown cb_type\n");
             continue;
         }
+        if (is_decoder != av_codec_is_decoder(codec) ||
+            is_encoder != av_codec_is_encoder(codec)) {
+            ERR("Codec %s cb_type and av_codec_is_(de|en)coder inconsistent.\n");
+            continue;
+        }
+#define CHECK(TYPE, type) (codec2->cb_type == FF_CODEC_CB_TYPE_ ## TYPE && !codec2->cb.type)
+        if (CHECK(DECODE, decode) || CHECK(DECODE_SUB, decode_sub) ||
+            CHECK(RECEIVE_PACKET, receive_packet) ||
+            CHECK(ENCODE, encode) || CHECK(ENCODE_SUB, encode_sub) ||
+            CHECK(RECEIVE_FRAME, receive_frame)) {
+            ERR_EXT("Codec %s does not implement its %s callback.\n",
+                    is_decoder ? "decoding" : "encoding");
+        }
+#undef CHECK
         if (is_encoder) {
-            if (codec->type == AVMEDIA_TYPE_SUBTITLE ^ !!codec2->encode_sub)
+            if ((codec->type == AVMEDIA_TYPE_SUBTITLE) != (codec2->cb_type == FF_CODEC_CB_TYPE_ENCODE_SUB))
                 ERR("Encoder %s is both subtitle encoder and not subtitle encoder.");
-            if (!!codec2->encode_sub + !!codec2->encode2 + !!codec2->receive_packet != 1)
-                ERR("Encoder %s does not implement exactly one encode API.\n");
             if (codec2->update_thread_context || codec2->update_thread_context_for_user || codec2->bsfs)
                 ERR("Encoder %s has decoder-only thread functions or bsf.\n");
             if (codec->type == AVMEDIA_TYPE_AUDIO) {
@@ -135,14 +156,11 @@ int main(void){
                 codec->capabilities & AV_CODEC_CAP_ENCODER_FLUSH)
                 ERR("Frame-threaded encoder %s claims to support flushing\n");
         } else {
-            if (codec->type == AVMEDIA_TYPE_SUBTITLE && !codec2->decode_sub)
+            if ((codec->type == AVMEDIA_TYPE_SUBTITLE) != (codec2->cb_type == FF_CODEC_CB_TYPE_DECODE_SUB))
                 ERR("Subtitle decoder %s does not implement decode_sub callback\n");
             if (codec->type == AVMEDIA_TYPE_SUBTITLE && codec2->bsfs)
                 ERR("Automatic bitstream filtering unsupported for subtitles; "
                     "yet decoder %s has it set\n");
-            if ((codec->type != AVMEDIA_TYPE_SUBTITLE) !=
-                (!!codec2->decode + !!codec2->receive_frame))
-                ERR("Decoder %s does not implement exactly one decode API.\n");
             if (codec->capabilities & (AV_CODEC_CAP_SMALL_LAST_FRAME    |
                                        AV_CODEC_CAP_VARIABLE_FRAME_SIZE |
                                        AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE |