Addressed Seeking Quirks in FLAC Reader

src/SFML/Audio/SoundFileReaderFlac.cpp

@@ -107,10 +107,6 @@ namespace
     {
         sf::priv::SoundFileReaderFlac::ClientData* data = static_cast<sf::priv::SoundFileReaderFlac::ClientData*>(clientData);
 
-        // If there's no output buffer, it means that we are seeking
-        if (!data->buffer)
-            return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
-
         // Reserve memory if we're going to use the leftovers buffer
         unsigned int frameSamples = frame->header.blocksize * frame->header.channels;
         if (data->remaining < frameSamples)
@@ -142,10 +138,12 @@ namespace
                         break;
                 }
 
+                // If there's room in the output buffer, copy the sample there
                 if (data->remaining > 0)
                 {
-                    // There's room in the output buffer, copy the sample there
-                    *data->buffer++ = sample;
+                    // If there's no output buffer, it means that we are seeking, so just skip the output write
+                    if (data->buffer)
+                        *data->buffer++ = sample;
                     data->remaining--;
                 }
                 else
@@ -210,8 +208,7 @@ bool SoundFileReaderFlac::check(InputStream& stream)
 ////////////////////////////////////////////////////////////
 SoundFileReaderFlac::SoundFileReaderFlac() :
 m_decoder(NULL),
-m_clientData(),
-m_channelCount(0)
+m_clientData()
 {
 }
 
@@ -249,9 +246,6 @@ bool SoundFileReaderFlac::open(InputStream& stream, Info& info)
     // Retrieve the sound properties
     info = m_clientData.info; // was filled in the "metadata" callback
 
-    // We must keep the channel count for the seek function
-    m_channelCount = info.channelCount;
-
     return true;
 }
 
@@ -267,7 +261,21 @@ void SoundFileReaderFlac::seek(Uint64 sampleOffset)
     m_clientData.leftovers.clear();
 
     // FLAC decoder expects absolute sample offset, so we take the channel count out
-    FLAC__stream_decoder_seek_absolute(m_decoder, sampleOffset / m_channelCount);
+    if (sampleOffset < m_clientData.info.sampleCount)
+    {
+        // The "write" callback will populate the leftovers buffer with the first batch of samples from the
+        // seek destination, and since we want that data in this typical case, we don't re-clear it afterward
+        FLAC__stream_decoder_seek_absolute(m_decoder, sampleOffset / m_clientData.info.channelCount);
+    }
+    else
+    {
+        // FLAC decoder can't skip straight to EOF, so we short-seek by one sample and skip the rest
+        FLAC__stream_decoder_seek_absolute(m_decoder, (sampleOffset / m_clientData.info.channelCount) - 1);
+        FLAC__stream_decoder_skip_single_frame(m_decoder);
+
+        // This was re-populated during the seek, but we're skipping everything in this, so we need it emptied
+        m_clientData.leftovers.clear();
+    }
 }
 
 
@@ -283,7 +291,7 @@ Uint64 SoundFileReaderFlac::read(Int16* samples, Uint64 maxCount)
         if (left > maxCount)
         {
             // There are more leftovers than needed
-            std::copy(m_clientData.leftovers.begin(), m_clientData.leftovers.end(), samples);
+            std::copy(m_clientData.leftovers.begin(), m_clientData.leftovers.begin() + maxCount, samples);
             std::vector<Int16> leftovers(m_clientData.leftovers.begin() + maxCount, m_clientData.leftovers.end());
             m_clientData.leftovers.swap(leftovers);
             return maxCount;

src/SFML/Audio/SoundFileReaderFlac.hpp

@@ -133,7 +133,6 @@ class SoundFileReaderFlac : public SoundFileReader
     ////////////////////////////////////////////////////////////
     FLAC__StreamDecoder* m_decoder;      ///< FLAC decoder
     ClientData           m_clientData;   ///< Structure passed to the decoder callbacks
-    unsigned int         m_channelCount; ///< number of channels of the sound file
 };
 
 } // namespace priv