LibAudio: Support FLAC files with unknown amount of samples

This is a special case of the sample count field in the header which we
treated as a format error before. Now we just take care to check stream
EOF before reading chunks.

This makes the final FLAC spec test pass, making us one of the most
compliant loaders! :^)

Userland/Libraries/LibAudio/FlacLoader.cpp

@@ -109,7 +109,11 @@ MaybeLoaderError FlacLoaderPlugin::parse_header()
     }
 
     m_total_samples = LOADER_TRY(streaminfo_data.read_bits<u64>(36));
-    FLAC_VERIFY(m_total_samples > 0, LoaderError::Category::Format, "Number of samples is zero");
+    if (m_total_samples == 0) {
+        // "A value of zero here means the number of total samples is unknown."
+        dbgln("FLAC Warning: File has unknown amount of samples, the loader will not stop before EOF");
+        m_total_samples = NumericLimits<decltype(m_total_samples)>::max();
+    }
 
     VERIFY(streaminfo_data.is_aligned_to_byte_boundary());
     LOADER_TRY(streaminfo_data.read_until_filled({ m_md5_checksum, sizeof(m_md5_checksum) }));
@@ -129,7 +133,7 @@ MaybeLoaderError FlacLoaderPlugin::parse_header()
             break;
         case FlacMetadataBlockType::APPLICATION:
             // Note: Third-party library can encode specific data in this.
-            dbgln("Unknown 'Application' metadata block encountered.");
+            dbgln("FLAC Warning: Unknown 'Application' metadata block encountered.");
             [[fallthrough]];
         case FlacMetadataBlockType::PADDING:
             // Note: A padding block is empty and does not need any treatment.
@@ -330,14 +334,15 @@ bool FlacLoaderPlugin::should_insert_seekpoint_at(u64 sample_index) const
 ErrorOr<Vector<FixedArray<Sample>>, LoaderError> FlacLoaderPlugin::load_chunks(size_t samples_to_read_from_input)
 {
     ssize_t remaining_samples = static_cast<ssize_t>(m_total_samples - m_loaded_samples);
-    if (remaining_samples <= 0)
+    // The first condition is relevant for unknown-size streams (total samples = 0 in the header)
+    if (m_stream->is_eof() || remaining_samples <= 0)
         return Vector<FixedArray<Sample>> {};
 
     size_t samples_to_read = min(samples_to_read_from_input, remaining_samples);
     Vector<FixedArray<Sample>> frames;
     size_t sample_index = 0;
 
-    while (sample_index < samples_to_read) {
+    while (!m_stream->is_eof() && sample_index < samples_to_read) {
         TRY(frames.try_append(TRY(next_frame())));
         sample_index += m_current_frame->sample_count;
     }