Problem Analysis:
- All FLAC files had the same pk (071c5713d5cf485ca688832207bef0f9)
- Root cause: read() can return < 1024 bytes on first call
- If read returned only 400 bytes:
* header.len() = 400
* 400 > 512 = false
* Used header[..] (first 400 bytes = FLAC header)
* All FLAC files have identical headers → same pk!
Solution:
- Added read_exact_or_eof() that loops until 1024 bytes read (or EOF)
- Guarantees we skip FLAC header and use actual audio content
- Works for small files (< 512 bytes) and large files (>= 1024 bytes)
Additional Feature:
- Added AudioSink::with_null_output() for testing without audio device
- Added --null-audio flag to play_and_cache example
- Allows testing in containerized environments
Changes:
1. pmocache/src/download.rs: Added read_exact_or_eof()
2. pmocache/src/cache.rs: Use read_exact_or_eof() for pk calculation
3. pmoaudio/src/nodes/audio_sink.rs: Added null output mode
4. pmoparadise/examples/play_and_cache.rs: Added --null-audio flag
Test Results:
- New pk: 83702c1cbca72074ebf7c123336786ea (was 071c...)
- Null audio output works correctly
- Ready for full testing
