sceMp3: point the game at the end of the buffered data, not the start

sceMp3GetInfoToAddStreamData always handed back the start of the work
area, so the pointer never moved as data was added - the hardware walks
it forward past what's already buffered. AuNotifyAddStreamData now
takes the new bytes from where the game was actually told to write, and
checks that range fits the buffer rather than just comparing the size.

Also compare readPos against endPos as signed. readPos is an int and a
game can notify a negative size, which made it promote to a huge u64
and look like the end of the stream, so we reported nothing left to
write where the hardware still wanted 6721 bytes.

Fixes audio/mp3/infotoadd, moved to tests_good. audio/mp3/notifyadd
gets both of its value differences fixed but still fails: after a
decode the hardware reports no space at all, while we free what the
decode consumed, so we do one round more than it does.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JvJR8oJNSCimCM9KXVLjfq

Core/HW/SimpleAudioDec.cpp

@@ -572,7 +572,10 @@ int AuCtx::AuCheckStreamDataNeeded() {
 int AuCtx::AuStreamBytesNeeded() {
 	if (decoder->GetAudioType() == PSP_CODEC_MP3) {
 		// The endPos and readPos are not considered, except when you've read to the end.
-		if (readPos >= endPos)
+		// Compare signed: readPos is an int and can legitimately go negative (a game can notify
+		// a negative size), and promoting that to u64 would make it look like the end of the
+		// stream instead of what the hardware reports.
+		if ((int64_t)readPos >= (int64_t)endPos)
 			return 0;
 		// Account for the workarea.
 		int offset = AuStreamWorkareaSize();
@@ -593,6 +596,9 @@ int AuCtx::AuStreamWorkareaSize() {
 // check how many bytes we have read from source file
 u32 AuCtx::AuNotifyAddStreamData(int size) {
 	int offset = AuStreamWorkareaSize();
+	// Where AuGetInfoToAddStreamData pointed the game, i.e. where the bytes it just added start.
+	// Data accumulates in the buffer rather than always landing at the beginning.
+	const int writeOffset = AuBufAvailable;
 
 	if (askedReadSize != 0) {
 		// Old save state, numbers already adjusted.
@@ -613,9 +619,10 @@ u32 AuCtx::AuNotifyAddStreamData(int size) {
 	// and an unbounded positive value would grow sourcebuff without limit (DoS).
 	// The validated range also has to match what's actually read below - it was
 	// checking [AuBuf, AuBuf+size) while the copy reads from [AuBuf+offset, ...).
-	if (size > 0 && size <= (int)AuBufSize && Memory::IsValidRange(AuBuf + offset, size)) {
+	if (size > 0 && (int64_t)offset + writeOffset + size <= (int64_t)AuBufSize &&
+		Memory::IsValidRange(AuBuf + offset + writeOffset, size)) {
 		sourcebuff.resize(sourcebuff.size() + size);
-		Memory::MemcpyUnchecked(&sourcebuff[sourcebuff.size() - size], AuBuf + offset, size);
+		Memory::MemcpyUnchecked(&sourcebuff[sourcebuff.size() - size], AuBuf + offset + writeOffset, size);
 	}
 
 	return 0;
@@ -627,10 +634,11 @@ u32 AuCtx::AuGetInfoToAddStreamData(u32 bufPtr, u32 sizePtr, u32 srcPosPtr) {
 	int readsize = AuStreamBytesNeeded();
 	int offset = AuStreamWorkareaSize();
 
-	// we can recharge AuBuf from its beginning
+	// The game appends to what's already buffered, so point it past that rather than at the
+	// start of the work area - the hardware's pointer walks forward as data is added.
 	if (readsize != 0) {
 		if (Memory::IsValidAddress(bufPtr))
-			Memory::WriteUnchecked_U32(AuBuf + offset, bufPtr);
+			Memory::WriteUnchecked_U32(AuBuf + offset + AuBufAvailable, bufPtr);
 		if (Memory::IsValidAddress(sizePtr))
 			Memory::WriteUnchecked_U32(readsize, sizePtr);
 		if (Memory::IsValidAddress(srcPosPtr))

test.py

@@ -105,6 +105,7 @@ tests_good = [
   "audio/mp3/getmpegversion",
   "audio/mp3/getsamplerate",
   "audio/mp3/getsumdecoded",
+  "audio/mp3/infotoadd",
   "audio/mp3/initresource",
   "audio/mp3/mp3test",
   "audio/mp3/release",
@@ -400,7 +401,6 @@ tests_next = [
   "audio/sceaudio/output",
   "audio/sceaudio/reserve",
   "audio/sascore/setadsr",
-  "audio/mp3/infotoadd",
   "audio/mp3/init",
   "audio/mp3/notifyadd",
   "audio/output2/frequency",