From 066a2e218273cbac0e745158adb4dca10ba0c7de Mon Sep 17 00:00:00 2001
From: oioitff <oioitff@gmail.com>
Date: Sun, 12 May 2013 21:14:41 +0800
Subject: [PATCH] Add some comments for sceAtrac

---
 Core/HLE/sceAtrac.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/Core/HLE/sceAtrac.cpp b/Core/HLE/sceAtrac.cpp
index e8cddf1f79..1266c2e565 100644
--- a/Core/HLE/sceAtrac.cpp
+++ b/Core/HLE/sceAtrac.cpp
@@ -427,6 +427,12 @@ u32 sceAtracGetAtracID(int codecType)
 	return atracID;
 }
 
+// PSP allow games to add stream data to a temp buf, the buf size is given by "atracBufSize "here. 
+// "first.offset" means how many bytes the temp buf has been written, 
+// and "first.writableBytes" means how many bytes the temp buf is allowed to write 
+// (We always have "first.offset + first.writableBytes = atracBufSize"). 
+// We only reset the temp buf when games call sceAtracGetStreamDataInfo, 
+// because that function would tell games how to add the left stream data.
 u32 sceAtracAddStreamData(int atracID, u32 bytesToAdd)
 {
 	INFO_LOG(HLE, "sceAtracAddStreamData(%i, %08x)", atracID, bytesToAdd);
@@ -738,6 +744,9 @@ u32 sceAtracGetSoundSample(int atracID, u32 outEndSampleAddr, u32 outLoopStartSa
 	return 0;
 }
 
+// Games call this function to get some info for add more stream data,
+// such as where the data read from, where the data add to, 
+// and how many bytes are allowed to add.
 u32 sceAtracGetStreamDataInfo(int atracID, u32 writeAddr, u32 writableBytesAddr, u32 readOffsetAddr)
 {
 	DEBUG_LOG(HLE, "sceAtracGetStreamDataInfo(%i, %08x, %08x, %08x)", atracID, writeAddr, writableBytesAddr, readOffsetAddr);
@@ -745,8 +754,10 @@ u32 sceAtracGetStreamDataInfo(int atracID, u32 writeAddr, u32 writableBytesAddr,
 	if (!atrac) {
 		//return -1;
 	} else {
+		// reset the temp buf for adding more stream data
 		atrac->first.writableBytes = std::min(atrac->first.filesize - atrac->first.size, atrac->atracBufSize);
 		atrac->first.offset = 0;
+
 		if (Memory::IsValidAddress(writeAddr))
 		Memory::Write_U32(atrac->first.addr, writeAddr);
 		if (Memory::IsValidAddress(writableBytesAddr))
@@ -887,10 +898,12 @@ int __AtracSetContext(Atrac *atrac, u32 buffer, u32 bufferSize)
 
 int _AtracSetData(Atrac *atrac, u32 buffer, u32 bufferSize)
 {
-	atrac->atracBufSize = bufferSize;
 	if (atrac->first.size > atrac->first.filesize)
 		atrac->first.size = atrac->first.filesize;
 	atrac->first.fileoffset = atrac->first.size;
+
+	// got the size of temp buf, and calculate writableBytes and offset
+	atrac->atracBufSize = bufferSize;
 	atrac->first.writableBytes = (u32)std::max((int)bufferSize - (int)atrac->first.size, 0);
 	atrac->first.offset = atrac->first.size;