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Use bitfield for BIOS Huffman nodes

This commit is contained in:
Jeffrey Pfau 2014-10-09 03:02:35 -07:00
parent f9e79a1a42
commit 8ae1a3a3a3
1 changed files with 13 additions and 15 deletions
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28
src/gba/gba-bios.c
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@ -283,6 +283,11 @@ static void _unLz77(struct GBA* gba, uint32_t source, uint8_t* dest) {
}
}
DECL_BITFIELD(HuffmanNode, uint8_t);
DECL_BITS(HuffmanNode, Offset, 0, 6);
DECL_BIT(HuffmanNode, RTerm, 6);
DECL_BIT(HuffmanNode, LTerm, 7);
static void _unHuffman(struct GBA* gba, uint32_t source, uint32_t* dest) {
struct ARMCore* cpu = gba->cpu;
source = source & 0xFFFFFFFC;
@ -303,39 +308,32 @@ static void _unHuffman(struct GBA* gba, uint32_t source, uint32_t* dest) {
uint32_t sPointer = source + 5 + treesize;
uint32_t* dPointer = dest;
uint32_t nPointer = treeBase;
union HuffmanNode {
struct {
unsigned offset : 6;
unsigned rTerm : 1;
unsigned lTerm : 1;
};
uint8_t packed;
} node;
HuffmanNode node;
int bitsRemaining;
int readBits;
int bitsSeen = 0;
node.packed = cpu->memory.load8(cpu, nPointer, 0);
node = cpu->memory.load8(cpu, nPointer, 0);
while (remaining > 0) {
uint32_t bitstream = cpu->memory.load32(cpu, sPointer, 0);
sPointer += 4;
for (bitsRemaining = 32; bitsRemaining > 0; --bitsRemaining, bitstream <<= 1) {
uint32_t next = (nPointer & ~1) + node.offset * 2 + 2;
uint32_t next = (nPointer & ~1) + HuffmanNodeGetOffset(node) * 2 + 2;
if (bitstream & 0x80000000) {
// Go right
if (node.rTerm) {
if (HuffmanNodeIsRTerm(node)) {
readBits = cpu->memory.load8(cpu, next + 1, 0);
} else {
nPointer = next + 1;
node.packed = cpu->memory.load8(cpu, nPointer, 0);
node = cpu->memory.load8(cpu, nPointer, 0);
continue;
}
} else {
// Go left
if (node.lTerm) {
if (HuffmanNodeIsLTerm(node)) {
readBits = cpu->memory.load8(cpu, next, 0);
} else {
nPointer = next;
node.packed = cpu->memory.load8(cpu, nPointer, 0);
node = cpu->memory.load8(cpu, nPointer, 0);
continue;
}
}
@ -343,7 +341,7 @@ static void _unHuffman(struct GBA* gba, uint32_t source, uint32_t* dest) {
block |= (readBits & ((1 << bits) - 1)) << bitsSeen;
bitsSeen += bits;
nPointer = treeBase;
node.packed = cpu->memory.load8(cpu, nPointer, 0);
node = cpu->memory.load8(cpu, nPointer, 0);
if (bitsSeen == 32) {
bitsSeen = 0;
*dPointer = block;