Mirrors/cartreader
2
0
Fork 0
mirror of https://github.com/sanni/cartreader.git synced 2024-11-10 23:15:08 +01:00
Code Issues Projects Releases Wiki Activity

N64.ino: Optimise controller CRC functions for speed

Browse Source 
Also, shave off 5 bytes from a local initializer.
Saves 22 bytes of program space and of global ram space.
This commit is contained in:
Vincent Pelletier 2022-10-22 05:22:59 +00:00
parent 3826f5aa10
commit a43b2553cd
1 changed files with 11 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
Cart_Reader/N64.ino
View File

@ -597,35 +597,25 @@ void writeWord_N64(word myWord) {
N64 Controller CRC Functions
*****************************************/
static word addrCRC(word address) {
// CRC table
word xor_table[16] = { 0x0, 0x0, 0x0, 0x0, 0x0, 0x15, 0x1F, 0x0B, 0x16, 0x19, 0x07, 0x0E, 0x1C, 0x0D, 0x1A, 0x01 };
word crc = 0;
// Make sure we have a valid address
address &= ~0x1F;
// Go through each bit in the address, and if set, xor the right value into the output
for (int i = 15; i >= 5; i--) {
// Is this bit set?
if (((address >> i) & 0x1)) {
crc ^= xor_table[i];
const char n64_address_crc_table[] = { 0x15, 0x1F, 0x0B, 0x16, 0x19, 0x07, 0x0E, 0x1C, 0x0D, 0x1A, 0x01 };
const char *cur_xor = n64_address_crc_table;
byte crc = 0;
for (word mask = 0x0020; mask; mask <<= 1, cur_xor++) {
if (address & mask) {
crc ^= *cur_xor;
}
}
// Just in case
crc &= 0x1F;
// Create a new address with the CRC appended
return address | crc;
return (address & 0xFFE0) | crc;
}
static uint8_t dataCRC(uint8_t* data) {
uint8_t ret = 0;
for (int i = 0; i <= 32; i++) {
for (int j = 7; j >= 0; j--) {
int tmp = 0;
if (ret & 0x80) {
tmp = 0x85;
}
for (uint8_t i = 0; i <= 32; i++) {
for (uint8_t mask = 0x80; mask; mask >>= 1) {
uint8_t tmp = ret & 0x80 ? 0x85 : 0;
ret <<= 1;
if (i < 32) {
if (data[i] & (0x01 << j)) {
if (data[i] & mask) {
ret |= 0x1;
}
}