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CDImage/ECM: Use EDC/ECC functions from libchdr

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Stenzek 2024-09-01 19:43:39 +10:00
parent 1b7c56ece5
commit 998de9de91
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1 changed files with 7 additions and 149 deletions
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156
src/util/cd_image_ecm.cpp
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@ -10,157 +10,13 @@
#include "common/log.h"
#include "common/path.h"
#include "libchdr/cdrom.h"
#include <array>
#include <map>
Log_SetChannel(CDImageEcm);
// unecm.c by Neill Corlett (c) 2002, GPL licensed
/* LUTs used for computing ECC/EDC */
static constexpr std::array<u8, 256> ComputeECCFLUT()
{
std::array<u8, 256> ecc_lut{};
for (u32 i = 0; i < 256; i++)
{
u32 j = (i << 1) ^ (i & 0x80 ? 0x11D : 0);
ecc_lut[i] = static_cast<u8>(j);
}
return ecc_lut;
}
static constexpr std::array<u8, 256> ComputeECCBLUT()
{
std::array<u8, 256> ecc_lut{};
for (u32 i = 0; i < 256; i++)
{
u32 j = (i << 1) ^ (i & 0x80 ? 0x11D : 0);
ecc_lut[i ^ j] = static_cast<u8>(i);
}
return ecc_lut;
}
static constexpr std::array<u32, 256> ComputeEDCLUT()
{
std::array<u32, 256> edc_lut{};
for (u32 i = 0; i < 256; i++)
{
u32 edc = i;
for (u32 k = 0; k < 8; k++)
edc = (edc >> 1) ^ (edc & 1 ? 0xD8018001 : 0);
edc_lut[i] = edc;
}
return edc_lut;
}
static constexpr std::array<u8, 256> ecc_f_lut = ComputeECCFLUT();
static constexpr std::array<u8, 256> ecc_b_lut = ComputeECCBLUT();
static constexpr std::array<u32, 256> edc_lut = ComputeEDCLUT();
/***************************************************************************/
/*
** Compute EDC for a block
*/
static u32 edc_partial_computeblock(u32 edc, const u8* src, u16 size)
{
while (size--)
edc = (edc >> 8) ^ edc_lut[(edc ^ (*src++)) & 0xFF];
return edc;
}
static void edc_computeblock(const u8* src, u16 size, u8* dest)
{
u32 edc = edc_partial_computeblock(0, src, size);
dest[0] = (edc >> 0) & 0xFF;
dest[1] = (edc >> 8) & 0xFF;
dest[2] = (edc >> 16) & 0xFF;
dest[3] = (edc >> 24) & 0xFF;
}
/***************************************************************************/
/*
** Compute ECC for a block (can do either P or Q)
*/
static void ecc_computeblock(u8* src, u32 major_count, u32 minor_count, u32 major_mult, u32 minor_inc, u8* dest)
{
u32 size = major_count * minor_count;
u32 major, minor;
for (major = 0; major < major_count; major++)
{
u32 index = (major >> 1) * major_mult + (major & 1);
u8 ecc_a = 0;
u8 ecc_b = 0;
for (minor = 0; minor < minor_count; minor++)
{
u8 temp = src[index];
index += minor_inc;
if (index >= size)
index -= size;
ecc_a ^= temp;
ecc_b ^= temp;
ecc_a = ecc_f_lut[ecc_a];
}
ecc_a = ecc_b_lut[ecc_f_lut[ecc_a] ^ ecc_b];
dest[major] = ecc_a;
dest[major + major_count] = ecc_a ^ ecc_b;
}
}
/*
** Generate ECC P and Q codes for a block
*/
static void ecc_generate(u8* sector, int zeroaddress)
{
u8 address[4], i;
/* Save the address and zero it out */
if (zeroaddress)
for (i = 0; i < 4; i++)
{
address[i] = sector[12 + i];
sector[12 + i] = 0;
}
/* Compute ECC P code */
ecc_computeblock(sector + 0xC, 86, 24, 2, 86, sector + 0x81C);
/* Compute ECC Q code */
ecc_computeblock(sector + 0xC, 52, 43, 86, 88, sector + 0x8C8);
/* Restore the address */
if (zeroaddress)
for (i = 0; i < 4; i++)
sector[12 + i] = address[i];
}
/***************************************************************************/
/*
** Generate ECC/EDC information for a sector (must be 2352 = 0x930 bytes)
** Returns 0 on success
*/
static void eccedc_generate(u8* sector, int type)
{
switch (type)
{
case 1: /* Mode 1 */
/* Compute EDC */
edc_computeblock(sector + 0x00, 0x810, sector + 0x810);
/* Write out zero bytes */
for (u32 i = 0; i < 8; i++)
sector[0x814 + i] = 0;
/* Generate ECC P/Q codes */
ecc_generate(sector, 0);
break;
case 2: /* Mode 2 form 1 */
/* Compute EDC */
edc_computeblock(sector + 0x10, 0x808, sector + 0x818);
/* Generate ECC P/Q codes */
ecc_generate(sector, 1);
break;
case 3: /* Mode 2 form 2 */
/* Compute EDC */
edc_computeblock(sector + 0x10, 0x91C, sector + 0x92C);
break;
}
}
namespace {
class CDImageEcm : public CDImage
@ -459,7 +315,8 @@ bool CDImageEcm::ReadChunks(u32 disc_offset, u32 size)
if (std::fread(sector + 0x00C, 0x003, 1, m_fp) != 1 || std::fread(sector + 0x010, 0x800, 1, m_fp) != 1)
return false;
eccedc_generate(sector, 1);
edc_set(&sector[2064], edc_compute(sector, 2064));
ecc_generate(sector);
skip = 0;
}
break;
@ -475,7 +332,8 @@ bool CDImageEcm::ReadChunks(u32 disc_offset, u32 size)
sector[0x12] = sector[0x16];
sector[0x13] = sector[0x17];
eccedc_generate(sector, 2);
edc_set(&sector[2072], edc_compute(&sector[16], 2056));
ecc_generate(sector);
skip = 0x10;
}
break;
@ -491,7 +349,7 @@ bool CDImageEcm::ReadChunks(u32 disc_offset, u32 size)
sector[0x12] = sector[0x16];
sector[0x13] = sector[0x17];
eccedc_generate(sector, 3);
edc_set(&sector[2348], edc_compute(&sector[16], 2332));
skip = 0x10;
}
break;