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Merge branch 'dev' of https://gitlab.com/mkxp-z/mkxp-z into dev

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Struma 2022-01-13 15:04:09 -05:00
commit 385060094c
1 changed files with 43 additions and 2 deletions
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45
src/crypto/rgssad.cpp
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@ -25,6 +25,32 @@
#include <stdint.h>
#include <string.h>
/* Equivalent Linear Congruential Generator (LCG) constants for iteration 2^n
* all the way up to 2^32/4 (the largest dword offset possible in
* RGSS{AD,[23]A}).
*
* This table can be easily calculated by taking the original LCG parameter
* m[0] and a[0] and write them down as LCG_TABLE[0]. Then for the rest of
* the 29 entries, LGC_TABLE[n] = {m[n], a[n]} where m[n] = pow(m[n-1], 2)
* and a[n] = a[n-1] * (m[n-1] + 1). */
constexpr static uint32_t LCG_TABLE[30][2] = {
{0x00000007, 0x00000003}, {0x00000031, 0x00000018},
{0x00000961, 0x000004b0}, {0x0057f6c1, 0x002bfb60},
{0xa5057d81, 0xd282bec0}, {0x6e913b01, 0x37489d80},
{0xc0bb7601, 0x605dbb00}, {0x1bdaec01, 0x8ded7600},
{0x0145d801, 0x80a2ec00}, {0x28cbb001, 0x1465d800},
{0xea976001, 0x754bb000}, {0x392ec001, 0x1c976000},
{0x025d8001, 0x012ec000}, {0x44bb0001, 0x225d8000},
{0x89760001, 0xc4bb0000}, {0x12ec0001, 0x89760000},
{0x25d80001, 0x12ec0000}, {0x4bb00001, 0x25d80000},
{0x97600001, 0x4bb00000}, {0x2ec00001, 0x97600000},
{0x5d800001, 0x2ec00000}, {0xbb000001, 0x5d800000},
{0x76000001, 0xbb000000}, {0xec000001, 0x76000000},
{0xd8000001, 0xec000000}, {0xb0000001, 0xd8000000},
{0x60000001, 0xb0000000}, {0xc0000001, 0x60000000},
{0x80000001, 0xc0000000}, {0x00000001, 0x80000000},
};
struct RGSS_entryData
{
int64_t offset;
@ -98,6 +124,22 @@ advanceMagic(uint32_t &magic)
return old;
}
static inline uint32_t
advanceMagicN(uint32_t &magic, uint32_t n) {
uint32_t old = magic;
int table_index = 0;
while (n != 0) {
if (n & 1) {
magic = magic * LCG_TABLE[table_index][0] + LCG_TABLE[table_index][1];
}
n >>= 1;
table_index++;
}
return old;
}
static PHYSFS_sint64
RGSS_ioRead(PHYSFS_Io *self, void *buffer, PHYSFS_uint64 len)
{
@ -217,8 +259,7 @@ RGSS_ioSeek(PHYSFS_Io *self, PHYSFS_uint64 offset)
uint64_t targetDword = offset / 4;
uint64_t dwordsSought = targetDword - currentDword;
for (uint64_t i = 0; i < dwordsSought; ++i)
advanceMagic(entry->currentMagic);
advanceMagicN(entry->currentMagic, (uint32_t) dwordsSought);
entry->currentOffset = offset;
entry->io->seek(entry->io, entry->data.offset + entry->currentOffset);