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mirror of https://github.com/libretro/RetroArch synced 2025-02-16 21:40:04 +00:00

384 lines
12 KiB
C

/* RetroArch - A frontend for libretro.
* Copyright (C) 2010-2014 - Hans-Kristian Arntzen
*
* RetroArch is free software: you can redistribute it and/or modify it under the terms
* of the GNU General Public License as published by the Free Software Found-
* ation, either version 3 of the License, or (at your option) any later version.
*
* RetroArch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with RetroArch.
* If not, see <http://www.gnu.org/licenses/>.
*/
#define __STDC_LIMIT_MACROS
#include "rewind.h"
#include <stdlib.h>
#include "msvc/msvc-stdint/stdint.h"
//#define NO_UNALIGNED_MEM
//Uncomment the above if alignment is enforced.
//Format per frame:
//size nextstart;
//repeat {
// uint16 numchanged; // everything is counted in units of uint16
// if (numchanged) {
// uint16 numunchanged; // skip these before handling numchanged
// uint16[numchanged] changeddata;
// }
// else
// {
// uint32 numunchanged;
// if (!numunchanged) break;
// }
//}
//size thisstart;
//
//The start offsets point to 'nextstart' of any given compressed frame.
//Each uint16 is stored native endian; anything that claims any other endianness refers to the endianness of this specific item.
//The uint32 is stored little endian.
//Each size value is stored native endian if alignment is not enforced; if it is, they're little endian.
//The start of the buffer contains a size pointing to the end of the buffer; the end points to its start.
//Wrapping is handled by returning to the start of the buffer if the compressed data could potentially hit the edge;
// if the compressed data could potentially overwrite the tail pointer, the tail retreats until it can no longer collide.
//This means that on average, ~2*maxcompsize is unused at any given moment.
#if SIZE_MAX == 0xFFFFFFFF
extern char double_check_sizeof_size_t[(sizeof(size_t)==4)?1:-1];
#elif SIZE_MAX == 0xFFFFFFFFFFFFFFFF
extern char double_check_sizeof_size_t[(sizeof(size_t)==8)?1:-1];
#define USE_64BIT
#else
#error This item is only tested on 32bit and 64bit.
#endif
#ifdef NO_UNALIGNED_MEM
//These functions assume 16bit alignment.
//They do not make any attempt at matching system native endian; values written by these can only be read by the matching partner.
#ifdef USE_64BIT
static inline void write_size_t(uint16_t* ptr, size_t val)
{
ptr[0] = val>>0;
ptr[1] = val>>16;
ptr[2] = val>>32;
ptr[3] = val>>48;
}
static inline size_t read_size_t(uint16_t* ptr)
{
return ((size_t)ptr[0]<<0 |
(size_t)ptr[1]<<16 |
(size_t)ptr[2]<<32 |
(size_t)ptr[3]<<48);
}
#else
static inline void write_size_t(uint16_t* ptr, size_t val)
{
ptr[0] = val;
ptr[1] = val>>16;
}
static inline size_t read_size_t(uint16_t* ptr)
{
return (ptr[0] | (size_t)ptr[1]<<16);
}
#endif
#else
#define read_size_t(ptr) (*(size_t*)(ptr))
#define write_size_t(ptr, val) (*(size_t*)(ptr) = (val))
#endif
struct state_manager {
char *data;
size_t capacity;
char *head;//Reading and writing is done here.
char *tail;//If head comes close to this, discard a frame.
char *thisblock;
char *nextblock;
bool thisblock_valid;
size_t blocksize;//This one is runded up from reset::blocksize.
size_t maxcompsize;//size_t+(blocksize+131071)/131072*(blocksize+u16+u16)+u16+u32+size_t (yes, the math is a bit ugly)
unsigned int entries;
};
state_manager_t *state_manager_new(size_t state_size, size_t buffer_size)
{
state_manager_t *state = (state_manager_t*)malloc(sizeof(*state));
state->capacity = 0;
state->blocksize = 0;
int newblocksize = ((state_size-1)|(sizeof(uint16_t)-1))+1;
state->blocksize = newblocksize;
const int maxcblkcover = UINT16_MAX*sizeof(uint16_t);
const int maxcblks = (state->blocksize+maxcblkcover-1)/maxcblkcover;
state->maxcompsize = state->blocksize + maxcblks*sizeof(uint16_t)*2 + sizeof(uint16_t)+sizeof(uint32_t) + sizeof(size_t)*2;
state->data = (char*)malloc(buffer_size);
state->thisblock = (char*)calloc(state->blocksize+sizeof(uint16_t)*8, 1);
state->nextblock = (char*)calloc(state->blocksize+sizeof(uint16_t)*8, 1);
if (!state->data || !state->thisblock || !state->nextblock)
{
free(state->data);
free(state->thisblock);
free(state->nextblock);
free(state);
return NULL;
}
//Force in a different byte at the end, so we don't need to check bounds in the innermost loop (it's expensive).
//There is also a large amount of data that's the same, to stop the other scan
//There is also some padding at the end. This is so we don't read outside the buffer end if we're reading in large blocks;
// it doesn't make any difference to us, but sacrificing 16 bytes to get Valgrind happy is worth it.
*(uint16_t*)(state->thisblock+state->blocksize+sizeof(uint16_t)*3) = 0xFFFF;
*(uint16_t*)(state->nextblock+state->blocksize+sizeof(uint16_t)*3) = 0x0000;
state->capacity=buffer_size;
state->head = state->data+sizeof(size_t);
state->tail = state->data+sizeof(size_t);
state->thisblock_valid = false;
state->entries = 0;
return state;
}
void state_manager_free(state_manager_t *state)
{
free(state->data);
free(state->thisblock);
free(state->nextblock);
free(state);
}
bool state_manager_pop(state_manager_t *state, const void **data)
{
*data = NULL;
if (state->thisblock_valid)
{
state->thisblock_valid = false;
state->entries--;
*data = state->thisblock;
return true;
}
if (state->head == state->tail) return false;
size_t start = read_size_t((uint16_t*)(state->head - sizeof(size_t)));
state->head = state->data+start;
const char *compressed = state->data+start+sizeof(size_t);
char *out = state->thisblock;
//Begin decompression code
//out is the last pushed (or returned) state
const uint16_t *compressed16 = (const uint16_t*)compressed;
uint16_t *out16 = (uint16_t*)out;
while (true)
{
uint16_t numchanged = *(compressed16++);
if (numchanged)
{
out16 += *(compressed16++);
//We could do memcpy, but it seems that memcpy has a constant-per-call overhead that actually shows up.
//Our average size in here seems to be 8 or something.
//Therefore, we do something with lower overhead.
for (int i=0;i<numchanged;i++) out16[i] = compressed16[i];
compressed16 += numchanged;
out16 += numchanged;
}
else
{
uint32_t numunchanged = compressed16[0] | compressed16[1]<<16;
if (!numunchanged) break;
compressed16 += 2;
out16 += numunchanged;
}
}
//End decompression code
state->entries--;
*data = state->thisblock;
return true;
}
void state_manager_push_where(state_manager_t *state, void **data)
{
//We need to ensure we have an uncompressed copy of the last pushed state, or we could
// end up applying a 'patch' to wrong savestate, and that'd blow up rather quickly.
if (!state->thisblock_valid)
{
const void *ignored;
if (state_manager_pop(state, &ignored))
{
state->thisblock_valid = true;
}
}
*data=state->nextblock;
}
void state_manager_push_do(state_manager_t *state)
{
if (state->thisblock_valid)
{
if (state->capacity<sizeof(size_t)+state->maxcompsize) return;
recheckcapacity:;
size_t headpos = (state->head-state->data);
size_t tailpos = (state->tail-state->data);
size_t remaining = (tailpos+state->capacity-sizeof(size_t)-headpos-1)%state->capacity + 1;
if (remaining <= state->maxcompsize)
{
state->tail = state->data + read_size_t((uint16_t*)state->tail);
state->entries--;
goto recheckcapacity;
}
const char *oldb = state->thisblock;
const char *newb = state->nextblock;
char *compressed = state->head+sizeof(size_t);
//Begin compression code; 'compressed' will point to the end of the compressed data (excluding the prev pointer).
const uint16_t *old16 = (const uint16_t*)oldb;
const uint16_t *new16 = (const uint16_t*)newb;
uint16_t *compressed16 = (uint16_t*)compressed;
size_t num16s = state->blocksize/sizeof(uint16_t);
while (num16s)
{
const uint16_t *oldprev = old16;
#ifdef NO_UNALIGNED_MEM
while ((uintptr_t)old16 & (sizeof(size_t)-1) && *old16==*new16)
{
old16++;
new16++;
}
if (*old16==*new16)
#endif
{
const size_t *olds = (const size_t*)old16;
const size_t *news = (const size_t*)new16;
while (*olds == *news)
{
olds++;
news++;
}
old16 = (const uint16_t*)olds;
new16 = (const uint16_t*)news;
while (*old16 == *new16)
{
old16++;
new16++;
}
}
size_t skip = (old16-oldprev);
if (skip >= num16s) break;
num16s -= skip;
if (skip > UINT16_MAX)
{
if (skip > UINT32_MAX)
{
// This will make it scan the entire thing again, but it only hits on 8GB unchanged
// data anyways, and if you're doing that, you've got bigger problems.
old16 -= skip;
new16 -= skip;
skip = UINT32_MAX;
old16 += skip;
new16 += skip;
}
*(compressed16++) = 0;
*(compressed16++) = skip;
*(compressed16++) = skip>>16;
skip = 0;
continue;
}
size_t changed;
const uint16_t *old16prev = old16;
//Comparing two or three words makes no real difference.
//With two, the smaller blocks are less likely to be chopped up elsewhere due to 64KB;
// with three, we get larger blocks which should be a minuscle bit faster to decompress,
// but probably a little slower to compress. Since compression is more bottleneck than decompression is, we favor that.
while (old16[0] != new16[0] || old16[1] != new16[1])
{
old16++;
new16++;
//Optimize this by only checking one at the time for as long as possible.
while (*old16 != *new16)
{
old16++;
new16++;
}
}
changed = (old16-old16prev);
if (!changed) continue;
if (changed > UINT16_MAX)
{
old16 -= changed;
new16 -= changed;
changed = UINT16_MAX;
old16 += changed;
new16 += changed;
}
num16s -= changed;
*(compressed16++) = changed;
*(compressed16++) = skip;
for (int i=0;i<changed;i++) compressed16[i] = old16prev[i];
compressed16 += changed;
}
compressed16[0] = 0;
compressed16[1] = 0;
compressed16[2] = 0;
compressed = (char*)(compressed16+3);
//End compression code.
if (compressed - state->data + state->maxcompsize > state->capacity)
{
compressed = state->data;
if (state->tail == state->data+sizeof(size_t)) state->tail = state->data + *(size_t*)state->tail;
}
write_size_t((uint16_t*)compressed, state->head-state->data);
compressed += sizeof(size_t);
write_size_t((uint16_t*)state->head, compressed-state->data);
state->head = compressed;
}
else
{
state->thisblock_valid = true;
}
char *swap = state->thisblock;
state->thisblock = state->nextblock;
state->nextblock = swap;
state->entries++;
return;
}
void state_manager_capacity(state_manager_t *state, unsigned int * entries, size_t * bytes, bool * full)
{
size_t headpos = (state->head-state->data);
size_t tailpos = (state->tail-state->data);
size_t remaining = (tailpos+state->capacity-sizeof(size_t)-headpos-1)%state->capacity + 1;
if (entries) *entries = state->entries;
if (bytes) *bytes = (state->capacity-remaining);
if (full) *full = (remaining<=state->maxcompsize*2);
}