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/* RetroArch - A frontend for libretro.
* Copyright (C) 2010-2012 - 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/>.
*/
#include "rewind.h"
#include <stdlib.h>
#include <stdint.h>
#include "boolean.h"
#include <string.h>
#include <limits.h>
#include "general.h"
struct state_manager
{
uint64_t *buffer;
size_t buf_size;
size_t buf_size_mask;
uint32_t *tmp_state;
size_t top_ptr;
size_t bottom_ptr;
size_t state_size;
bool first_pop;
};
static inline size_t nearest_pow2_size(size_t v)
{
size_t orig = v;
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
#if SIZE_MAX >= UINT16_C(0xffff)
v |= v >> 8;
#endif
#if SIZE_MAX >= UINT32_C(0xffffffff)
v |= v >> 16;
#endif
#if SIZE_MAX >= UINT64_C(0xffffffffffffffff)
v |= v >> 32;
#endif
v++;
size_t next = v;
size_t prev = v >> 1;
if ((next - orig) < (orig - prev))
return next;
else
return prev;
}
state_manager_t *state_manager_new(size_t state_size, size_t buffer_size, void *init_buffer)
{
if (buffer_size <= state_size * 4) // Need a sufficient buffer size.
return NULL;
state_manager_t *state = (state_manager_t*)calloc(1, sizeof(*state));
if (!state)
return NULL;
// We need 4-byte aligned state_size to avoid having to enforce this with unneeded memcpy's!
rarch_assert(state_size % 4 == 0);
state->top_ptr = 1;
state->state_size = state_size / sizeof(uint32_t); // Works in multiple of 4.
state->buf_size = nearest_pow2_size(buffer_size) / sizeof(uint64_t); // Works in multiple of 8.
state->buf_size_mask = state->buf_size - 1;
RARCH_LOG("Readjusted rewind buffer size to %u MiB\n", (unsigned)(sizeof(uint64_t) * (state->buf_size >> 20)));
if (!(state->buffer = (uint64_t*)calloc(1, state->buf_size * sizeof(uint64_t))))
goto error;
if (!(state->tmp_state = (uint32_t*)calloc(1, state->state_size * sizeof(uint32_t))))
goto error;
memcpy(state->tmp_state, init_buffer, state_size);
return state;
error:
if (state)
{
free(state->buffer);
free(state->tmp_state);
free(state);
}
return NULL;
}
void state_manager_free(state_manager_t *state)
{
free(state->buffer);
free(state->tmp_state);
free(state);
}
bool state_manager_pop(state_manager_t *state, void **data)
{
*data = state->tmp_state;
if (state->first_pop)
{
state->first_pop = false;
return true;
}
state->top_ptr = (state->top_ptr - 1) & state->buf_size_mask;
if (state->top_ptr == state->bottom_ptr) // Our stack is completely empty... :v
{
state->top_ptr = (state->top_ptr + 1) & state->buf_size_mask;
return false;
}
while (state->buffer[state->top_ptr])
{
// Apply the xor patch.
uint32_t addr = state->buffer[state->top_ptr] >> 32;
uint32_t xor_ = state->buffer[state->top_ptr] & 0xFFFFFFFFU;
state->tmp_state[addr] ^= xor_;
state->top_ptr = (state->top_ptr - 1) & state->buf_size_mask;
}
if (state->top_ptr == state->bottom_ptr) // Our stack is completely empty... :v
{
state->top_ptr = (state->top_ptr + 1) & state->buf_size_mask;
return true;
}
return true;
}
static void reassign_bottom(state_manager_t *state)
{
state->bottom_ptr = (state->top_ptr + 1) & state->buf_size_mask;
while (state->buffer[state->bottom_ptr]) // Skip ahead until we find the first 0 (boundary for state delta).
state->bottom_ptr = (state->bottom_ptr + 1) & state->buf_size_mask;
}
static void generate_delta(state_manager_t *state, const void *data)
{
bool crossed = false;
const uint32_t *old_state = state->tmp_state;
const uint32_t *new_state = (const uint32_t*)data;
state->buffer[state->top_ptr++] = 0; // For each separate delta, we have a 0 value sentinel in between.
state->top_ptr &= state->buf_size_mask;
// Check if top_ptr and bottom_ptr crossed each other, which means we need to delete old cruft.
if (state->top_ptr == state->bottom_ptr)
crossed = true;
for (uint64_t i = 0; i < state->state_size; i++)
{
uint64_t xor_ = old_state[i] ^ new_state[i];
// If the data differs (xor != 0), we push that xor on the stack with index and xor.
// This can be reversed by reapplying the xor.
// This, if states don't really differ much, we'll save lots of space :)
// Hopefully this will work really well with save states.
if (xor_)
{
state->buffer[state->top_ptr] = (i << 32) | xor_;
state->top_ptr = (state->top_ptr + 1) & state->buf_size_mask;
if (state->top_ptr == state->bottom_ptr)
crossed = true;
}
}
if (crossed)
reassign_bottom(state);
}
bool state_manager_push(state_manager_t *state, const void *data)
{
generate_delta(state, data);
memcpy(state->tmp_state, data, state->state_size * sizeof(uint32_t));
state->first_pop = true;
return true;
}
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