snes9x/win32/StateManager.cpp

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2012-03-27 22:18:03 +00:00
#include "statemanager.h"
#include "snapshot.h"
/* Snapshot Manager Class that records snapshot data for rewinding
mostly based on SSNES's rewind code by Themaister
*/
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 >= 0xffff
v |= v >> 8;
#endif
#if SIZE_MAX >= 0xffffffff
v |= v >> 16;
#endif
#if SIZE_MAX >= 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;
}
void StateManager::deallocate() {
if(buffer) {
delete [] buffer;
buffer = NULL;
}
if(tmp_state) {
delete [] tmp_state;
tmp_state = NULL;
}
if(in_state) {
delete [] in_state;
in_state = NULL;
}
}
StateManager::StateManager()
{
buffer = NULL;
tmp_state = NULL;
in_state = NULL;
init_done = false;
}
StateManager::~StateManager() {
deallocate();
}
bool StateManager::init(size_t buffer_size) {
init_done = false;
deallocate();
real_state_size = S9xFreezeSize();
state_size = real_state_size / sizeof(uint32_t); // Works in multiple of 4.
// We need 4-byte aligned state_size to avoid having to enforce this with unneeded memcpy's!
if(real_state_size % sizeof(uint32_t)) state_size ++;
if (buffer_size <= real_state_size) // Need a sufficient buffer size.
return false;
top_ptr = 1;
buf_size = nearest_pow2_size(buffer_size) / sizeof(uint64_t); // Works in multiple of 8.
buf_size_mask = buf_size - 1;
if (!(buffer = new uint64_t[buf_size]))
return false;
if (!(tmp_state = new uint32_t[state_size]))
return false;
if (!(in_state = new uint32_t[state_size]))
return false;
memset(tmp_state,0,state_size * sizeof(uint32_t));
memset(in_state,0,state_size * sizeof(uint32_t));
init_done = true;
return true;
}
int StateManager::pop()
{
if(!init_done)
return 0;
if (first_pop)
{
first_pop = false;
return S9xUnfreezeGameMem((uint8 *)tmp_state,real_state_size);
}
top_ptr = (top_ptr - 1) & buf_size_mask;
if (top_ptr == bottom_ptr) // Our stack is completely empty... :v
{
top_ptr = (top_ptr + 1) & buf_size_mask;
return 0;
}
while (buffer[top_ptr])
{
// Apply the xor patch.
uint32_t addr = buffer[top_ptr] >> 32;
uint32_t xor_ = buffer[top_ptr] & 0xFFFFFFFFU;
tmp_state[addr] ^= xor_;
top_ptr = (top_ptr - 1) & buf_size_mask;
}
if (top_ptr == bottom_ptr) // Our stack is completely empty... :v
{
top_ptr = (top_ptr + 1) & buf_size_mask;
}
return S9xUnfreezeGameMem((uint8 *)tmp_state,real_state_size);
}
void StateManager::reassign_bottom()
{
bottom_ptr = (top_ptr + 1) & buf_size_mask;
while (buffer[bottom_ptr]) // Skip ahead until we find the first 0 (boundary for state delta).
bottom_ptr = (bottom_ptr + 1) & buf_size_mask;
}
void StateManager::generate_delta(const void *data)
{
bool crossed = false;
const uint32_t *old_state = tmp_state;
const uint32_t *new_state = (const uint32_t*)data;
buffer[top_ptr++] = 0; // For each separate delta, we have a 0 value sentinel in between.
top_ptr &= buf_size_mask;
// Check if top_ptr and bottom_ptr crossed each other, which means we need to delete old cruft.
if (top_ptr == bottom_ptr)
crossed = true;
for (uint64_t i = 0; i < 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_)
{
buffer[top_ptr] = (i << 32) | xor_;
top_ptr = (top_ptr + 1) & buf_size_mask;
if (top_ptr == bottom_ptr)
crossed = true;
}
}
if (crossed)
reassign_bottom();
}
bool StateManager::push()
{
if(!init_done)
return false;
if(!S9xFreezeGameMem((uint8 *)in_state,real_state_size))
return false;
generate_delta(in_state);
uint32 *tmp = tmp_state;
tmp_state = in_state;
in_state = tmp;
first_pop = true;
return true;
}