Add initial state manager code.

rewind.c

@@ -0,0 +1,165 @@
+/*  SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
+ *  Copyright (C) 2010-2011 - Hans-Kristian Arntzen
+ *
+ *  Some code herein may be based on code found in BSNES.
+ * 
+ *  SSNES 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.
+ *
+ *  SSNES 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 SSNES.
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "rewind.h"
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+struct state_manager
+{
+   uint64_t *buffer;
+   size_t buf_size;
+   uint32_t *tmp_state;
+   uint32_t *scratch_buf;
+   size_t top_ptr;
+   size_t bottom_ptr;
+   size_t state_size;
+};
+
+state_manager_t *state_manager_new(size_t state_size, size_t buffer_size, void *init_buffer)
+{
+   if (buffer_size <= state_size * 2 + 1) // Need a sufficient buffer size.
+      return NULL;
+
+   state_manager_t *state = calloc(1, sizeof(*state));
+   if (!state)
+      return NULL;
+
+   state->top_ptr = 1;
+   state->state_size = (state_size + 3) >> 2; // Multiple of 4.
+   state->buf_size = (buffer_size + 7) >> 3; // Multiple of 8.
+   if (!(state->buffer = calloc(1, state->buf_size * sizeof(uint64_t))))
+      goto error;
+   if (!(state->tmp_state = calloc(1, state->state_size * sizeof(uint32_t))))
+      goto error;
+   if (!(state->scratch_buf = 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->scratch_buf);
+      free(state);
+   }
+   return NULL;
+}
+
+void state_manager_free(state_manager_t *state)
+{
+   free(state->buffer);
+   free(state->tmp_state);
+   free(state->scratch_buf);
+   free(state);
+}
+
+bool state_manager_pop(state_manager_t *state, void **data)
+{ 
+   *data = state->tmp_state;
+
+   if (state->top_ptr == 0)
+      state->top_ptr = state->buf_size - 1;
+   else
+      state->top_ptr--;
+
+   if (state->top_ptr == state->bottom_ptr) // Our stack is completely empty... :v
+   {
+      state->top_ptr = (state->top_ptr + 1) % state->buf_size;
+      print_status(state);
+      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;
+
+      if (state->top_ptr == 0)
+         state->top_ptr = state->buf_size - 1;
+      else
+         state->top_ptr--;
+   }
+
+   if (state->top_ptr == state->bottom_ptr) // Our stack is completely empty... :v
+   {
+      state->top_ptr = (state->top_ptr + 1) % state->buf_size;
+      print_status(state);
+      return true;
+   }
+
+   print_status(state);
+   return true;
+}
+
+static void reassign_bottom(state_manager_t *state)
+{
+   state->bottom_ptr = (state->top_ptr + 1) % state->buf_size;
+   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;
+}
+
+static void generate_delta(state_manager_t *state, const void *data, bool aligned)
+{
+   bool crossed = false;
+   const uint32_t *old_state = state->tmp_state;
+   uint32_t *new_state = aligned ? (uint32_t*)data : state->scratch_buf;
+   if (!aligned)
+      memcpy(new_state, data, state->state_size * sizeof(uint32_t)); // If not guaranteed to be aligned, we need to make sure it is.
+
+   state->buffer[state->top_ptr++] = 0; // For each separate delta, we have a 0 value sentinel in between.
+   if (state->top_ptr == state->bottom_ptr) // Check if top_ptr and bottom_ptr crossed eachother, which means we need to delete old cruft.
+      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;
+
+         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, bool aligned)
+{
+   generate_delta(state, data, aligned);
+   memcpy(state->tmp_state, data, state->state_size * sizeof(uint32_t));
+
+   print_status(state);
+
+   return true;
+}
+

rewind.h

@@ -0,0 +1,30 @@
+/*  SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
+ *  Copyright (C) 2010-2011 - Hans-Kristian Arntzen
+ *
+ *  Some code herein may be based on code found in BSNES.
+ * 
+ *  SSNES 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.
+ *
+ *  SSNES 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 SSNES.
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __SSNES_REWIND_H
+#define __SSNES_REWIND_H
+
+#include <stddef.h>
+
+typedef struct state_manager state_manager_t;
+
+state_manager_t *state_manager_new(size_t state_size, size_t buffer_size, void *init_buffer);
+void state_manager_free(state_manager_t *state);
+bool state_manager_pop(state_manager_t *state, void **data);
+bool state_manager_push(state_manager_t *state, const void *data, bool aligned);
+
+#endif