BizHawk/waterbox/libco/amd64.c

/*
  libco.amd64 (2016-09-14)
  author: byuu
  license: public domain
*/

#define LIBCO_C
#include "libco.h"

#include <assert.h>
#include <stdlib.h>
#include <string.h>

#ifdef __cplusplus
extern "C" {
#endif

static long long co_active_buffer[64];
static cothread_t co_active_handle = 0;

static void* smalloc(size_t size)
{
  char* ret = malloc(size + 16);
  if (ret)
  {
    *(size_t*)ret = size;
    return ret + 16;
  }
  return NULL;
}

static void sfree(void* ptr)
{
  char* original = (char*)ptr - 16;
  size_t size = *(size_t*)original + 16;
  memset(original, 0, size);
  free(original);
}

extern void co_swap(cothread_t, cothread_t);

static void crash() {
  assert(0);  /* called only if cothread_t entrypoint returns */
}

void co_clean() {
  memset(co_active_buffer, 0, sizeof(co_active_buffer));
}

cothread_t co_active() {
  if(!co_active_handle) co_active_handle = &co_active_buffer;
  return co_active_handle;
}

cothread_t co_create(unsigned int size, void (*entrypoint)(void)) {
  cothread_t handle;
  if(!co_active_handle) co_active_handle = &co_active_buffer;
  size += 512;  /* allocate additional space for storage */
  size &= ~15;  /* align stack to 16-byte boundary */

  if(handle = (cothread_t)smalloc(size)) {
    long long *p = (long long*)((char*)handle + size);  /* seek to top of stack */
    *--p = (long long)crash;                            /* crash if entrypoint returns */
    *--p = (long long)entrypoint;                       /* start of function */
    *(long long*)handle = (long long)p;                 /* stack pointer */
  }

  return handle;
}

void co_delete(cothread_t handle) {
  sfree(handle);
}

void co_switch(cothread_t handle) {
  register cothread_t co_previous_handle = co_active_handle;
  co_swap(co_active_handle = handle, co_previous_handle);
}

#ifdef __cplusplus
}
#endif