/*
  libco.arm (2016-08-14)
  author: frangarcj
  license: public domain
*/

#define LIBCO_C
#include "libco.h"

#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <psp2/kernel/sysmem.h>
#include <stdio.h>
#include <string.h>
#ifdef __cplusplus
extern "C" {
#endif

static inline int align(int x, int n) {
  return (((x >> n) + 1) << n );
}
#define FOUR_KB_ALIGN(x) align(x, 12)
#define MB_ALIGN(x) align(x, 20)

static thread_local unsigned long co_active_buffer[64];
static thread_local cothread_t co_active_handle = 0;
static void (*co_swap)(cothread_t, cothread_t) = 0;
static int block;
static uint32_t co_swap_function[] = {
  0xe8a16ff0,  /* stmia r1!, {r4-r11,sp,lr} */
  0xe8b0aff0,  /* ldmia r0!, {r4-r11,sp,pc} */
  0xe12fff1e,  /* bx lr                     */
};

void co_init() {
  int ret;
  void *base;

  block = sceKernelAllocMemBlockForVM("libco", MB_ALIGN(FOUR_KB_ALIGN(sizeof co_swap_function)));
  if (block < 0)
  {
    return;
  }
  
  // get base address
  ret = sceKernelGetMemBlockBase(block, &base);
  if (ret < 0)
  {
    return;
  }

  // set domain to be writable by user
  ret = sceKernelOpenVMDomain();
  if (ret < 0)
  {
    return;
  }


  memcpy(base,co_swap_function,sizeof co_swap_function);

  // set domain back to read-only
  ret = sceKernelCloseVMDomain();
  if (ret < 0)
  {
    return;
  }

  // flush icache
  ret = sceKernelSyncVMDomain(block, base, MB_ALIGN(FOUR_KB_ALIGN(sizeof co_swap_function)));
  if (ret < 0)
  {
    return;
  }
  
  co_swap = (void (*)(cothread_t, cothread_t))base;
  

}

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)) {
  unsigned long* handle = 0;
  if(!co_swap) {
    co_init();
  }
  if(!co_active_handle) co_active_handle = &co_active_buffer;
  size += 256;
  size &= ~15;

  if((handle = (unsigned long*)malloc(size))) {
    unsigned long* p = (unsigned long*)((unsigned char*)handle + size);
    handle[8] = (unsigned long)p;
    handle[9] = (unsigned long)entrypoint;
  }

  return handle;
}

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

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

#ifdef __cplusplus
}
#endif