#include "brk_shim.h"

#include <errno.h>

/*
 * The idea is to just allocate a large buffer and rely on lazy page
 * loading to not use more physical memory than necessary.
 */

#ifdef LARGEF
#define SHIMSIZE 0x4000000
/* 64MB */
#else
#define SHIMSIZE 0x200000
/* 2MB */
#endif

static char shim_space[SHIMSIZE];
static intptr_t shim_size = 0;

void *shim_sbrk(intptr_t increment) {
  void* current = (void*)(shim_space + shim_size);
  shim_size += increment;
  if (shim_size < 0) {
    shim_size = 0;
    return (void*)-1;
  } else if (shim_size > SHIMSIZE) {
    shim_size = SHIMSIZE;
    return (void*)-1;
  }
  return current;
}

int shim_brk(void* addr) {
  if (addr < (void*)shim_space ||
      addr > (void*)(shim_space + SHIMSIZE)) {
    errno = EINVAL;
    return -1;    
  }
  shim_size = ((void*)shim_space) - addr;
  return 0;
}