/* Experimental code, extends Lua
 * 02/02/2001 info@equi4.com
 */
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <io.h>
#include <fcntl.h>
#include <sys/stat.h>
#else
#include <sys/types.h>
#include <sys/mman.h>
#endif
#include <malloc.h>
/* prototype */
LUALIB_API void xyzlib_open(lua_State *L);
/* TODO: get rid of static ints, use closures instead */
static int xyzmemtag;
/* xyz_Type - type of memory chunks */
enum { xyz_raw, xyz_heap, xyz_str, xyz_file };
/* xyz_Mem - userdata for each memmap */
typedef struct {
  char *ptr;
  size_t len;
  int type;
  union { FILE* fp; int ref; } u;
} xyz_Mem;
/* xyz_memhandle - type-safe conversion of userdata to xyz_Mem ptr */
static xyz_Mem* xyz_memhandle(lua_State *L, int f) {
  void *p = lua_touserdata(L, f);
  if (p == NULL || lua_tag(L, f) != xyzmemtag)
    lua_error(L, "wrong type - mem map expected");
  return p;
}
/* xyz_mmclose - close memmap, cleaning up as appropriate */
static int xyz_mmclose(lua_State *L) {
  xyz_Mem *m = (xyz_Mem*) xyz_memhandle(L, -1);
  switch (m->type) {
    case xyz_heap: free(m->ptr); break;
    case xyz_str: lua_unref(L, m->u.ref); break;
    case xyz_file:
#ifdef WIN32
      UnmapViewOfFile(m->ptr);
#else
      munmap(m->ptr, m->len);
#endif
      fclose(m->u.fp); break;
  }
  m->type = xyz_raw;
  m->ptr = 0;
  m->len = 0;
  return 0;
}
/* xyz_newmem - create a new memmap, as userdata structure */
static xyz_Mem *xyz_newmem(lua_State *L, int t, char *p, size_t n) {
  xyz_Mem *m = (xyz_Mem*) lua_newuserdata(L, sizeof (xyz_Mem));
  lua_settag(L, xyzmemtag);
  m->type = t;
  m->ptr = p;
  m->len = n;
  return m; /* also leaves new userdata on stack */
}
/* xyz_mmraw - create a memmap from raw memory (dangerous) */
static int xyz_mmraw(lua_State *L) {
  void* ptr = (void*) luaL_check_long(L, 1);
  size_t len = luaL_check_long(L, 2);
  (void) xyz_newmem(L, xyz_raw, ptr, len);
  return 1;
}
/* xyz_mmheap - create a memmap from an allocated chunk of memory */
static int xyz_mmheap(lua_State *L) {
  size_t len = luaL_check_long(L, 1);
  (void) xyz_newmem(L, xyz_heap, malloc(len), len);
  return 1;
}
/* xyz_mmstr - create a memmap from a Lua string (shares memory) */
static int xyz_mmstr(lua_State *L) {
  size_t len;
  char *ptr = (char*) luaL_check_lstr(L, -1, &len);
  int ref = lua_ref(L, 1);
  xyz_Mem *m = xyz_newmem(L, xyz_str, ptr, len);
  m->u.ref = ref;
  return 1;
}
/* xyz_mmfile - create a memmap from a file, specified by name */
static int xyz_mmfile(lua_State *L) {
  char *ptr;
  size_t len;
  xyz_Mem *m;
  FILE *fp = fopen(luaL_check_string(L, 1), "rb");
  if (fp == NULL) lua_error(L, "cannot open file");
  fseek(fp, 0, SEEK_END);
  len = ftell(fp);
#ifdef WIN32
  {
    HANDLE h = CreateFileMapping((HANDLE) _get_osfhandle(_fileno(fp)), 0, PAGE_READONLY, 0, len, 0);
    ptr = h ? MapViewOfFile(h, FILE_MAP_READ, 0, 0, len) : NULL;
  }
#else
  ptr = mmap(0, len, PROT_READ, MAP_PRIVATE, fileno(fp), 0);
#endif
  if (ptr == NULL) {
    fclose(fp);
    lua_error(L, "cannot map file");
  }
  m = xyz_newmem(L, xyz_file, ptr, len);
  m->u.fp = fp;
  return 1;
}
/* xyz_mminfo - return type, address, and length of this memmap */
static int xyz_mminfo(lua_State *L) {
  xyz_Mem *m = xyz_memhandle(L, 1);
  if (m->len <= 0) return 0;
  lua_pushnumber(L, (long) m->ptr);
  lua_pushnumber(L, m->len);
  lua_pushnumber(L, m->type);
  return 3;
}
/* xyz_mmsub - return a sub-string copy made from this memmap */
static int xyz_mmsub(lua_State *L) {
  xyz_Mem *m = xyz_memhandle(L, 1);
  int i = luaL_opt_int(L, 2, 1);
  int j = luaL_opt_int(L, 3, -1);
  /* note: the following code also converts to 0-based [i..j) */
  i += i < 0 ? m->len : -1;
  if (j < 0) j += m->len + 1;
  /* if (i < 0 || j > m->len || i > j) return 0; */
  if (i < 0) i = 0;
  if (j > m->len) j = m->len;
  if (i > j) i = j;
  lua_pushlstring(L, m->ptr + i, j - i);
  return 1;
}
/* xyz_xyzlibvers - get at the library version info and such */
static int xyz_xyzlibvers(lua_State *L) {
  lua_pushstring(L, __DATE__);
  lua_pushnumber(L, 8);
  lua_pushnumber(L, xyzmemtag);
  return 4;
}
/* xyzlib - functions defined in this extension */
static struct luaL_reg xyzlib[] = {
  {"mmraw", xyz_mmraw},
  {"mmheap", xyz_mmheap},
  {"mmstr", xyz_mmstr},
  {"mmfile", xyz_mmfile},
  {"mmclose", xyz_mmclose},
  {"mminfo", xyz_mminfo},
  {"mmsub", xyz_mmsub},
  {"xyzlibvers", xyz_xyzlibvers},
};
/* xyzlib_open - the one and only public entry point */
void xyzlib_open(lua_State *L) {
  xyzmemtag = lua_newtag(L);
  lua_pushcfunction(L, xyz_mmclose);
  lua_settagmethod(L, xyzmemtag, "gc");
  luaL_openl(L, xyzlib);
}