/*

** $Id: lzio.c $

** Buffered streams

** See Copyright Notice in lua.h

*/

#define lzio_c

#define LUA_CORE

#include "lprefix.h"

#include <string.h>

#include "lua.h"

#include "lapi.h"

#include "llimits.h"

#include "lmem.h"

#include "lstate.h"

#include "lzio.h"

int luaZ_fill (ZIO *z) {

  size_t size;

  lua_State *L = z->L;

  const char *buff;

  lua_unlock(L);

  buff = z->reader(L, z->data, &size);

  lua_lock(L);

  if (buff == NULL || size == 0)

    return EOZ;

  z->n = size - 1;  /* discount char being returned */

  z->p = buff;

  return cast_uchar(*(z->p++));

}

void luaZ_init (lua_State *L, ZIO *z, lua_Reader reader, void *data) {

  z->L = L;

  z->reader = reader;

  z->data = data;

  z->n = 0;

  z->p = NULL;

}

/* --------------------------------------------------------------- read --- */

static int checkbuffer (ZIO *z) {

  if (z->n == 0) {  /* no bytes in buffer? */

    if (luaZ_fill(z) == EOZ)  /* try to read more */

      return 0;  /* no more input */

    else {

      z->n++;  /* luaZ_fill consumed first byte; put it back */

      z->p--;

    }

  }

  return 1;  /* now buffer has something */

}

size_t luaZ_read (ZIO *z, void *b, size_t n) {

  while (n) {

    size_t m;

    if (!checkbuffer(z))

      return n;  /* no more input; return number of missing bytes */

    m = (n <= z->n) ? n : z->n;  /* min. between n and z->n */

    memcpy(b, z->p, m);

    z->n -= m;

    z->p += m;

    b = (char *)b + m;

    n -= m;

  }

  return 0;

}

const void *luaZ_getaddr (ZIO* z, size_t n) {

  const void *res;

  if (!checkbuffer(z))

    return NULL;  /* no more input */

  if (z->n < n)  /* not enough bytes? */

    return NULL;  /* block not whole; cannot give an address */

  res = z->p;  /* get block address */

  z->n -= n;  /* consume these bytes */

  z->p += n;

  return res;

}