misc/liblua/lzio.c
author nemo
Thu, 01 Jul 2010 23:41:10 -0400
changeset 3608 c509bbc779e7
parent 2812 0a24853de796
permissions -rw-r--r--
Revert prior attempted optimisation. Gridding the land pays in some situations, but not all. Restricting to an upper bound might help, but overall, seems too fuzzy to be worth it. On one side is increased cost of Add/Delete + extra test on collision check, on the other is skipping the list iteration. Perhaps for large lists.

/*
** $Id: lzio.c,v 1.31.1.1 2007/12/27 13:02:25 roberto Exp $
** a generic input stream interface
** See Copyright Notice in lua.h
*/


#include <string.h>

#define lzio_c
#define LUA_CORE

#include "lua.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;
  z->p = buff;
  return char2int(*(z->p++));
}


int luaZ_lookahead (ZIO *z) {
  if (z->n == 0) {
    if (luaZ_fill(z) == EOZ)
      return EOZ;
    else {
      z->n++;  /* luaZ_fill removed first byte; put back it */
      z->p--;
    }
  }
  return char2int(*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 --- */
size_t luaZ_read (ZIO *z, void *b, size_t n) {
  while (n) {
    size_t m;
    if (luaZ_lookahead(z) == EOZ)
      return n;  /* 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;
}

/* ------------------------------------------------------------------------ */
char *luaZ_openspace (lua_State *L, Mbuffer *buff, size_t n) {
  if (n > buff->buffsize) {
    if (n < LUA_MINBUFFER) n = LUA_MINBUFFER;
    luaZ_resizebuffer(L, buff, n);
  }
  return buff->buffer;
}