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/*
** $Id: lzio.c,v 1.35 2012/05/14 13:34:18 roberto Exp $
** Buffered streams
** 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;  /* 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 --- */
size_t luaZ_read (ZIO *z, void *b, size_t n) {
	while (n) {
	size_t m;
	if (z->n == 0) {  /* no bytes in buffer? */
		if (luaZ_fill(z) == EOZ)  /* try to read more */
		return n;  /* no more input; return number of missing bytes */
		else {
		z->n++;  /* luaZ_fill consumed first byte; put it back */
		z->p--;
		}
	}
	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;
}