/*
** $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;
}


