/***********************************************************
    io.c -- input/output
***********************************************************/
#include "ar.h"
#include <stdlib.h>
#include <stdarg.h>

#define CRCPOLY  0xA001  /* ANSI CRC-16 */
                         /* CCITT: 0x8408 */
#define UPDATE_CRC(c) \
    crc = crctable[(crc ^ (c)) & 0xFF] ^ (crc >> CHAR_BIT)

FILE *arcfile, *infile, *outfile;
uint crc, bitbuf;

static ushort crctable[UCHAR_MAX + 1];
static uint  subbitbuf;
static int   bitcount;

void error(char *fmt, ...)
{
    va_list args;

    va_start(args, fmt);
    putc('\n', stderr);
    vfprintf(stderr, fmt, args);
    putc('\n', stderr);
    va_end(args);
    exit(EXIT_FAILURE);
}

void make_crctable(void)
{
    uint i, j, r;

    for (i = 0; i <= UCHAR_MAX; i++) {
        r = i;
        for (j = 0; j < CHAR_BIT; j++)
            if (r & 1) r = (r >> 1) ^ CRCPOLY;
            else       r >>= 1;
        crctable[i] = r;
    }
}

void fillbuf(int n)  /* Shift bitbuf n bits left, read n bits */
{
    bitbuf <<= n;
    while (n > bitcount) {
        bitbuf |= subbitbuf << (n -= bitcount);
        if (compsize != 0) {
            compsize--;  subbitbuf = (uchar) getc(arcfile);
        } else subbitbuf = 0;
        bitcount = CHAR_BIT;
    }
    bitbuf |= subbitbuf >> (bitcount -= n);
}

uint getbits(int n)
{
    uint x;

    if (n == 0) return 0;
    /* The above line added 2003-03-02.
       unsigned bitbuf used to be 16 bits, but now it's 32 bits,
       and (bitbuf >> 32) is equivalent to (bitbuf >> 0) (at least for ix86 and SPARC).
       Thanks: CheMaRy.
    */

    x = bitbuf >> (BITBUFSIZ - n);  fillbuf(n);
    return x;
}

void putbits(int n, uint x)  /* Write rightmost n bits of x */
{
    if (n < bitcount) {
        subbitbuf |= x << (bitcount -= n);
    } else {
        if (compsize < origsize) {
            putc(subbitbuf | (x >> (n -= bitcount)), outfile);
            compsize++;
        } else unpackable = 1;
        if (n < CHAR_BIT) {
            subbitbuf = x << (bitcount = CHAR_BIT - n);
        } else {
            if (compsize < origsize) {
                putc(x >> (n - CHAR_BIT), outfile);
                compsize++;
            } else unpackable = 1;
            subbitbuf = x << (bitcount = 2 * CHAR_BIT - n);
        }
    }
}

int fread_crc(uchar *p, int n, FILE *f)
{
    int i;

    i = n = fread(p, 1, n, f);  origsize += n;
    while (--i >= 0) UPDATE_CRC(*p++);
    return n;
}

void fwrite_crc(uchar *p, int n, FILE *f)
{
    if (fwrite(p, 1, n, f) < n) error("Unable to write");
    while (--n >= 0) UPDATE_CRC(*p++);
}

void init_getbits(void)
{
    bitbuf = 0;  subbitbuf = 0;  bitcount = 0;
    fillbuf(BITBUFSIZ);
}

void init_putbits(void)
{
    bitcount = CHAR_BIT;  subbitbuf = 0;
}