at91/libat91/xmodem.c

/*-
 * Copyright (c) 2006 M. Warner Losh.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software is derived from software provide by Kwikbyte who specifically
 * disclaimed copyright on the code.  This version of xmodem has been nearly
 * completely rewritten, but the CRC is from the original.
 *
 * $FreeBSD$
 */

#include "lib.h"

#define PACKET_SIZE 128

/* Line control codes */
#define SOH         0x01    /* start of header */
#define ACK         0x06    /* Acknowledge */
#define NAK         0x15    /* Negative acknowledge */
#define CAN         0x18    /* Cancel */
#define EOT         0x04    /* end of text */

#define TO  10
/*
 * int GetRecord(char , char *)
 *  This private function receives a x-modem record to the pointer and
 * returns non-zero on success.
 */
static int
GetRecord(char blocknum, char *dest)
{
    int     size;
    int     ch;
    unsigned    chk, j;

    chk = 0;

    if ((ch = getc(TO)) == -1)
        goto err;
    if (ch != blocknum)
        goto err;
    if ((ch = getc(TO)) == -1)
        goto err;
    if (ch != (~blocknum & 0xff))
        goto err;

    for (size = 0; size < PACKET_SIZE; ++size) {
        if ((ch = getc(TO)) == -1)
            goto err;
        chk = chk ^ ch << 8;
        for (j = 0; j < 8; ++j) {
            if (chk & 0x8000)
                chk = chk << 1 ^ 0x1021;
            else
                chk = chk << 1;
        }
        *dest++ = ch;
    }

    chk &= 0xFFFF;

    if (((ch = getc(TO)) == -1) || ((ch & 0xff) != ((chk >> 8) & 0xFF)))
        goto err;
    if (((ch = getc(TO)) == -1) || ((ch & 0xff) != (chk & 0xFF)))
        goto err;
    putchar(ACK);

    return (1);
err:;
    putchar(CAN);
    // We should allow for resend, but we don't.
    return (0);
}

/*
 * int xmodem_rx(char *)
 *  This global function receives a x-modem transmission consisting of
 * (potentially) several blocks.  Returns the number of bytes received or
 * -1 on error.
 */
int
xmodem_rx(char *dest)
{
    int     starting, ch;
    char        packetNumber, *startAddress = dest;

    packetNumber = 1;
    starting = 1;

    while (1) {
        if (starting)
            putchar('C');
        if (((ch = getc(1)) == -1) || (ch != SOH && ch != EOT))
            continue;
        if (ch == EOT) {
            putchar(ACK);
            return (dest - startAddress);
        }
        starting = 0;
        // Xmodem packets: SOH PKT# ~PKT# 128-bytes CRC16
        if (!GetRecord(packetNumber, dest))
            return (-1);
        dest += PACKET_SIZE;
        packetNumber++;
    }

    // the loop above should return in all cases
    return (-1);
}