source: MondoRescue/branches/stable/mindi-busybox/miscutils/rx.c

/* vi: set sw=4 ts=4: */
/*-------------------------------------------------------------------------
 * Filename:      xmodem.c
 * Copyright:     Copyright (C) 2001, Hewlett-Packard Company
 * Author:        Christopher Hoover <ch@hpl.hp.com>
 * Description:   xmodem functionality for uploading of kernels
 *                and the like
 * Created at:    Thu Dec 20 01:58:08 PST 2001
 *-----------------------------------------------------------------------*/
/*
 * xmodem.c: xmodem functionality for uploading of kernels and
 *            the like
 *
 * Copyright (C) 2001 Hewlett-Packard Laboratories
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 *
 * This was originally written for blob and then adapted for busybox.
 *
 */

#include "libbb.h"

#define SOH 0x01
#define STX 0x02
#define EOT 0x04
#define ACK 0x06
#define NAK 0x15
#define BS  0x08

/*

Cf:

  http://www.textfiles.com/apple/xmodem
  http://www.phys.washington.edu/~belonis/xmodem/docxmodem.txt
  http://www.phys.washington.edu/~belonis/xmodem/docymodem.txt
  http://www.phys.washington.edu/~belonis/xmodem/modmprot.col

*/

#define TIMEOUT 1
#define TIMEOUT_LONG 10
#define MAXERRORS 10

static int read_byte(int fd, unsigned int timeout)
{
    char buf[1];
    int n;

    alarm(timeout);

    n = read(fd, &buf, 1);

    alarm(0);

    if (n == 1)
        return buf[0] & 0xff;
    else
        return -1;
}

static int receive(char *error_buf, size_t error_buf_size,
                   int ttyfd, int filefd)
{
    char blockBuf[1024];
    unsigned int errors = 0;
    unsigned int wantBlockNo = 1;
    unsigned int length = 0;
    int docrc = 1;
    char nak = 'C';
    unsigned int timeout = TIMEOUT_LONG;

#define note_error(fmt,args...) \
    snprintf(error_buf, error_buf_size, fmt,##args)

    /* Flush pending input */
    tcflush(ttyfd, TCIFLUSH);

    /* Ask for CRC; if we get errors, we will go with checksum */
    write(ttyfd, &nak, 1);

    for (;;) {
        int blockBegin;
        int blockNo, blockNoOnesCompl;
        int blockLength;
        int cksum = 0;
        int crcHi = 0;
        int crcLo = 0;

        blockBegin = read_byte(ttyfd, timeout);
        if (blockBegin < 0)
            goto timeout;

        timeout = TIMEOUT;
        nak = NAK;

        switch (blockBegin) {
        case SOH:
        case STX:
            break;

        case EOT:
            nak = ACK;
            write(ttyfd, &nak, 1);
            goto done;

        default:
            goto error;
        }

        /* block no */
        blockNo = read_byte(ttyfd, TIMEOUT);
        if (blockNo < 0)
            goto timeout;

        /* block no one's compliment */
        blockNoOnesCompl = read_byte(ttyfd, TIMEOUT);
        if (blockNoOnesCompl < 0)
            goto timeout;

        if (blockNo != (255 - blockNoOnesCompl)) {
            note_error("bad block ones compl");
            goto error;
        }

        blockLength = (blockBegin == SOH) ? 128 : 1024;

        {
            int i;

            for (i = 0; i < blockLength; i++) {
                int cc = read_byte(ttyfd, TIMEOUT);
                if (cc < 0)
                    goto timeout;
                blockBuf[i] = cc;
            }
        }

        if (docrc) {
            crcHi = read_byte(ttyfd, TIMEOUT);
            if (crcHi < 0)
                goto timeout;

            crcLo = read_byte(ttyfd, TIMEOUT);
            if (crcLo < 0)
                goto timeout;
        } else {
            cksum = read_byte(ttyfd, TIMEOUT);
            if (cksum < 0)
                goto timeout;
        }

        if (blockNo == ((wantBlockNo - 1) & 0xff)) {
            /* a repeat of the last block is ok, just ignore it. */
            /* this also ignores the initial block 0 which is */
            /* meta data. */
            goto next;
        } else if (blockNo != (wantBlockNo & 0xff)) {
            note_error("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
            goto error;
        }

        if (docrc) {
            int crc = 0;
            int i, j;
            int expectedCrcHi;
            int expectedCrcLo;

            for (i = 0; i < blockLength; i++) {
                crc = crc ^ (int) blockBuf[i] << 8;
                for (j = 0; j < 8; j++)
                    if (crc & 0x8000)
                        crc = crc << 1 ^ 0x1021;
                    else
                        crc = crc << 1;
            }

            expectedCrcHi = (crc >> 8) & 0xff;
            expectedCrcLo = crc & 0xff;

            if ((crcHi != expectedCrcHi) ||
                (crcLo != expectedCrcLo)) {
                note_error("crc error, expected 0x%02x 0x%02x, got 0x%02x 0x%02x", expectedCrcHi, expectedCrcLo, crcHi, crcLo);
                goto error;
            }
        } else {
            unsigned char expectedCksum = 0;
            int i;

            for (i = 0; i < blockLength; i++)
                expectedCksum += blockBuf[i];

            if (cksum != expectedCksum) {
                note_error("checksum error, expected 0x%02x, got 0x%02x", expectedCksum, cksum);
                goto error;
            }
        }

        wantBlockNo++;
        length += blockLength;

        if (full_write(filefd, blockBuf, blockLength) < 0) {
            note_error("write to file failed: %m");
            goto fatal;
        }

    next:
        errors = 0;
        nak = ACK;
        write(ttyfd, &nak, 1);
        continue;

    error:
    timeout:
        errors++;
        if (errors == MAXERRORS) {
            /* Abort */

            // if using crc, try again w/o crc
            if (nak == 'C') {
                nak = NAK;
                errors = 0;
                docrc = 0;
                goto timeout;
            }

            note_error("too many errors; giving up");

        fatal:
            /* 5 CAN followed by 5 BS */
            write(ttyfd, "\030\030\030\030\030\010\010\010\010\010", 10);
            return -1;
        }

        /* Flush pending input */
        tcflush(ttyfd, TCIFLUSH);

        write(ttyfd, &nak, 1);
    }

 done:
    return length;

#undef note_error
}

static void sigalrm_handler(int ATTRIBUTE_UNUSED signum)
{
}

int rx_main(int argc, char **argv);
int rx_main(int argc, char **argv)
{
    char *fn;
    int ttyfd, filefd;
    struct termios tty, orig_tty;
    struct sigaction act;
    int n;
    char error_buf[256];

    if (argc != 2)
            bb_show_usage();

    fn = argv[1];
    ttyfd = xopen(CURRENT_TTY, O_RDWR);
    filefd = xopen(fn, O_RDWR|O_CREAT|O_TRUNC);

    if (tcgetattr(ttyfd, &tty) < 0)
            bb_perror_msg_and_die("tcgetattr");

    orig_tty = tty;

    cfmakeraw(&tty);
    tcsetattr(ttyfd, TCSAFLUSH, &tty);

    memset(&act, 0, sizeof(act));
    act.sa_handler = sigalrm_handler;
    sigaction(SIGALRM, &act, 0);

    n = receive(error_buf, sizeof(error_buf), ttyfd, filefd);

    close(filefd);

    tcsetattr(ttyfd, TCSAFLUSH, &orig_tty);

    if (n < 0)
        bb_error_msg_and_die("\nreceive failed:\n  %s", error_buf);

    fflush_stdout_and_exit(EXIT_SUCCESS);
}