source: MondoRescue/branches/3.2/mindi-busybox/miscutils/rx.c

/* vi: set sw=4 ts=4: */
/*
 * 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 functionality for uploading of kernels and the like
 *
 * Copyright (C) 2001 Hewlett-Packard Laboratories
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * This was originally written for blob and then adapted for busybox.
 */

//usage:#define rx_trivial_usage
//usage:       "FILE"
//usage:#define rx_full_usage "\n\n"
//usage:       "Receive a file using the xmodem protocol"
//usage:
//usage:#define rx_example_usage
//usage:       "$ rx /tmp/foo\n"

#include "libbb.h"

#define SOH 0x01
#define STX 0x02
#define EOT 0x04
#define ACK 0x06
#define NAK 0x15
#define BS  0x08
#define PAD 0x1A

/*
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

#define read_fd  STDIN_FILENO
#define write_fd STDOUT_FILENO

static int read_byte(unsigned timeout)
{
    unsigned char buf;
    int n;

    alarm(timeout);
    /* NOT safe_read! We want ALRM to interrupt us */
    n = read(read_fd, &buf, 1);
    alarm(0);
    if (n == 1)
        return buf;
    return -1;
}

static int receive(/*int read_fd, */int file_fd)
{
    unsigned char blockBuf[1024];
    unsigned blockLength = 0;
    unsigned errors = 0;
    unsigned wantBlockNo = 1;
    unsigned length = 0;
    int do_crc = 1;
    char reply_char;
    unsigned timeout = TIMEOUT_LONG;

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

    /* Ask for CRC; if we get errors, we will go with checksum */
    reply_char = 'C';
    full_write(write_fd, &reply_char, 1);

    for (;;) {
        int blockBegin;
        int blockNo, blockNoOnesCompl;
        int cksum_or_crc;
        int expected;
        int i, j;

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

        /* If last block, remove padding */
        if (blockBegin == EOT) {
            /* Data blocks can be padded with ^Z characters */
            /* This code tries to detect and remove them */
            if (blockLength >= 3
             && blockBuf[blockLength - 1] == PAD
             && blockBuf[blockLength - 2] == PAD
             && blockBuf[blockLength - 3] == PAD
            ) {
                while (blockLength
                       && blockBuf[blockLength - 1] == PAD
                ) {
                    blockLength--;
                }
            }
        }
        /* Write previously received block */
        errno = 0;
        if (full_write(file_fd, blockBuf, blockLength) != blockLength) {
            bb_perror_msg(bb_msg_write_error);
            goto fatal;
        }

        timeout = TIMEOUT;
        reply_char = NAK;

        switch (blockBegin) {
        case SOH:
        case STX:
            break;
        case EOT:
            reply_char = ACK;
            full_write(write_fd, &reply_char, 1);
            return length;
        default:
            goto error;
        }

        /* Block no */
        blockNo = read_byte(TIMEOUT);
        if (blockNo < 0)
            goto timeout;

        /* Block no, in one's complement form */
        blockNoOnesCompl = read_byte(TIMEOUT);
        if (blockNoOnesCompl < 0)
            goto timeout;

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

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

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

        cksum_or_crc = read_byte(TIMEOUT);
        if (cksum_or_crc < 0)
            goto timeout;
        if (do_crc) {
            cksum_or_crc = (cksum_or_crc << 8) | read_byte(TIMEOUT);
            if (cksum_or_crc < 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. */
            blockLength = 0;
            goto next;
        }
        if (blockNo != (wantBlockNo & 0xff)) {
            bb_error_msg("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
            goto error;
        }

        expected = 0;
        if (do_crc) {
            for (i = 0; i < blockLength; i++) {
                expected = expected ^ blockBuf[i] << 8;
                for (j = 0; j < 8; j++) {
                    if (expected & 0x8000)
                        expected = (expected << 1) ^ 0x1021;
                    else
                        expected = (expected << 1);
                }
            }
            expected &= 0xffff;
        } else {
            for (i = 0; i < blockLength; i++)
                expected += blockBuf[i];
            expected &= 0xff;
        }
        if (cksum_or_crc != expected) {
            bb_error_msg(do_crc ? "crc error, expected 0x%04x, got 0x%04x"
                    : "checksum error, expected 0x%02x, got 0x%02x",
                expected, cksum_or_crc);
            goto error;
        }

        wantBlockNo++;
        length += blockLength;
 next:
        errors = 0;
        reply_char = ACK;
        full_write(write_fd, &reply_char, 1);
        continue;
 error:
 timeout:
        blockLength = 0;
        errors++;
        if (errors == MAXERRORS) {
            /* Abort */

            /* If were asking for crc, try again w/o crc */
            if (reply_char == 'C') {
                reply_char = NAK;
                errors = 0;
                do_crc = 0;
                goto timeout;
            }
            bb_error_msg("too many errors; giving up");
 fatal:
            /* 5 CAN followed by 5 BS. Don't try too hard... */
            safe_write(write_fd, "\030\030\030\030\030\010\010\010\010\010", 10);
            return -1;
        }

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

        full_write(write_fd, &reply_char, 1);
    } /* for (;;) */
}

static void sigalrm_handler(int UNUSED_PARAM signum)
{
}

int rx_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int rx_main(int argc UNUSED_PARAM, char **argv)
{
    struct termios tty, orig_tty;
    int termios_err;
    int file_fd;
    int n;

    /* Disabled by vda:
     * why we can't receive from stdin? Why we *require*
     * controlling tty?? */
    /*read_fd = xopen(CURRENT_TTY, O_RDWR);*/
    file_fd = xopen(single_argv(argv), O_RDWR|O_CREAT|O_TRUNC);

    termios_err = tcgetattr(read_fd, &tty);
    if (termios_err == 0) {
        orig_tty = tty;
        cfmakeraw(&tty);
        tcsetattr(read_fd, TCSAFLUSH, &tty);
    }

    /* No SA_RESTART: we want ALRM to interrupt read() */
    signal_no_SA_RESTART_empty_mask(SIGALRM, sigalrm_handler);

    n = receive(file_fd);

    if (termios_err == 0)
        tcsetattr(read_fd, TCSAFLUSH, &orig_tty);
    if (ENABLE_FEATURE_CLEAN_UP)
        close(file_fd);
    fflush_stdout_and_exit(n >= 0);
}