xmodem.c

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#include "xmodem.h"

#include "cfg/cfg_xmodem.h"
#include <cfg/debug.h>

#include <algo/crc.h>

#include <string.h> /* for memset() */

#define XM_SOH  0x01  
#define XM_STX  0x02  
#define XM_EOT  0x04  
#define XM_ACK  0x06  
#define XM_NAK  0x15  
#define XM_C    0x43  
#define XM_CAN  0x18  
/*\}*/

#if CONFIG_XMODEM_1KCRC == 1
    #define XM_BUFSIZE       1024  
#else
    #define XM_BUFSIZE       128   
#endif


#if CONFIG_XMODEM_RECV

bool xmodem_recv(KFile *ch, KFile *fd)
{
    char block_buffer[XM_BUFSIZE]; /* Buffer to hold a block of data */
    int c, i, blocksize;
    int blocknr = 0, last_block_done = 0, retries = 0;
    char *buf;
    uint8_t checksum;
    uint16_t crc;
    bool purge = false;
    bool usecrc = true;


    XMODEM_PROGRESS("Starting Transfer...\n");
    purge = true;
    kfile_clearerr(ch);

    /* Send initial NAK to start transmission */
    for(;;)
    {
        if (XMODEM_CHECK_ABORT)
        {
            kfile_putc(XM_CAN, ch);
            kfile_putc(XM_CAN, ch);
            XMODEM_PROGRESS("Transfer aborted\n");
            return false;
        }

        /*
         * Discard incoming input until a timeout occurs, then send
         * a NAK to the transmitter.
         */
        if (purge)
        {
            purge = false;

            if (kfile_error(ch))
                XMODEM_PROGRESS("Retries %d\n", retries);

            kfile_resync(ch, 200);
            retries++;

            if (retries >= CONFIG_XMODEM_MAXRETRIES)
            {
                kfile_putc(XM_CAN, ch);
                kfile_putc(XM_CAN, ch);
                XMODEM_PROGRESS("Transfer aborted\n");
                return false;
            }

            /* Transmission start? */
            if (blocknr == 0)
            {
                if (retries < CONFIG_XMODEM_MAXCRCRETRIES)
                {
                    XMODEM_PROGRESS("Request Tx (CRC)\n");
                    kfile_putc(XM_C, ch);
                }
                else
                {
                    /* Give up with CRC and fall back to checksum */
                    usecrc = false;
                    XMODEM_PROGRESS("Request Tx (BCC)\n");
                    kfile_putc(XM_NAK, ch);
                }
            }
            else
                kfile_putc(XM_NAK, ch);
        }

        switch (kfile_getc(ch))
        {
        #if XM_BUFSIZE >= 1024
        case XM_STX:  /* Start of header (1024-byte block) */
            blocksize = 1024;
            goto getblock;
        #endif

        case XM_SOH:  /* Start of header (128-byte block) */
            blocksize = 128;
            /* Needed to avoid warning if XM_BUFSIZE < 1024 */

        getblock:
            /* Get block number */
            c = kfile_getc(ch);

            /* Check complemented block number */
            if ((~c & 0xff) != kfile_getc(ch))
            {
                XMODEM_PROGRESS("Bad blk (%d)\n", c);
                purge = true;
                break;
            }

            /* Determine which block is being sent */
            if (c == (blocknr & 0xff))
                /* Last block repeated */
                XMODEM_PROGRESS("Repeat blk %d\n", blocknr);
            else if (c == ((blocknr + 1) & 0xff))
                /* Next block */
                XMODEM_PROGRESS("Recv blk %d\n", ++blocknr);
            else
            {
                /* Sync lost */
                XMODEM_PROGRESS("Sync lost (%d/%d)\n", c, blocknr);
                purge = true;
                break;
            }

            buf = block_buffer; /* Reset pointer to start of buffer */
            checksum = 0;
            crc = 0;
            for (i = 0; i < blocksize; i++)
            {
                if ((c = kfile_getc(ch)) == EOF)
                {
                    purge = true;
                    break;
                }

                /* Store in buffer */
                *buf++ = (char)c;

                /* Calculate block checksum or CRC */
                if (usecrc)
                    crc = UPDCRC16(c, crc);
                else
                    checksum += (char)c;
            }

            if (purge)
                break;

            /* Get the checksum byte or the CRC-16 MSB */
            if ((c = kfile_getc(ch)) == EOF)
            {
                purge = true;
                break;
            }

            if (usecrc)
            {
                crc = UPDCRC16(c, crc);

                /* Get CRC-16 LSB */
                if ((c = kfile_getc(ch)) == EOF)
                {
                    purge = true;
                    break;
                }

                crc = UPDCRC16(c, crc);

                if (crc)
                {
                    XMODEM_PROGRESS("Bad CRC: %04x\n", crc);
                    purge = true;
                    break;
                }
            }
            /* Compare the checksum */
            else if (c != checksum)
            {
                XMODEM_PROGRESS("Bad sum: %04x/%04x\n", checksum, c);
                purge = true;
                break;
            }

            /*
             * Avoid flushing the same block twice.
             * This could happen when the sender does not receive our
             * acknowledge and resends the same block.
             */
            if (last_block_done < blocknr)
            {
                /* Call user function to flush the buffer */
                if (kfile_write(fd, block_buffer, blocksize))
                {
                    /* Acknowledge block and clear error counter */
                    kfile_putc(XM_ACK, ch);
                    retries = 0;
                    last_block_done = blocknr;
                }
                else
                {
                    /* User callback failed: abort transfer immediately */
                    retries = CONFIG_XMODEM_MAXRETRIES;
                    purge = true;
                }
            }
            break;

        case XM_EOT:    /* End of transmission */
            kfile_putc(XM_ACK, ch);
            XMODEM_PROGRESS("Transfer completed\n");
            return true;

        case EOF: /* Timeout or serial error */
            purge = true;
            break;

        default:
            XMODEM_PROGRESS("Skipping garbage\n");
            purge = true;
            break;
        }
    } /* End forever */
}
#endif


#if CONFIG_XMODEM_SEND

bool xmodem_send(KFile *ch, KFile *fd)
{
    char block_buffer[XM_BUFSIZE]; /* Buffer to hold a block of data */
    size_t size = -1;
    int blocknr = 1, retries = 0, c, i;
    bool proceed, usecrc = false;
    uint16_t crc;
    uint8_t sum;

    /*
     * Reading a block can be very slow, so we read the first block early
     * to avoid receiving double XM_C char.
     * This could happen if we check for XM_C and then read the block, giving
     * the receiving device time to send another XM_C char misinterpretating
     * the blocks sent.
     */
    size = kfile_read(fd, block_buffer, XM_BUFSIZE);

    kfile_clearerr(ch);
    XMODEM_PROGRESS("Wait remote host\n");

    for(;;)
    {
        proceed = false;
        do
        {
            if (XMODEM_CHECK_ABORT)
                return false;

            switch (c = kfile_getc(ch))
            {
            case XM_NAK:
                XMODEM_PROGRESS("Resend blk %d\n", blocknr);
                proceed = true;
                break;

            case XM_C:
                if (c == XM_C)
                {
                    XMODEM_PROGRESS("Tx start (CRC)\n");
                    usecrc = true;
                }
                else
                    XMODEM_PROGRESS("Tx start (BCC)\n");

                proceed = true;
                break;

            case XM_ACK:
                /* End of transfer? */
                if (!size)
                    return true;

                /* Call user function to read in one block */
                size = kfile_read(fd, block_buffer, XM_BUFSIZE);
                XMODEM_PROGRESS("Send blk %d\n", blocknr);
                blocknr++;
                retries = 0;
                proceed = true;
                break;

            case EOF:
                kfile_clearerr(ch);
                retries++;
                XMODEM_PROGRESS("Retries %d\n", retries);
                if (retries <= CONFIG_XMODEM_MAXRETRIES)
                    break;
                /* falling through! */

            case XM_CAN:
                XMODEM_PROGRESS("Transfer aborted\n");
                return false;

            default:
                XMODEM_PROGRESS("Skipping garbage\n");
                break;
            }
        }
        while (!proceed);

        if (!size)
        {
            kfile_putc(XM_EOT, ch);
            continue;
        }

        /* Pad block with 0xFF if it's partially full */
        memset(block_buffer + size, 0xFF, XM_BUFSIZE - size);

        /* Send block header (STX, blocknr, ~blocknr) */
        #if XM_BUFSIZE == 128
            kfile_putc(XM_SOH, ch);
        #else
            kfile_putc(XM_STX, ch);
        #endif
        kfile_putc(blocknr & 0xFF, ch);
        kfile_putc(~blocknr & 0xFF, ch);

        /* Send block and compute its CRC/checksum */
        sum = 0;
        crc = 0;
        for (i = 0; i < XM_BUFSIZE; i++)
        {
            kfile_putc(block_buffer[i], ch);
            crc = UPDCRC16(block_buffer[i], crc);
            sum += block_buffer[i];
        }

        /* Send CRC/Checksum */
        if (usecrc)
        {
            crc = UPDCRC16(0, crc);
            crc = UPDCRC16(0, crc);
            kfile_putc(crc >> 8, ch);
            kfile_putc(crc & 0xFF, ch);
        }
        else
            kfile_putc(sum, ch);
    }
}
#endif