ymodem_rx.cpp

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/*
This program is distributed under the terms of the 'MIT license'. The text
of this licence follows...

Copyright (c) 2006 J.D.Medhurst (a.k.a. Tixy)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#include "../common/common.h"
#include "ymodem_rx.h"


#include <string.h> // for memcpy and memset


const unsigned ReceiveTimeout = 1*1000;


YModemRx::YModemRx(SerialPort& port)
    : YModem(port)
    {
    }


int YModemRx::OutChar(uint8_t c)
    {
    int result = Port.Out(&c,1,1000);
    if(result==0)
        return ErrorTimeout;
    return result;
    }


int YModemRx::ReceiveBlock(OutStream& out)
    {
    uint8_t block[1+2+1024+2];  // buffer to hold data for the block

    int retryCount = 10;        // number of attempts to send the block
do_retry:
    // count attenpts...
    if(!retryCount--)
        return ErrorBlockRetriesExceded;

    size_t blockSize = 128;     // assume 128 byte blocks until we know better
    uint8_t* data = block;
    size_t size = 1+2+blockSize+1+ExpectCRC;
    do
        {
        // receive some data...
        int result = Port.In(data,size,ReceiveTimeout);
        if(result<0)
            return result;

        // check for timeout...
        if(result==0)
            {
            if(data==block)
                return ErrorTimeout; // nothing received
            // not all data received so some may have been lost...
            goto retry;
            }

        // check for end of transmission...
        if(block[0]==EOT)
            {
            int result = OutChar(ACK);
            if(result<0)
                return result;
            return out.Out(0,0); // store zero bytes to signal end
            }

        // check for 1K blocks...
        if(block[0]==STX && blockSize!=1024)
            {
            blockSize = 1024;
            size += 1024-128;
            }

        // adjust pointers for next chunk of data...
        data += result;
        size -= result;
        }
    while(size);

    if(block[0] != (blockSize==1024 ? STX : SOH))
        goto retry; // block start invalid
    if(block[1] != (block[2]^0xff))
        goto retry; // block number invalid
    if(block[1] != (BlockNumber&0xffu))
        goto retry; // block number invalid

    if(ExpectCRC)
        {
        uint16_t crc = CRC16(block+1+2,blockSize);
        uint16_t receiveCrc = (block[1+2+blockSize+0]<<8)+block[1+2+blockSize+1];
        if(crc!=receiveCrc)
            goto retry; // crc invalid
        }
    else
        {
        uint8_t sum = Checksum(block+1+2,blockSize);
        if(sum!=block[1+2+blockSize])
            goto retry; // checksum invalid
        }

    {
    //  output received data...
    int result = out.Out(block+3,blockSize);
    if(result<0)
        return result;

    // block transferred OK...
    if(SendBlockACK)
        {
        result = OutChar(ACK);
        if(result<0)
            return result;
        }
    ++BlockNumber;
    return blockSize;
    }

retry:
    while(InChar(ReceiveTimeout)>=0) // flush input buffers
        {}
    int result = OutChar(NAKChar);
    if(result<0)
        return result;
    goto do_retry;
    }


int YModemRx::ReceiveInitialise(OutStream& out, unsigned timeout)
    {
    for(;;)
        {
        int result = OutChar(ModeChar);
        if(result!=ErrorTimeout)
            {
            if(result<0)
                return result;
            result = ReceiveBlock(out);
            if(result!=ErrorTimeout)
                return result;
            }
        if(timeout<ReceiveTimeout)
            return ErrorTimeout;
        timeout -= ReceiveTimeout;
        }
    }


int YModemRx::ReceiveX(OutStream& out, unsigned timeout, bool useCrc)
    {
    ModeChar = useCrc ? (uint8_t)'C' : (uint8_t)NAK;
    ExpectCRC = useCrc;
    SendBlockACK = true;
    NAKChar = ModeChar;

    // get first block...
    BlockNumber = 1;
    int result = ReceiveInitialise(out,timeout);
    if(result==ErrorTimeout)
        return result;

    // get rest of data...
    while(result)
        {
        if(result<0)
            goto error;
        result = ReceiveBlock(out);
        }

    // done...
    return 0;

error:
    Cancel();
    return result;
    }


inline YModemRx::OutBlock0::OutBlock0()
    : Size(0)
    {}


int YModemRx::OutBlock0::Open(const char* /*fileName*/, size_t /*size*/)
    {
    return ErrorOutputStreamError;
    }


int YModemRx::OutBlock0::Out(const uint8_t* data, size_t size)
    {
    memcpy(Buffer,data,size);
    Size = size;
    return 0;
    }


int YModemRx::OutBlock0::Parse(const char*& fileName, size_t& fileSize)
    {
    const char* buffer = (char*)Buffer;
    size_t bufferSize = Size;

    // fileName is at start of block...
    fileName = (char*)buffer;
    const char* bufferEnd = buffer+bufferSize;
    while(*buffer++)
        {
        if(buffer>=bufferEnd)
            return YModemRx::ErrorReceivedBadData;
        }

    // size (as decimal number) follows name string...
    size_t size = 0;
    while(buffer<bufferEnd)
        {
        unsigned digit = *buffer++;
        if(!digit)
            break;
        if(digit==' ')
            break;
        digit -= '0';
        if(digit>9)
            return YModemRx::ErrorReceivedBadData;
        size_t oldSize = size;
        size = size*10+digit;
        if(size<oldSize)
            return YModemRx::ErrorReceivedBadData; // overflow
        }
    fileSize = size;

    // done...
    return 0;
    }


int YModemRx::ReceiveY(OutStream& out, unsigned timeout, bool gMode)
    {
    ModeChar = gMode ? 'G' : 'C';
    ExpectCRC = true;
    SendBlockACK = !gMode;
    NAKChar = ModeChar;
    unsigned fileCount = 0;
    int result;

    for(;;)
        {
        // get block zero...
        YModemRx::OutBlock0 block0;
        BlockNumber = 0;
        result = ReceiveInitialise(block0,timeout);
        if(result==ErrorTimeout && !fileCount)
            return result; // sender not ready
        if(result<0)
            goto error;
        if(result!=128)
            return 0;

        // process block zero...
        const char* fileName;
        size_t size;
        result = block0.Parse(fileName,size);
        if(result<0)
            goto error;
        if(fileName[0]==0)
            return 0; // empty file name indicates end of transfer
        if(fileCount)
            return ErrorMultipleFilesSent; // we only support single file transfers
        result = out.Open(fileName,size);
        if(result<0)
            goto error;

        // get rest of data...
        NAKChar = NAK;
        result = OutChar(ModeChar);
        while(result)
            {
            if(result<0)
                goto error;
            result = ReceiveBlock(out);
            }

        // file received OK.
        ++fileCount;
        }
error:
    Cancel();
    return result;
    }