rthread Y-Modem组件,数据错误重发修复

//ymodem.c

static rt_err_t _rym_do_trans(struct rym_ctx *ctx)
{
    _rym_putchar(ctx, RYM_CODE_ACK);
    _rym_putchar(ctx, RYM_CODE_C);
    ctx->stage = RYM_STAGE_ESTABLISHED;
    rt_size_t errors;

    while (1)
    {
        rt_err_t err;
        enum rym_code code;
        rt_size_t data_sz, i;

        code = _rym_read_code(ctx,
                              RYM_WAIT_PKG_TICK);
        switch (code)
        {
        case RYM_CODE_SOH:
            data_sz = 128;
            break;
        case RYM_CODE_STX:
            data_sz = 1024;
            break;
        case RYM_CODE_EOT:
            return RT_EOK;
        default:
            return -RYM_ERR_CODE;
        };

        err = _rym_trans_data(ctx, data_sz, &code);
        if (err != RT_EOK)
        {
            errors++;
            if(errors > RYM_MAX_ERRORS)
            {
                return err;/* Abort communication */
            }
            else
            {
                _rym_putchar(ctx, RYM_CODE_NAK);/* Ask for a packet */
                continue;
            }
        }
        else
        {
            errors = 0;
        }
        switch (code)
        {
        case RYM_CODE_CAN:
            /* the spec require multiple CAN */
            for (i = 0; i < RYM_END_SESSION_SEND_CAN_NUM; i++)
            {
                _rym_putchar(ctx, RYM_CODE_CAN);
            }
            return -RYM_ERR_CAN;
        case RYM_CODE_ACK:
            _rym_putchar(ctx, RYM_CODE_ACK);
            break;
        default:
            // wrong code
            break;
        };
    }
}

//ymodem.h

/* how many retries were made when the error occurred */
#ifndef RYM_MAX_ERRORS
#define RYM_MAX_ERRORS    ((rt_size_t)5)
#endif