robot/peripheral/ymodem.c

/*
 * COPYRIGHT (C) 2011-2023, Real-Thread Information Technology Ltd
 * All rights reserved
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2013-04-14     Grissiom     initial implementation
 * 2019-12-09     Steven Liu   add YMODEM send protocol
 *
 * Radkil adapted in 2026: 移除 RT-Thread 依赖, 使用 rd_time/Rd_Delay
 */

#include "ymodem.h"

#ifdef YMODEM_USING_CRC_TABLE
static const uint16_t ccitt_table[256] =
{
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
    0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
    0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
    0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
    0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
    0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
    0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
    0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
    0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
    0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
    0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
    0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
    0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
    0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
    0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
    0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
    0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
    0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
    0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
    0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
    0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
    0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
    0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};
static uint16_t CRC16(unsigned char *q, int len)
{
    uint16_t crc = 0;

    while (len-- > 0)
        crc = (crc << 8) ^ ccitt_table[((crc >> 8) ^ *q++) & 0xff];
    return crc;
}
#else
static uint16_t CRC16(unsigned char *q, int len)
{
    uint16_t crc;
    char i;

    crc = 0;
    while (--len >= 0)
    {
        crc = crc ^ (int) * q++ << 8;
        i = 8;
        do
        {
            if (crc & 0x8000)
                crc = crc << 1 ^ 0x1021;
            else
                crc = crc << 1;
        }
        while (--i);
    }

    return (crc);
}
#endif

/* SOH/STX + seq + payload + crc */
#define _RYM_SOH_PKG_SZ (1+2+128+2)
#define _RYM_STX_PKG_SZ (1+2+1024+2)

static enum rym_code _rym_read_code(struct rym_ctx *ctx, uint32_t timeout_ms)
{
    uint32_t start = Rd_GetTime();
    while (Rd_GetTime() - start < timeout_ms)
    {
        size_t rsz = ctx->dev.read(ctx->dev.opaque, ctx->buf, 1);
        if (rsz == 1)
            return (enum rym_code)(*ctx->buf);
        Rd_Delay(1);
    }
    return RYM_CODE_NONE;
}

static ssize_t _rym_read_data(struct rym_ctx *ctx, size_t len)
{
    uint8_t *buf = ctx->buf + 1;
    size_t readlen = 0;
    uint32_t start = Rd_GetTime();

    while (Rd_GetTime() - start < RYM_WAIT_CHR_MS)
    {
        size_t n = ctx->dev.read(ctx->dev.opaque, buf + readlen, len - readlen);
        if (n > 0)
        {
            readlen += n;
            if (readlen >= len)
                return readlen;
            /* 还有数据就继续搬, 不要在这里白等 1ms */
            continue;
        }

        /* 只有真的没数据可读时才让出 CPU */
        Rd_Delay(1);
    }
    return readlen;
}

static int _rym_send_packet(struct rym_ctx *ctx, enum rym_code code, uint8_t index)
{
    uint16_t send_crc;
    uint8_t index_inv = ~index;
    size_t packetlen = 0;

    switch (code)
    {
    case RYM_CODE_SOH:
        packetlen = _RYM_SOH_PKG_SZ;
        break;
    case RYM_CODE_STX:
        packetlen = _RYM_STX_PKG_SZ;
        break;
    default:
        return RD_FAILURE;
    }

    send_crc = CRC16(ctx->buf + 3, packetlen - 5);
    ctx->buf[0] = code;
    ctx->buf[1] = index;
    ctx->buf[2] = index_inv;
    ctx->buf[packetlen - 2] = (uint8_t)(send_crc >> 8);
    ctx->buf[packetlen - 1] = (uint8_t)send_crc & 0xff;

    /* DEBUG: 发包前确认 CRC + 序号正确 */
    char hex_buf[16];
    RD_SNPRINTF(hex_buf, sizeof(hex_buf), "%02X:%02X crc=%04X", index, index_inv, send_crc);
    log_d("ymodem TX pkt: %s [%uB]", hex_buf, (unsigned)packetlen);

    size_t writelen = 0;
    uint32_t retry = 0;

    while (writelen < packetlen)
    {
        size_t n = ctx->dev.write(ctx->dev.opaque, ctx->buf + writelen, packetlen - writelen);
        if (n == 0)
        {
            /* 底层写回调返回 0 (未写出任何字节) 时不能原地死循环:
             * 比如它误把 HAL_OK(0) 当作"已写字节数"返回 */
            if (++retry >= (uint32_t)(RYM_WAIT_CHR_MS / 10u))
                return RD_FAILURE;
            Rd_Delay(1);
            continue;
        }
        writelen += n;
        retry = 0;
    }

    return RD_SUCCESS;
}

static void _rym_putchar(struct rym_ctx *ctx, uint8_t code)
{
    ctx->dev.write(ctx->dev.opaque, &code, 1);
}

static uint8_t _rym_getchar(struct rym_ctx *ctx)
{
    /* 带超时的等应答: 不能无限等 (对端无响应时旧实现会把 lua 线程永久卡住),
     * 超时返回 RYM_CODE_NONE, 由调用方按"应答不对"上报 -RYM_ERR_ACK */
    return (uint8_t)_rym_read_code(ctx, RYM_WAIT_PKG_MS);
}

static int _rym_do_handshake(struct rym_ctx *ctx, int tm_sec)
{
    enum rym_code code;
    size_t i;
    uint16_t recv_crc, cal_crc;
    size_t data_sz = 0;

    ctx->stage = RYM_STAGE_ESTABLISHING;
    log_i("ymodem RX handshake: start polling, %d rounds x %u ms", tm_sec, (unsigned)RYM_CHD_INTV_MS);
    for (i = 0; i < (size_t)tm_sec; i++)
    {
        _rym_putchar(ctx, RYM_CODE_C);
        log_i("ymodem RX handshake: sent 'C' #%u, waiting header...", (unsigned)(i + 1));
        code = _rym_read_code(ctx, RYM_CHD_INTV_MS);
        if (code == RYM_CODE_SOH)
        {
            data_sz = _RYM_SOH_PKG_SZ;
            break;
        }
        else if (code == RYM_CODE_STX)
        {
            data_sz = _RYM_STX_PKG_SZ;
            break;
        }
        else if (code != RYM_CODE_NONE)
        {
            /* 有字节但不是包头: 说明链路通, 问题在协议/对端 */
            log_w("ymodem RX handshake: got 0x%02X while waiting header", (unsigned)code);
        }
    }
    if (i == (size_t)tm_sec)
    {
        log_e("ymodem RX handshake: no packet header in %d rounds x %u ms (一个字节都没收到 -> 查端口/接线)",
              tm_sec, (unsigned)RYM_CHD_INTV_MS);
        return -RYM_ERR_TMO;
    }

    /* 接收剩余数据: 必须一次读完.
     * _rym_read_data 每次都是从 ctx->buf + 1 的偏移 0 开始写, 分多次调用会互相覆盖,
     * 而外层用 i 累加长度会误判为"已收齐"; 原来的 100ms 窗口也和
     * _rym_read_data 内部的 RYM_WAIT_CHR_MS 超时自相矛盾 (根本来不及). */
    i = _rym_read_data(ctx, data_sz - 1);
    if (i != (data_sz - 1))
    {
        log_e("ymodem RX HANDSHAKE: header short read %u/%u", (unsigned)i, (unsigned)(data_sz - 1));
        return -RYM_ERR_DSZ;
    }

    if (ctx->buf[1] != 0 || ctx->buf[2] != 0xFF)
    {
        log_e("ymodem RX HANDSHAKE: bad header seq 0x%02X/0x%02X", ctx->buf[1], ctx->buf[2]);
        return -RYM_ERR_SEQ;
    }

    recv_crc = (uint16_t)(*(ctx->buf + data_sz - 2) << 8) | *(ctx->buf + data_sz - 1);
    cal_crc = CRC16(ctx->buf + 3, data_sz - 5);
    if (recv_crc != cal_crc)
    {
        log_e("ymodem RX HANDSHAKE: header crc mismatch recv=0x%04X calc=0x%04X", recv_crc, cal_crc);
        return -RYM_ERR_CRC;
    }

    if (ctx->on_begin && ctx->on_begin(ctx, ctx->buf + 3, data_sz - 5) != RYM_CODE_ACK)
    {
        log_e("ymodem RX HANDSHAKE: create/open file failed");
        return -RYM_ERR_CAN;
    }

    log_i("ymodem RX: handshake done");

    return RD_SUCCESS;
}

static int _rym_do_send_handshake(struct rym_ctx *ctx, int tm_sec)
{
    enum rym_code code;
    size_t i;
    size_t data_sz;
    size_t retry;
    uint8_t getc_ack;

    ctx->stage = RYM_STAGE_ESTABLISHING;
    data_sz = _RYM_SOH_PKG_SZ;

    log_i("ymodem TX handshake: waiting for receiver's 'C' (%d rounds x %u ms)...",
          tm_sec, (unsigned)RYM_CHD_INTV_MS);
    for (i = 0; i < (size_t)tm_sec; i++)
    {
        code = _rym_read_code(ctx, RYM_CHD_INTV_MS);
        if (code == RYM_CODE_C)
            break;
        if (code != RYM_CODE_NONE)
        {
            /* 收到别的字节也报出来: 区分"链路完全没数据"与"有数据但不是 'C'" */
            log_w("ymodem TX handshake: got 0x%02X while waiting 'C'", (unsigned)code);
        }
    }
    if (i == (size_t)tm_sec)
    {
        log_e("ymodem TX handshake: no 'C' in %d rounds x %u ms (一个字节都没收到 -> 查端口/接线)",
              tm_sec, (unsigned)RYM_CHD_INTV_MS);
        return -RYM_ERR_TMO;
    }

    if (ctx->on_begin && ctx->on_begin(ctx, ctx->buf + 3, data_sz - 5) != RYM_CODE_SOH)
    {
        log_e("ymodem TX handshake: build file header failed");
        return -RYM_ERR_CODE;
    }

    /* 发包头. 对端可能还没准备好(比如正在建文件)而回 NAK 或干脆不回,
     * 这两种都是"重发", 不能当失败退出 */
    for (retry = 0; ; retry++)
    {
        _rym_send_packet(ctx, RYM_CODE_SOH, 0);

        /* 接收端在等包头期间会反复发 'C', 环里可能残留多个;
         * 先跳过它们, 否则后面读到的"应答"会整体错位 */
        do
        {
            getc_ack = _rym_getchar(ctx);
        }
        while (getc_ack == RYM_CODE_C);

        if (getc_ack == RYM_CODE_ACK)
            break;

        if (getc_ack == RYM_CODE_CAN)
        {
            log_e("ymodem TX handshake: receiver cancelled (CAN)");
            return -RYM_ERR_CAN;
        }

        if (retry + 1 >= (size_t)RYM_TX_RETRY_MAX)
        {
            log_e("ymodem TX HANDSHAKE: header not ACKed after %u tries, last=0x%02X (0x00=timeout)",
                  (unsigned)RYM_TX_RETRY_MAX, getc_ack);
            return -RYM_ERR_ACK;
        }

        log_w("ymodem TX handshake: header %s -> resend (%u/%u)",
              (getc_ack == RYM_CODE_NAK) ? "NAKed" : "no reply",
              (unsigned)(retry + 1), (unsigned)RYM_TX_RETRY_MAX);
    }

    getc_ack = _rym_getchar(ctx);
    if (getc_ack != RYM_CODE_C)
    {
        log_e("ymodem TX HANDSHAKE: no 'C' after header ACK, got=0x%02X (0x00=timeout)", getc_ack);
        return -RYM_ERR_ACK;
    }

    log_i("ymodem TX: handshake done");
    ctx->stage = RYM_STAGE_ESTABLISHED;
    return RD_SUCCESS;
}

static int _rym_trans_data(struct rym_ctx *ctx, size_t data_sz, enum rym_code *code)
{
    const size_t tsz = 2 + data_sz + 2;
    uint16_t recv_crc;

    size_t i = _rym_read_data(ctx, tsz);
    if (i != tsz)
    {
        log_e("ymodem RX data: short read %u/%u", (unsigned)i, (unsigned)tsz);
        return -RYM_ERR_DSZ;
    }

    if ((ctx->buf[1] + ctx->buf[2]) != 0xFF)
    {
        log_e("ymodem RX data: bad seq 0x%02X/0x%02X", ctx->buf[1], ctx->buf[2]);
        return -RYM_ERR_SEQ;
    }

    if (ctx->stage == RYM_STAGE_ESTABLISHED && ctx->buf[1] == 0x00)
    {
        *code = RYM_CODE_NONE;
        return RD_SUCCESS;
    }

    ctx->stage = RYM_STAGE_TRANSMITTING;

    recv_crc = (uint16_t)(*(ctx->buf + tsz - 1) << 8) | *(ctx->buf + tsz);
    if (recv_crc != CRC16(ctx->buf + 3, data_sz))
    {
        log_e("ymodem RX data: crc mismatch recv=0x%04X", recv_crc);
        return -RYM_ERR_CRC;
    }

    if (ctx->on_data)
        *code = ctx->on_data(ctx, ctx->buf + 3, data_sz);
    else
        *code = RYM_CODE_ACK;

    return RD_SUCCESS;
}

static int _rym_do_trans(struct rym_ctx *ctx)
{
    _rym_putchar(ctx, RYM_CODE_ACK);
    _rym_putchar(ctx, RYM_CODE_C);
    ctx->stage = RYM_STAGE_ESTABLISHED;
    size_t errors = 0;

    while (1)
    {
        int err;
        enum rym_code code;
        size_t data_sz, i;

        code = _rym_read_code(ctx, RYM_WAIT_PKG_MS);
        switch (code)
        {
        case RYM_CODE_SOH:
            data_sz = 128;
            break;
        case RYM_CODE_STX:
            data_sz = 1024;
            break;
        case RYM_CODE_EOT:
            log_i("ymodem RX: EOT received, data phase done");
            return RD_SUCCESS;
        default:
            errors++;
            log_w("ymodem RX: unexpected code 0x%02X (error %u/%u)",
                  (unsigned)code, (unsigned)errors, (unsigned)RYM_MAX_ERRORS);
            if (errors > RYM_MAX_ERRORS)
                return -RYM_ERR_CODE;
            _rym_putchar(ctx, RYM_CODE_NAK);
            continue;
        }

        err = _rym_trans_data(ctx, data_sz, &code);
        if (err != RD_SUCCESS)
        {
            errors++;
            log_e("ymodem RX: block error %d (error %u/%u)",
                  err, (unsigned)errors, (unsigned)RYM_MAX_ERRORS);
            if (errors > RYM_MAX_ERRORS)
                return err;
            _rym_putchar(ctx, RYM_CODE_NAK);
            continue;
        }
        errors = 0;

        switch (code)
        {
        case RYM_CODE_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:
            break;
        }
    }
}

static int _rym_do_send_trans(struct rym_ctx *ctx)
{
    ctx->stage = RYM_STAGE_TRANSMITTING;
    enum rym_code code;
    uint32_t index = 1;
    uint8_t getc_ack;
    size_t data_sz = _RYM_STX_PKG_SZ;
    size_t retry;

    while (1)
    {
        if (!ctx->on_data)
            return -RYM_ERR_CODE;

        /* 注意: 一个块只读一次文件. 下面重传时必须直接复用 ctx->buf,
         * 不能再调 on_data, 否则每重传一次就往后多吃一段数据, 文件就乱了 */
        code = ctx->on_data(ctx, ctx->buf + 3, data_sz - 5);
        log_i("ymodem TX data: block %u sending (code=0x%02X%s)",
              (unsigned)(uint8_t)index, (unsigned)code,
              (ctx->stage == RYM_STAGE_FINISHING) ? ", last block" : "");

        for (retry = 0; ; retry++)
        {
            _rym_send_packet(ctx, code, index);

            /* 接收端偶尔会在数据阶段夹发 'C' 催包, 直接跳过, 否则应答会整体错位 */
            do
            {
                getc_ack = _rym_getchar(ctx);
                if (getc_ack == RYM_CODE_C)
                    log_w("ymodem TX data: skip stray 'C' while waiting ACK of block %u",
                          (unsigned)(uint8_t)index);
            }
            while (getc_ack == RYM_CODE_C);

            if (getc_ack == RYM_CODE_ACK)
                break;

            if (getc_ack == RYM_CODE_CAN)
            {
                log_e("ymodem TX data: receiver cancelled (CAN) at block %u", (unsigned)(uint8_t)index);
                return -RYM_ERR_CAN;
            }

            /* NAK / 超时 = "这一块没收好, 请重发" (复用同一块数据) */
            if (retry + 1 >= (size_t)RYM_TX_RETRY_MAX)
            {
                log_e("ymodem TX DATA PHASE: block %u not ACKed after %u tries, last=0x%02X (0x00=timeout, 0x15=NAK, 0x18=CAN)",
                      (unsigned)(uint8_t)index, (unsigned)RYM_TX_RETRY_MAX, getc_ack);
                return -RYM_ERR_ACK;
            }

            log_w("ymodem TX data: block %u %s -> resend (%u/%u)",
                  (unsigned)(uint8_t)index, (getc_ack == RYM_CODE_NAK) ? "NAKed" : "no reply",
                  (unsigned)(retry + 1), (unsigned)RYM_TX_RETRY_MAX);
        }

        index++;

        if (ctx->stage == RYM_STAGE_FINISHING)
        {
            log_i("ymodem TX: all data blocks sent (%u block(s))", (unsigned)index - 1);
            break;
        }
    }

    return RD_SUCCESS;
}

static int _rym_do_fin(struct rym_ctx *ctx)
{
    enum rym_code code;
    uint16_t recv_crc;
    size_t i;
    size_t data_sz;

    ctx->stage = RYM_STAGE_FINISHING;
    if (ctx->on_end)
        ctx->on_end(ctx, ctx->buf + 3, 128);

    _rym_putchar(ctx, RYM_CODE_NAK);
    code = _rym_read_code(ctx, RYM_WAIT_PKG_MS);
    if (code != RYM_CODE_EOT)
    {
        log_e("ymodem RX FIN phase: expected EOT, got 0x%02X (0x00=timeout)", (unsigned)code);
        return -RYM_ERR_CODE;
    }

    _rym_putchar(ctx, RYM_CODE_ACK);
    _rym_putchar(ctx, RYM_CODE_C);

    code = _rym_read_code(ctx, RYM_WAIT_PKG_MS);
    if (code == RYM_CODE_SOH)
        data_sz = _RYM_SOH_PKG_SZ;
    else if (code == RYM_CODE_STX)
        data_sz = _RYM_STX_PKG_SZ;
    else
        return -RYM_ERR_CODE;

    i = _rym_read_data(ctx, data_sz - 1);
    if (i != (data_sz - 1))
        return -RYM_ERR_DSZ;

    if (ctx->buf[1] != 0 || ctx->buf[2] != 0xFF)
        return -RYM_ERR_SEQ;

    recv_crc = (uint16_t)(*(ctx->buf + data_sz - 2) << 8) | *(ctx->buf + data_sz - 1);
    if (recv_crc != CRC16(ctx->buf + 3, data_sz - 5))
        return -RYM_ERR_CRC;

    /* 多文件传输 */
    if (ctx->buf[3] != 0)
    {
        if (ctx->on_begin && ctx->on_begin(ctx, ctx->buf + 3, data_sz - 5) != RYM_CODE_ACK)
            return -RYM_ERR_CAN;
        return RD_SUCCESS;
    }

    ctx->stage = RYM_STAGE_FINISHED;
    _rym_putchar(ctx, RYM_CODE_ACK);
    log_i("ymodem RX: session finished");
    return RD_SUCCESS;
}

static int _rym_do_send_fin(struct rym_ctx *ctx)
{
    size_t data_sz;
    uint8_t index = 0;
    size_t retry;
    uint8_t getc_ack;

    data_sz = _RYM_SOH_PKG_SZ;

    /* EOT 阶段: 对端回 NAK 表示"请再发一次 EOT", 直接回 ACK 表示收到,
     * 不回(超时)也重发; 三种情况都不能当失败退出 (有些接收端要两三次才确认) */
    for (retry = 0; ; retry++)
    {
        _rym_putchar(ctx, RYM_CODE_EOT);
        getc_ack = _rym_getchar(ctx);

        if (getc_ack == RYM_CODE_ACK)
            break;

        if (getc_ack == RYM_CODE_CAN)
        {
            log_e("ymodem TX fin: receiver cancelled (CAN)");
            return -RYM_ERR_CAN;
        }

        if (retry + 1 >= (size_t)RYM_TX_RETRY_MAX)
        {
            log_e("ymodem TX FIN PHASE: EOT not ACKed after %u tries, last=0x%02X (0x00=timeout, 0x06=ACK, 0x15=NAK)",
                  (unsigned)RYM_TX_RETRY_MAX, getc_ack);
            return -RYM_ERR_ACK;
        }

        log_w("ymodem TX fin: EOT %s -> resend (%u/%u)",
              (getc_ack == RYM_CODE_NAK) ? "NAKed" : "no reply",
              (unsigned)(retry + 1), (unsigned)RYM_TX_RETRY_MAX);
    }

    /* 等接收端的 'C' (表示准备接收下一个文件).
     * 不把这一步当致命错误: 数据已经全部发完并被 ACK, 部分接收端不发 'C'
     * 而是直接等结束帧; 因为这个地方返回 -118 会误报"传输失败"并且结束帧发不出去,
     * 接收端就会一直等下去 (表现就是"不会自动停止") */
    (void)_rym_getchar(ctx);

    if (ctx->on_end && ctx->on_end(ctx, ctx->buf + 3, data_sz - 5) != RYM_CODE_SOH)
        return -RYM_ERR_CODE;

    _rym_send_packet(ctx, RYM_CODE_SOH, index);

    /* 结束帧的 ACK 只做尽力而为的清理: 拿到了就不会残留到下一次会话,
     * 拿不到 (超时/对端已收工) 也不影响本次传输结果 */
    (void)_rym_getchar(ctx);

    log_i("ymodem TX: session finished");
    ctx->stage = RYM_STAGE_FINISHED;
    return RD_SUCCESS;
}

static int _rym_do_recv(struct rym_ctx *ctx, int handshake_timeout)
{
    int err;

    ctx->stage = RYM_STAGE_NONE;
    ctx->buf = RD_MALLOC(_RYM_STX_PKG_SZ);
    if (ctx->buf == NULL)
        return RD_FAILURE;

    err = _rym_do_handshake(ctx, handshake_timeout);
    if (err != RD_SUCCESS)
    {
        RD_FREE(ctx->buf);
        ctx->buf = NULL;
        return err;
    }

    while (1)
    {
        err = _rym_do_trans(ctx);
        err = _rym_do_fin(ctx);
        if (err != RD_SUCCESS)
        {
            RD_FREE(ctx->buf);
            ctx->buf = NULL;
            return err;
        }
        if (ctx->stage == RYM_STAGE_FINISHED)
            break;
    }

    RD_FREE(ctx->buf);
    ctx->buf = NULL;
    return err;
}

static int _rym_do_send(struct rym_ctx *ctx, int handshake_timeout)
{
    int err;

    ctx->stage = RYM_STAGE_NONE;
    ctx->buf = RD_MALLOC(_RYM_STX_PKG_SZ);
    if (ctx->buf == NULL)
        return RD_FAILURE;

    err = _rym_do_send_handshake(ctx, handshake_timeout);
    if (err != RD_SUCCESS) goto __exit;

    err = _rym_do_send_trans(ctx);
    if (err != RD_SUCCESS) goto __exit;

    err = _rym_do_send_fin(ctx);

__exit:
    RD_FREE(ctx->buf);
    ctx->buf = NULL;
    return err;
}

int rym_recv_on_device(
    struct rym_ctx *ctx,
    rym_device_t *dev,
    rym_callback on_begin,
    rym_callback on_data,
    rym_callback on_end,
    int handshake_timeout_sec)
{
    int res;

    RD_MEMSET(ctx, 0, sizeof(*ctx));
    ctx->on_begin = on_begin;
    ctx->on_data  = on_data;
    ctx->on_end   = on_end;
    RD_MEMCPY(&ctx->dev, dev, sizeof(rym_device_t));

    res = _rym_do_recv(ctx, handshake_timeout_sec);

    return res;
}

int rym_send_on_device(
    struct rym_ctx *ctx,
    rym_device_t *dev,
    rym_callback on_begin,
    rym_callback on_data,
    rym_callback on_end,
    int handshake_timeout_sec)
{
    int res;

    RD_MEMSET(ctx, 0, sizeof(*ctx));
    ctx->on_begin = on_begin;
    ctx->on_data  = on_data;
    ctx->on_end   = on_end;
    RD_MEMCPY(&ctx->dev, dev, sizeof(rym_device_t));

    res = _rym_do_send(ctx, handshake_timeout_sec);

    return res;
}