Public bytenuts repository creation

src/xmodem.c

@@ -0,0 +1,203 @@
+#include <poll.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "xmodem.h"
+
+int _xmodem_wait(int fd, uint8_t *ret, int timeout_ms);
+
+uint16_t _xmodem_crc(void *buf, size_t len);
+uint8_t _xmodem_csum(void *buf, size_t len);
+void _xmodem_status_print(size_t sent, size_t total);
+
+int
+xmodem_send(
+    int dest_fd,
+    int in_fd,
+    size_t sz,
+    int block_sz,
+    void (*status_cb)(size_t sent, size_t total)
+)
+{
+    uint8_t start_byte;
+    size_t sent;
+    uint8_t *buf;
+    size_t buf_sz;
+    uint8_t packet_num;
+    int retries;
+    int ret = 0;
+
+    if (block_sz != 128 && block_sz != 1024) {
+        return -1;
+    }
+
+    /* wait for start byte, 'C' for CRC, NAK for CSUM */
+    for (int i = 0; i < 11; i++) {
+        if (i == 10) {
+            return XMODEM_ERR_TIMEOUT;
+        }
+
+        if (
+            !_xmodem_wait(dest_fd, &start_byte, XMODEM_TIMEOUT) &&
+            (start_byte == XMODEM_CRC || start_byte == XMODEM_NAK)
+        ) {
+            break;
+        }
+    }
+
+    /* start sendin' bytes */
+    buf_sz = 3 + block_sz; /* SOH/STX | idx | ~idx | payload */
+    if (start_byte == XMODEM_NAK) {
+        buf_sz += 1;
+    } else {
+        buf_sz += 2;
+    }
+    buf = malloc(buf_sz);
+    sent = 0;
+    packet_num = 1; /* yes, this starts at 1 */
+
+    while (sent < sz) {
+        size_t read_len;
+
+        if (block_sz == 128) {
+            buf[0] = XMODEM_SOH;
+        } else {
+            buf[0] = XMODEM_STX;
+        }
+
+        buf[1] = packet_num;
+        buf[2] = ~packet_num;
+
+        if ((sz - sent) >= block_sz) {
+            read_len = block_sz;
+        } else {
+            /* back fill payload with pad */
+            read_len = sz - sent;
+            for (int i = read_len; i < block_sz; i++) {
+                buf[i] = XMODEM_PAD;
+            }
+        }
+
+        if (read(in_fd, &buf[3], read_len) != read_len) {
+            return XMODEM_ERR_FILEIO;
+        }
+
+        if (start_byte == XMODEM_CRC) {
+            /* write CRC big endian */
+            uint16_t crc = _xmodem_crc(&buf[3], block_sz);
+            buf[buf_sz-2] = (uint8_t)((0xFF00 & crc) >> 8);
+            buf[buf_sz-1] = (uint8_t)(0x00FF & crc);
+        } else {
+            buf[buf_sz-1] = _xmodem_csum(&buf[3], block_sz);
+        }
+
+        /* try to send this packet until we get an ACK */
+        retries = 0;
+        while (1) {
+            uint8_t recv_char;
+
+            if (retries == 10) {
+                ret = XMODEM_ERR_TIMEOUT;
+                goto end_of_transmission;
+            }
+
+            if (write(dest_fd, buf, buf_sz) != buf_sz){
+                return XMODEM_ERR_WRITE;
+            }
+
+            if (_xmodem_wait(dest_fd, &recv_char, XMODEM_TIMEOUT)) {
+                return XMODEM_ERR_READ;
+            }
+
+            if (recv_char == XMODEM_ACK) {
+                break;
+            }
+
+            retries++;
+        }
+
+        sent += read_len;
+        packet_num++; /* expect overflow */
+        status_cb(sent, sz);
+    }
+
+end_of_transmission:
+    retries = 0;
+    while (1) {
+        uint8_t ack_char;
+
+        if (retries == 10) {
+            return XMODEM_ERR_TIMEOUT;
+        }
+
+        write(dest_fd, &(uint8_t){XMODEM_EOT}, 1);
+
+        if (
+            !_xmodem_wait(dest_fd, &ack_char, XMODEM_TIMEOUT) &&
+            ack_char == XMODEM_ACK
+        ) {
+            break;
+        }
+
+        retries++;
+    }
+
+    return ret;
+}
+
+int
+_xmodem_wait(int fd, uint8_t *ret, int timeout_ms)
+{
+    struct pollfd pfd;
+
+    pfd.fd = fd;
+    pfd.events = POLLIN;
+    pfd.revents = 0;
+
+    if (poll(&pfd, 1, timeout_ms) <= 0) {
+        return -1;
+    }
+
+    read(fd, ret, 1);
+
+    return 0;
+}
+
+uint16_t
+_xmodem_crc(void *buf, size_t len)
+{
+    uint16_t crc;
+    char i;
+
+    crc = 0;
+    while (--len >= 0)
+    {
+        crc = crc ^ (uint16_t) (*(uint8_t *)buf++) << 8;
+        i = 8;
+        do
+        {
+            if (crc & 0x8000)
+                crc = crc << 1 ^ 0x1021;
+            else
+                crc = crc << 1;
+        } while(--i);
+    }
+
+    return (crc);
+}
+
+uint8_t
+_xmodem_csum(void *buf, size_t len)
+{
+    uint8_t ret = 0;
+
+    for (size_t i = 0; i < len; i++) {
+        ret += ((uint8_t *)buf)[i];
+    }
+
+    return ret;
+}