Add xmodem and ymodem file send support

src/xymodem.c

@@ -0,0 +1,219 @@
+/*
+ * Minimalistic implementation of the xmodem-1k and ymodem sender protocol.
+ * https://en.wikipedia.org/wiki/XMODEM
+ * https://en.wikipedia.org/wiki/YMODEM
+ * 
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <termios.h>
+#include "misc.h"
+
+#define X_STX 0x02
+#define X_ACK 0x06
+#define X_NAK 0x15
+#define X_CAN 0x18
+
+#define EOT "\004"
+
+#define min(a, b)       ((a) < (b) ? (a) : (b))
+
+struct xpacket {
+    uint8_t  start;
+    uint8_t  seq;
+    uint8_t  nseq;
+    uint8_t  data[1024];
+    uint16_t crc;
+} __attribute__((packed));
+
+/* See https://en.wikipedia.org/wiki/Computation_of_cyclic_redundancy_checks */
+static uint16_t crc16(const uint8_t *data, uint16_t size)
+{
+    uint16_t crc, s;
+
+    for (crc = 0; size > 0; size--) {
+        s = *data++ ^ (crc >> 8);
+        s ^= (s >> 4);
+        crc = (crc << 8) ^ s ^ (s << 5) ^ (s << 12);
+    }
+    return crc;
+}
+
+static uint16_t swap16(uint16_t in)
+{
+    return (in >> 8) | ((in & 0xff) << 8);
+}
+
+static int xmodem(int sio, const void *data, size_t len, int seq)
+{
+    struct xpacket  packet;
+    const uint8_t  *buf = data;
+    char            resp = 0;
+    int             rc;
+    
+    /* Drain pending characters from serial line. Insist on the
+     * last drained character being 'C'.
+     */
+    while(1) {
+        if (key_hit)
+            return -1;
+        if (read(sio, &resp, 1) < 0) {
+            if (errno == EWOULDBLOCK) {
+                if (resp == 'C')   break;
+                if (resp == X_CAN) return -1;
+                usleep(50000);
+                continue;
+            }
+            perror("Read sync from serial failed");
+            return -1;
+        }
+    }
+
+    /* Always work with 1K packets */
+    packet.seq   = seq;
+    packet.start = X_STX; 
+
+    while (len) {
+        size_t  sz, z = 0;
+        char   *from, status;
+
+        /* Build next packet, pad with 0 to full seq */
+        z = min(len, sizeof(packet.data));
+        memcpy(packet.data, buf, z);
+        memset(packet.data + z, 0, sizeof(packet.data) - z);
+        packet.crc  = swap16(crc16(packet.data, sizeof(packet.data)));
+        packet.nseq = 0xff - packet.seq;
+
+        /* Send packet */
+        from = (char *) &packet;
+        sz =  sizeof(packet);
+        while (sz) {
+            if (key_hit)
+                return -1;
+            if ((rc = write(sio, from, sz)) < 0 ) {
+                if (errno ==  EWOULDBLOCK) {
+                    usleep(1000);
+                    continue;
+                }
+                perror("Write packet to serial failed");
+                return -1;
+            }
+            from += rc;
+            sz   -= rc;
+        }
+        
+        /* Read receiver response, timeout 1 s */
+        resp = X_ACK;
+        for(int n=0; n < 20; n++) {
+            if (key_hit)
+                return -1;
+            if (read(sio, &resp, 1) < 0) {
+                if (errno ==  EWOULDBLOCK) {
+                    usleep(50000);
+                    continue;
+                }
+                perror("Read ack/nak from serial failed");
+                return -1;
+            }
+            break;
+        }
+        
+        /* Update "progress bar" */
+        switch (resp) {
+        case X_NAK: status = 'N'; break;
+        case X_ACK: status = '.'; break;
+        case 'C':   status = 'C'; break;
+        case X_CAN: status = '!'; return -1;
+        default:    status = '?';
+        }
+        write(STDOUT_FILENO, &status, 1);
+
+        /* Move to next block after ACK */
+        if (resp == X_ACK) {
+            packet.seq++;
+            len -= z;
+            buf += z;
+        }
+    }
+
+    /* Send EOT at 1 Hz until ACK or CAN received */
+    while (seq) {
+        if (key_hit)
+            return -1;
+        if (write(sio, EOT, 1) < 0) {
+            perror("Write EOT to serial failed");
+            return -1;
+        }
+        write(STDOUT_FILENO, "|", 1);
+        usleep(1000000); /* 1 s timeout*/
+        if (read(sio, &resp, 1) < 0) {
+            if (errno == EWOULDBLOCK) continue;
+            perror("Read from serial failed");
+            return -1;
+        }
+        if (resp == X_ACK || resp == X_CAN) {
+            write(STDOUT_FILENO, "\r\n", 2);
+            return (resp == X_ACK) ? 0 : -1;
+        }
+    }
+    return 0; /* not reached */
+}
+
+int xymodem_send(int sio, const char *filename, char mode)
+{
+    size_t         len;
+    int            rc, fd;
+    struct stat    stat;
+    const uint8_t *buf;
+    
+    /* Open file, map into memory */
+    fd = open(filename, O_RDONLY);
+    if (fd < 0) {
+        perror("Could not open file");
+        return -1;
+    }
+    fstat(fd, &stat);
+    len = stat.st_size;
+    buf = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
+    if (!buf) {
+        close(fd);
+        perror("Could not mmap file");
+        return -1;
+    }
+
+    /* Do transfer */
+    key_hit = 0;
+    if (mode == 'x') {
+        rc = xmodem(sio, buf, len, 1);
+    }
+    else {
+        /* Ymodem: hdr + file + fin */
+        while(1) {
+            char hdr[128], *p;
+            p  = stpcpy(hdr, filename) + 1;
+            p += sprintf(p, "%ld %lo %o", len, stat.st_mtime, stat.st_mode);
+
+            rc = -1;
+            if (xmodem(sio, hdr, p - hdr, 0) < 0) break; /* hdr with metadata */
+            if (xmodem(sio, buf, len,     1) < 0) break; /* xmodem file */
+            if (xmodem(sio, "",  1,       0) < 0) break; /* empty hdr = fin */
+            rc = 0;                               break;
+        }
+    }
+    key_hit = 0xff;
+    
+    /* Flush serial and release resources */
+    tcflush(sio, TCIOFLUSH);
+    munmap((void *)buf, len);
+    close(fd);
+    return rc;
+}