Hahahahahalol I don't even need to calculate an FCS here!

include/patty/ax25.h

@@ -51,12 +51,13 @@ typedef struct _patty_ax25_frame {
 
     enum patty_ax25_frame_type type;
 
-    void * payload;
+    uint8_t control;
-    size_t len;
+    uint8_t proto;
 
-    uint8_t  control;
+    void * payload;
-    uint8_t  proto;
+    size_t payloadsz;
-    uint16_t fcs;
+
+    size_t size;
 } patty_ax25_frame;
 
 int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len);

src/ax25.c

@@ -4,62 +4,18 @@
 
 #include <patty/ax25.h>
 
-uint16_t fcs_table[256] = {
+#include "byteorder.h"
-    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
-    0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
-    0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
-    0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
-    0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
-    0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
-    0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
-    0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
-    0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
-    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
-    0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
-    0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
-    0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
-    0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
-    0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
-    0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
-    0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
-    0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
-    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
-    0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
-    0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
-    0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
-    0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
-    0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
-    0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
-    0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
-    0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
-    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
-    0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
-    0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
-    0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
-    0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
-};
-
-static inline uint16_t fcs_compute(uint8_t *data, size_t len) {
-    uint16_t fcs = 0xffff;
-
-    while (len--) {
-        fcs = (fcs >> 8) ^ fcs_table[(fcs ^ ((uint16_t)*data)) & 0x00ff];
-        data++;
-    }
-
-    return fcs;
-}
 
 static ssize_t frame_decode_address(patty_ax25_address *address, void *data, off_t offset) {
     int i, space = 0;
-    uint8_t ssid = (((uint8_t *)data) + offset)[6];
+    uint8_t ssid = ((uint8_t *)data + offset)[6];
 
     /*
      * First, unpack each callsign octet, ensuring all are within the 7 bit
      * ASCII space and do not have the extended bit set to 1.
      */
     for (i=0; i<6; i++) {
-        uint8_t b = (((uint8_t *)data) + offset)[i];
+        uint8_t b = ((uint8_t *)data + offset)[i];
         uint8_t c = b >> 1;
 
         if (!PATTY_AX25_ADDRESS_CHAR_VALID(c) || PATTY_AX25_ADDRESS_OCTET_LAST(b)) {
@@ -148,31 +104,27 @@ error:
     return -1;
 }
 
-static ssize_t frame_decode_payload(patty_ax25_frame *frame, void *data, off_t offset) {
+static ssize_t frame_decode_control(patty_ax25_frame *frame, void *data, off_t offset) {
-    uint8_t control = ((uint8_t *)data)[0];
+    uint8_t control = ((uint8_t *)data + offset)[0];
      size_t decoded = 0;
 
-    /*
+    int info = 0;
-     * First, decode the control byte.
+
-     */
     frame->control = control;
 
     decoded++;
 
     if (PATTY_AX25_CONTROL_INFO(control)) {
-        frame->type  = PATTY_AX25_FRAME_INFO;
+        frame->type = PATTY_AX25_FRAME_INFO;
-        frame->proto = ((uint8_t *)data)[1];
 
-        decoded++;
+        info = 1;
     } else if (PATTY_AX25_CONTROL_SUPER(control)) {
         frame->type = PATTY_AX25_FRAME_SUPER;
     } else if (PATTY_AX25_CONTROL_UNNUMBERED(control)) {
         frame->type = PATTY_AX25_FRAME_UNNUMBERED;
 
         if (PATTY_AX25_CONTROL_UNNUMBERED_INFO(control)) {
-            frame->proto = ((uint8_t *)data)[1];
+            info = 1;
-
-            decoded++;
         }
     } else {
         frame->type = PATTY_AX25_FRAME_UNKNOWN;
@@ -182,7 +134,20 @@ static ssize_t frame_decode_payload(patty_ax25_frame *frame, void *data, off_t o
         goto error;
     }
 
-    fprintf(stderr, "Decoded %lu bytes\n", decoded);
+    /*
+     * If we've received either an Info or Unnumbered Info frame, then decode
+     * the Protocol Identifier field, and calculate the location and size of
+     * the payload as well.
+     */
+    if (info) {
+        decoded++;
+
+        frame->proto     = ((uint8_t *)data + offset)[1];
+        frame->payload   = (void *)((uint8_t *)data + offset + decoded);
+        frame->payloadsz = frame->size - offset - decoded;
+
+        decoded += frame->payloadsz;
+    }
 
     return decoded;
 
@@ -190,12 +155,14 @@ error:
     return -1;
 }
 
-int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) {
+int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t size) {
     ssize_t decoded;
       off_t offset = 0;
 
     memset(frame, '\0', sizeof(*frame));
 
+    frame->size = size;
+
     if ((decoded = frame_decode_address(&frame->dest, data, offset)) < 0) {
         goto error_decode;
     } else {
@@ -213,8 +180,8 @@ int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) {
     }
 
     /*
-     * Now, if the source address is not the final address in the frame, then
+     * If the source address is not the final address in the frame, begin
-     * begin decoding repeater addresses.
+     * decoding repeater addresses.
      */
     if (!frame->src.last) {
         if ((decoded = frame_decode_hops(frame, data, offset)) < 0) {
@@ -224,18 +191,18 @@ int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) {
         }
     }
 
-    fprintf(stderr, "Decoded %ld/%lu\n", offset, len);
-
     /*
-     * Time to decode the rest of the payload, including control, PID, and
+     * Now, decode the Control Field, as well as any Protocol Identifier that
-     * Frame Check Sequence.
+     * may follow.
      */
-    if ((decoded = frame_decode_payload(frame, data, offset)) < 0) {
+    if ((decoded = frame_decode_control(frame, data, offset)) < 0) {
         goto error_decode;
     } else {
         offset += decoded;
     }
 
+    fprintf(stderr, "Decoded %lld/%lu bytes\n", offset, size);
+
     return offset;
 
 error_decode: