Refactor patty_ax25_frame_decode_xid()

Refactor patty_ax25_frame_decode_xid() to support the remote possibility
of multiple ISO 8885 groups

include/patty/ax25/frame.h

@@ -79,21 +79,13 @@ typedef struct _patty_ax25_frame {
     size_t infolen;
 } patty_ax25_frame;
 
-#pragma pack(push)
+enum patty_ax25_frame_xid_group_format {
-#pragma pack(1)
+    PATTY_AX25_FRAME_XID_GROUP_ISO8885 = 0x82
+};
 
-typedef struct _patty_ax25_frame_xid_element {
+enum patty_ax25_frame_xid_group_type {
-    uint8_t format,
+    PATTY_AX25_FRAME_XID_GROUP_PARAMS = 0x80
-            group;
+};
-
-    uint16_t len;
-} patty_ax25_frame_xid_element;
-
-typedef struct _patty_ax25_frame_xid_param {
-    uint8_t id, len;
-} patty_ax25_frame_xid_param;
-
-#pragma pack(pop)
 
 enum patty_ax25_frame_xid_param_type {
     PATTY_AX25_FRAME_XID_PARAM_CLASS     = 2,
@@ -105,9 +97,40 @@ enum patty_ax25_frame_xid_param_type {
     PATTY_AX25_FRAME_XID_PARAM_ACK       = 9
 };
 
+enum patty_ax25_frame_xid_param_class_flags {
+    PATTY_AX25_FRAME_XID_PARAM_CLASS_ABM         = (1 << 1),
+    PATTY_AX25_FRAME_XID_PARAM_CLASS_HALF_DUPLEX = (1 << 6),
+    PATTY_AX25_FRAME_XID_PARAM_CLASS_FULL_DUPLEX = (1 << 7)
+};
+
+enum patty_ax25_frame_xid_param_hdlc_flags {
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_REJ        = (1 <<  1),
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_SREJ       = (1 <<  2),
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_XADDR      = (1 <<  8),
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_MODULO_8   = (1 << 11),
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_MODULO_128 = (1 << 12),
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_TEST       = (1 << 14),
+    PATTY_AX25_FRAME_XID_PARAM_HDLC_SYNC_TX    = (1 << 18)
+};
+
+#pragma pack(push)
+#pragma pack(1)
+
+typedef struct _patty_ax25_frame_xid_group {
+    uint8_t format,
+            type;
+
+    uint16_t len;
+} patty_ax25_frame_xid_group;
+
+typedef struct _patty_ax25_frame_xid_param {
+    uint8_t id, len;
+} patty_ax25_frame_xid_param;
+
+#pragma pack(pop)
+
 typedef int (*patty_ax25_frame_xid_callback)(enum patty_ax25_frame_xid_param_type type,
-                                             size_t len,
+                                             uint32_t value,
-                                             uint8_t *data,
                                              void *ctx);
 
 ssize_t patty_ax25_frame_decode_address(patty_ax25_frame *frame,

src/frame.c

@@ -271,37 +271,45 @@ error:
     return -1;
 }
 
-ssize_t patty_ax25_frame_decode_xid(patty_ax25_frame_xid_callback callback,
+ssize_t decode_xid_group(patty_ax25_frame_xid_callback callback,
-                                    void *data,
+                         void *data,
-                                    size_t offset,
+                         size_t offset,
-                                    size_t len,
+                         size_t len,
-                                    void *ctx) {
+                         void *ctx) {
-    size_t start = offset;
+    patty_ax25_frame_xid_group *group = (patty_ax25_frame_xid_group *)
-
-    patty_ax25_frame_xid_element *elem = (patty_ax25_frame_xid_element *)
         ((uint8_t *)data + offset);
 
-    if (elem->format != 0x82 || elem->group != 0x80) {
+    size_t grouplen,
-        errno = EIO;
+           start = offset;
 
+    if (len - offset < sizeof(*group)) {
         goto error;
     }
 
-    if (be16toh(elem->len) != len - sizeof(*elem) - offset) {
+    grouplen = be16toh(group->len);
-        errno = EIO;
 
-        goto error;
+    offset += sizeof(*group);
+
+    if (group->format != PATTY_AX25_FRAME_XID_GROUP_ISO8885
+     || group->type   != PATTY_AX25_FRAME_XID_GROUP_PARAMS) {
+        offset += grouplen;
+
+        goto done;
     }
 
-    offset += sizeof(*elem);
+    while (offset - start < sizeof(*group) + grouplen) {
-
-    while (offset < len) {
         patty_ax25_frame_xid_param *param = (patty_ax25_frame_xid_param *)
             ((uint8_t *)data + offset);
 
+        uint32_t value = 0;
+        size_t i;
+
+        for (i=0; i<param->len; i++) {
+            value |= ((uint8_t *)(param + 1))[param->len-1-i] << (i << 3);
+        }
+
         if (callback(param->id,
-                     (size_t)param->len,
+                     value,
-                     (uint8_t *)(param + 1),
                      ctx) < 0) {
             goto error_callback;
         }
@@ -309,9 +317,38 @@ ssize_t patty_ax25_frame_decode_xid(patty_ax25_frame_xid_callback callback,
         offset += sizeof(*param) + param->len;
     }
 
-    if (offset != len) {
+    if (offset != start + sizeof(*group) + grouplen) {
-        errno = EIO;
+        goto error;
+    }
 
+done:
+    return offset - start;
+
+error:
+    errno = EIO;
+
+error_callback:
+    return -1;
+}
+
+ssize_t patty_ax25_frame_decode_xid(patty_ax25_frame_xid_callback callback,
+                                    void *data,
+                                    size_t offset,
+                                    size_t len,
+                                    void *ctx) {
+    size_t start = offset;
+
+    while (offset < len) {
+        ssize_t decoded;
+
+        if ((decoded = decode_xid_group(callback, data, offset, len, ctx)) < 0) {
+            goto error_decode_xid_group;
+        } else {
+            offset += decoded;
+        }
+    }
+
+    if (offset != len) {
         goto error;
     }
 
@@ -319,8 +356,10 @@ ssize_t patty_ax25_frame_decode_xid(patty_ax25_frame_xid_callback callback,
 
     return offset - start;
 
-error_callback:
 error:
+    errno = EIO;
+
+error_decode_xid_group:
     return -1;
 }