Index: ossp-pkg/sio/al.c
RCS File: /v/ossp/cvs/ossp-pkg/sio/Attic/al.c,v
rcsdiff -q -kk '-r1.30' '-r1.31' -u '/v/ossp/cvs/ossp-pkg/sio/Attic/al.c,v' 2>/dev/null
--- al.c	2002/10/23 13:59:30	1.30
+++ al.c	2002/10/23 16:49:29	1.31
@@ -579,7 +579,7 @@
     al_chunk_t  *cur;
 
     /* argument sanity check(s) */
-    if (al == NULL || p == NULL || n < 0)
+    if (al == NULL || p == NULL || n <= 0)
         return AL_RC(AL_ERR_ARG);
 
     rc = make_buffer(al, p, n, freemem, u, &buf);
@@ -874,12 +874,27 @@
         tx->view.end    = tx->view.begin + step;
 
         switch (tx->dir) {
+        case AL_FORWARD:
+        case AL_BACKWARD:
+            break;
+        case AL_FORWARD_SPAN:
+        case AL_BACKWARD_SPAN:
+            if (!AL_SAME_LABEL(&tx->view, tx->label)) {
+                tx->togo = 0;
+                return AL_ERR_EOF;
+            }
+            break;
+        }
+
+        switch (tx->dir) {
             case AL_FORWARD:
+            case AL_FORWARD_SPAN:
                 tx->cur   = NEXT(tx->cur,chunks);
                 tx->togo -= step;
                 tx->skip  = 0;
                 break;
             case AL_BACKWARD:
+            case AL_BACKWARD_SPAN:
                 tx->cur   = PREV(tx->cur,chunks);
                 tx->togo -= step;
                 tx->skip  = 0;
@@ -948,7 +963,7 @@
  * traversal context is kept on stack (XXX ?)
  */
 al_rc_t
-al_flatten(al_t *al, size_t off, size_t n, al_label_t label,
+al_flatten(al_t *al, size_t off, size_t n, al_td_t dir, al_label_t label,
            char *dst, size_t *lenp)
 {
     al_rc_t rc;
@@ -958,20 +973,42 @@
 
     *lenp = 0; /* keep caller on safe side */
 
-    rc = al_traverse(al, off, n, AL_FORWARD, label, &tx);
+    rc = al_traverse(al, off, n, dir, label, &tx);
     if (rc != AL_OK)
         return AL_RC(rc);
 
+    switch (dir) {
+    case AL_FORWARD:
+    case AL_FORWARD_SPAN:
+        break;
+    case AL_BACKWARD:
+    case AL_BACKWARD_SPAN:
+        dst += n;
+        break;
+    }
+
     total = 0;
-    while ((rc = al_traverse_next(al, &tx, &view)) == AL_OK) {
-        step = AL_CHUNK_LEN(view);
 
-        if (dst != NULL) {
-            memmove(dst, AL_CHUNK_PTR(view, 0), step);
-            dst   += step;
+    if (dst == NULL) {
+        while ((rc = al_traverse_next(al, &tx, &view)) == AL_OK)
+            total += AL_CHUNK_LEN(view);
+    } else {
+        while ((rc = al_traverse_next(al, &tx, &view)) == AL_OK) {
+            step = AL_CHUNK_LEN(view);
+            switch (dir) {
+            case AL_FORWARD:
+            case AL_FORWARD_SPAN:
+                memmove(dst, AL_CHUNK_PTR(view, 0), step);
+                dst   += step;
+                break;
+            case AL_BACKWARD:
+            case AL_BACKWARD_SPAN:
+                dst   -= step;
+                memmove(dst, AL_CHUNK_PTR(view, 0), step);
+                break;
+            }
+            total += step;
         }
-
-        total += step;
     }
     *lenp = total;
 
@@ -1014,6 +1051,31 @@
 }
 
 /*
+ * traverse assembly line and retrieve first chunk
+ *
+ * traversal context is kept on stack (XXX ?)
+ */
+al_rc_t
+al_firstlabel(al_t *al, size_t off, size_t n, al_td_t dir, al_label_t label,
+              al_label_t *labelp)
+{
+    al_rc_t rc;
+    al_tx_t tx;                /* XXX - private tx structure on stack */
+    al_chunk_t *view;
+
+    rc = al_traverse(al, off, n, dir, label, &tx);
+    if (rc != AL_OK)
+        return AL_RC(rc);
+
+    if ((rc = al_traverse_next(al, &tx, &view)) == AL_OK)
+        *labelp = AL_CHUNK_LABEL(view);
+
+    al_traverse_end(al, &tx, 1);
+
+    return rc;
+}
+
+/*
  * relay macros to caller
  *
  * al_bytes      - total number of bytes in assembly line
Index: ossp-pkg/sio/al.h
RCS File: /v/ossp/cvs/ossp-pkg/sio/Attic/al.h,v
rcsdiff -q -kk '-r1.13' '-r1.14' -u '/v/ossp/cvs/ossp-pkg/sio/Attic/al.h,v' 2>/dev/null
--- al.h	2002/10/22 15:33:16	1.13
+++ al.h	2002/10/23 16:49:29	1.14
@@ -50,7 +50,9 @@
 
 typedef enum {
     AL_FORWARD,
-    AL_BACKWARD
+    AL_BACKWARD,
+    AL_FORWARD_SPAN,
+    AL_BACKWARD_SPAN
 } al_td_t;
 
 struct al_tx_st;
@@ -69,7 +71,8 @@
 al_rc_t al_traverse_cb  (al_t *al, size_t off, size_t n, al_td_t dir, al_label_t, al_rc_t (*cb)(al_chunk_t *, void *), void *u);
 al_rc_t al_copy         (al_t *al, size_t off, size_t n, al_label_t label, al_t *tal);
 al_rc_t al_splice       (al_t *al, size_t off, size_t n, al_t *nal, al_t *tal);
-al_rc_t al_flatten      (al_t *al, size_t off, size_t n, al_label_t label, char *dst, size_t *lenp);
+al_rc_t al_flatten      (al_t *al, size_t off, size_t n, al_td_t dir, al_label_t label, char *dst, size_t *lenp);
+al_rc_t al_firstlabel   (al_t *al, size_t off, size_t n, al_td_t dir, al_label_t label, al_label_t *labelp);
 
 size_t     al_bytes      (const al_t *al);
 size_t     al_chunk_len  (al_chunk_t *alc);
Index: ossp-pkg/sio/al.pod
RCS File: /v/ossp/cvs/ossp-pkg/sio/Attic/al.pod,v
rcsdiff -q -kk '-r1.11' '-r1.12' -u '/v/ossp/cvs/ossp-pkg/sio/Attic/al.pod,v' 2>/dev/null
--- al.pod	2002/10/22 15:33:16	1.11
+++ al.pod	2002/10/23 16:49:29	1.12
@@ -122,6 +122,14 @@
 This is an opaque data type representing a data buffer.
 Only pointers to this abstract data type are used in the API.
 
+=item B<al_label_t> (Label Type)
+
+This is an opaque pointer type representing a specific data flavour.
+You can restrict traversal operations to data that was marked with
+the specific flavour. Usually you would cast a pointer to the
+object that maintains the data to B<al_label_t>. You may use
+NULL as a label but on traversal NULL matches any label.
+
 =item B<al_tx_t> (Traversal Context Type)
 
 This is an opaque data type representing the state of a buffer
@@ -133,8 +141,10 @@
 This is an exported enumerated integer type with the following possible
 values:
 
- AL_FORWARD    traverse assembly line from beginning to end
- AL_BACKWARD   traverse assembly line from end to beginning
+ AL_FORWARD        traverse assembly line from beginning to end
+ AL_BACKWARD       traverse assembly line from end to beginning
+ AL_FORWARD_SPAN   like AL_FORWARD, but stop when label does not match
+ AL_BACKWARD_SPAN  like AL_BACKWARD, but stop when label does not match
 
 =item B<al_chunk_t> (Chunk Type)
 
@@ -143,14 +153,6 @@
 used in the API. The B<al_chunk_t> type is used to generate a pointer
 and byte count to access the data in the buffer.
 
-=item B<al_label_t> (Label Type)
-
-This is a pointer type representing a specific data flavour. You
-can restrict traversal operations to data that was marked with
-the specific flavour. Usually you would cast a pointer to the
-object that maintains the data to B<al_label_t>. You may use
-NULL as a label but on traversal NULL matches any label.
-
 =back
 
 =head1 FUNCTIONS
@@ -335,7 +337,7 @@
 
 =over 4
 
-=item al_rc_t B<al_flatten>(al_t *I<al>, size_t I<off>, size_t I<n>, char *I<dst>, size_t *I<lenp>);
+=item al_rc_t B<al_flatten>(al_t *I<al>, size_t I<off>, size_t I<n>, al_td_t I<dir>, char *I<dst>, size_t *I<lenp>);
 
 I<off> and I<n> are byte counts that define a span of bytes with the
 assembly line I<al>. These bytes are copied to the storage array I<dst>
@@ -348,6 +350,8 @@
 still counted in I<lenp>. This can be used to precalculate the size
 of the needed storage array by passing an arbitrary high maximum size
 as I<n>.
+If I<dir> denotes a backwards traversal the storage array is filled
+from its end.
 
 Example:
 
@@ -355,7 +359,7 @@
  char buffer[42];
  size_t actual;
 
- al_flatten(al, 500, 42, buffer, &actual);
+ al_flatten(al, 500, 42, AL_FORWARD, buffer, &actual);
 
 =item al_rc_t B<al_copy>(al_t *I<al>, size_t I<off>, size_t I<n>, al_t *I<tal>);
 
Index: ossp-pkg/sio/al_test.c
RCS File: /v/ossp/cvs/ossp-pkg/sio/Attic/al_test.c,v
rcsdiff -q -kk '-r1.14' '-r1.15' -u '/v/ossp/cvs/ossp-pkg/sio/Attic/al_test.c,v' 2>/dev/null
--- al_test.c	2002/10/22 15:33:16	1.14
+++ al_test.c	2002/10/23 16:49:29	1.15
@@ -104,7 +104,7 @@
     buf = (char *)malloc(n);
     if (buf == NULL) abort();
 
-    al_flatten(al, 0, n, LABEL, buf, &len);
+    al_flatten(al, 0, n, AL_FORWARD, LABEL, buf, &len);
 
     printf("%s = %d of %d\n",tag,len,n);
     fwrite(">>", 2, 1, stdout);