[PATCH 1/3] mime node: Record depth-first part numbers

[Austin Clements <amdragon@MIT.EDU>]

This makes the part numbers readily accessible to formatters.
Hierarchical part numbering would be a more natural and efficient fit
for MIME and may be the way to go in the future, but depth-first
numbering maintains compatibility with what we currently do.
---
 mime-node.c      |   33 ++++++++++++++++++++++++++++++++-
 notmuch-client.h |   11 +++++++++++
 2 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/mime-node.c b/mime-node.c
index d26bb44..30b542f 100644
--- a/mime-node.c
+++ b/mime-node.c
@@ -104,6 +104,10 @@ mime_node_open (const void *ctx, notmuch_message_t *message,
     root->nchildren = 1;
     root->ctx = mctx;
 
+    root->part_num = 0;
+    root->next_child = 0;
+    root->next_part_num = 1;
+
     *root_out = root;
     return NOTMUCH_STATUS_SUCCESS;
 
@@ -133,6 +137,8 @@ _mime_node_create (const mime_node_t *parent, GMimeObject *part)
 	talloc_free (node);
 	return NULL;
     }
+    node->parent = parent;
+    node->part_num = node->next_part_num = -1;
 
     /* Deal with the different types of parts */
     if (GMIME_IS_PART (part)) {
@@ -217,6 +223,7 @@ mime_node_t *
 mime_node_child (const mime_node_t *parent, int child)
 {
     GMimeObject *sub;
+    mime_node_t *node;
 
     if (!parent || child < 0 || child >= parent->nchildren)
 	return NULL;
@@ -234,7 +241,31 @@ mime_node_child (const mime_node_t *parent, int child)
 	INTERNAL_ERROR ("Unexpected GMimeObject type: %s",
 			g_type_name (G_OBJECT_TYPE (parent->part)));
     }
-    return _mime_node_create (parent, sub);
+    node = _mime_node_create (parent, sub);
+
+    if (child == parent->next_child && parent->next_part_num != -1) {
+	/* We're traversing in depth-first order.  Record the child's
+	 * depth-first numbering. */
+	node->part_num = parent->next_part_num;
+	node->next_part_num = node->part_num + 1;
+
+	/* Drop the const qualifier because these are internal fields
+	 * whose mutability doesn't affect the interface. */
+	((mime_node_t*)parent)->next_child++;
+	((mime_node_t*)parent)->next_part_num = -1;
+
+	if (node->nchildren == 0) {
+	    /* We've reached a leaf, so find the parent that has more
+	     * children and set it up to number its next child. */
+	    const mime_node_t *it = node;
+	    while (it && it->next_child == it->nchildren)
+		it = it->parent;
+	    if (it)
+		((mime_node_t*)it)->next_part_num = node->part_num + 1;
+	}
+    }
+
+    return node;
 }
 
 static mime_node_t *
diff --git a/notmuch-client.h b/notmuch-client.h
index 62ede28..b3dcb6b 100644
--- a/notmuch-client.h
+++ b/notmuch-client.h
@@ -281,6 +281,13 @@ typedef struct mime_node {
     /* The number of children of this part. */
     int nchildren;
 
+    /* The parent of this node or NULL if this is the root node. */
+    const struct mime_node *parent;
+
+    /* The depth-first part number of this child if the MIME tree is
+     * being traversed in depth-first order, or -1 otherwise. */
+    int part_num;
+
     /* True if decryption of this part was attempted. */
     notmuch_bool_t decrypt_attempted;
     /* True if decryption of this part's child succeeded.  In this
@@ -302,6 +309,10 @@ typedef struct mime_node {
     /* Internal: For successfully decrypted multipart parts, the
      * decrypted part to substitute for the second child. */
     GMimeObject *decrypted_child;
+
+    /* Internal: The next child for depth-first traversal and the part
+     * number to assign it (or -1 if unknown). */
+    int next_child, next_part_num;
 } mime_node_t;
 
 /* Construct a new MIME node pointing to the root message part of
-- 
1.7.7.3