Ticket #810: net_buffer.diff

net_buffer.cpp

@@ -146 +146 @@
 
 
 static status_t append_data(net_buffer *buffer, const void *data, size_t size);
+static status_t append_data_from_buffer(net_buffer *from, net_buffer *to, 
+                    size_t size);
 static status_t trim_data(net_buffer *_buffer, size_t newSize);
 static status_t remove_header(net_buffer *_buffer, size_t bytes);
 static status_t remove_trailer(net_buffer *_buffer, size_t bytes);
@@ -1213 +1215 @@
 /*!
     Split the buffer at offset, the header data
     is returned as new buffer.
-    TODO: optimize and avoid making a copy.
 */
 static net_buffer *
 split_buffer(net_buffer *from, uint32 offset)
 {
-    // TODO: Copying the whole buffer becomes less and less efficient with
-    // greater size - offset differences. What we actually want is a method
-    // to copy data from one buffer to another. Then the following should be:
-    // create buffer, resize, copy data. An additional append_data_from_buffer()
-    // method would be even better.
-    net_buffer *buffer = duplicate_buffer(from);
+    net_buffer *buffer = create_buffer(DATA_NODE_SIZE);
     if (buffer == NULL)
         return NULL;
+    copy_metadata(buffer, from);
 
     ParanoiaChecker _(from);
     ParanoiaChecker _2(buffer);
@@ -1233 +1230 @@
     TRACE(("%ld: split_buffer(buffer %p -> %p, offset %ld)\n",
         find_thread(NULL), from, buffer, offset));
 
-    if (trim_data(buffer, offset) == B_OK) {
+    if (append_data_from_buffer(from, buffer, offset) == B_OK) {
         if (remove_header(from, offset) == B_OK) {
             CHECK_BUFFER(from);
             CHECK_BUFFER(buffer);
@@ -1649 +1646 @@
 }
 
 
+static status_t
+append_data_from_buffer(net_buffer *from, net_buffer *to, size_t size)
+{
+    net_buffer_private *source = (net_buffer_private *)from;
+    net_buffer_private *dest = (net_buffer_private *)to;
+
+    if (size > from->size)
+        return B_BAD_VALUE;
+    if (size == 0)
+        return B_OK;
+
+    data_node *nodeTo = get_node_at_offset(source, size);
+    if (nodeTo == NULL) {
+        return B_BAD_VALUE;
+    }
+
+    data_node *node = (data_node *)list_get_first_item(&source->buffers);
+    if (node == NULL) {
+        CHECK_BUFFER(source);
+        return B_ERROR;
+    }
+
+    while (node != nodeTo) {
+        if (append_data(dest, node->start, node->used) < B_OK) {
+            CHECK_BUFFER(dest);
+            return B_ERROR;
+        }
+
+        node = (data_node *)list_get_next_item(&source->buffers, node);
+    }
+
+    int32 diff = node->offset + node->used - size;
+    if (append_data(dest, node->start, node->used - diff) < B_OK) {
+        CHECK_BUFFER(dest);
+        return B_ERROR;
+    }
+
+    CHECK_BUFFER(dest);
+
+    return B_OK;
+}
+
+
 /*!
     Removes bytes from the beginning of the buffer.
 */