From fe6f8b92c7f1f72a0eb677f01899f1dfa07b5342 Mon Sep 17 00:00:00 2001
From: Kovarththanan Rajaratnam <kovarththanan.rajaratnam@gmail.com>
Date: Sun, 16 Aug 2009 10:53:47 +0000
Subject: Add a new function, tvb_new_subset_remaining(), which is a sligtly
 optimized version of tvb_new_subset(). The latter can be mapped to the former
 by tvb_new_subset(tvb, offset, -1 /* backing_length */, -1 /* reported_length
 */). We can disable some bounds checking because 'backing_length' and
 'reported_length' are hardcoded to -1.

The current implementation of tvb_new_subset_remaining() only has the THROW_ON(reported_length < 1) check removed when compared to tvb_new_subset(). So there's room for improvement in this function. We should be able to disable some more (redundant) bounds checking.

svn path=/trunk/; revision=29445
---
 epan/tvbuff.c | 38 +++++++++++++++++++++++++++++++++++---
 epan/tvbuff.h |  4 ++++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/epan/tvbuff.c b/epan/tvbuff.c
index b875446642..25dc16f675 100644
--- a/epan/tvbuff.c
+++ b/epan/tvbuff.c
@@ -145,6 +145,16 @@ tvb_new(tvbuff_type type)
 	return tvb;
 }
 
+static tvbuff_t*
+tvb_new_with_subset(tvbuff_type type, guint subset_tvb_offset, guint subset_tvb_length)
+{
+	tvbuff_t *tvb = tvb_new(type);
+	tvb->tvbuffs.subset.offset = subset_tvb_offset;
+	tvb->tvbuffs.subset.length = subset_tvb_length;
+
+	return tvb;
+}
+
 void
 tvb_free(tvbuff_t* tvb)
 {
@@ -513,9 +523,7 @@ tvb_new_subset(tvbuff_t *backing, gint backing_offset, gint backing_length, gint
 			&subset_tvb_offset,
 			&subset_tvb_length);
 
-	tvb = tvb_new(TVBUFF_SUBSET);
-	tvb->tvbuffs.subset.offset = subset_tvb_offset;
-	tvb->tvbuffs.subset.length = subset_tvb_length;
+	tvb = tvb_new_with_subset(TVBUFF_SUBSET, subset_tvb_offset, subset_tvb_length);
 
 	tvb_set_subset_no_exceptions(tvb, backing, reported_length);
 
@@ -528,6 +536,30 @@ tvb_new_subset(tvbuff_t *backing, gint backing_offset, gint backing_length, gint
 	return tvb;
 }
 
+tvbuff_t*
+tvb_new_subset_remaining(tvbuff_t *backing, gint backing_offset)
+{
+	tvbuff_t	*tvb;
+	guint		subset_tvb_offset;
+	guint		subset_tvb_length;
+
+	check_offset_length(backing->length, backing->reported_length, backing_offset, -1 /* backing_length */,
+			&subset_tvb_offset,
+			&subset_tvb_length);
+
+	tvb = tvb_new_with_subset(TVBUFF_SUBSET, subset_tvb_offset, subset_tvb_length);
+
+	tvb_set_subset_no_exceptions(tvb, backing, -1 /* reported_length */);
+
+	/*
+	 * The top-level data source of this tvbuff is the top-level
+	 * data source of its parent.
+	 */
+	tvb->ds_tvb = backing->ds_tvb;
+
+	return tvb;
+}
+
 void
 tvb_composite_append(tvbuff_t* tvb, tvbuff_t* member)
 {
diff --git a/epan/tvbuff.h b/epan/tvbuff.h
index 06adc07c8f..8632b4da28 100644
--- a/epan/tvbuff.h
+++ b/epan/tvbuff.h
@@ -241,6 +241,10 @@ extern void tvb_set_subset(tvbuff_t* tvb, tvbuff_t* backing,
 extern tvbuff_t* tvb_new_subset(tvbuff_t* backing,
 		gint backing_offset, gint backing_length, gint reported_length);
 
+/** Similar to tvb_new_subset() but with backing_length and reported_length set to -1.
+ * Can throw ReportedBoundsError. */
+extern tvbuff_t* tvb_new_subset_remaining(tvbuff_t* backing,
+		gint backing_offset);
 
 /** Both tvb_composite_append and tvb_composite_prepend can throw
  * BoundsError if member_offset/member_length goes beyond bounds of
-- 
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