From 8a99083f0123765b6b73d7b5efccae1e88fff608 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Fri, 7 Aug 2009 17:16:52 +0000
Subject: [PATCH] Add an	evbuffer_search_range() to search a bounded range of a
 buffer

This can be handy when you have	one search to find the end of a	header
section, and then you want to find a substring within the header
section without looking at the body.

svn:r1410
---
 buffer.c                | 22 +++++++++++++++++++---
 include/event2/buffer.h | 16 ++++++++++++++++
 test/regress_buffer.c   | 14 +++++++++++++-
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/buffer.c b/buffer.c
index e54d7df4..c369f0ca 100644
--- a/buffer.c
+++ b/buffer.c
@@ -1967,9 +1967,15 @@ evbuffer_ptr_memcmp(const struct evbuffer *buf, const struct evbuffer_ptr *pos,
 
 struct evbuffer_ptr
 evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start)
+{
+	return evbuffer_search_range(buffer, what, len, start, NULL);
+}
+
+struct evbuffer_ptr
+evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start, const struct evbuffer_ptr *end)
 {
         struct evbuffer_ptr pos;
-        struct evbuffer_chain *chain;
+        struct evbuffer_chain *chain, *last_chain = NULL;
 	const unsigned char *p;
         char first;
 
@@ -1984,6 +1990,9 @@ evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const str
                 pos._internal.pos_in_chain = 0;
         }
 
+	if (end)
+		last_chain = end->_internal.chain;
+
         if (!len)
                 goto done;
 
@@ -1998,8 +2007,12 @@ evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const str
                 if (p) {
                         pos.pos += p - start_at;
                         pos._internal.pos_in_chain += p - start_at;
-                        if (!evbuffer_ptr_memcmp(buffer, &pos, what, len))
-                                goto done;
+                        if (!evbuffer_ptr_memcmp(buffer, &pos, what, len)) {
+				if (end && pos.pos + len > end->pos)
+					goto not_found;
+				else
+					goto done;
+			}
                         ++pos.pos;
                         ++pos._internal.pos_in_chain;
                         if (pos._internal.pos_in_chain == chain->off) {
@@ -2007,12 +2020,15 @@ evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const str
                                 pos._internal.pos_in_chain = 0;
                         }
                 } else {
+			if (chain == last_chain)
+				goto not_found;
                         pos.pos += chain->off - pos._internal.pos_in_chain;
                         chain = pos._internal.chain = chain->next;
                         pos._internal.pos_in_chain = 0;
                 }
         }
 
+not_found:
         pos.pos = -1;
         pos._internal.chain = NULL;
 done:
diff --git a/include/event2/buffer.h b/include/event2/buffer.h
index 50ea90f9..2a8e8378 100644
--- a/include/event2/buffer.h
+++ b/include/event2/buffer.h
@@ -456,6 +456,22 @@ int evbuffer_read(struct evbuffer *buffer, evutil_socket_t fd, int howmuch);
  */
 struct evbuffer_ptr evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start);
 
+/**
+   Search for a string within part of an evbuffer.
+
+   @param buffer the evbuffer to be searched
+   @param what the string to be searched for
+   @param len the length of the search string
+   @param start NULL or a pointer to a valid struct evbuffer_ptr that
+     indicates where we should start searching.
+   @param end NULL or a pointer to a valid struct evbuffer_ptr that
+     indicates where we should stop searching.
+   @return a struct evbuffer_ptr whose 'pos' field has the offset of the
+     first occurrence of the string in the buffer after 'start'.  The 'pos'
+     field of the result is -1 if the string was not found.
+ */
+struct evbuffer_ptr evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start, const struct evbuffer_ptr *end);
+
 enum evbuffer_ptr_how {
 	/** Sets the pointer to the position; can be called on with an
 	    uninitialized evbuffer_ptr. */
diff --git a/test/regress_buffer.c b/test/regress_buffer.c
index ff7cccad..a6031a02 100644
--- a/test/regress_buffer.c
+++ b/test/regress_buffer.c
@@ -715,7 +715,7 @@ test_evbuffer_search(void *ptr)
 {
 	struct evbuffer *buf = evbuffer_new();
 	struct evbuffer *tmp = evbuffer_new();
-	struct evbuffer_ptr pos;
+	struct evbuffer_ptr pos, end;
 
 	/* set up our chains */
 	evbuffer_add_printf(tmp, "hello");  /* 5 chars */
@@ -748,6 +748,18 @@ test_evbuffer_search(void *ptr)
 	pos = evbuffer_search(buf, "tat", 3, &pos);
 	tt_int_op(pos.pos, ==, 10);
 
+	/* test bounded search. */
+	/* Set "end" to the first t in "attack". */
+	evbuffer_ptr_set(buf, &end, 12, EVBUFFER_PTR_SET);
+	pos = evbuffer_search_range(buf, "foo", 3, NULL, &end);
+	tt_int_op(pos.pos, ==, 5);
+	pos = evbuffer_search_range(buf, "foocata", 7, NULL, &end);
+	tt_int_op(pos.pos, ==, 5);
+	pos = evbuffer_search_range(buf, "foocatat", 8, NULL, &end);
+	tt_int_op(pos.pos, ==, -1);
+	pos = evbuffer_search_range(buf, "ack", 3, NULL, &end);
+	tt_int_op(pos.pos, ==, -1);
+
 end:
 	if (buf)
 		evbuffer_free(buf);