Merge remote-tracking branch 'origin/topic/jazoff/fuzz-size-limit-speedup'

- Factored check into more descriptive function: ExceedsChunkLimit()

* origin/topic/jazoff/fuzz-size-limit-speedup:
  Speed up ChunkCount validity check

CHANGES

@@ -1,4 +1,8 @@
 
+3.2.0-dev.557 | 2020-05-21 11:41:12 -0700
+
+  * Speed up FuzzBuffer ChunkCount validity check (Justin Azoff, Corelight)
+
 3.2.0-dev.555 | 2020-05-20 11:19:08 -0700
 
   * Disable output of Reporter messages to stderr in fuzz targets (Jon Siwek, Corelight)

VERSION

@@ -1 +1 @@
-3.2.0-dev.555
+3.2.0-dev.557

src/fuzzers/FuzzBuffer.cc

@@ -14,18 +14,18 @@ bool zeek::detail::FuzzBuffer::Valid(int chunk_count_limit) const
 	if ( memcmp(begin, PKT_MAGIC, PKT_MAGIC_LEN) != 0)
 		return false;
 
-	if ( ChunkCount() > chunk_count_limit )
+	if ( ExceedsChunkLimit(chunk_count_limit) )
 		return false;
 
 	return true;
 	}
 
-int zeek::detail::FuzzBuffer::ChunkCount() const
+int zeek::detail::FuzzBuffer::ChunkCount(int chunk_count_limit) const
 	{
 	auto pos = begin;
 	int chunks = 0;
 
-	while ( pos < end )
+	while ( pos < end && (chunks < chunk_count_limit || chunk_count_limit == 0) )
 		{
 		pos = (const unsigned char*)memmem(pos, end - pos,
 		                                   PKT_MAGIC, PKT_MAGIC_LEN);

src/fuzzers/FuzzBuffer.h

@@ -47,9 +47,18 @@ public:
 	bool Valid(int chunk_count_limit = MAX_CHUNK_COUNT) const;
 
 	/**
+	 * @param chunk_count_limit  Number of chunks to stop counting at (zero
+	 * means "never stop").
 	 * @return  the number of chunks in the fuzz buffer object
 	 */
-	int ChunkCount() const;
+	int ChunkCount(int chunk_count_limit = 0) const;
+
+	/**
+	 * @param  Maximum number of chunks to permit the FuzzBuffer to have.
+	 * @return  Whether the FuzzBuffer exceeds the desired chunk count limit.
+	 */
+	bool ExceedsChunkLimit(int chunk_count_limit) const
+		{ return ChunkCount(chunk_count_limit + 1) > chunk_count_limit; }
 
 	/**
 	 * @return  the next chunk to deliver, if one could be extracted