1 files changed, 70 insertions, 16 deletions

diff --git a/src/utils/buffer.c b/src/utils/buffer.c
index 716e67c..5e0f58c 100644
--- a/src/utils/buffer.c
+++ b/src/utils/buffer.c
@@ -30,12 +30,13 @@ parserutils_error parserutils_buffer_create(parserutils_buffer **buffer)
 	if (b == NULL)
 		return PARSERUTILS_NOMEM;
 
-	b->data = malloc(DEFAULT_SIZE);
-	if (b->data == NULL) {
+	b->alloc = malloc(DEFAULT_SIZE);
+	if (b->alloc == NULL) {
 		free(b);
 		return PARSERUTILS_NOMEM;
 	}
 
+	b->data = b->alloc;
 	b->length = 0;
 	b->allocated = DEFAULT_SIZE;
 
@@ -55,13 +56,59 @@ parserutils_error parserutils_buffer_destroy(parserutils_buffer *buffer)
 	if (buffer == NULL)
 		return PARSERUTILS_BADPARM;
 
-	free(buffer->data);
+	free(buffer->alloc);
 	free(buffer);
 
 	return PARSERUTILS_OK;
 }
 
 /**
+ * Get current data offset within buffer's allocation.
+ *
+ * \param[in]  buffer  The buffer object.
+ * \return data offset in bytes.
+ */
+static inline size_t get_offset(parserutils_buffer *buffer)
+{
+	return buffer->data - buffer->alloc;
+}
+
+/**
+ * Try moving the data to the start of the allocation.
+ *
+ * \param[in]  buffer  The buffer object.
+ */
+static inline void try_rebase(parserutils_buffer *buffer)
+{
+	if (get_offset(buffer) >= buffer->length) {
+		memcpy(buffer->alloc, buffer->data, buffer->length);
+		buffer->data = buffer->alloc;
+	}
+}
+
+/**
+ * Ensure that the buffer has enough space at the end to add len bytes.
+ *
+ * \param[in]  buffer  The buffer object.
+ * \param[in]  len     Number of bytes to ensure there is space for.
+ * \return PARSERUTILS_OK on success, appropriate error otherwise.
+ */
+static inline parserutils_error ensure_space(
+		parserutils_buffer *buffer,
+		size_t len)
+{
+	try_rebase(buffer);
+
+	while (len >= buffer->allocated - buffer->length - get_offset(buffer)) {
+		parserutils_error error = parserutils_buffer_grow(buffer);
+		if (error != PARSERUTILS_OK)
+			return error;
+	}
+
+	return PARSERUTILS_OK;
+}
+
+/**
  * Append data to a memory buffer
  *
  * \param buffer  The buffer to append to
@@ -72,11 +119,9 @@ parserutils_error parserutils_buffer_destroy(parserutils_buffer *buffer)
 parserutils_error parserutils_buffer_append(parserutils_buffer *buffer, 
 		const uint8_t *data, size_t len)
 {
-	while (len >= buffer->allocated - buffer->length) {
-		parserutils_error error = parserutils_buffer_grow(buffer);
-		if (error != PARSERUTILS_OK)
-			return error;
-	}
+	parserutils_error error = ensure_space(buffer, len);
+	if (error != PARSERUTILS_OK)
+		return error;
 
 	memcpy(buffer->data + buffer->length, data, len);
 
@@ -97,17 +142,17 @@ parserutils_error parserutils_buffer_append(parserutils_buffer *buffer,
 parserutils_error parserutils_buffer_insert(parserutils_buffer *buffer, 
 		size_t offset, const uint8_t *data, size_t len)
 {
+	parserutils_error error;
+
 	if (offset > buffer->length)
 		return PARSERUTILS_BADPARM;
 
 	if (offset == buffer->length)
 		return parserutils_buffer_append(buffer, data, len);
 
-	while (len >= buffer->allocated - buffer->length) {
-		parserutils_error error = parserutils_buffer_grow(buffer);
-		if (error != PARSERUTILS_OK)
-			return error;
-	}
+	error = ensure_space(buffer, len);
+	if (error != PARSERUTILS_OK)
+		return error;
 
 	memmove(buffer->data + offset + len,
 			buffer->data + offset, buffer->length - offset);
@@ -133,6 +178,13 @@ parserutils_error parserutils_buffer_discard(parserutils_buffer *buffer,
 	if (offset >= buffer->length || offset + len > buffer->length)
 		return PARSERUTILS_BADPARM;
 
+	if (offset == 0) {
+		buffer->data += len;
+		buffer->length -= len;
+		try_rebase(buffer);
+		return PARSERUTILS_OK;
+	}
+
 	memmove(buffer->data + offset, buffer->data + offset + len, 
 			buffer->length - (len + offset));
 
@@ -149,11 +201,13 @@ parserutils_error parserutils_buffer_discard(parserutils_buffer *buffer,
  */
 parserutils_error parserutils_buffer_grow(parserutils_buffer *buffer)
 {
-	uint8_t *temp = realloc(buffer->data, buffer->allocated * 2);
+	size_t offset = get_offset(buffer);
+	uint8_t *temp = realloc(buffer->alloc, buffer->allocated * 2);
 	if (temp == NULL)
 		return PARSERUTILS_NOMEM;
 
-	buffer->data = temp;
+	buffer->alloc = temp;
+	buffer->data = buffer->alloc + offset;
 	buffer->allocated *= 2;
 
 	return PARSERUTILS_OK;
@@ -180,7 +234,7 @@ parserutils_error parserutils_buffer_randomise(parserutils_buffer *buffer)
 	/* Leak the buffer's current data, so we don't reuse it */
 	/* buffer->alloc(buffer->data, 0, buffer->pw); */
 
-	buffer->data = temp;
+	buffer->alloc = buffer->data = temp;
 #endif