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#include <string.h>
#include "bytequeue.h"
struct ByteQueue
{
gsize segment_size;
guint8 * segment;
guint8 * start;
guint8 * end;
};
ByteQueue *
byte_queue_new (void)
{
ByteQueue *queue = g_new0 (ByteQueue, 1);
queue->segment_size = 0;
queue->segment = NULL;
queue->start = NULL;
queue->end = NULL;
return queue;
}
guint8 *
byte_queue_free (ByteQueue *queue,
gboolean free_data)
{
guint8 *result;
if (free_data)
{
g_free (queue->segment);
result = NULL;
}
else
{
memmove (queue->segment, queue->start, queue->end - queue->start);
result = queue->segment;
}
g_free (queue);
return result;
}
/* The data returned is owned by the byte queue and becomes invalid
* as soon as any method is called on the queue. It is explicitly
* allowed to push the returned data back into the queue, and indeed
* in that case the queue will avoid copying if it can. The push
* must be the first method called on the queue after the read.
*/
const guint8 *
byte_queue_get_data (ByteQueue *queue,
gsize *n_bytes)
{
guint8 *result;
if (n_bytes)
*n_bytes = queue->end - queue->start;
result = queue->start;
queue->start = queue->segment;
queue->end = queue->segment;
return result;
}
static gboolean
in_segment (ByteQueue *queue,
const guint8 *bytes,
gsize n_bytes)
{
return bytes >= queue->segment && bytes + n_bytes < queue->end;
}
static gboolean
is_empty (ByteQueue *queue)
{
return queue->start == queue->end;
}
static gsize
power_of_two_bigger_than (gsize n)
{
gsize result = 1;
while (result <= n)
result *= 2;
return result;
}
static void
ensure_room (ByteQueue *queue,
gsize extra)
{
gsize old_data_size = queue->end - queue->start;
gsize new_data_size = old_data_size + extra;
if (queue->end + new_data_size > queue->segment + queue->segment_size)
{
gsize new_segment_size = power_of_two_bigger_than (2 * new_data_size);
memmove (queue->start, queue->segment, old_data_size);
if (new_segment_size > queue->segment_size)
{
queue->segment_size = new_segment_size;
queue->segment = g_realloc (queue->segment, new_segment_size);
}
queue->start = queue->segment;
queue->end = queue->start + new_data_size;
}
}
guint8 *
byte_queue_alloc_tail (ByteQueue *queue,
gsize size)
{
ensure_room (queue, size);
queue->end += size;
return queue->end - size;
}
void
byte_queue_delete_tail (ByteQueue *queue,
gsize size)
{
if (queue->end - queue->start < size)
queue->end = queue->start;
else
queue->end -= size;
}
void
byte_queue_append (ByteQueue *queue,
const guint8 *bytes,
gsize n_bytes)
{
if (in_segment (queue, bytes, n_bytes) && is_empty (queue))
{
queue->start = (guint8 *)bytes;
queue->end = (guint8 *)bytes + n_bytes;
}
else
{
guint8 *tail = byte_queue_alloc_tail (queue, n_bytes);
memcpy (tail, bytes, n_bytes);
}
}
/* Transfer data from @src to @dest, if possible without copying.
* The data is appended to @dest's data if @dest is not empty
*/
void
byte_queue_steal_data (ByteQueue *dest,
ByteQueue *src)
{
if (is_empty (dest))
{
if (dest->segment)
g_free (dest->segment);
dest->segment_size = src->segment_size;
dest->segment = src->segment;
dest->start = src->start;
dest->end = src->end;
src->segment_size = 0;
src->segment = NULL;
src->start = NULL;
src->end = NULL;
}
else
{
const guint8 *data;
gsize size;
data = byte_queue_get_data (src, &size);
byte_queue_append (dest, data, size);
}
}
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