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/**
@file packet.c
@brief ENet packet management functions
*/
#include <string.h>
#define ENET_BUILDING_LIB 1
#include "enet.h"
/** @defgroup Packet ENet packet functions
@{
*/
/** Creates a packet that may be sent to a peer.
@param data initial contents of the packet's data; the packet's data will remain uninitialized if data is NULL.
@param dataLength size of the data allocated for this packet
@param flags flags for this packet as described for the ENetPacket structure.
@returns the packet on success, NULL on failure
*/
ENetPacket *
enet_packet_create (const void * data, size_t dataLength, enet_uint32 flags)
{
ENetPacket * packet = (ENetPacket *) enet_malloc (sizeof (ENetPacket));
if (packet == NULL)
return NULL;
if (flags & ENET_PACKET_FLAG_NO_ALLOCATE)
packet -> data = const_cast<enet_uint8 *>(static_cast<const enet_uint8 *>(data));
else
if (dataLength <= 0)
packet -> data = NULL;
else
{
packet -> data = (enet_uint8 *) enet_malloc (dataLength);
if (packet -> data == NULL)
{
enet_free (packet);
return NULL;
}
if (data != NULL)
memcpy (packet -> data, data, dataLength);
}
packet -> referenceCount = 0;
packet -> flags = flags;
packet -> dataLength = dataLength;
packet -> freeCallback = NULL;
packet -> userData = NULL;
return packet;
}
/** Destroys the packet and deallocates its data.
@param packet packet to be destroyed
*/
void
enet_packet_destroy (ENetPacket * packet)
{
if (packet == NULL)
return;
if (packet -> freeCallback != NULL)
(* packet -> freeCallback) (packet);
if (! (packet -> flags & ENET_PACKET_FLAG_NO_ALLOCATE) &&
packet -> data != NULL)
enet_free (packet -> data);
enet_free (packet);
}
/** Attempts to resize the data in the packet to length specified in the
dataLength parameter
@param packet packet to resize
@param dataLength new size for the packet data
@returns 0 on success, < 0 on failure
*/
int
enet_packet_resize (ENetPacket * packet, size_t dataLength)
{
enet_uint8 * newData;
if (dataLength <= packet -> dataLength || (packet -> flags & ENET_PACKET_FLAG_NO_ALLOCATE))
{
packet -> dataLength = dataLength;
return 0;
}
newData = (enet_uint8 *) enet_malloc (dataLength);
if (newData == NULL)
return -1;
memcpy (newData, packet -> data, packet -> dataLength);
enet_free (packet -> data);
packet -> data = newData;
packet -> dataLength = dataLength;
return 0;
}
static int initializedCRC32 = 0;
static enet_uint32 crcTable [256];
static enet_uint32
reflect_crc (int val, int bits)
{
int result = 0, bit;
for (bit = 0; bit < bits; bit ++)
{
if(val & 1) result |= 1 << (bits - 1 - bit);
val >>= 1;
}
return result;
}
static void
initialize_crc32 (void)
{
int byte;
for (byte = 0; byte < 256; ++ byte)
{
enet_uint32 crc = reflect_crc (byte, 8) << 24;
int offset;
for(offset = 0; offset < 8; ++ offset)
{
if (crc & 0x80000000)
crc = (crc << 1) ^ 0x04c11db7;
else
crc <<= 1;
}
crcTable [byte] = reflect_crc (crc, 32);
}
initializedCRC32 = 1;
}
enet_uint32
enet_crc32 (const ENetBuffer * buffers, size_t bufferCount)
{
enet_uint32 crc = 0xFFFFFFFF;
if (! initializedCRC32) initialize_crc32 ();
while (bufferCount -- > 0)
{
const enet_uint8 * data = (const enet_uint8 *) buffers -> data,
* dataEnd = & data [buffers -> dataLength];
while (data < dataEnd)
{
crc = (crc >> 8) ^ crcTable [(crc & 0xFF) ^ *data++];
}
++ buffers;
}
return ENET_HOST_TO_NET_32 (~ crc);
}
/** @} */
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