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- /**
- @file packet.c
- @brief ENet packet management functions
- */
- #include <string.h>
- #define ENET_BUILDING_LIB 1
- #include "enet/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 = (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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