File: packet.c

package info (click to toggle)
enet 1.3.13+ds-1
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 564 kB
  • sloc: ansic: 4,734; xml: 179; makefile: 42
file content (165 lines) | stat: -rw-r--r-- 3,904 bytes parent folder | download | duplicates (7)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
/** 
 @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);
}

/** @} */