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1/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
2 It is considered beerware. Prost. Skol. Cheers or whatever. */
3
4/* System */
5#include <stdlib.h>
6#include <string.h>
7
8/* Opentracker */
9#include "trackerlogic.h"
10#include "ot_vector.h"
11
12/* This function gives us a binary search that returns a pointer, even if
13 no exact match is found. In that case it sets exactmatch 0 and gives
14 calling functions the chance to insert data
15*/
16void *binary_search( const void * const key, const void * base, const size_t member_count, const size_t member_size,
17 size_t compare_size, int *exactmatch ) {
18 size_t mc = member_count;
19 ot_byte *lookat = ((ot_byte*)base) + member_size * (member_count >> 1);
20 *exactmatch = 1;
21
22 while( mc ) {
23 int cmp = memcmp( lookat, key, compare_size);
24 if (cmp == 0) return (void *)lookat;
25 if (cmp < 0) {
26 base = (void*)(lookat + member_size);
27 --mc;
28 }
29 mc >>= 1;
30 lookat = ((ot_byte*)base) + member_size * (mc >> 1);
31 }
32 *exactmatch = 0;
33 return (void*)lookat;
34}
35
36/* This is the generic insert operation for our vector type.
37 It tries to locate the object at "key" with size "member_size" by comparing its first "compare_size" bytes with
38 those of objects in vector. Our special "binary_search" function does that and either returns the match or a
39 pointer to where the object is to be inserted. vector_find_or_insert makes space for the object and copies it,
40 if it wasn't found in vector. Caller needs to check the passed "exactmatch" variable to see, whether an insert
41 took place. If resizing the vector failed, NULL is returned, else the pointer to the object in vector.
42*/
43void *vector_find_or_insert( ot_vector *vector, void *key, size_t member_size, size_t compare_size, int *exactmatch ) {
44 ot_byte *match = binary_search( key, vector->data, vector->size, member_size, compare_size, exactmatch );
45
46 if( *exactmatch ) return match;
47
48 if( vector->size + 1 >= vector->space ) {
49 size_t new_space = vector->space ? OT_VECTOR_GROW_RATIO * vector->space : OT_VECTOR_MIN_MEMBERS;
50 ot_byte *new_data = realloc( vector->data, new_space * member_size );
51 if( !new_data ) return NULL;
52
53 /* Adjust pointer if it moved by realloc */
54 match = new_data + (match - (ot_byte*)vector->data);
55
56 vector->data = new_data;
57 vector->space = new_space;
58 }
59 memmove( match + member_size, match, ((ot_byte*)vector->data) + member_size * vector->size - match );
60 vector->size++;
61 return match;
62}
63
64/* This is the non-generic delete from vector-operation specialized for peers in pools.
65 Set hysteresis == 0 if you expect the vector not to ever grow again.
66 It returns 0 if no peer was found (and thus not removed)
67 1 if a non-seeding peer was removed
68 2 if a seeding peer was removed
69*/
70int vector_remove_peer( ot_vector *vector, ot_peer *peer, int hysteresis ) {
71 int exactmatch;
72 size_t shrink_thresh = hysteresis ? OT_VECTOR_SHRINK_THRESH : OT_VECTOR_SHRINK_RATIO;
73 ot_peer *end = ((ot_peer*)vector->data) + vector->size;
74 ot_peer *match;
75
76 if( !vector->size ) return 0;
77 match = binary_search( peer, vector->data, vector->size, sizeof( ot_peer ), OT_PEER_COMPARE_SIZE, &exactmatch );
78
79 if( !exactmatch ) return 0;
80 exactmatch = ( OT_FLAG( match ) & PEER_FLAG_SEEDING ) ? 2 : 1;
81 memmove( match, match + 1, sizeof(ot_peer) * ( end - match - 1 ) );
82 if( ( --vector->size * shrink_thresh < vector->space ) && ( vector->space > OT_VECTOR_MIN_MEMBERS ) ) {
83 vector->space /= OT_VECTOR_SHRINK_RATIO;
84 vector->data = realloc( vector->data, vector->space * sizeof( ot_peer ) );
85 }
86 if( !vector->size ) {
87 /* for peer pools its safe to let them go,
88 in 999 of 1000 this happens in older pools, that won't ever grow again */
89 free( vector->data );
90 vector->data = NULL;
91 vector->space = 0;
92 }
93 return exactmatch;
94}
95
96void vector_remove_torrent( ot_vector *vector, ot_torrent *match ) {
97 ot_torrent *end = ((ot_torrent*)vector->data) + vector->size;
98
99 if( !vector->size ) return;
100
101 /* If this is being called after a unsuccessful malloc() for peer_list
102 in add_peer_to_torrent, match->peer_list actually might be NULL */
103 if( match->peer_list) free_peerlist( match->peer_list );
104
105 memmove( match, match + 1, sizeof(ot_torrent) * ( end - match - 1 ) );
106 if( ( --vector->size * OT_VECTOR_SHRINK_THRESH < vector->space ) && ( vector->space > OT_VECTOR_MIN_MEMBERS ) ) {
107 vector->space /= OT_VECTOR_SHRINK_RATIO;
108 vector->data = realloc( vector->data, vector->space * sizeof( ot_torrent ) );
109 }
110}