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/* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
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* Copyright (C) 2011-2012 Data Differential, http://datadifferential.com/
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* Copyright (C) 2006-2009 Brian Aker All rights reserved.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* * The names of its contributors may not be used to endorse or
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* promote products derived from this software without specific prior
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include <libhashkit/common.h>
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static uint32_t ketama_server_hash(const char *key, unsigned int key_length, int alignment)
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unsigned char results[16];
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md5_signature((unsigned char*)key, key_length, results);
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return ((uint32_t) (results[3 + alignment * 4] & 0xFF) << 24)
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| ((uint32_t) (results[2 + alignment * 4] & 0xFF) << 16)
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| ((uint32_t) (results[1 + alignment * 4] & 0xFF) << 8)
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| (results[0 + alignment * 4] & 0xFF);
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static int continuum_points_cmp(const void *t1, const void *t2)
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hashkit_continuum_point_st *ct1= (hashkit_continuum_point_st *)t1;
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hashkit_continuum_point_st *ct2= (hashkit_continuum_point_st *)t2;
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if (ct1->value == ct2->value)
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else if (ct1->value > ct2->value)
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int update_continuum(hashkit_st *hashkit)
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uint32_t continuum_index= 0;
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uint32_t points_index;
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uint32_t points_count= 0;
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uint32_t points_per_server;
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uint32_t points_per_hash;
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uint64_t total_weight= 0;
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uint32_t live_servers;
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if (hashkit->active_fn != NULL || hashkit->weight_fn != NULL)
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for (count= 0, context= hashkit->list; count < hashkit->list_size;
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count++, context+= hashkit->context_size)
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if (hashkit->active_fn != NULL)
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if (hashkit->active_fn(context))
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if (hashkit->weight_fn != NULL)
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total_weight+= hashkit->weight_fn(context);
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if (hashkit->active_fn == NULL)
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live_servers= (uint32_t)hashkit->list_size;
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if (live_servers == 0)
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if (hashkit->weight_fn == NULL)
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points_per_server= HASHKIT_POINTS_PER_NODE;
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points_per_server= HASHKIT_POINTS_PER_NODE_WEIGHTED;
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if (live_servers > hashkit->continuum_count)
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hashkit_continuum_point_st *new_continuum;
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new_continuum= realloc(hashkit->continuum,
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sizeof(hashkit_continuum_point_st) *
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(live_servers + HASHKIT_CONTINUUM_ADDITION) *
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if (new_continuum == NULL)
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hashkit->continuum= new_continuum;
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hashkit->continuum_count= live_servers + HASHKIT_CONTINUUM_ADDITION;
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for (count= 0, context= hashkit->list; count < hashkit->list_size;
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count++, context+= hashkit->context_size)
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if (hashkit->active_fn != NULL && hashkit->active_fn(context) == false)
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if (hashkit->weight_fn != NULL)
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float pct = (float)hashkit->weight_fn(context) / (float)total_weight;
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points_per_server= (uint32_t) ((floorf((float) (pct * HASHKIT_POINTS_PER_NODE_WEIGHTED / 4 * (float)live_servers + 0.0000000001))) * 4);
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for (points_index= 0;
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points_index < points_per_server / points_per_hash;
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char sort_host[HASHKIT_CONTINUUM_KEY_SIZE]= "";
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size_t sort_host_length;
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if (hashkit->continuum_key_fn == NULL)
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sort_host_length= (size_t) snprintf(sort_host, HASHKIT_CONTINUUM_KEY_SIZE, "%u",
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sort_host_length= hashkit->continuum_key_fn(sort_host, HASHKIT_CONTINUUM_KEY_SIZE,
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points_index, context);
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if (hashkit->weight_fn == NULL)
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if (hashkit->continuum_hash_fn == NULL)
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value= hashkit_default(sort_host, sort_host_length);
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value= hashkit->continuum_hash_fn(sort_host, sort_host_length);
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hashkit->continuum[continuum_index].index= count;
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hashkit->continuum[continuum_index++].value= value;
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for (i = 0; i < points_per_hash; i++)
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value= ketama_server_hash(sort_host, (uint32_t) sort_host_length, (int) i);
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hashkit->continuum[continuum_index].index= count;
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hashkit->continuum[continuum_index++].value= value;
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points_count+= points_per_server;
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hashkit->continuum_points_count= points_count;
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qsort(hashkit->continuum, hashkit->continuum_points_count, sizeof(hashkit_continuum_point_st),
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continuum_points_cmp);