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/* $OpenBSD: shuffle.c,v 1.4 2015/01/22 17:42:09 reyk Exp $ */ |
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/* |
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* Portions Copyright (C) 2008 Theo de Raadt |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM |
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* DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL |
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL |
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* INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, |
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* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING |
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* FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, |
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* NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION |
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* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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/* based on: bind/lib/isc/shuffle.c,v 1.4 2008/07/09 17:07:32 reyk Exp $ */ |
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#include <sys/types.h> |
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#include <stdlib.h> |
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#include <assert.h> |
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#include "relayd.h" |
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#define VALID_SHUFFLE(x) (x != NULL) |
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void |
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shuffle_init(struct shuffle *shuffle) |
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{ |
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int i, i2; |
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assert(VALID_SHUFFLE(shuffle)); |
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shuffle->isindex = 0; |
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/* Initialize using a Knuth shuffle */ |
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for (i = 0; i < 65536; ++i) { |
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i2 = arc4random_uniform(i + 1); |
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shuffle->id_shuffle[i] = shuffle->id_shuffle[i2]; |
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shuffle->id_shuffle[i2] = i; |
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} |
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} |
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u_int16_t |
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shuffle_generate16(struct shuffle *shuffle) |
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{ |
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u_int32_t si; |
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u_int16_t r; |
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int i, i2; |
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assert(VALID_SHUFFLE(shuffle)); |
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do { |
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si = arc4random(); |
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i = shuffle->isindex & 0xFFFF; |
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i2 = (shuffle->isindex - (si & 0x7FFF)) & 0xFFFF; |
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r = shuffle->id_shuffle[i]; |
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shuffle->id_shuffle[i] = shuffle->id_shuffle[i2]; |
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shuffle->id_shuffle[i2] = r; |
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shuffle->isindex++; |
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} while (r == 0); |
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return (r); |
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} |