1 | |
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2 | (use eggdoc) |
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3 | |
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4 | (define doc |
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5 | `((eggdoc:begin |
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6 | (name "sfht") |
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7 | (description "A dictionary data structure based on counting Bloom filters.") |
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8 | (author (url "mailto:iraikov@ece.gatech.edu" "Ivan Raikov")) |
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9 | |
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10 | (history |
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11 | (version "1.1" "Added random-swb to the list of dependencies") |
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12 | (version "1.0" "Initial release")) |
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13 | |
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14 | (requires (url "random-swb.html" "random-swb") |
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15 | (url "sparse-vectors.html" "sparse-vectors")) |
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16 | |
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17 | (usage "(require-extension sfht)") |
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18 | |
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19 | (download "sfht.egg") |
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20 | |
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21 | (documentation |
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22 | |
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23 | (p "The sfht library is an implementation of the Shared-node " |
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24 | "Fast Hash Table (SFHT) data structure described by Song, et al., in " |
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25 | (pre "_Fast Hash Table Lookup Using Extended Bloom Filter: " |
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26 | "An Aid to Network Processing_. (SIGCOMM'05)") ". ") |
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27 | |
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28 | (p "This code defines an " (tt "sfht") " object that implements a " |
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29 | "dictionary mapping of keys to values. The object responds to " |
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30 | "messages for querying, insertion of new elements, and deletion " |
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31 | "of existing elements. The interface of the " (tt "sfht") " object " |
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32 | "is particularly suitable for situations where the keys are " |
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33 | "represented by bit vectors or vectors of fixnum values. ") |
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34 | |
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35 | (p "A counting Bloom filter is a Bloom filter that has been extended so " |
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36 | "that each bit of the filter has a counter associated with it. Upon " |
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37 | "insertion or deletion of an element, the counter is incremented or " |
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38 | "decremented, respectively. In order to find an element efficiently, " |
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39 | "we need to compute the " (tt "k") " hash values, read the counters " |
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40 | "at the " (tt "k") " locations, determine the smallest bucket size, " |
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41 | "and perform a linear search of that bucket for the element. ") |
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42 | |
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43 | |
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44 | (subsection "SFHT procedures" |
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45 | |
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46 | (p "The sfht object is created by a make-sfht function, " |
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47 | "the only user-visible function defined in this egg: ") |
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48 | |
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49 | (procedure "make-sfht:: N P KEY->VECTOR KEY-VECTOR-REF KEY-VECTOR-LENGTH [KEY-EQUAL?] -> SELECTOR" |
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50 | (p "where " |
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51 | (symbol-table |
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52 | (describe "KEY->VECTOR" |
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53 | ("is a user-supplied function that takes a key value " |
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54 | "and returns a vector.")) |
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55 | (describe "KEY-VECTOR-REF" |
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56 | ("is a user-supplied function that retrieves an element from " |
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57 | "the vector returned by " (tt "KEY-VECTOR") ". ")) |
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58 | (describe "KEY-VECTOR-LENGTH" |
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59 | ("is a user-supplied function that returns the length " |
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60 | "of the key vector.")) |
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61 | (describe "KEY->EQUAL?" |
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62 | ("is a user-supplied predicate that takes two keys and returns " |
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63 | (tt "#t") " if they are equal. The default function used is " |
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64 | (tt "equal?"))))) |
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65 | |
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66 | (p "The returned selector procedure can take one of the following arguments: " |
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67 | (symbol-table |
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68 | (describe "'get" |
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69 | ("returns a procedure " (tt "LAMBDA KEY . DEFAULT-CLAUSE") |
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70 | " which searches the hash table for an association with a given " |
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71 | (tt "KEY") ", and returns a (key . value) pair of the found association. " |
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72 | "If an association with " (tt "KEY") " cannot be located in the hash table, " |
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73 | "the PROC returns the result of evaluating the " (tt "DEFAULT-CLAUSE") ". " |
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74 | "If the default clause is omitted, an error is signaled. " |
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75 | (tt "KEY") " must be comparable to the keys in the hash table " |
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76 | "by the " (tt "KEY-EQUAL?") " predicate specified " |
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77 | "when the hash table was created)")) |
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78 | |
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79 | (describe "'empty?" |
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80 | ("returns " (tt "#t") " if the hash table is empty")) |
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81 | |
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82 | (describe "'size" |
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83 | ("returns the size (the number of associations) in the hash table")) |
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84 | |
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85 | (describe "'clear!" |
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86 | ("removes all associations from the hash table (thus making it empty)")) |
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87 | |
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88 | (describe "'put!" |
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89 | ("returns a procedure " (tt "LAMBDA KEY VALUE") |
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90 | " which, given a " (tt "KEY") " and a " (tt "VALUE") |
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91 | ", adds the corresponding association to the hash table. " |
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92 | "If an association with the same " (tt "KEY") |
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93 | " already exists, its value is replaced with the " |
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94 | (tt "VALUE") ". The return value is " (tt "#f") ".")) |
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95 | |
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96 | (describe "'delete!" |
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97 | ("returns a procedure " (tt "LAMBDA KEY . DEFAULT-CLAUSE") |
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98 | " which searches the hash table for an association with a given " |
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99 | (tt "KEY") ", deletes it, and returns a (key . value) pair of the found " |
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100 | "and deleted association. If an association with the KEY cannot be located " |
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101 | "in the hash table, the " (tt "PROC") " returns the result of evaluating " |
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102 | (tt "DEFAULT-CLAUSE") ". " |
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103 | "If the default clause is omitted, an error is signaled. ")) |
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104 | |
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105 | (describe "'debugprint" |
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106 | ("prints out all the buckets in the Bloom filter, for debug purposes"))))))) |
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107 | |
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108 | |
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109 | (examples (pre #<<EOF |
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110 | (require-extension iset) |
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111 | (require-extension sfht) |
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112 | |
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113 | (define sfht (make-sfht 100000 0.0001 |
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114 | integer->bit-vector |
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115 | (compose (lambda (x) (if x 1 0)) bit-vector-ref) |
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116 | bit-vector-length)) |
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117 | |
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118 | ((sfht 'put!) 1 'one) |
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119 | |
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120 | ((sfht 'get)) |
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121 | |
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122 | EOF |
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123 | )) |
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124 | |
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125 | (license |
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126 | "Copyright 2007 Ivan Raikov and the Okinawa Institute of Science and Technology |
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127 | |
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128 | This program is free software; you can redistribute it and/or |
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129 | modify it under the terms of the GNU General Public License as |
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130 | published by the Free Software Foundation; either version 2 of the |
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131 | License, or (at your option) any later version. |
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132 | |
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133 | This program is distributed in the hope that it will be useful, but |
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134 | WITHOUT ANY WARRANTY; without even the implied warranty of |
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135 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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136 | General Public License for more details. |
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137 | |
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138 | You should have received a copy of the GNU General Public License |
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139 | along with this program; if not, write to the Free Software |
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140 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA |
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141 | 02110-1301 USA |
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142 | |
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143 | A full copy of the GPL license can be found on Debian systems in |
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144 | /usr/share/common-licenses/GPL-2")))) |
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145 | |
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146 | (if (eggdoc->html doc) (void)) |
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