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annotate oldclasslib/source/strdict.cpp @ 0:13d2b8934445

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Import AnaGram (near-)release tree into Mercurial.
author David A. Holland
date Sat, 22 Dec 2007 17:52:45 -0500
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children 607e3be6bad8
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1 /*
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2 * AnaGram, a System for Syntax Directed Parsing
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3 * String Dictionary Class Definition
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4 *
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5 * Copyright 1993 Parsifal Software. All Rights Reserved.
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6 *
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7 * This software is provided 'as-is', without any express or implied
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8 * warranty. In no event will the authors be held liable for any damages
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9 * arising from the use of this software.
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10 *
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11 * Permission is granted to anyone to use this software for any purpose,
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12 * including commercial applications, and to alter it and redistribute it
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13 * freely, subject to the following restrictions:
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14 *
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15 * 1. The origin of this software must not be misrepresented; you must not
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16 * claim that you wrote the original software. If you use this software
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17 * in a product, an acknowledgment in the product documentation would be
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18 * appreciated but is not required.
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19 * 2. Altered source versions must be plainly marked as such, and must not be
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20 * misrepresented as being the original software.
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21 * 3. This notice may not be removed or altered from any source distribution.
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22 */
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23
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24 #include "strdict.h"
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25 #include <assert.h>
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26 #include <string.h>
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27
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28
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29 // Constructor
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30
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31 string_dictionary::string_dictionary(unsigned size, unsigned wl) {
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32 assert((size << 1) > size);
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33 assert((long) size * wl < 65536L);
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34
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35 sxs = new unsigned[size]; // allocate index storage
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36 csxmax = wl*size; // calculate char storage rqmt
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37 cs = new char[csxmax]; // allocate character storage
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38 csx = 1; // can't use byte zero
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39 for (htl = 1; htl < size; htl <<= 1); // calculate size of hash table
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40 htmask = htl - 1; // htl is a power of two
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41 ht = new unsigned[htl]; // allocate storage for hash table
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42 memset(ht, 0, htl*sizeof(unsigned)); // init to zeros
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43 nsmax = size;
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44 ns = 1; // can't use zero
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45 n_calls = n_collisions = 0; // clear statistics
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46 copy_flag = 0; // live
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47 }
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48
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49 string_dictionary::string_dictionary(string_dictionary &s) {
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50 *this = s;
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51 copy_flag++; //memorex
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52 }
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53
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54
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55 // Reset Dictionary
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56
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57 string_dictionary &reset(string_dictionary &d) {
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58 assert(d.copy_flag == 0);
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59 d.csx = 1; // can't use byte zero
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60 memset(d.ht, 0, d.htl*sizeof(unsigned)); // init to zeros
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61 d.ns = 1; // can't use zero
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62 d.n_calls = d.n_collisions = 0; // reset statistics
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63 return d;
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64 }
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65
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66
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67 // Destructor
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68
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69 string_dictionary::~string_dictionary() {
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70 if (copy_flag) return;
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71 delete [] sxs;
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72 delete [] cs;
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73 delete [] ht;
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74 }
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75
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76
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77 // Hash Utility
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78
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79 unsigned string_dictionary::hash(const char *s) {
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80 unsigned char k1 = 1, k2 = 1;
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81 unsigned char c;
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82 unsigned hx; // hash index
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83 unsigned sx; // string index
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84 int k = 0;
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85 while((c = s[k++]) != 0) { // accumulate hash code elements
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86 if ((k1 += c) < c) k1++;
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87 if ((k2 += k1) < k1) k2++;
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88 }
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89 k1--;
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90 k2--;
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91 hx = (255*k1 + k2) & htmask; // calculate hash code
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92 sx = ht[hx];
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93 n_calls++; // count number of calls
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94 if (sx && strcmp(s, &cs[sxs[sx]])) {
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95 unsigned dx = (2*(255*k2 + k1) + 1) & htmask;
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96 do { // no cycles, since dx and htl are relatively prime
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97 n_collisions++; // count collisions
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98 sx = ht[hx = htmask & (hx+dx)];
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99 } while (sx && strcmp(s, &cs[sxs[sx]]));
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100 }
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101 return hx;
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102 }
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103
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104
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105 // Recover String
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106
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107 unsigned string_dictionary::operator [] (const char *s) {
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108 return ht[hash(s)];
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109 }
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110
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111
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112 // Enter String in Dictionary
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113
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114 unsigned string_dictionary::operator << (const char *s) {
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115 unsigned hx = hash(s); // get hash code
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116 unsigned k;
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117 if (ht[hx]) return ht[hx]; // return index if already there
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118 assert(copy_flag == 0);
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119 assert (ns < nsmax); // make sure table's not full
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120 if (s) k = strlen(s) + 1; // get string length
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121 else k = 1;
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122 assert(csx + k < csxmax); // make sure there's room
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123 strcpy(&cs[csx],s); // save string
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124 sxs[ns] = csx; // save string index
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125 csx += k; // advance storage index
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126 return ht[hx] = ns++; // return index
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127 }
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128
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129
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130 // Look up String in Dictionary
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131
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132 char *string_dictionary::operator [] (unsigned sx) {
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133 if (sx && sx <= ns) return &cs[sxs[sx]];
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134 return 0;
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135 }
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136
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137
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138 // Find Number of Entries in Dictionary
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139
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140 unsigned size(string_dictionary &sd) {
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141 return sd.ns - 1;
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142 }