1 | /*
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2 | =============================================================================
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3 | dec2fr.c -- Buchla 700 fractional 2's complement conversion functions
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4 | Version 10 -- 1987-12-06 -- D.N. Lynx Crowe
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5 | =============================================================================
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6 | */
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7 |
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8 | #define TESTER 0
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9 |
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10 | #include "stddefs.h"
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11 |
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12 | #define SFACT 1000L /* scale factor */
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13 |
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14 | static long d2f[][10] = { /* decimal to fraction table */
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15 |
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16 | {0x00000000L, 0x000019A0L, 0x00003336L, 0x00004CD0L, 0x00006668L,
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17 | 0x00008000L, 0x000099A0L, 0x0000B336L, 0x0000CCCEL, 0x0000E668L},
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18 |
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19 | {0x00000000L, 0x00000290L, 0x00000520L, 0x000007B0L, 0x00000A40L,
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20 | 0x00000CD0L, 0x00000F60L, 0x000011F0L, 0x00001480L, 0x00001710L}
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21 | };
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22 |
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23 | static long f2d[] = { /* fraction to decimal table */
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24 |
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25 | 50000L, 25000L, 12500L, 6250L,
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26 | 3125L, 1562L, 781L, 390L,
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27 | 195L, 97L, 48L, 24L,
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28 | 12L, 6L, 3L, 1L
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29 | };
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30 |
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31 | /* |
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32 |
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33 | */
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34 |
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35 | /*
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36 | =============================================================================
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37 | dec2fr() -- convert an ASCII decimal string to fractional binary
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38 |
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39 | The input string is 4 characters in the range 100- to 100+ inclusive.
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40 | The result is a 2's complement binary fractional value.
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41 | =============================================================================
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42 | */
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43 |
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44 | short dec2fr(char *s)
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45 | {
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46 | register short i;
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47 |
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48 | if (s[0] EQ '1') {
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49 |
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50 | if (s[1] EQ '0') {
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51 |
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52 | if (s[2] EQ '0') {
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53 |
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54 | if (s[3] EQ '-')
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55 | return(0x8000); /* -100 */
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56 | else
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57 | return(0x7FFF); /* +100 */
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58 |
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59 | } else {
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60 |
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61 | return(0xFFFF); /* ERROR */
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62 | }
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63 |
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64 | } else {
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65 |
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66 | return(0xFFFF); /* ERROR */
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67 |
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68 | }
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69 |
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70 | /* |
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71 |
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72 | */
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73 |
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74 | } else if (s[0] EQ '0') {
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75 |
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76 | i = (d2f[0][s[1] - '0'] + d2f[1][s[2] - '0']) >> 1;
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77 |
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78 | if (s[3] EQ '-') {
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79 |
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80 | if (i)
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81 | return(~i); /* negative number */
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82 | else
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83 | return(0); /* zero is always 0 */
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84 |
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85 | } else {
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86 |
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87 | return(i); /* positive number */
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88 | }
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89 | }
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90 |
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91 | return(0xFFFF); /* ERROR */
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92 | }
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93 |
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94 | /* |
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95 |
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96 | */
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97 |
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98 | /*
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99 | =============================================================================
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100 | fr2dec() -- convert a 2's complement fraction to decimal ASCII notation
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101 |
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102 | The input is a 2's complement binary fractional value.
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103 | The result string is 4 characters in the range 100- to 100+ inclusive.
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104 | =============================================================================
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105 | */
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106 |
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107 | char *fr2dec(short v, char *s)
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108 | {
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109 | register long acc, sc;
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110 | register short i, p;
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111 |
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112 | if (v EQ 0x7FFF) { /* +100 */
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113 |
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114 | sprintf(s, "100+");
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115 | return(s);
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116 | }
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117 |
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118 | if (v EQ 0x8000) { /* -100 */
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119 |
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120 | sprintf(s, "100-");
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121 | return(s);
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122 | }
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123 |
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124 | if (v & 0x8000) {
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125 |
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126 | v = ~v; /* negative number */
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127 | p = '-';
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128 |
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129 | } else {
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130 |
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131 | p = '+'; /* positive number */
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132 | }
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133 |
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134 | acc = 0;
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135 |
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136 | for (i = 0; i LT 15; i++)
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137 | if (v & (1 << (14 - i)))
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138 | acc += f2d[i];
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139 |
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140 | sc = SFACT;
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141 | acc /= sc;
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142 | sprintf(s, "%03d%c", (short)acc, p);
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143 | return(s);
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144 | }
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145 |
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146 | /* |
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147 |
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148 | */
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149 |
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150 | #if TESTER
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151 |
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152 | #include "stdio.h"
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153 |
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154 | extern int memcmp();
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155 |
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156 | char t[8], v[8];
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157 |
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158 | /*
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159 | =============================================================================
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160 | test program for fractional two's complement conversion functions
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161 | =============================================================================
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162 | */
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163 |
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164 | main()
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165 | {
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166 | register short i;
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167 | register short u;
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168 |
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169 | for (i = 0; i < 101; i++) {
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170 |
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171 | if (i EQ 50)
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172 | printf("\f");
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173 |
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174 | sprintf(t, "%03d+", i);
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175 | u = dec2fr(t);
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176 |
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177 | if (u EQ 0xFFFF) {
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178 |
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179 | printf("[%s] = ERROR = ?????? ", t);
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180 |
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181 | } else {
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182 |
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183 | fr2dec(u, v);
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184 | printf("[%s] = 0x%04x = [%s]", t, u, v);
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185 | }
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186 |
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187 | printf(" %s ", memcmp(t, v, 4) ? "<--" : " ");
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188 |
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189 | sprintf(t, "%03d-", i);
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190 | u = dec2fr(t);
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191 |
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192 | if (u EQ 0xFFFF) {
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193 |
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194 | printf(" [%s] = ERROR = ??????\n", t);
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195 |
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196 | } else {
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197 |
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198 | fr2dec(u, v);
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199 | printf(" [%s] = 0x%04x = [%s]", t, u, v);
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200 | }
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201 |
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202 | printf(" %s\n", memcmp(t, v, 4) ? "<--" : "");
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203 |
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204 | }
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205 | }
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206 |
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207 | #endif
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