1 | /* IEEE floating point support routines, for GDB, the GNU Debugger. |
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2 | Copyright (C) 1991, 1994, 1999, 2000 Free Software Foundation, Inc. |
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3 | |
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4 | This file is part of GDB. |
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5 | |
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6 | This program is free software; you can redistribute it and/or modify |
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7 | it under the terms of the GNU General Public License as published by |
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8 | the Free Software Foundation; either version 2 of the License, or |
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9 | (at your option) any later version. |
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10 | |
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11 | This program is distributed in the hope that it will be useful, |
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12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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14 | GNU General Public License for more details. |
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15 | |
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16 | You should have received a copy of the GNU General Public License |
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17 | along with this program; if not, write to the Free Software |
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18 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ |
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19 | |
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20 | #include "floatformat.h" |
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21 | #include <math.h> /* ldexp */ |
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22 | #ifdef __STDC__ |
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23 | #include <stddef.h> |
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24 | extern void *memcpy (void *s1, const void *s2, size_t n); |
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25 | extern void *memset (void *s, int c, size_t n); |
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26 | #else |
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27 | extern char *memcpy (); |
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28 | extern char *memset (); |
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29 | #endif |
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30 | |
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31 | /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not |
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32 | going to bother with trying to muck around with whether it is defined in |
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33 | a system header, what we do if not, etc. */ |
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34 | #define FLOATFORMAT_CHAR_BIT 8 |
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35 | |
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36 | /* floatformats for IEEE single and double, big and little endian. */ |
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37 | const struct floatformat floatformat_ieee_single_big = |
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38 | { |
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39 | floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, |
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40 | floatformat_intbit_no, |
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41 | "floatformat_ieee_single_big" |
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42 | }; |
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43 | const struct floatformat floatformat_ieee_single_little = |
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44 | { |
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45 | floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, |
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46 | floatformat_intbit_no, |
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47 | "floatformat_ieee_single_little" |
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48 | }; |
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49 | const struct floatformat floatformat_ieee_double_big = |
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50 | { |
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51 | floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, |
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52 | floatformat_intbit_no, |
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53 | "floatformat_ieee_double_big" |
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54 | }; |
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55 | const struct floatformat floatformat_ieee_double_little = |
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56 | { |
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57 | floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, |
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58 | floatformat_intbit_no, |
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59 | "floatformat_ieee_double_little" |
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60 | }; |
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61 | |
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62 | /* floatformat for IEEE double, little endian byte order, with big endian word |
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63 | ordering, as on the ARM. */ |
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64 | |
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65 | const struct floatformat floatformat_ieee_double_littlebyte_bigword = |
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66 | { |
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67 | floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52, |
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68 | floatformat_intbit_no, |
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69 | "floatformat_ieee_double_littlebyte_bigword" |
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70 | }; |
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71 | |
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72 | const struct floatformat floatformat_i387_ext = |
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73 | { |
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74 | floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, |
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75 | floatformat_intbit_yes, |
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76 | "floatformat_i387_ext" |
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77 | }; |
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78 | const struct floatformat floatformat_m68881_ext = |
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79 | { |
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80 | /* Note that the bits from 16 to 31 are unused. */ |
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81 | floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, |
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82 | floatformat_intbit_yes, |
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83 | "floatformat_m68881_ext" |
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84 | }; |
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85 | const struct floatformat floatformat_i960_ext = |
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86 | { |
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87 | /* Note that the bits from 0 to 15 are unused. */ |
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88 | floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64, |
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89 | floatformat_intbit_yes, |
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90 | "floatformat_i960_ext" |
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91 | }; |
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92 | const struct floatformat floatformat_m88110_ext = |
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93 | { |
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94 | floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, |
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95 | floatformat_intbit_yes, |
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96 | "floatformat_m88110_ext" |
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97 | }; |
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98 | const struct floatformat floatformat_m88110_harris_ext = |
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99 | { |
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100 | /* Harris uses raw format 128 bytes long, but the number is just an ieee |
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101 | double, and the last 64 bits are wasted. */ |
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102 | floatformat_big,128, 0, 1, 11, 0x3ff, 0x7ff, 12, 52, |
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103 | floatformat_intbit_no, |
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104 | "floatformat_m88110_ext_harris" |
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105 | }; |
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106 | const struct floatformat floatformat_arm_ext = |
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107 | { |
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108 | /* Bits 1 to 16 are unused. */ |
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109 | floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, |
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110 | floatformat_intbit_yes, |
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111 | "floatformat_arm_ext" |
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112 | }; |
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113 | const struct floatformat floatformat_arm_ext_big = |
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114 | { |
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115 | /* Bits 1 to 16 are unused. */ |
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116 | floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, |
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117 | floatformat_intbit_yes, |
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118 | "floatformat_arm_ext_big" |
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119 | }; |
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120 | const struct floatformat floatformat_arm_ext_littlebyte_bigword = |
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121 | { |
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122 | /* Bits 1 to 16 are unused. */ |
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123 | floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, |
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124 | floatformat_intbit_yes, |
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125 | "floatformat_arm_ext_littlebyte_bigword" |
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126 | }; |
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127 | const struct floatformat floatformat_ia64_spill_big = |
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128 | { |
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129 | floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64, |
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130 | floatformat_intbit_yes, |
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131 | "floatformat_ia64_spill_big" |
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132 | }; |
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133 | const struct floatformat floatformat_ia64_spill_little = |
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134 | { |
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135 | floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64, |
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136 | floatformat_intbit_yes, |
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137 | "floatformat_ia64_spill_little" |
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138 | }; |
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139 | const struct floatformat floatformat_ia64_quad_big = |
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140 | { |
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141 | floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112, |
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142 | floatformat_intbit_no, |
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143 | "floatformat_ia64_quad_big" |
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144 | }; |
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145 | const struct floatformat floatformat_ia64_quad_little = |
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146 | { |
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147 | floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112, |
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148 | floatformat_intbit_no, |
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149 | "floatformat_ia64_quad_little" |
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150 | }; |
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151 | |
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152 | static unsigned long get_field PARAMS ((unsigned char *, |
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153 | enum floatformat_byteorders, |
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154 | unsigned int, |
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155 | unsigned int, |
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156 | unsigned int)); |
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157 | |
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158 | /* Extract a field which starts at START and is LEN bytes long. DATA and |
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159 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ |
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160 | static unsigned long |
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161 | get_field (data, order, total_len, start, len) |
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162 | unsigned char *data; |
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163 | enum floatformat_byteorders order; |
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164 | unsigned int total_len; |
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165 | unsigned int start; |
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166 | unsigned int len; |
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167 | { |
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168 | unsigned long result; |
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169 | unsigned int cur_byte; |
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170 | int cur_bitshift; |
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171 | |
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172 | /* Start at the least significant part of the field. */ |
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173 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; |
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174 | if (order == floatformat_little) |
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175 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; |
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176 | cur_bitshift = |
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177 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; |
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178 | result = *(data + cur_byte) >> (-cur_bitshift); |
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179 | cur_bitshift += FLOATFORMAT_CHAR_BIT; |
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180 | if (order == floatformat_little) |
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181 | ++cur_byte; |
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182 | else |
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183 | --cur_byte; |
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184 | |
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185 | /* Move towards the most significant part of the field. */ |
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186 | while ((unsigned int) cur_bitshift < len) |
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187 | { |
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188 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) |
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189 | /* This is the last byte; zero out the bits which are not part of |
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190 | this field. */ |
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191 | result |= |
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192 | (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1)) |
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193 | << cur_bitshift; |
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194 | else |
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195 | result |= *(data + cur_byte) << cur_bitshift; |
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196 | cur_bitshift += FLOATFORMAT_CHAR_BIT; |
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197 | if (order == floatformat_little) |
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198 | ++cur_byte; |
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199 | else |
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200 | --cur_byte; |
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201 | } |
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202 | return result; |
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203 | } |
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204 | |
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205 | #ifndef min |
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206 | #define min(a, b) ((a) < (b) ? (a) : (b)) |
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207 | #endif |
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208 | |
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209 | /* Convert from FMT to a double. |
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210 | FROM is the address of the extended float. |
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211 | Store the double in *TO. */ |
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212 | |
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213 | void |
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214 | floatformat_to_double (fmt, from, to) |
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215 | const struct floatformat *fmt; |
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216 | char *from; |
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217 | double *to; |
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218 | { |
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219 | unsigned char *ufrom = (unsigned char *)from; |
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220 | double dto; |
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221 | long exponent; |
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222 | unsigned long mant; |
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223 | unsigned int mant_bits, mant_off; |
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224 | int mant_bits_left; |
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225 | int special_exponent; /* It's a NaN, denorm or zero */ |
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226 | |
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227 | exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize, |
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228 | fmt->exp_start, fmt->exp_len); |
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229 | /* Note that if exponent indicates a NaN, we can't really do anything useful |
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230 | (not knowing if the host has NaN's, or how to build one). So it will |
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231 | end up as an infinity or something close; that is OK. */ |
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232 | |
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233 | mant_bits_left = fmt->man_len; |
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234 | mant_off = fmt->man_start; |
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235 | dto = 0.0; |
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236 | |
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237 | special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan; |
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238 | |
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239 | /* Don't bias zero's, denorms or NaNs. */ |
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240 | if (!special_exponent) |
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241 | exponent -= fmt->exp_bias; |
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242 | |
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243 | /* Build the result algebraically. Might go infinite, underflow, etc; |
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244 | who cares. */ |
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245 | |
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246 | /* If this format uses a hidden bit, explicitly add it in now. Otherwise, |
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247 | increment the exponent by one to account for the integer bit. */ |
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248 | |
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249 | if (!special_exponent) |
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250 | { |
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251 | if (fmt->intbit == floatformat_intbit_no) |
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252 | dto = ldexp (1.0, exponent); |
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253 | else |
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254 | exponent++; |
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255 | } |
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256 | |
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257 | while (mant_bits_left > 0) |
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258 | { |
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259 | mant_bits = min (mant_bits_left, 32); |
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260 | |
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261 | mant = get_field (ufrom, fmt->byteorder, fmt->totalsize, |
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262 | mant_off, mant_bits); |
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263 | |
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264 | dto += ldexp ((double)mant, exponent - mant_bits); |
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265 | exponent -= mant_bits; |
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266 | mant_off += mant_bits; |
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267 | mant_bits_left -= mant_bits; |
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268 | } |
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269 | |
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270 | /* Negate it if negative. */ |
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271 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1)) |
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272 | dto = -dto; |
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273 | *to = dto; |
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274 | } |
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275 | |
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276 | static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders, |
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277 | unsigned int, |
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278 | unsigned int, |
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279 | unsigned int, |
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280 | unsigned long)); |
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281 | |
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282 | /* Set a field which starts at START and is LEN bytes long. DATA and |
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283 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ |
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284 | static void |
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285 | put_field (data, order, total_len, start, len, stuff_to_put) |
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286 | unsigned char *data; |
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287 | enum floatformat_byteorders order; |
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288 | unsigned int total_len; |
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289 | unsigned int start; |
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290 | unsigned int len; |
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291 | unsigned long stuff_to_put; |
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292 | { |
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293 | unsigned int cur_byte; |
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294 | int cur_bitshift; |
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295 | |
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296 | /* Start at the least significant part of the field. */ |
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297 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; |
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298 | if (order == floatformat_little) |
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299 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; |
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300 | cur_bitshift = |
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301 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; |
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302 | *(data + cur_byte) &= |
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303 | ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift)); |
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304 | *(data + cur_byte) |= |
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305 | (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift); |
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306 | cur_bitshift += FLOATFORMAT_CHAR_BIT; |
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307 | if (order == floatformat_little) |
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308 | ++cur_byte; |
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309 | else |
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310 | --cur_byte; |
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311 | |
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312 | /* Move towards the most significant part of the field. */ |
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313 | while ((unsigned int) cur_bitshift < len) |
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314 | { |
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315 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) |
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316 | { |
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317 | /* This is the last byte. */ |
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318 | *(data + cur_byte) &= |
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319 | ~((1 << (len - cur_bitshift)) - 1); |
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320 | *(data + cur_byte) |= (stuff_to_put >> cur_bitshift); |
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321 | } |
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322 | else |
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323 | *(data + cur_byte) = ((stuff_to_put >> cur_bitshift) |
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324 | & ((1 << FLOATFORMAT_CHAR_BIT) - 1)); |
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325 | cur_bitshift += FLOATFORMAT_CHAR_BIT; |
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326 | if (order == floatformat_little) |
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327 | ++cur_byte; |
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328 | else |
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329 | --cur_byte; |
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330 | } |
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331 | } |
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332 | |
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333 | /* The converse: convert the double *FROM to an extended float |
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334 | and store where TO points. Neither FROM nor TO have any alignment |
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335 | restrictions. */ |
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336 | |
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337 | void |
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338 | floatformat_from_double (fmt, from, to) |
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339 | const struct floatformat *fmt; |
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340 | double *from; |
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341 | char *to; |
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342 | { |
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343 | double dfrom; |
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344 | int exponent; |
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345 | double mant; |
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346 | unsigned int mant_bits, mant_off; |
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347 | int mant_bits_left; |
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348 | unsigned char *uto = (unsigned char *)to; |
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349 | |
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350 | memcpy (&dfrom, from, sizeof (dfrom)); |
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351 | memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT); |
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352 | if (dfrom == 0) |
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353 | return; /* Result is zero */ |
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354 | if (dfrom != dfrom) |
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355 | { |
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356 | /* From is NaN */ |
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357 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, |
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358 | fmt->exp_len, fmt->exp_nan); |
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359 | /* Be sure it's not infinity, but NaN value is irrel */ |
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360 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start, |
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361 | 32, 1); |
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362 | return; |
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363 | } |
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364 | |
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365 | /* If negative, set the sign bit. */ |
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366 | if (dfrom < 0) |
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367 | { |
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368 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1); |
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369 | dfrom = -dfrom; |
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370 | } |
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371 | |
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372 | /* How to tell an infinity from an ordinary number? FIXME-someday */ |
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373 | |
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374 | mant = frexp (dfrom, &exponent); |
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375 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len, |
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376 | exponent + fmt->exp_bias - 1); |
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377 | |
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378 | mant_bits_left = fmt->man_len; |
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379 | mant_off = fmt->man_start; |
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380 | while (mant_bits_left > 0) |
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381 | { |
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382 | unsigned long mant_long; |
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383 | mant_bits = mant_bits_left < 32 ? mant_bits_left : 32; |
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384 | |
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385 | mant *= 4294967296.0; |
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386 | mant_long = (unsigned long)mant; |
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387 | mant -= mant_long; |
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388 | |
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389 | /* If the integer bit is implicit, then we need to discard it. |
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390 | If we are discarding a zero, we should be (but are not) creating |
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391 | a denormalized number which means adjusting the exponent |
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392 | (I think). */ |
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393 | if ((unsigned int) mant_bits_left == fmt->man_len |
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394 | && fmt->intbit == floatformat_intbit_no) |
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395 | { |
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396 | mant_long &= 0x7fffffff; |
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397 | mant_bits -= 1; |
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398 | } |
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399 | else if (mant_bits < 32) |
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400 | { |
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401 | /* The bits we want are in the most significant MANT_BITS bits of |
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402 | mant_long. Move them to the least significant. */ |
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403 | mant_long >>= 32 - mant_bits; |
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404 | } |
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405 | |
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406 | put_field (uto, fmt->byteorder, fmt->totalsize, |
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407 | mant_off, mant_bits, mant_long); |
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408 | mant_off += mant_bits; |
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409 | mant_bits_left -= mant_bits; |
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410 | } |
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411 | } |
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412 | |
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413 | |
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414 | #ifdef IEEE_DEBUG |
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415 | |
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416 | /* This is to be run on a host which uses IEEE floating point. */ |
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417 | |
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418 | void |
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419 | ieee_test (n) |
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420 | double n; |
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421 | { |
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422 | double result; |
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423 | char exten[16]; |
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424 | |
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425 | floatformat_to_double (&floatformat_ieee_double_big, &n, &result); |
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426 | if (n != result) |
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427 | printf ("Differ(to): %.20g -> %.20g\n", n, result); |
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428 | floatformat_from_double (&floatformat_ieee_double_big, &n, &result); |
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429 | if (n != result) |
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430 | printf ("Differ(from): %.20g -> %.20g\n", n, result); |
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431 | |
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432 | floatformat_from_double (&floatformat_m68881_ext, &n, exten); |
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433 | floatformat_to_double (&floatformat_m68881_ext, exten, &result); |
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434 | if (n != result) |
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435 | printf ("Differ(to+from): %.20g -> %.20g\n", n, result); |
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436 | |
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437 | #if IEEE_DEBUG > 1 |
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438 | /* This is to be run on a host which uses 68881 format. */ |
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439 | { |
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440 | long double ex = *(long double *)exten; |
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441 | if (ex != n) |
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442 | printf ("Differ(from vs. extended): %.20g\n", n); |
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443 | } |
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444 | #endif |
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445 | } |
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446 | |
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447 | int |
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448 | main () |
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449 | { |
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450 | ieee_test (0.5); |
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451 | ieee_test (256.0); |
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452 | ieee_test (0.12345); |
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453 | ieee_test (234235.78907234); |
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454 | ieee_test (-512.0); |
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455 | ieee_test (-0.004321); |
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456 | return 0; |
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457 | } |
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458 | #endif |
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