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1 //=========================================================================== |
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2 // |
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3 // strtod.cxx |
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4 // |
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5 // ANSI String to double-precision floating point conversion |
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6 // |
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7 //=========================================================================== |
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8 //####COPYRIGHTBEGIN#### |
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9 // |
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10 // ------------------------------------------- |
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11 // The contents of this file are subject to the Cygnus eCos Public License |
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12 // Version 1.0 (the "License"); you may not use this file except in |
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13 // compliance with the License. You may obtain a copy of the License at |
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14 // http://sourceware.cygnus.com/ecos |
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15 // |
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16 // Software distributed under the License is distributed on an "AS IS" |
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17 // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the |
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18 // License for the specific language governing rights and limitations under |
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19 // the License. |
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20 // |
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21 // The Original Code is eCos - Embedded Cygnus Operating System, released |
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22 // September 30, 1998. |
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23 // |
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24 // The Initial Developer of the Original Code is Cygnus. Portions created |
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25 // by Cygnus are Copyright (C) 1998,1999 Cygnus Solutions. All Rights Reserved. |
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26 // ------------------------------------------- |
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27 // |
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28 //####COPYRIGHTEND#### |
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29 //=========================================================================== |
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30 //#####DESCRIPTIONBEGIN#### |
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31 // |
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32 // Author(s): jlarmour |
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33 // Contributors: jlarmour |
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34 // Date: 1998-02-13 |
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35 // Purpose: |
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36 // Description: |
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37 // Usage: |
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38 // |
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39 //####DESCRIPTIONEND#### |
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40 // |
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41 //=========================================================================== |
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42 |
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43 // CONFIGURATION |
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44 |
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45 #include <pkgconf/libc.h> // Configuration header |
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46 |
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47 // Include the C library? And strtod()? |
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48 #if defined(CYGPKG_LIBC) && defined(CYGFUN_LIBC_strtod) |
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49 |
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50 // INCLUDES |
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51 |
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52 #include <cyg/infra/cyg_type.h> // Common type definitions and support |
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53 #include <cyg/infra/cyg_trac.h> // Tracing support |
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54 #include <cyg/infra/cyg_ass.h> // Assertion support |
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55 #include <stddef.h> // NULL, wchar_t and size_t from compiler |
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56 #include <stdlib.h> // Main header for stdlib functions |
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57 #include <ctype.h> // isspace() and isdigit() |
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58 #include "clibincl/stdlibsupp.hxx" // Support for stdlib functions |
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59 #include <float.h> // DBL_MIN_10_EXP and DBL_MAX_10_EXP |
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60 #include <math.h> // HUGE_VAL |
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61 #include <errno.h> // errno |
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62 |
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63 // EXPORTED SYMBOLS |
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64 |
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65 externC double |
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66 strtod( const char *, char ** ) CYGPRI_LIBC_WEAK_ALIAS("_strtod"); |
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67 |
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68 // CONSTANTS |
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69 |
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70 #define MAXE (DBL_MAX_10_EXP) |
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71 #define MINE (DBL_MIN_10_EXP) |
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72 |
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73 // flags |
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74 #define SIGN 0x01 |
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75 #define ESIGN 0x02 |
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76 #define DECP 0x04 |
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77 |
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78 |
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79 // MACROS |
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80 |
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81 #define Ise(c) ((c == 'e') || (c == 'E') || (c == 'd') || (c == 'D')) |
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82 #define Issign(c) ((c == '-') || (c == '+')) |
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83 #define Val(c) ((c - '0')) |
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84 |
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85 |
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86 // FUNCTIONS |
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87 |
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88 /* |
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89 * [atw] multiply 64 bit accumulator by 10 and add digit. |
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90 * The KA/CA way to do this should be to use |
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91 * a 64-bit integer internally and use "adjust" to |
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92 * convert it to float at the end of processing. |
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93 */ |
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94 static int |
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95 ten_mul(double *acc, int digit) |
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96 { |
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97 /* [atw] Crude, but effective (at least on a KB)... |
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98 */ |
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99 *acc *= 10; |
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100 *acc += digit; |
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101 |
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102 return 0; /* no overflow */ |
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103 } // ten_mul() |
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104 |
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105 |
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106 /* |
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107 * compute 10**x by successive squaring. |
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108 */ |
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109 |
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110 static const double |
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111 exp10(unsigned x) |
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112 { |
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113 static double powtab[] = {1.0, |
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114 10.0, |
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115 100.0, |
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116 1000.0, |
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117 10000.0}; |
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118 |
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119 if (x < (sizeof(powtab)/sizeof(double))) |
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120 return powtab[x]; |
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121 else if (x & 1) |
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122 return 10.0 * exp10(x-1); |
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123 else |
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124 return exp10(x/2) * exp10(x/2); |
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125 } // exp10() |
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126 |
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127 |
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128 /* |
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129 * return (*acc) scaled by 10**dexp. |
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130 */ |
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131 |
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132 static double |
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133 adjust(double *acc, int dexp, int sign) |
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134 /* *acc the 64 bit accumulator */ |
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135 /* dexp decimal exponent */ |
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136 /* sign sign flag */ |
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137 { |
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138 double r; |
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139 |
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140 if (dexp > MAXE) |
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141 { |
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142 errno = ERANGE; |
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143 return (sign) ? -HUGE_VAL : HUGE_VAL; |
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144 } |
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145 else if (dexp < MINE) |
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146 { |
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147 errno = ERANGE; |
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148 return 0.0; |
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149 } |
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150 |
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151 r = *acc; |
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152 if (sign) |
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153 r = -r; |
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154 if (dexp==0) |
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155 return r; |
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156 |
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157 if (dexp < 0) |
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158 return r / exp10(abs(dexp)); |
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159 else |
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160 return r * exp10(dexp); |
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161 } // adjust() |
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162 |
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163 |
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164 externC double |
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165 _strtod( const char *nptr, char **endptr ) |
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166 { |
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167 const char *start=nptr; |
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168 double accum = 0.0; |
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169 int flags = 0; |
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170 int texp = 0; |
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171 int e = 0; |
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172 int conv_done = 0; |
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173 |
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174 double retval; |
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175 |
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176 CYG_REPORT_FUNCNAMETYPE( "_strtod", "returning %f" ); |
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177 |
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178 CYG_CHECK_DATA_PTR( nptr, "nptr is an invalid pointer!" ); |
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179 |
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180 // endptr is allowed to be NULL, but if it isn't, we check it |
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181 if (endptr != NULL) |
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182 CYG_CHECK_DATA_PTR( endptr, "endptr is an invalid pointer!" ); |
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183 |
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184 while(isspace(*nptr)) nptr++; |
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185 if(*nptr == '\0') |
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186 { /* just leading spaces */ |
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187 if(endptr != NULL) *endptr = (char *)start; |
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188 return 0.0; |
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189 } |
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190 |
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191 |
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192 if(Issign(*nptr)) |
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193 { |
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194 if(*nptr == '-') flags = SIGN; |
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195 if(*++nptr == '\0') |
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196 { /* "+|-" : should be an error ? */ |
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197 if(endptr != NULL) *endptr = (char *)start; |
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198 return 0.0; |
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199 } |
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200 } |
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201 |
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202 for(; (isdigit(*nptr) || (*nptr == '.')); nptr++) |
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203 { |
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204 conv_done = 1; |
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205 if(*nptr == '.') |
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206 flags |= DECP; |
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207 else |
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208 { |
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209 if( ten_mul(&accum, Val(*nptr)) ) texp++; |
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210 if(flags & DECP) texp--; |
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211 } |
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212 } |
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213 |
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214 if(Ise(*nptr)) |
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215 { |
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216 conv_done = 1; |
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217 if(*++nptr != '\0') /* skip e|E|d|D */ |
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218 { /* ! ([nptr]xxx[.[yyy]]e) */ |
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219 |
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220 while(isspace(*nptr)) nptr++; /* Ansi allows spaces after e */ |
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221 if(*nptr != '\0') |
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222 { /* ! ([nptr]xxx[.[yyy]]e[space]) */ |
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223 |
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224 if(Issign(*nptr)) |
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225 if(*nptr++ == '-') flags |= ESIGN; |
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226 |
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227 if(*nptr != '\0') |
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228 { /* ! ([nptr]xxx[.[yyy]]e[nptr]) -- error?? */ |
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229 |
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230 for(; isdigit(*nptr); nptr++) |
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231 if (e < MAXE) /* prevent from grossly overflowing */ |
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232 e = e*10 + Val(*nptr); |
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233 |
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234 /* dont care what comes after this */ |
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235 if(flags & ESIGN) |
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236 texp -= e; |
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237 else |
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238 texp += e; |
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239 } |
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240 } |
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241 } |
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242 } |
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243 |
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244 if(endptr != NULL) |
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245 *endptr = (char *)((conv_done) ? nptr : start); |
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246 |
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247 retval = adjust(&accum, (int)texp, (int)(flags & SIGN)); |
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248 |
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249 |
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250 CYG_REPORT_RETVAL( retval ); |
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251 |
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252 return retval; |
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253 } // _strtod() |
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254 |
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255 |
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256 #endif // if defined(CYGPKG_LIBC) && defined(CYGFUN_LIBC_strtod) |
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257 |
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258 // EOF strtod.cxx |
