1 // Copyright 2012 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #ifndef DOUBLE_CONVERSION_DOUBLE_TO_STRING_H_ 29 #define DOUBLE_CONVERSION_DOUBLE_TO_STRING_H_ 30 31 #include "mozilla/Types.h" 32 #include "utils.h" 33 34 namespace double_conversion { 35 36 class DoubleToStringConverter { 37 public: 38 // When calling ToFixed with a double > 10^kMaxFixedDigitsBeforePoint 39 // or a requested_digits parameter > kMaxFixedDigitsAfterPoint then the 40 // function returns false. 41 static const int kMaxFixedDigitsBeforePoint = 60; 42 static const int kMaxFixedDigitsAfterPoint = 60; 43 44 // When calling ToExponential with a requested_digits 45 // parameter > kMaxExponentialDigits then the function returns false. 46 static const int kMaxExponentialDigits = 120; 47 48 // When calling ToPrecision with a requested_digits 49 // parameter < kMinPrecisionDigits or requested_digits > kMaxPrecisionDigits 50 // then the function returns false. 51 static const int kMinPrecisionDigits = 1; 52 static const int kMaxPrecisionDigits = 120; 53 54 enum Flags { 55 NO_FLAGS = 0, 56 EMIT_POSITIVE_EXPONENT_SIGN = 1, 57 EMIT_TRAILING_DECIMAL_POINT = 2, 58 EMIT_TRAILING_ZERO_AFTER_POINT = 4, 59 UNIQUE_ZERO = 8 60 }; 61 62 // Flags should be a bit-or combination of the possible Flags-enum. 63 // - NO_FLAGS: no special flags. 64 // - EMIT_POSITIVE_EXPONENT_SIGN: when the number is converted into exponent 65 // form, emits a '+' for positive exponents. Example: 1.2e+2. 66 // - EMIT_TRAILING_DECIMAL_POINT: when the input number is an integer and is 67 // converted into decimal format then a trailing decimal point is appended. 68 // Example: 2345.0 is converted to "2345.". 69 // - EMIT_TRAILING_ZERO_AFTER_POINT: in addition to a trailing decimal point 70 // emits a trailing '0'-character. This flag requires the 71 // EXMIT_TRAILING_DECIMAL_POINT flag. 72 // Example: 2345.0 is converted to "2345.0". 73 // - UNIQUE_ZERO: "-0.0" is converted to "0.0". 74 // 75 // Infinity symbol and nan_symbol provide the string representation for these 76 // special values. If the string is NULL and the special value is encountered 77 // then the conversion functions return false. 78 // 79 // The exponent_character is used in exponential representations. It is 80 // usually 'e' or 'E'. 81 // 82 // When converting to the shortest representation the converter will 83 // represent input numbers in decimal format if they are in the interval 84 // [10^decimal_in_shortest_low; 10^decimal_in_shortest_high[ 85 // (lower boundary included, greater boundary excluded). 86 // Example: with decimal_in_shortest_low = -6 and 87 // decimal_in_shortest_high = 21: 88 // ToShortest(0.000001) -> "0.000001" 89 // ToShortest(0.0000001) -> "1e-7" 90 // ToShortest(111111111111111111111.0) -> "111111111111111110000" 91 // ToShortest(100000000000000000000.0) -> "100000000000000000000" 92 // ToShortest(1111111111111111111111.0) -> "1.1111111111111111e+21" 93 // 94 // When converting to precision mode the converter may add 95 // max_leading_padding_zeroes before returning the number in exponential 96 // format. 97 // Example with max_leading_padding_zeroes_in_precision_mode = 6. 98 // ToPrecision(0.0000012345, 2) -> "0.0000012" 99 // ToPrecision(0.00000012345, 2) -> "1.2e-7" 100 // Similarily the converter may add up to 101 // max_trailing_padding_zeroes_in_precision_mode in precision mode to avoid 102 // returning an exponential representation. A zero added by the 103 // EMIT_TRAILING_ZERO_AFTER_POINT flag is counted for this limit. 104 // Examples for max_trailing_padding_zeroes_in_precision_mode = 1: 105 // ToPrecision(230.0, 2) -> "230" 106 // ToPrecision(230.0, 2) -> "230." with EMIT_TRAILING_DECIMAL_POINT. 107 // ToPrecision(230.0, 2) -> "2.3e2" with EMIT_TRAILING_ZERO_AFTER_POINT. 108 // 109 // The min_exponent_width is used for exponential representations. 110 // The converter adds leading '0's to the exponent until the exponent 111 // is at least min_exponent_width digits long. 112 // The min_exponent_width is clamped to 5. 113 // As such, the exponent may never have more than 5 digits in total. 114 DoubleToStringConverter(int flags, 115 const char* infinity_symbol, 116 const char* nan_symbol, 117 char exponent_character, 118 int decimal_in_shortest_low, 119 int decimal_in_shortest_high, 120 int max_leading_padding_zeroes_in_precision_mode, 121 int max_trailing_padding_zeroes_in_precision_mode, 122 int min_exponent_width = 0) flags_(flags)123 : flags_(flags), 124 infinity_symbol_(infinity_symbol), 125 nan_symbol_(nan_symbol), 126 exponent_character_(exponent_character), 127 decimal_in_shortest_low_(decimal_in_shortest_low), 128 decimal_in_shortest_high_(decimal_in_shortest_high), 129 max_leading_padding_zeroes_in_precision_mode_( 130 max_leading_padding_zeroes_in_precision_mode), 131 max_trailing_padding_zeroes_in_precision_mode_( 132 max_trailing_padding_zeroes_in_precision_mode), 133 min_exponent_width_(min_exponent_width) { 134 // When 'trailing zero after the point' is set, then 'trailing point' 135 // must be set too. 136 DOUBLE_CONVERSION_ASSERT(((flags & EMIT_TRAILING_DECIMAL_POINT) != 0) || 137 !((flags & EMIT_TRAILING_ZERO_AFTER_POINT) != 0)); 138 } 139 140 // Returns a converter following the EcmaScript specification. 141 static MFBT_API const DoubleToStringConverter& EcmaScriptConverter(); 142 143 // Computes the shortest string of digits that correctly represent the input 144 // number. Depending on decimal_in_shortest_low and decimal_in_shortest_high 145 // (see constructor) it then either returns a decimal representation, or an 146 // exponential representation. 147 // Example with decimal_in_shortest_low = -6, 148 // decimal_in_shortest_high = 21, 149 // EMIT_POSITIVE_EXPONENT_SIGN activated, and 150 // EMIT_TRAILING_DECIMAL_POINT deactived: 151 // ToShortest(0.000001) -> "0.000001" 152 // ToShortest(0.0000001) -> "1e-7" 153 // ToShortest(111111111111111111111.0) -> "111111111111111110000" 154 // ToShortest(100000000000000000000.0) -> "100000000000000000000" 155 // ToShortest(1111111111111111111111.0) -> "1.1111111111111111e+21" 156 // 157 // Note: the conversion may round the output if the returned string 158 // is accurate enough to uniquely identify the input-number. 159 // For example the most precise representation of the double 9e59 equals 160 // "899999999999999918767229449717619953810131273674690656206848", but 161 // the converter will return the shorter (but still correct) "9e59". 162 // 163 // Returns true if the conversion succeeds. The conversion always succeeds 164 // except when the input value is special and no infinity_symbol or 165 // nan_symbol has been given to the constructor. ToShortest(double value,StringBuilder * result_builder)166 bool ToShortest(double value, StringBuilder* result_builder) const { 167 return ToShortestIeeeNumber(value, result_builder, SHORTEST); 168 } 169 170 // Same as ToShortest, but for single-precision floats. ToShortestSingle(float value,StringBuilder * result_builder)171 bool ToShortestSingle(float value, StringBuilder* result_builder) const { 172 return ToShortestIeeeNumber(value, result_builder, SHORTEST_SINGLE); 173 } 174 175 176 // Computes a decimal representation with a fixed number of digits after the 177 // decimal point. The last emitted digit is rounded. 178 // 179 // Examples: 180 // ToFixed(3.12, 1) -> "3.1" 181 // ToFixed(3.1415, 3) -> "3.142" 182 // ToFixed(1234.56789, 4) -> "1234.5679" 183 // ToFixed(1.23, 5) -> "1.23000" 184 // ToFixed(0.1, 4) -> "0.1000" 185 // ToFixed(1e30, 2) -> "1000000000000000019884624838656.00" 186 // ToFixed(0.1, 30) -> "0.100000000000000005551115123126" 187 // ToFixed(0.1, 17) -> "0.10000000000000001" 188 // 189 // If requested_digits equals 0, then the tail of the result depends on 190 // the EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT. 191 // Examples, for requested_digits == 0, 192 // let EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT be 193 // - false and false: then 123.45 -> 123 194 // 0.678 -> 1 195 // - true and false: then 123.45 -> 123. 196 // 0.678 -> 1. 197 // - true and true: then 123.45 -> 123.0 198 // 0.678 -> 1.0 199 // 200 // Returns true if the conversion succeeds. The conversion always succeeds 201 // except for the following cases: 202 // - the input value is special and no infinity_symbol or nan_symbol has 203 // been provided to the constructor, 204 // - 'value' > 10^kMaxFixedDigitsBeforePoint, or 205 // - 'requested_digits' > kMaxFixedDigitsAfterPoint. 206 // The last two conditions imply that the result will never contain more than 207 // 1 + kMaxFixedDigitsBeforePoint + 1 + kMaxFixedDigitsAfterPoint characters 208 // (one additional character for the sign, and one for the decimal point). 209 MFBT_API bool ToFixed(double value, 210 int requested_digits, 211 StringBuilder* result_builder) const; 212 213 // Computes a representation in exponential format with requested_digits 214 // after the decimal point. The last emitted digit is rounded. 215 // If requested_digits equals -1, then the shortest exponential representation 216 // is computed. 217 // 218 // Examples with EMIT_POSITIVE_EXPONENT_SIGN deactivated, and 219 // exponent_character set to 'e'. 220 // ToExponential(3.12, 1) -> "3.1e0" 221 // ToExponential(5.0, 3) -> "5.000e0" 222 // ToExponential(0.001, 2) -> "1.00e-3" 223 // ToExponential(3.1415, -1) -> "3.1415e0" 224 // ToExponential(3.1415, 4) -> "3.1415e0" 225 // ToExponential(3.1415, 3) -> "3.142e0" 226 // ToExponential(123456789000000, 3) -> "1.235e14" 227 // ToExponential(1000000000000000019884624838656.0, -1) -> "1e30" 228 // ToExponential(1000000000000000019884624838656.0, 32) -> 229 // "1.00000000000000001988462483865600e30" 230 // ToExponential(1234, 0) -> "1e3" 231 // 232 // Returns true if the conversion succeeds. The conversion always succeeds 233 // except for the following cases: 234 // - the input value is special and no infinity_symbol or nan_symbol has 235 // been provided to the constructor, 236 // - 'requested_digits' > kMaxExponentialDigits. 237 // The last condition implies that the result will never contain more than 238 // kMaxExponentialDigits + 8 characters (the sign, the digit before the 239 // decimal point, the decimal point, the exponent character, the 240 // exponent's sign, and at most 3 exponent digits). 241 MFBT_API bool ToExponential(double value, 242 int requested_digits, 243 StringBuilder* result_builder) const; 244 245 // Computes 'precision' leading digits of the given 'value' and returns them 246 // either in exponential or decimal format, depending on 247 // max_{leading|trailing}_padding_zeroes_in_precision_mode (given to the 248 // constructor). 249 // The last computed digit is rounded. 250 // 251 // Example with max_leading_padding_zeroes_in_precision_mode = 6. 252 // ToPrecision(0.0000012345, 2) -> "0.0000012" 253 // ToPrecision(0.00000012345, 2) -> "1.2e-7" 254 // Similarily the converter may add up to 255 // max_trailing_padding_zeroes_in_precision_mode in precision mode to avoid 256 // returning an exponential representation. A zero added by the 257 // EMIT_TRAILING_ZERO_AFTER_POINT flag is counted for this limit. 258 // Examples for max_trailing_padding_zeroes_in_precision_mode = 1: 259 // ToPrecision(230.0, 2) -> "230" 260 // ToPrecision(230.0, 2) -> "230." with EMIT_TRAILING_DECIMAL_POINT. 261 // ToPrecision(230.0, 2) -> "2.3e2" with EMIT_TRAILING_ZERO_AFTER_POINT. 262 // Examples for max_trailing_padding_zeroes_in_precision_mode = 3, and no 263 // EMIT_TRAILING_ZERO_AFTER_POINT: 264 // ToPrecision(123450.0, 6) -> "123450" 265 // ToPrecision(123450.0, 5) -> "123450" 266 // ToPrecision(123450.0, 4) -> "123500" 267 // ToPrecision(123450.0, 3) -> "123000" 268 // ToPrecision(123450.0, 2) -> "1.2e5" 269 // 270 // Returns true if the conversion succeeds. The conversion always succeeds 271 // except for the following cases: 272 // - the input value is special and no infinity_symbol or nan_symbol has 273 // been provided to the constructor, 274 // - precision < kMinPericisionDigits 275 // - precision > kMaxPrecisionDigits 276 // The last condition implies that the result will never contain more than 277 // kMaxPrecisionDigits + 7 characters (the sign, the decimal point, the 278 // exponent character, the exponent's sign, and at most 3 exponent digits). 279 MFBT_API bool ToPrecision(double value, 280 int precision, 281 bool* used_exponential_notation, 282 StringBuilder* result_builder) const; 283 284 enum DtoaMode { 285 // Produce the shortest correct representation. 286 // For example the output of 0.299999999999999988897 is (the less accurate 287 // but correct) 0.3. 288 SHORTEST, 289 // Same as SHORTEST, but for single-precision floats. 290 SHORTEST_SINGLE, 291 // Produce a fixed number of digits after the decimal point. 292 // For instance fixed(0.1, 4) becomes 0.1000 293 // If the input number is big, the output will be big. 294 FIXED, 295 // Fixed number of digits (independent of the decimal point). 296 PRECISION 297 }; 298 299 // The maximal number of digits that are needed to emit a double in base 10. 300 // A higher precision can be achieved by using more digits, but the shortest 301 // accurate representation of any double will never use more digits than 302 // kBase10MaximalLength. 303 // Note that DoubleToAscii null-terminates its input. So the given buffer 304 // should be at least kBase10MaximalLength + 1 characters long. 305 static const MFBT_DATA int kBase10MaximalLength = 17; 306 307 // Converts the given double 'v' to digit characters. 'v' must not be NaN, 308 // +Infinity, or -Infinity. In SHORTEST_SINGLE-mode this restriction also 309 // applies to 'v' after it has been casted to a single-precision float. That 310 // is, in this mode static_cast<float>(v) must not be NaN, +Infinity or 311 // -Infinity. 312 // 313 // The result should be interpreted as buffer * 10^(point-length). 314 // 315 // The digits are written to the buffer in the platform's charset, which is 316 // often UTF-8 (with ASCII-range digits) but may be another charset, such 317 // as EBCDIC. 318 // 319 // The output depends on the given mode: 320 // - SHORTEST: produce the least amount of digits for which the internal 321 // identity requirement is still satisfied. If the digits are printed 322 // (together with the correct exponent) then reading this number will give 323 // 'v' again. The buffer will choose the representation that is closest to 324 // 'v'. If there are two at the same distance, than the one farther away 325 // from 0 is chosen (halfway cases - ending with 5 - are rounded up). 326 // In this mode the 'requested_digits' parameter is ignored. 327 // - SHORTEST_SINGLE: same as SHORTEST but with single-precision. 328 // - FIXED: produces digits necessary to print a given number with 329 // 'requested_digits' digits after the decimal point. The produced digits 330 // might be too short in which case the caller has to fill the remainder 331 // with '0's. 332 // Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. 333 // Halfway cases are rounded towards +/-Infinity (away from 0). The call 334 // toFixed(0.15, 2) thus returns buffer="2", point=0. 335 // The returned buffer may contain digits that would be truncated from the 336 // shortest representation of the input. 337 // - PRECISION: produces 'requested_digits' where the first digit is not '0'. 338 // Even though the length of produced digits usually equals 339 // 'requested_digits', the function is allowed to return fewer digits, in 340 // which case the caller has to fill the missing digits with '0's. 341 // Halfway cases are again rounded away from 0. 342 // DoubleToAscii expects the given buffer to be big enough to hold all 343 // digits and a terminating null-character. In SHORTEST-mode it expects a 344 // buffer of at least kBase10MaximalLength + 1. In all other modes the 345 // requested_digits parameter and the padding-zeroes limit the size of the 346 // output. Don't forget the decimal point, the exponent character and the 347 // terminating null-character when computing the maximal output size. 348 // The given length is only used in debug mode to ensure the buffer is big 349 // enough. 350 static MFBT_API void DoubleToAscii(double v, 351 DtoaMode mode, 352 int requested_digits, 353 char* buffer, 354 int buffer_length, 355 bool* sign, 356 int* length, 357 int* point); 358 359 private: 360 // Implementation for ToShortest and ToShortestSingle. 361 MFBT_API bool ToShortestIeeeNumber(double value, 362 StringBuilder* result_builder, 363 DtoaMode mode) const; 364 365 // If the value is a special value (NaN or Infinity) constructs the 366 // corresponding string using the configured infinity/nan-symbol. 367 // If either of them is NULL or the value is not special then the 368 // function returns false. 369 MFBT_API bool HandleSpecialValues(double value, StringBuilder* result_builder) const; 370 // Constructs an exponential representation (i.e. 1.234e56). 371 // The given exponent assumes a decimal point after the first decimal digit. 372 MFBT_API void CreateExponentialRepresentation(const char* decimal_digits, 373 int length, 374 int exponent, 375 StringBuilder* result_builder) const; 376 // Creates a decimal representation (i.e 1234.5678). 377 MFBT_API void CreateDecimalRepresentation(const char* decimal_digits, 378 int length, 379 int decimal_point, 380 int digits_after_point, 381 StringBuilder* result_builder) const; 382 383 const int flags_; 384 const char* const infinity_symbol_; 385 const char* const nan_symbol_; 386 const char exponent_character_; 387 const int decimal_in_shortest_low_; 388 const int decimal_in_shortest_high_; 389 const int max_leading_padding_zeroes_in_precision_mode_; 390 const int max_trailing_padding_zeroes_in_precision_mode_; 391 const int min_exponent_width_; 392 393 DOUBLE_CONVERSION_DISALLOW_IMPLICIT_CONSTRUCTORS(DoubleToStringConverter); 394 }; 395 396 } // namespace double_conversion 397 398 #endif // DOUBLE_CONVERSION_DOUBLE_TO_STRING_H_ 399