js/src/jsdtoa.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * vim: set ts=8 sts=4 et sw=4 tw=99:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef jsdtoa_h
   8 #define jsdtoa_h
   9
  10 /*
  11  * Public interface to portable double-precision floating point to string
  12  * and back conversion package.
  13  */
  14
  15 #include <stddef.h>
  16
  17 struct DtoaState;
  18
  19 DtoaState*
  20 js_NewDtoaState();
  21
  22 void
  23 js_DestroyDtoaState(DtoaState* state);
  24
  25 /*
  26  * js_strtod_harder() returns as a double-precision floating-point number the
  27  * value represented by the character string pointed to by s00. The string is
  28  * scanned up to the first unrecognized character.
  29  *
  30  * If se is not nullptr, *se receives a pointer to the character terminating
  31  * the scan. If no number can be formed, *se receives a pointer to the first
  32  * unparseable character in s00, and zero is returned.
  33  *
  34  * On overflow, this function returns infinity and does not indicate an error.
  35  *
  36  * *err is set to zero on success; it's set to JS_DTOA_ENOMEM on memory failure.
  37  */
  38 #define JS_DTOA_ENOMEM 2
  39 double
  40 js_strtod_harder(DtoaState* state, const char* s00, char** se, int* err);
  41
  42 /*
  43  * Modes for converting floating-point numbers to strings.
  44  *
  45  * Some of the modes can round-trip; this means that if the number is converted to
  46  * a string using one of these mode and then converted back to a number, the result
  47  * will be identical to the original number (except that, due to ECMA, -0 will get converted
  48  * to +0).  These round-trip modes return the minimum number of significand digits that
  49  * permit the round trip.
  50  *
  51  * Some of the modes take an integer parameter <precision>.
  52  */
  53 /* NB: Keep this in sync with number_constants[]. */
  54 typedef enum JSDToStrMode {
  55     DTOSTR_STANDARD,              /* Either fixed or exponential format; round-trip */
  56     DTOSTR_STANDARD_EXPONENTIAL,  /* Always exponential format; round-trip */
  57     DTOSTR_FIXED,                 /* Round to <precision> digits after the decimal point; exponential if number is large */
  58     DTOSTR_EXPONENTIAL,           /* Always exponential format; <precision> significant digits */
  59     DTOSTR_PRECISION              /* Either fixed or exponential format; <precision> significant digits */
  60 } JSDToStrMode;
  61
  62
  63 /* Maximum number of characters (including trailing null) that a DTOSTR_STANDARD or DTOSTR_STANDARD_EXPONENTIAL
  64  * conversion can produce.  This maximum is reached for a number like -0.0000012345678901234567. */
  65 #define DTOSTR_STANDARD_BUFFER_SIZE 26
  66
  67 /* Maximum number of characters (including trailing null) that one of the other conversions
  68  * can produce.  This maximum is reached for TO_FIXED, which can generate up to 21 digits before the decimal point. */
  69 #define DTOSTR_VARIABLE_BUFFER_SIZE(precision) ((precision)+24 > DTOSTR_STANDARD_BUFFER_SIZE ? (precision)+24 : DTOSTR_STANDARD_BUFFER_SIZE)
  70
  71 /*
  72  * DO NOT USE THIS FUNCTION IF YOU CAN AVOID IT.  js::NumberToCString() is a
  73  * better function to use.
  74  *
  75  * Convert dval according to the given mode and return a pointer to the
  76  * resulting ASCII string.  If mode == DTOSTR_STANDARD and precision == 0 it's
  77  * equivalent to ToString() as specified by ECMA-262-5 section 9.8.1, but it
  78  * doesn't handle integers specially so should be avoided in that case (that's
  79  * why js::NumberToCString() is better).
  80  *
  81  * The result is held somewhere in buffer, but not necessarily at the
  82  * beginning.  The size of buffer is given in bufferSize, and must be at least
  83  * as large as given by the above macros.
  84  *
  85  * Return nullptr if out of memory.
  86  */
  87 char*
  88 js_dtostr(DtoaState* state, char* buffer, size_t bufferSize, JSDToStrMode mode, int precision,
  89           double dval);
  90
  91 /*
  92  * DO NOT USE THIS FUNCTION IF YOU CAN AVOID IT.  js::NumberToCString() is a
  93  * better function to use.
  94  *
  95  * Convert d to a string in the given base.  The integral part of d will be
  96  * printed exactly in that base, regardless of how large it is, because there
  97  * is no exponential notation for non-base-ten numbers.  The fractional part
  98  * will be rounded to as few digits as possible while still preserving the
  99  * round-trip property (analogous to that of printing decimal numbers).  In
 100  * other words, if one were to read the resulting string in via a hypothetical
 101  * base-number-reading routine that rounds to the nearest IEEE double (and to
 102  * an even significand if there are two equally near doubles), then the result
 103  * would equal d (except for -0.0, which converts to "0", and NaN, which is
 104  * not equal to itself).
 105  *
 106  * Return nullptr if out of memory.  If the result is not nullptr, it must be
 107  * released via js_free().
 108  */
 109 char*
 110 js_dtobasestr(DtoaState* state, int base, double d);
 111
 112 #endif /* jsdtoa_h */