365 lines
9.2 KiB
C++
365 lines
9.2 KiB
C++
// Copyright (C) 2002-2012 Nikolaus Gebhardt
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// This file is part of the "Irrlicht Engine" and the "irrXML" project.
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// For conditions of distribution and use, see copyright notice in irrlicht.h and irrXML.h
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#ifndef __FAST_ATOF_H_INCLUDED__
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#define __FAST_ATOF_H_INCLUDED__
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#include "irrMath.h"
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#include "irrString.h"
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namespace irr
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{
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namespace core
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{
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//! Selection of characters which count as decimal point in fast_atof
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// TODO: This should probably also be used in irr::core::string, but the float-to-string code
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// used there has to be rewritten first.
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IRRLICHT_API extern irr::core::stringc LOCALE_DECIMAL_POINTS;
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// we write [17] here instead of [] to work around a swig bug
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const float fast_atof_table[17] = {
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0.f,
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0.1f,
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0.01f,
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0.001f,
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0.0001f,
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0.00001f,
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0.000001f,
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0.0000001f,
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0.00000001f,
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0.000000001f,
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0.0000000001f,
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0.00000000001f,
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0.000000000001f,
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0.0000000000001f,
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0.00000000000001f,
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0.000000000000001f,
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0.0000000000000001f
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};
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//! Convert a simple string of base 10 digits into an unsigned 32 bit integer.
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/** \param[in] in: The string of digits to convert. No leading chars are
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allowed, only digits 0 to 9. Parsing stops at the first non-digit.
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\param[out] out: (optional) If provided, it will be set to point at the
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first character not used in the calculation.
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\return The unsigned integer value of the digits. If the string specifies
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too many digits to encode in an u32 then INT_MAX will be returned.
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*/
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inline u32 strtoul10(const char* in, const char** out=0)
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{
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if (!in)
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{
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if (out)
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*out = in;
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return 0;
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}
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bool overflow=false;
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u32 unsignedValue = 0;
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while ( ( *in >= '0') && ( *in <= '9' ))
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{
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const u32 tmp = ( unsignedValue * 10 ) + ( *in - '0' );
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if (tmp<unsignedValue)
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{
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unsignedValue=(u32)0xffffffff;
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overflow=true;
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}
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if (!overflow)
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unsignedValue = tmp;
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++in;
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}
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if (out)
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*out = in;
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return unsignedValue;
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}
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//! Convert a simple string of base 10 digits into a signed 32 bit integer.
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/** \param[in] in: The string of digits to convert. Only a leading - or +
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followed by digits 0 to 9 will be considered. Parsing stops at the first
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non-digit.
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\param[out] out: (optional) If provided, it will be set to point at the
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first character not used in the calculation.
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\return The signed integer value of the digits. If the string specifies
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too many digits to encode in an s32 then +INT_MAX or -INT_MAX will be
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returned.
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*/
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inline s32 strtol10(const char* in, const char** out=0)
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{
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if (!in)
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{
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if (out)
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*out = in;
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return 0;
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}
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const bool negative = ('-' == *in);
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if (negative || ('+' == *in))
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++in;
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const u32 unsignedValue = strtoul10(in,out);
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if (unsignedValue > (u32)INT_MAX)
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{
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if (negative)
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return (s32)INT_MIN;
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else
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return (s32)INT_MAX;
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}
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else
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{
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if (negative)
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return -((s32)unsignedValue);
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else
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return (s32)unsignedValue;
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}
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}
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//! Convert a hex-encoded character to an unsigned integer.
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/** \param[in] in The digit to convert. Only digits 0 to 9 and chars A-F,a-f
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will be considered.
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\return The unsigned integer value of the digit. 0xffffffff if the input is
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not hex
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*/
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inline u32 ctoul16(char in)
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{
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if (in >= '0' && in <= '9')
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return in - '0';
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else if (in >= 'a' && in <= 'f')
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return 10u + in - 'a';
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else if (in >= 'A' && in <= 'F')
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return 10u + in - 'A';
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else
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return 0xffffffff;
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}
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//! Convert a simple string of base 16 digits into an unsigned 32 bit integer.
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/** \param[in] in: The string of digits to convert. No leading chars are
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allowed, only digits 0 to 9 and chars A-F,a-f are allowed. Parsing stops
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at the first illegal char.
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\param[out] out: (optional) If provided, it will be set to point at the
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first character not used in the calculation.
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\return The unsigned integer value of the digits. If the string specifies
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too many digits to encode in an u32 then INT_MAX will be returned.
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*/
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inline u32 strtoul16(const char* in, const char** out=0)
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{
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if (!in)
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{
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if (out)
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*out = in;
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return 0;
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}
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bool overflow=false;
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u32 unsignedValue = 0;
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while (true)
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{
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u32 tmp = 0;
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if ((*in >= '0') && (*in <= '9'))
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tmp = (unsignedValue << 4u) + (*in - '0');
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else if ((*in >= 'A') && (*in <= 'F'))
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tmp = (unsignedValue << 4u) + (*in - 'A') + 10;
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else if ((*in >= 'a') && (*in <= 'f'))
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tmp = (unsignedValue << 4u) + (*in - 'a') + 10;
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else
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break;
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if (tmp<unsignedValue)
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{
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unsignedValue=(u32)INT_MAX;
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overflow=true;
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}
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if (!overflow)
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unsignedValue = tmp;
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++in;
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}
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if (out)
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*out = in;
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return unsignedValue;
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}
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//! Convert a simple string of base 8 digits into an unsigned 32 bit integer.
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/** \param[in] in The string of digits to convert. No leading chars are
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allowed, only digits 0 to 7 are allowed. Parsing stops at the first illegal
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char.
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\param[out] out (optional) If provided, it will be set to point at the
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first character not used in the calculation.
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\return The unsigned integer value of the digits. If the string specifies
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too many digits to encode in an u32 then INT_MAX will be returned.
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*/
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inline u32 strtoul8(const char* in, const char** out=0)
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{
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if (!in)
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{
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if (out)
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*out = in;
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return 0;
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}
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bool overflow=false;
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u32 unsignedValue = 0;
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while (true)
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{
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u32 tmp = 0;
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if ((*in >= '0') && (*in <= '7'))
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tmp = (unsignedValue << 3u) + (*in - '0');
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else
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break;
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if (tmp<unsignedValue)
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{
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unsignedValue=(u32)INT_MAX;
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overflow=true;
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}
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if (!overflow)
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unsignedValue = tmp;
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++in;
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}
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if (out)
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*out = in;
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return unsignedValue;
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}
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//! Convert a C-style prefixed string (hex, oct, integer) into an unsigned 32 bit integer.
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/** \param[in] in The string of digits to convert. If string starts with 0x the
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hex parser is used, if only leading 0 is used, oct parser is used. In all
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other cases, the usual unsigned parser is used.
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\param[out] out (optional) If provided, it will be set to point at the
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first character not used in the calculation.
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\return The unsigned integer value of the digits. If the string specifies
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too many digits to encode in an u32 then INT_MAX will be returned.
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*/
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inline u32 strtoul_prefix(const char* in, const char** out=0)
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{
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if (!in)
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{
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if (out)
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*out = in;
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return 0;
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}
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if ('0'==in[0])
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return ('x'==in[1] ? strtoul16(in+2,out) : strtoul8(in+1,out));
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return strtoul10(in,out);
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}
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//! Converts a sequence of digits into a whole positive floating point value.
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/** Only digits 0 to 9 are parsed. Parsing stops at any other character,
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including sign characters or a decimal point.
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\param in: the sequence of digits to convert.
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\param out: (optional) will be set to point at the first non-converted
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character.
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\return The whole positive floating point representation of the digit
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sequence.
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*/
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inline f32 strtof10(const char* in, const char** out = 0)
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{
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if (!in)
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{
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if (out)
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*out = in;
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return 0.f;
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}
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const u32 MAX_SAFE_U32_VALUE = UINT_MAX / 10 - 10;
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u32 intValue = 0;
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// Use integer arithmetic for as long as possible, for speed
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// and precision.
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while ( ( *in >= '0') && ( *in <= '9' ) )
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{
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// If it looks like we're going to overflow, bail out
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// now and start using floating point.
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if (intValue >= MAX_SAFE_U32_VALUE)
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break;
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intValue = (intValue * 10) + (*in - '0');
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++in;
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}
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f32 floatValue = (f32)intValue;
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// If there are any digits left to parse, then we need to use
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// floating point arithmetic from here.
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while ( ( *in >= '0') && ( *in <= '9' ) )
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{
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floatValue = (floatValue * 10.f) + (f32)(*in - '0');
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++in;
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if (floatValue > FLT_MAX) // Just give up.
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break;
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}
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if (out)
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*out = in;
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return floatValue;
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}
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//! Provides a fast function for converting a string into a float.
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/** This is not guaranteed to be as accurate as atof(), but is
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approximately 6 to 8 times as fast.
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\param[in] in The string to convert.
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\param[out] result The resultant float will be written here.
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\return Pointer to the first character in the string that wasn't used
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to create the float value.
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*/
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inline const char* fast_atof_move(const char* in, f32& result)
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{
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// Please run the regression test when making any modifications to this function.
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result = 0.f;
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if (!in)
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return 0;
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const bool negative = ('-' == *in);
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if (negative || ('+'==*in))
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++in;
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f32 value = strtof10(in, &in);
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if ( LOCALE_DECIMAL_POINTS.findFirst(*in) >= 0 )
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{
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const char* afterDecimal = ++in;
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const f32 decimal = strtof10(in, &afterDecimal);
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value += decimal * fast_atof_table[afterDecimal - in];
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in = afterDecimal;
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}
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if ('e' == *in || 'E' == *in)
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{
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++in;
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// Assume that the exponent is a whole number.
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// strtol10() will deal with both + and - signs,
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// but calculate as f32 to prevent overflow at FLT_MAX
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value *= powf(10.f, (f32)strtol10(in, &in));
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}
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result = negative?-value:value;
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return in;
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}
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//! Convert a string to a floating point number
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/** \param floatAsString The string to convert.
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\param out Optional pointer to the first character in the string that
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wasn't used to create the float value.
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\result Float value parsed from the input string
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*/
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inline float fast_atof(const char* floatAsString, const char** out=0)
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{
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float ret;
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if (out)
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*out=fast_atof_move(floatAsString, ret);
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else
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fast_atof_move(floatAsString, ret);
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return ret;
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}
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} // end namespace core
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} // end namespace irr
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#endif
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