assimp/code/fast_atof.h

252 lines
6.4 KiB
C++

// Copyright (C) 2002-2007 Nikolaus Gebhardt
// This file is part of the "Irrlicht Engine" and the "irrXML" project.
// For conditions of distribution and use, see copyright notice in irrlicht.h and irrXML.h
// ------------------------------------------------------------------------------------
// Original description: (Schrompf)
// Adapted to the ASSIMP library because the builtin atof indeed takes AGES to parse a
// float inside a large string. Before parsing, it does a strlen on the given point.
// Changes:
// 22nd October 08 (Aramis_acg): Added temporary cast to double, added strtol10_64
// to ensure long numbers are handled correctly
// ------------------------------------------------------------------------------------
#ifndef __FAST_A_TO_F_H_INCLUDED__
#define __FAST_A_TO_F_H_INCLUDED__
#include <math.h>
namespace Assimp
{
const float fast_atof_table[16] = { // we write [16] here instead of [] to work around a swig bug
0.f,
0.1f,
0.01f,
0.001f,
0.0001f,
0.00001f,
0.000001f,
0.0000001f,
0.00000001f,
0.000000001f,
0.0000000001f,
0.00000000001f,
0.000000000001f,
0.0000000000001f,
0.00000000000001f,
0.000000000000001f
};
// ------------------------------------------------------------------------------------
// convert a string in decimal format to a number
// ------------------------------------------------------------------------------------
inline unsigned int strtol10( const char* in, const char** out=0)
{
unsigned int value = 0;
while ( 1 )
{
if ( *in < '0' || *in > '9' )
break;
value = ( value * 10 ) + ( *in - '0' );
++in;
}
if (out)*out = in;
return value;
}
// ------------------------------------------------------------------------------------
// convert a string in octal format to a number
// ------------------------------------------------------------------------------------
inline unsigned int strtol8( const char* in, const char** out=0)
{
unsigned int value = 0;
while ( 1 )
{
if ( *in < '0' || *in > '7' )
break;
value = ( value << 3 ) + ( *in - '0' );
++in;
}
if (out)*out = in;
return value;
}
// ------------------------------------------------------------------------------------
// convert a string in hex format to a number
// ------------------------------------------------------------------------------------
inline unsigned int strtol16( const char* in, const char** out=0)
{
unsigned int value = 0;
while ( 1 )
{
if ( *in >= '0' && *in <= '9' )
{
value = ( value << 4u ) + ( *in - '0' );
}
else if (*in >= 'A' && *in <= 'F')
{
value = ( value << 4u ) + ( *in - 'A' ) + 10;
}
else if (*in >= 'a' && *in <= 'f')
{
value = ( value << 4u ) + ( *in - 'a' ) + 10;
}
else break;
++in;
}
if (out)*out = in;
return value;
}
// ------------------------------------------------------------------------------------
// convert just one hex digit
// ------------------------------------------------------------------------------------
inline unsigned int HexDigitToDecimal(char in)
{
unsigned int out = 0xffffffff;
if (in >= '0' && in <= '9')
out = in - '0';
else if (in >= 'a' && in <= 'f')
out = 10u + in - 'a';
else if (in >= 'A' && in <= 'F')
out = 10u + in - 'A';
// return value is 0xffffffff if the input is not a hex digit
return out;
}
// ------------------------------------------------------------------------------------
// signed variant of strtol10
// ------------------------------------------------------------------------------------
inline int strtol10s( const char* in, const char** out=0)
{
bool bNeg = false;
if ('-' == *in){++in;bNeg = true;}
if ('+' == *in)++in;
int value = strtol10(in,out);
if (bNeg)value = -value;
return value;
}
// ------------------------------------------------------------------------------------
// Parse a C++-like integer literal - hex and oct prefixes.
// 0xNNNN - hex
// 0NNN - oct
// NNN - dec
// ------------------------------------------------------------------------------------
inline unsigned int strtol_cppstyle( const char* in, const char** out=0)
{
if ('0' == in[0])
{
return 'x' == in[1] ? strtol16(in+2,out) : strtol8(in+1,out);
}
return strtol10(in, out);
}
// ------------------------------------------------------------------------------------
// Special version of the function, providing higher accuracy
// It is mainly used bx fast_atof to prevent ugly integer overflows.
// ------------------------------------------------------------------------------------
inline uint64_t strtol10_64( const char* in, const char** out=0)
{
uint64_t value = 0;
while ( 1 )
{
if ( *in < '0' || *in > '9' )
break;
value = ( value * 10 ) + ( *in - '0' );
++in;
}
if (out)
*out = in;
return value;
}
// ------------------------------------------------------------------------------------
//! Provides a fast function for converting a string into a float,
//! about 6 times faster than atof in win32.
// If you find any bugs, please send them to me, niko (at) irrlicht3d.org.
// ------------------------------------------------------------------------------------
inline const char* fast_atof_move( const char* c, float& out)
{
bool inv = false;
const char *t;
float f;
if (*c=='-')
{
++c;
inv = true;
}
else if (*c=='+')++c;
f = (float) strtol10_64 ( c, &c );
if (*c == '.')
{
++c;
// NOTE: The original implementation is highly unaccurate here
// The precision of a single IEEE 754 float is not high enough
// everything behind the 6th digit tends to be more inaccurate
// than it would need to be.
// Casting to double seems to solve the problem.
// strtol_64 is used to prevent integer overflow.
//float pl = (float)strtol(c, &t, 10);
double pl = (double) strtol10_64 ( c, &t );
pl *= fast_atof_table[t-c];
f += (float)pl;
c = t;
// FIX: a large 'E' should be allowed, too
if (*c == 'e' || *c == 'E')
{
++c;
bool einv = (*c=='-');
if (einv)
++c;
float exp = (float)strtol10(c, &c);
if (einv)
exp *= -1.0f;
f *= pow(10.0f, exp);
}
}
if (inv)
f *= -1.0f;
out = f;
return c;
}
// ------------------------------------------------------------------------------------
inline float fast_atof(const char* c)
{
float ret;
fast_atof_move(c, ret);
return ret;
}
} // end of namespace Assimp
#endif