From 8f53239f4ceccfd747283c8f0d7968fa40731faf Mon Sep 17 00:00:00 2001
From: Mike Buland <eichlan@xagasoft.com>
Date: Tue, 8 Mar 2011 08:06:44 +0000
Subject: sigh, another program that's not realy a tool, it was the easiest
 place for it I should add a new class of program to libbu++ or clear out most
 of my old tests or something.  Anyway, almost fully C99 compliant float to
 normalized hex string and back functions in pure math.  Really slick, really
 portable.  they don't handle +/-NaN, +/-Inf, or the special alternate format
 for subnormal numbers, try entering a 0.0...01 where I cut out about 200
 zeros, you'll see what I mean.

---
 src/tools/float.cpp | 130 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 src/tools/float.cpp

diff --git a/src/tools/float.cpp b/src/tools/float.cpp
new file mode 100644
index 0000000..2c241f3
--- /dev/null
+++ b/src/tools/float.cpp
@@ -0,0 +1,130 @@
+#include <bu/sio.h>
+#include <bu/string.h>
+#include <stdlib.h>
+#include <math.h>
+
+using namespace Bu;
+
+Bu::String ftos( double dNum )
+{
+	if( dNum == 1.0 )
+		return "0x1p+0";
+	if( dNum == 0.0 )
+		return signbit(dNum)?"-0x0p+0":"0x0p+0";
+	if( dNum == -1.0 )
+		return "-0x1p+0";
+	Bu::String s("0x1.");
+	if( signbit(dNum) )
+	{
+		s.prepend("-");
+		dNum = -dNum;
+	}
+/*	
+	for( int j = 0; j < 150 && dNum; j++ )
+	{
+		dNum = dNum*2;
+		sio << dNum << " -- " << (int)dNum << sio.nl;
+		if( (int)dNum == 0 )
+			s += '0';
+		else
+		{
+			s += '1';
+			dNum -= 1.0;
+		}
+	}
+	return s;
+	*/
+	int iPower = 0;
+	if( dNum < 1.0 )
+	{
+		while( dNum < 1.0 )
+		{
+			dNum *= 2.0;
+			iPower--;
+		}
+	}
+	else if( dNum >= 2.0 )
+	{
+		while( dNum >= 2.0 )
+		{
+			dNum *= 0.5;
+			iPower++;
+		}
+	}
+	dNum -= (int)dNum;
+	for( int j = 0; j < 150 && dNum; j++ )
+	{
+		dNum = dNum*16.0;
+		s += "0123456789abcdef"[(int)dNum];
+		dNum -= (int)dNum;
+	}
+	s.formatAppend("p%+d", iPower );
+	return s;
+}
+
+double stof( const Bu::String &s )
+{
+	if( s == "0x1p+0" )
+		return 1.0;
+	if( s == "-0x1p+0" )
+		return -1.0;
+	if( s == "0x0p+0" )
+		return 0.0;
+	if( s == "-0x0p+0" )
+		return 0.0;
+	double dNum = 0.0;
+	int iPPos = s.getSize()-1;
+	for(; s[iPPos] != 'p'; iPPos--) { }
+	for( int i = iPPos-1; s[i] != '.'; i-- )
+	{
+		if( s[i]>='0' && s[i]<='9' )
+		{
+			dNum += s[i]-'0';
+		}
+		else if( s[i]>='a' && s[i]<='f' )
+		{
+			dNum += s[i]-'a'+10.0;
+		}
+		dNum *= 0.0625;
+	}
+
+	dNum += 1.0;
+
+	int iTop = strtol( s.getStr()+iPPos+1, NULL, 10 );
+	if( iTop < 0 )
+	{
+		for( int j = 0; j > iTop; j-- )
+		{
+			dNum *= 0.5;
+		}
+	}
+	else
+	{
+		for( int j = 0; j < iTop; j++ )
+		{
+			dNum *= 2.0;
+		}
+	}
+
+	if( s[0] == '-' )
+		return -dNum;
+	return dNum;
+}
+
+int main( int argc, char *argv[] )
+{
+	for( int j = 1; j < argc; j++ )
+	{
+		double dNum = strtod( argv[j], NULL );
+
+		String s = ftos( dNum );
+		sio << "in:     " << dNum << sio.nl;
+		sio << "mine:   " << s << sio.nl;
+		printf("printf: %a\n", dNum );
+		sio << "out:    " << stof( s ) << sio.nl;
+		sio << "match:  " << (stof( s ) == dNum) << sio.nl << sio.nl;
+	}
+
+	return 0;
+}
+
-- 
cgit v1.2.3