虽然我特别关注C ++和Java解决方案,但我想知道是否有任何语言使其特别容易,因此我将其设置为与语言无关。我希望能看到其他语言的解决方案。
编辑:我已经涵盖了C、C++、C#和Java。还有其他语言专家想要添加到列表中吗?
C/C++很容易。
union ufloat {
float f;
unsigned u;
};
ufloat u1;
u1.f = 0.3f;
然后你只需输出u1.u
。
双精度浮点数同样简单。
union udouble {
double d;
unsigned long u;
}
int fl = *(int*)&floatVar;
&floatVar
获取的是内存地址,然后 (int*)
是一个指向这个地址的指针,最后使用 * 来获取 int 中 4 字节的 float 值。然后你可以使用 printf 打印二进制格式或十六进制格式。
显然,没有人提到如何轻松获得十六进制指数表示法,所以在这里:
#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
// C++11 manipulator
cout << 23.0f << " : " << std::hexfloat << 23.0f << endl;
// C equivalent solution
printf("23.0 in hexadecimal is: %A\n", 23.0f);
}
Java:在谷歌搜索中,可以找到这个链接:Sun论坛
具体来说(我自己没有尝试过)
long binary = Double.doubleToLongBits(3.14159);
String strBinary = Long.toBinaryString(binary);
strBinary.length()
的值为64,但实际上却是63。有人知道为什么吗? - hiullerInteger.toBinaryString(Float.floatToIntBits(floatNumber));
将返回浮点数的字符串位表示。 - Rocky IndeBitConverter
接受许多类型并允许访问原始二进制数据;要获取十六进制表示形式,则最常见的选项是ToString("x2")
(可能会被封装在一个实用方法中)。 byte[] raw = BitConverter.GetBytes(123.45);
StringBuilder sb = new StringBuilder(raw.Length * 2);
foreach (byte b in raw)
{
sb.Append(b.ToString("x2"));
}
Console.WriteLine(sb);
奇怪的是,base-64有一个一行代码转换(Convert.ToBase64String
),但 base-16需要更多的努力。除非你引用Microsoft.VisualBasic,否则:
long tmp = BitConverter.DoubleToInt64Bits(123.45);
string hex = Microsoft.VisualBasic.Conversion.Hex(tmp);
/*
@(#)File: $RCSfile: dumpdblflt.c,v $
@(#)Version: $Revision: 1.1 $
@(#)Last changed: $Date: 2007/09/05 22:23:33 $
@(#)Purpose: Print C double and float data in bytes etc.
@(#)Author: J Leffler
@(#)Copyright: (C) JLSS 2007
@(#)Product: :PRODUCT:
*/
/*TABSTOP=4*/
#include <stdio.h>
#include "imageprt.h"
#ifndef lint
/* Prevent over-aggressive optimizers from eliminating ID string */
extern const char jlss_id_dumpdblflt_c[];
const char jlss_id_dumpdblflt_c[] = "@(#)$Id: dumpdblflt.c,v 1.1 2007/09/05 22:23:33 jleffler Exp $";
#endif /* lint */
union u_double
{
double dbl;
char data[sizeof(double)];
};
union u_float
{
float flt;
char data[sizeof(float)];
};
static void dump_float(union u_float f)
{
int exp;
long mant;
printf("32-bit float: sign: %d, ", (f.data[0] & 0x80) >> 7);
exp = ((f.data[0] & 0x7F) << 1) | ((f.data[1] & 0x80) >> 7);
printf("expt: %4d (unbiassed %5d), ", exp, exp - 127);
mant = ((((f.data[1] & 0x7F) << 8) | (f.data[2] & 0xFF)) << 8) | (f.data[3] & 0xFF);
printf("mant: %16ld (0x%06lX)\n", mant, mant);
}
static void dump_double(union u_double d)
{
int exp;
long long mant;
printf("64-bit float: sign: %d, ", (d.data[0] & 0x80) >> 7);
exp = ((d.data[0] & 0x7F) << 4) | ((d.data[1] & 0xF0) >> 4);
printf("expt: %4d (unbiassed %5d), ", exp, exp - 1023);
mant = ((((d.data[1] & 0x0F) << 8) | (d.data[2] & 0xFF)) << 8) |
(d.data[3] & 0xFF);
mant = (mant << 32) | ((((((d.data[4] & 0xFF) << 8) |
(d.data[5] & 0xFF)) << 8) | (d.data[6] & 0xFF)) << 8) |
(d.data[7] & 0xFF);
printf("mant: %16lld (0x%013llX)\n", mant, mant);
}
static void print_value(double v)
{
union u_double d;
union u_float f;
f.flt = v;
d.dbl = v;
printf("SPARC: float/double of %g\n", v);
image_print(stdout, 0, f.data, sizeof(f.data));
image_print(stdout, 0, d.data, sizeof(d.data));
dump_float(f);
dump_double(d);
}
int main(void)
{
print_value(+1.0);
print_value(+2.0);
print_value(+3.0);
print_value( 0.0);
print_value(-3.0);
print_value(+3.1415926535897932);
print_value(+1e126);
return(0);
}
SPARC: float/double of 1
0x0000: 3F 80 00 00 ?...
0x0000: 3F F0 00 00 00 00 00 00 ?.......
32-bit float: sign: 0, expt: 127 (unbiassed 0), mant: 0 (0x000000)
64-bit float: sign: 0, expt: 1023 (unbiassed 0), mant: 0 (0x0000000000000)
SPARC: float/double of 2
0x0000: 40 00 00 00 @...
0x0000: 40 00 00 00 00 00 00 00 @.......
32-bit float: sign: 0, expt: 128 (unbiassed 1), mant: 0 (0x000000)
64-bit float: sign: 0, expt: 1024 (unbiassed 1), mant: 0 (0x0000000000000)
SPARC: float/double of 3
0x0000: 40 40 00 00 @@..
0x0000: 40 08 00 00 00 00 00 00 @.......
32-bit float: sign: 0, expt: 128 (unbiassed 1), mant: 4194304 (0x400000)
64-bit float: sign: 0, expt: 1024 (unbiassed 1), mant: 2251799813685248 (0x8000000000000)
SPARC: float/double of 0
0x0000: 00 00 00 00 ....
0x0000: 00 00 00 00 00 00 00 00 ........
32-bit float: sign: 0, expt: 0 (unbiassed -127), mant: 0 (0x000000)
64-bit float: sign: 0, expt: 0 (unbiassed -1023), mant: 0 (0x0000000000000)
SPARC: float/double of -3
0x0000: C0 40 00 00 .@..
0x0000: C0 08 00 00 00 00 00 00 ........
32-bit float: sign: 1, expt: 128 (unbiassed 1), mant: 4194304 (0x400000)
64-bit float: sign: 1, expt: 1024 (unbiassed 1), mant: 2251799813685248 (0x8000000000000)
SPARC: float/double of 3.14159
0x0000: 40 49 0F DB @I..
0x0000: 40 09 21 FB 54 44 2D 18 @.!.TD-.
32-bit float: sign: 0, expt: 128 (unbiassed 1), mant: 4788187 (0x490FDB)
64-bit float: sign: 0, expt: 1024 (unbiassed 1), mant: 2570638124657944 (0x921FB54442D18)
SPARC: float/double of 1e+126
0x0000: 7F 80 00 00 ....
0x0000: 5A 17 A2 EC C4 14 A0 3F Z......?
32-bit float: sign: 0, expt: 255 (unbiassed 128), mant: 0 (0x000000)
64-bit float: sign: 0, expt: 1441 (unbiassed 418), mant: -1005281217 (0xFFFFFFFFC414A03F)
我考虑了一段时间是否要在这里发布,因为这可能会激励其他程序员用C做出一些恶意行为。不过我还是决定发出来,但请记住:如果没有适当的文档支持,甚至即使有也要三思而后行,不要将这种代码写入任何严肃的应用程序中。
除了免责声明,我们继续说下去。
首先编写一个函数,例如以二进制格式打印一个长无符号变量:
void printbin(unsigned long x, int n)
{
if (--n) printbin(x>>1, n);
putchar("01"[x&1]);
}
不幸的是,我们不能直接使用这个函数来打印我们的浮点变量,所以我们需要进行一些小小的黑客。这个黑客可能对那些阅读过Carmack's Inverse Square Root Quake 技巧的人来说很熟悉。其思想是为我们的浮点变量设置一个值,然后获取相同的位掩码作为我们的长整型变量。因此,我们获取f的内存地址,将其转换为long*值,并使用该指针将f的位掩码作为长无符号数获取。如果您将此值打印为长无符号数,结果会很混乱,但位与原始浮点值相同,因此并不重要。
int main(void)
{
long unsigned lu;
float f = -1.1f;
lu = *(long*)&f;
printbin(lu, 32);
printf("\n");
return 0;
}
module BinarySerial where
import Data.Bits
import Data.Binary
import qualified Data.ByteString.Lazy as B
elemToBits :: (Bits a) => a -> [Bool]
elemToBits a = map (testBit a) [0..7]
listToBits :: (Bits a) => [a] -> [Bool]
listToBits a = reverse $ concat $ map elemToBits a
rawBits :: (Binary a) => a -> [Bool]
rawBits a = listToBits $ B.unpack $ encode a
可以通过rawBits进行转换:
rawBits (3.14::Float)
但是,如果你需要以这种方式访问浮点值,那么你可能做错了什么。真正的问题可能是如何访问浮点数的指数和尾数?答案来自Prelude中的exponent和significand:
significand 3.14
0.785
exponent 3.14
2
在Java中,Float和Double类都有一个toHexString('float')方法,因此这基本上就可以用于十六进制转换。
Double.toHexString(42344);
Float.toHexString(42344);
Python:
Code:
import struct
def float2bin(number, hexdecimal=False, single=False):
bytes = struct.pack('>f' if single else '>d', number)
func, length = (hex, 2) if hexdecimal else (bin, 8)
byte2bin = lambda byte: func(ord(byte))[2:].rjust(length, '0')
return ''.join(map(byte2bin, bytes))
示例:
>>> float2bin(1.0)
'0011111111110000000000000000000000000000000000000000000000000000'
>>> float2bin(-1.0)
'1011111111110000000000000000000000000000000000000000000000000000'
>>> float2bin(1.0, True)
'3ff0000000000000'
>>> float2bin(1.0, True, True)
'3f800000'
>>> float2bin(-1.0, True)
'bff0000000000000'
rjust
吗? - kjo