求解IEEE-754格式转换
4个字节的浮点数(浮点数说明:采用IEEE-754格式的单精度4字节浮点数,按顺序共32位,第1位为符号位,为1时表示负数,为0时表示正数,第2~9位为阶码,其偏移量为127,即计算时应减去127,10~32位为尾数,尾数为一纯小数,计算时应在最前面加上一个整数位'1'和小数点.阶码为正时小数点右移,阶码为负时小数点左移.如果上位机软件采用同样的浮点数格式,可使用强制类型转换直接使用该浮点数)
例如浮点数C2 20 00 00 ,数值第一位为'1'表示负数,阶码为84H=132,132-127=5.尾数加上'1'和小数点,用二进制表示为:1.010 0000 0000 0000 0000 0000因为阶码为5,小数点右移5位,得出整数部分为101000即40,小数部分为0.综上,此浮点数值为-40.
再如浮点数41 46 66 66,数值第一位为'0'表示正数,阶码为82H=130,132-127=3.尾数加上'1'和小数点,用二进制表示为:1.100 0110 0110 0110 0110 0110因为阶码为3,小数点右移3位,得出整数部分为1100即12,小数部分为0110 0110 0110.转化为十进制约为0.39,综上,此浮点数值为12.39V.
懒得自己写,网上找了下发现一个很简单的实现方法。看不懂,求解,谢谢
union uu
{
char aa[4];
float bb;
} t;
DWORD dwValue = 0x41466666;
t.aa[3] = dwValue/0x1000000;
t.aa[2] = (dwValue%0x1000000)/0x10000;
t.aa[1] =(dwValue%0x10000)/0x100;
t.aa[0] = dwValue%0x100;
CString temp;
temp.Format("%08X = %02x,%02x,%02x,%02x,%.7f",dwValue,t.aa[3],t.aa[2],t.aa[1],t.aa[0],t.bb);
MessageBox(temp);
float f=-40f;
unsigned char *p;
p=(unsigned char *)&f;
printf("%02X %02X %02X %02X\n",p[0],p[1],p[2],p[3]);
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <locale.h>
int main() {
int i,v;
char bs[33];
char b[33];
char hs[9];
char h[9];
char s[4];
char *e;
// 十进制整数转二进制串;
i=1024;
ltoa(i,b,2);
sprintf(bs,"%032s",b);
printf("i=%d,bs=%s\n",i,bs);
// 十进制整数转十六进制串;
i=1024;
ltoa(i,h,16);
sprintf(hs,"%08s",h);
printf("i=%d,hs=%s\n",i,hs);
// 十六进制字符串转成十进制数
strcpy(hs,"00000400");
sscanf(hs,"%x",&i);
printf("hs=%s,i=%d\n",hs,i);
// 二进制字符串转化为十六进制字符串;
strcpy(bs,"00000000000000000000010000000000");
i=strtol(bs,&e,2);
ltoa(i,h,16);
sprintf(hs,"%08s",h);
printf("bs=%s,hs=%s\n",bs,hs);
// 二进制字符串转化为十进制数;
strcpy(bs,"00000000000000000000010000000000");
i=strtol(bs,&e,2);
printf("bs=%s,i=%d\n",bs,i);
// 十六进制字符串转成二进制串
strcpy(hs,"00000400");
sscanf(hs,"%x",&i);
ltoa(i,b,2);
sprintf(bs,"%032s",b);
printf("hs=%s,bs=%s\n",hs,bs);
// ASC\GBK字符串转十六进制串
strcpy(s,"a汉");
i=0;
while (1) {
if (0==s[i]) break;
sprintf(hs+i*2,"%02X",(unsigned char)s[i]);
i++;
}
setlocale(LC_ALL,"chs");
printf("s=%s,hs=%s\n",s,hs);
// 十六进制字符串转成汉字(GBK)及字符(ASC)
strcpy(hs,"61BABA");
i=0;
while (1) {
if (1!=sscanf(hs+i*2,"%2x",&v)) break;
s[i]=(char)v;
i++;
}
s[i]=0;
printf("hs=%s,s=%s\n",hs,s);
return 0;
}
//i=1024,bs=00000000000000000000010000000000
//i=1024,hs=00000400
//hs=00000400,i=1024
//bs=00000000000000000000010000000000,hs=00000400
//bs=00000000000000000000010000000000,i=1024
//hs=00000400,bs=00000000000000000000010000000000
//s=a汉,hs=61BABA
//hs=61BABA,s=a汉