C++ 如何从C中的二进制文件中读取浮点数？
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How to read a float from binary file in C?
提问by Polaris878
Everything I'm finding via google is garbage... Note that I want the answer inC, however if you supplement your answer with a C++ solution as wellthen you get bonus points!
一切我通过谷歌发现是垃圾......请注意，我想要的答案在Ç，但是如果你用C ++解决方案补充你的答案，以及那么你获得积分！
I just want to be able to read some floats into an array from a binary file
我只想能够从二进制文件中将一些浮点数读入数组
EDIT: Yes I know about Endian-ness... and no I don't care how it was stored.
编辑：是的，我知道 Endian-ness ......不，我不在乎它是如何存储的。
回答by sth
How you have to read the floats from the file completely depends on how the values were saved there in the first place. One common way could be:
您必须如何从文件中读取浮点数完全取决于这些值最初是如何保存在那里的。一种常见的方法可能是：
void writefloat(float v, FILE *f) {
fwrite((void*)(&v), sizeof(v), 1, f);
}
float readfloat(FILE *f) {
float v;
fread((void*)(&v), sizeof(v), 1, f);
return v;
}
回答by Michael Krelin - hacker
float f;
if(read(fd,&f,sizeof(f))==sizeof(f))
printf("%f\n",f);
else
printf("oops\n");
Provided that it's written as compatible binary representation.
前提是它以兼容的二进制表示形式编写。
readfor file descriptors, freadfor FILE*s and istream::readfor c++iostreams. Pick whatever pleases you:
read文件描述符，fread对于FILE*S和istream::read用于c++输入输出流。选择你喜欢的任何东西：
read(fd,&f,sizeof(f))==sizeof(f)
fread(&f,sizeof(f),1,fp)==1
fin.read((char*)&f,sizeof(f)).gcount()==sizeof(f)
回答by vpram86
回答by Christoph
Use fread()from <stdio.h>. The assertions should be replaced with actual error handling code.
fread()从使用<stdio.h>。断言应替换为实际的错误处理代码。
#include <stdio.h>
#include <assert.h>
#define countof(ARRAY) (sizeof (ARRAY) / sizeof *(ARRAY))
float data[5];
FILE *file = fopen("foo.bin", "rb");
assert(file);
size_t n = fread(data, sizeof(float), countof(data), file);
assert(n == countof(data));
Keep in mind that you might run into endian issues if you transfer files between different architectures.
请记住，如果您在不同架构之间传输文件，您可能会遇到字节序问题。
回答by Daniel
If the file is all "float" and you wanted to read it X number of times, all you have to do is this:
如果文件都是“浮动的”，并且您想读取它 X 次，您所要做的就是：
FILE *fp;
if((fp=fopen("filename.whatever", "rb"))==NULL)
return 0;
fseek(fp, 0, SEEK_END);
long size = ftell(fp);
fseek(fp, 0, SEEK_SET);
float *f = (float *)malloc(sizeof(float)*size);
if(f==NULL)
{
fclose(fp);
return 0;
}
if(fread(f, sizeof(float), size, fp)!=size)
{
fclose(fp);
return 0;
}
fclose(fp);
// do something with f
回答by aviraldg
FILE *thisFile=fopen("filename","fb");
float myFloat;
fscanf(thisFile,"%f",&myFloat);
fclose(thisFile);
This works if the data is written using fprintf (implementation specific)
However,you can also typecast your float to int32 and save , load and typecast.
如果使用 fprintf（特定于实现）写入数据，则此方法有效。
但是，您也可以将 float 类型转换为 int32 并保存、加载和类型转换。
std::fstream thisFile;
thisFile.open("filename",ios::read|ios::binary);
float myFloat;
thisFile>>myFloat;
thisFile.close();
May be wrong (I haven't used the C++ F.IO functions for a loooong loooong time)
可能是错误的（我已经很久没有使用 C++ F.IO 函数了）
回答by Charles
If these values are sequentially placed into a binary file you can do a read of sizeof(float) bytes per float value into a character array. You can then cast these into a float value.
如果这些值按顺序放入二进制文件中，您可以将每个浮点值的 sizeof(float) 字节读取到字符数组中。然后，您可以将这些转换为浮点值。
