不正确的读取浮动来自matlab中的二进制文件

时间:2013-10-07 20:17:10

标签: c++ arrays matlab floating-point binaryfiles

我正在尝试在matlab中读取存储在二进制文件中的浮点数组。最初文件是通过内存映射技巧在c ++代码中创建的。

C ++代码:

#include <iostream>
#include <sys/types.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main() 
{
    const char* filePath   = "test_file.dat";
    const size_t NUM_ELEMS = 11;

    /* Write the float array to the binary file via memory mapping */
    const size_t NUM_BYTES = NUM_ELEMS * sizeof(float);//array of the 11 floats;    
    int fd = open(filePath, O_RDWR | O_CREAT | O_TRUNC, 0);//open file
    lseek (fd, NUM_BYTES - 1, SEEK_SET);//stretch the file size
    write(fd, "", 1);//write empty string at the end of file
    float* mappedArray = (float*)mmap(0, NUM_BYTES, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);//map array to the file

    for(size_t i = 0; i < NUM_ELEMS; ++i)//fill array
        mappedArray[i] = static_cast<float>(i) / 10.0f;

    munmap(mappedArray, NUM_BYTES);
    close(fd);

    /* Test reading the recorded file*/    
    std::ifstream fl(filePath, std::ios::in | std::ios::binary);
    float data = 0.0f;
    for(size_t i = 0; i < NUM_ELEMS; ++i)
    {
        fl.read(reinterpret_cast<char*>(&data), sizeof(data)); 
        std::cout<<data<<"\n";
    }

    fl.close();
}

从C ++代码测试读取文件显示正确的结果 - 文件已成功记录。从C ++读取的结果:

  

0   0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8

但是,尝试从matlab读取此文件会产生错误(数据不正确):

Matlab代码:

function out = readDataFromFile()
    fid = fopen('test_file.dat','r','b'); 
    out = fread(fid, 11, '*float');  
    fclose(fid);
end

从matlab阅读的结果:

  

0   -429492128   -428443584   -6,3526893e-23   -429492160 8,8281803e-44   -6,3320104e-23 4,1723293e-08   -428443616 2,7200760e + 23 4,6006030e-41

我想注意,如果我编写uint8_t(或unsigned char)数组,从matlab读取此文件会成功。 我在matlab中做错了什么?

我的系统 - 64位Ubuntu 13.04, c ++编译器 - gcc 4.8, matlab - 2013a

1 个答案:

答案 0 :(得分:0)

通过替换

解决了这个问题
fid = fopen('test_file.dat','r','b');

fid = fopen('test_file.dat','r');