c++ - fseek 没有读取所有数据？

Question

我正在制作一个 C++ 安装程序，我已将要提取的文件和要在程序中提取的文件的 8 字节文件大小附加到可执行文件中。我的程序因文件读取错误而退出，出了什么问题？请注意，除了我今天学到的知识外，我对 c 文件管理一无所知。我正在编写文件 test_before.tar.gz，它有 161 个字节，可执行文件有 12335 个字节长，filesize 文件有 8 个字节长，包含 0000161。有什么问题吗？如果需要，请询问更多信息。

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

int main(int argc, char* argv[])
{
    cout << "Opening the executable as read-only!" << endl;
    FILE *exeFile; // The executable file pointer
    FILE *outFile; // The file to write pointer

    // Check whether a file name was supplied
    if(argc < 2)
    {
        cout << "Please enter the file to write!" << endl;
        return 1;
    }

    // Open the executable as read-only
    if((exeFile = fopen(argv[0], "rb")) == 0)
    {
        cout << "Error opening the executable!" << endl;
        return 1;
    }

    cout << "Getting the executables size!" << endl;

    // Get the files size
    fseek(exeFile, 0, SEEK_END);
    int size = ftell(exeFile);

    cout << "Reading ofset!" << endl;   

    // Read the ofset bytes contained in the last 7-bytes
    char filesize_char[9];
    fseek(exeFile, -8, SEEK_END);
    fgets(filesize_char, 9, exeFile);

    // Convert
    int filesize = atoi(filesize_char);
    int ofset = (size - filesize) - 8;

    cout << "The ofset size is " << ofset << " bytes!" << endl;
    cout << "The file size is " << filesize << " bytes!" << endl;

    cout << "Reading the file to extract!" << endl;

    // Create the variable to contain the file and goto the ofset
    char* contents = new char[filesize + 1];
    fseek(exeFile, ofset, SEEK_SET);

    // Read the file to extract
    if(fread(contents, sizeof(char), filesize + 1, exeFile) != sizeof(contents))
    {
        // Error has occured
        if(feof(exeFile)) {
            cout << "Premature end of file!" << endl;

            // Delete variables so they dont "leak"
            fclose(exeFile);
            delete[] contents;

            return 1;
        } else {
            cout << "File read error!" << endl;

            // Delete variables so they dont "leak"
            fclose(exeFile);
            delete[] contents;

            return 1;
        }
    }

    cout << "Writing the file to " << argv[1] << "!" << endl;

    // Write the file to extract
    if((outFile = fopen(argv[1], "wb")) == 0)
    {
        cout << "Error opening the file to write!" << endl;

        // Delete variables so they dont "leak"
        fclose(exeFile);
        fclose(outFile);
        delete[] contents;

        return 1;
    }

    fwrite(contents, 1, sizeof(contents), outFile);

    //delete variables
    fclose(exeFile);
    fclose(outFile);
    delete[] contents;

    return 0;
}

Answer 1

您根本不需要 while 循环。毕竟，您已经分配了包含所有数据的内存。将文件指针移动到数据的开头 fseek(exeFile, ofset, SEEK_SET)，然后使用 fread 整体读取它，然后使用 fwrite 将其写入 outFile。

你应该用 "rb" 和 "wb" 标志打开你的 exeFile 和 outFile 否则你的代码仅对文本数据可靠地工作。