c++ - C++中的文件拆分器

Question

我正在尝试用 C++ 制作文件拆分器/连接器，但我的拆分函数遇到了问题。我用一个 MP4 文件进行了快速测试，结果是:其他部分都可以，但最后一部分总是不起作用。我不明白这一点。谁能给我解释一下？这是我的拆分函数:

void split_F(const char* file_name, int number_of_part)
{
    FILE *fp_read = fopen(file_name, "rb");

    //calculate file size
    int file_size;
    fseek(fp_read, 0L, SEEK_END);
    file_size = ftell(fp_read);
    rewind(fp_read); //reset file pointer

    //calculate number of parts
    //int number_of_part = (int)ceil((double)file_size / size_of_part);
    long size_of_part;
    size_of_part = (int)floor((double)file_size / number_of_part);
    cout << "Total files after split: " << number_of_part << endl
        << "...Processing..." << endl;

    //main process
    char name[255] = "";
    for (int count = 1; count <= number_of_part; count++) 
    {
        sprintf(name, "%s.part_%03d", file_name, count);
        FILE *fp_write = fopen(name, "wb");

        //create buffer
        char *buffer = new char[size_of_part];
        memset(buffer, NULL, size_of_part); //reset buffer

        fread(buffer, size_of_part, 1, fp_read);
        fwrite(buffer, size_of_part, 1, fp_write);
        fseek(fp_read, count*size_of_part, SEEK_SET);

        cout << "> File: " << name << " done babe!" << endl;

        delete[] buffer;
        fclose(fp_write);
    }
        fclose(fp_read);
}

Answer 1

最后一部分可能会小于或大于 size_of_part，因为原始文件大小不是它的倍数。

您需要自动调整最后一部分的大小。

例如，如果您的文件大小为 1000 字节，分为 7 个部分。您计算出的文件大小将为 142。7*142 = 994，您缺少最后 6 个字节。这是你的问题吗？

fseek 不是必需的，为什么要使用它？你只需要顺序读取输入文件

void split_F(const char* file_name, int number_of_part)
{
    FILE *fp_read = fopen(file_name, "rb");

    //calculate file size
    int file_size;
    fseek(fp_read, 0L, SEEK_END);
    file_size = ftell(fp_read);
    rewind(fp_read); //reset file pointer

    //calculate number of parts
    long size_of_part;
    size_of_part = (int)ceil((double)file_size / number_of_part);
    cout << "Total files after split: " << number_of_part << endl
        << "...Processing..." << endl;

    //main process
    char name[255] = "";
    int bytesRemaining = file_size;

    //create buffer, we reuse it for each part
    char *buffer = new char[size_of_part];

    //No need to reset buffer
    //memset(buffer, NULL, partSize);


    for (int count = 1; count <= number_of_part; count++) 
    {
        sprintf(name, "%s.part_%03d", file_name, count);
        FILE *fp_write = fopen(name, "wb");

        int partSize;
        if(bytesRemaining > size_of_part)
        {
            partSize = size_of_part;
        }
        else
        {
            partSize = bytesRemaining;
        }

        fread(buffer, partSize, 1, fp_read);
        fwrite(buffer, partSize, 1, fp_write);

        cout << "> File: " << name << " done babe!" << endl;

        fclose(fp_write);
    }
    fclose(fp_read);
    delete[] buffer;
}