I'm trying to write a program that takes a large file (of any type) and splits it into many smaller "chunks". I think I have the basic idea down, but for some reason I cannot create a chunk size over 12 kb. I know there are a few solutions on google, etc. but I am more interested in learning what the origin of this limitation is then actually using the program to split files.
我正在编写一个程序，它接收一个大文件(任何类型的)，并将它分割成许多小的“块”。我认为我已经掌握了基本的思想，但是出于某种原因，我不能创建超过12 kb的块大小。我知道有一些关于谷歌等的解决方案，但是我更感兴趣的是了解这个限制的起源，然后使用这个程序来分割文件。
//This file splits are larger into smaller files of a user inputted size.
#include<iostream>
#include<fstream>
#include<string>
#include<sstream>
#include <direct.h>
#include <stdlib.h>
using namespace std;
void GetCurrentPath(char* buffer)
{
_getcwd(buffer, _MAX_PATH);
}
int main()
{
// use the function to get the path
char CurrentPath[_MAX_PATH];
GetCurrentPath(CurrentPath);//Get the current directory (used for displaying output)
fstream bigFile;
string filename;
int partsize;
cout << "Enter a file name: ";
cin >> filename; //Recieve target file
cout << "Enter the number of bites in each smaller file: ";
cin >> partsize; //Recieve volume size
bigFile.open(filename.c_str(),ios::in | ios::binary);
bigFile.seekg(0, ios::end); // position get-ptr 0 bytes from end
int size = bigFile.tellg(); // get-ptr position is now same as file size
bigFile.seekg(0, ios::beg); // position get-ptr 0 bytes from beginning
for (int i = 0; i <= (size / partsize); i++)
{
//Build File Name
string partname = filename; //The original filename
string charnum; //archive number
stringstream out; //stringstream object out, used to build the archive name
out << "." << i;
charnum = out.str();
partname.append(charnum); //put the part name together
//Write new file part
fstream filePart;
filePart.open(partname.c_str(),ios::out | ios::binary); //Open new file with the name built above
//Check if near the end of file
if (bigFile.tellg() < (size - (size%partsize)))
{
filePart.write(reinterpret_cast<char *>(&bigFile),partsize); //Write the selected amount to the file
filePart.close(); //close file
bigFile.seekg(partsize, ios::cur); //move pointer to next position to be written
}
//Changes the size of the last volume because it is the end of the file
else
{
filePart.write(reinterpret_cast<char *>(&bigFile),(size%partsize)); //Write the selected amount to the file
filePart.close(); //close file
}
cout << "File " << CurrentPath << partname << " produced" << endl; //display the progress of the split
}
bigFile.close();
cout << "Split Complete." << endl;
return 0;
}
Any ideas?
什么好主意吗?
1 个解决方案
#1
4
You are writing to the split file, but not reading from the bigfile. What you are writing it the in-memory structure of the bigfile, not the contents of bigfile. You need to allocate a buffer, read into it from bigfile and write it to the splitfile(s).
您正在写入分割文件，但没有从bigfile中读取。编写它的是bigfile的内存结构，而不是bigfile的内容。您需要分配一个缓冲区，从bigfile中读取并将其写入splitfile中。
#1
4
You are writing to the split file, but not reading from the bigfile. What you are writing it the in-memory structure of the bigfile, not the contents of bigfile. You need to allocate a buffer, read into it from bigfile and write it to the splitfile(s).
您正在写入分割文件，但没有从bigfile中读取。编写它的是bigfile的内存结构，而不是bigfile的内容。您需要分配一个缓冲区，从bigfile中读取并将其写入splitfile中。