In certain scenarios, reading a file into a std::vector
std::ifstream testFile("testfile", "rb"); std::vector<char> fileContents; int fileSize = getFileSize(testFile); fileContents.reserve(fileSize); testFile.read(&fileContents[0], fileSize);
However, this approach fails when resizing the vector with reserve(), as it does not actually insert elements into the vector. As a result, attempting to access fileContents[0] will cause an error.
A more comprehensive solution involves the usage of iterators. Using an input file stream, the following snippet allows for efficient file reading:
#include<iterator> //... std::ifstream testFile("testfile", std::ios::binary); std::vector<char> fileContents((std::istreambuf_iterator<char>(testFile)), std::istreambuf_iterator<char>());
This approach utilizes istreambuf_iterator to iterate over the input file stream and insert elements directly into the vector.
If reallocations are a concern, reserve() can be used to pre-allocate space in the vector:
#include<iterator> //... std::ifstream testFile("testfile", std::ios::binary); std::vector<char> fileContents; fileContents.reserve(fileSize); fileContents.assign(std::istreambuf_iterator<char>(testFile), std::istreambuf_iterator<char>());
In this variation, reserve() is used to allocate space based on the known file size, and assign() is employed to populate the vector using iterators.
The above is the detailed content of How to Efficiently Read a File into a std::vector?. For more information, please follow other related articles on the PHP Chinese website!