Zero-Copy File Reading in Go

Achieving zero-copy I/O is a crucial optimization for high-performance applications that deal with large amounts of data. In Go, this means reading data from a file directly into a user-space buffer without unnecessary intermediate copying. This challenge focuses on implementing a way to read file contents into a memory buffer efficiently.

Problem Description

Your task is to create a Go function that reads the entire content of a file into a byte slice using a mechanism that minimizes data copying between the kernel and user space. This is often achieved through techniques like mmap (memory-mapping) which maps a file directly into the process's address space.

Key Requirements:

• Implement a function ZeroCopyReadFile(filePath string) ([]byte, error) that takes a file path as input.
• The function should return a []byte containing the entire content of the file.
• The implementation should aim for zero-copy I/O, meaning data should ideally be read directly from the kernel's page cache into the returned byte slice, avoiding redundant copies.
• Handle potential errors during file opening, reading, or memory mapping gracefully.

Expected Behavior:

The function should successfully read the content of any accessible file and return it as a byte slice. For very large files, the performance benefit of zero-copy should be noticeable compared to standard ioutil.ReadFile.

Edge Cases:

• Empty files.
• Files that do not exist.
• Files with read permission issues.
• Very large files.

Examples

Example 1:

Input:
filePath = "my_test_file.txt" with content "Hello, Zero-Copy!"

Output:
[]byte{72, 101, 108, 108, 111, 44, 32, 90, 101, 114, 111, 44, 32, 67, 111, 112, 121, 33}
(This is the byte representation of "Hello, Zero-Copy!")

Explanation:
The function successfully reads the content of "my_test_file.txt" and returns it as a byte slice.

Example 2:

Input:
filePath = "non_existent_file.txt"

Output:
nil, an error indicating the file could not be found.

Explanation:
The function correctly handles the case where the input file does not exist.

Example 3:

Input:
filePath = "empty_file.txt" (an empty file)

Output:
[]byte{} (an empty byte slice), nil

Explanation:
The function correctly handles empty files, returning an empty byte slice without error.

Constraints

• The solution must be implemented in Go.
• The implementation should leverage system calls or libraries that enable memory mapping (mmap) to achieve zero-copy semantics. Directly using os.ReadFile or io.ReadAll will not fulfill the zero-copy requirement.
• Assume the operating system supports mmap or similar mechanisms.
• For simplicity, focus on reading from regular files. Do not consider pipes, sockets, or other special file types for this challenge.

Notes

Consider using the syscall package or third-party libraries designed for low-level file operations and memory mapping in Go. Research how mmap works on your target operating system and how it can be accessed from Go. Remember that mmap creates a mapping; you will need to handle unmapping the memory region when you are done to avoid resource leaks. The runtime.KeepAlive function might be useful to ensure the underlying file descriptor remains valid as long as the mapped memory is in use.