File Section Hasher

A Rust library to compute a 64-bit unsigned integer (u64) hash for a specific section of a file. Implements the Write trait for incremental hashing.

The hash algorithm is std::hash::DefaultHasher.

Overview

Use FileHasher::new() to create an instance. Write data into it, and each write operation updates the hash value. Once all data is written, the final u64 hash is generated.

Key features:

• Hash a specific portion of a file (e.g., skip header/footer).
• Incremental hashing via the Write trait.

Examples

Example: Hashing a File Section

use std::fs::File;
use std::io::{Read, Seek};
use fileparthasher::FileHasher;

fn main() -> std::io::Result<()> {
    let mut file = File::open("large_file.bin")?;
    let mut hasher = FileHasher::new();
    
    // Hash bytes 100 to 200 (inclusive)
    let hash = hasher.hash(&mut file, 100, 100)?;
    println!("Hash: {:x}", hash);
    
    Ok(())
}

Example: using Write Trait

use std::io::{Write, Read, Seek};
use fileparthasher::FileHasher;

let mut hasher = FileHasher::new();
hasher.write_all(b"Hello, ")?;
hasher.write_all(b"world!")?;
let hash = hasher.finish(); // Get the hash after all writes

Main Function: hash()

fn hash<R>(mut self, reader: &mut R, from_byte: u64, length: u64) -> io::Result<u64> where R: Read + Seek;

• reader: A readable and seekable input source (e.g., file).
• from_byte: Starting byte offset (0-based).
• length: Number of bytes to hash.
• Returns: Computed u64 hash or an I/O error.