generating-hash-of-a-path.md

Generating a Hash From Files in a Path

Source: https://github.com/sger/go-hashdir/blob/master/hashdir.go (Heavily modified)

The Walk method from path/filepath walks the file tree rooted at root, calling walkFn for each file or directory in the tree, including root. All errors that arise visiting files and directories are filtered by walkFn. The files are walked in lexical order, which makes the output deterministic but means that for very large directories Walk can be inefficient. Walk does not follow symbolic links.

package main

import (
    "crypto/sha256"
    "encoding/hex"
    "io"
    "os"
    "path/filepath"
)

// Create hash value with local path and a hash algorithm
func Create(path string, hashAlgorithm string) (string, error) {
    hash := sha256.New()

    walkFn := func(path string, info os.FileInfo, err error) error {
        if err != nil {
            return nil
        }

        // Ignore directories
        if info.IsDir() {
            return nil
        }

        // Open the file for reading
        file, err := os.Open(path)
        if err != nil {
            return err
        }

        // Make sure the file is closed when the function returns
        defer file.Close()

        // Copy the file in the hash interface and check for any error
        if _, err := io.Copy(hash, file); err != nil {
            return "", err
        }

        return nil
    }

    // Walk through the path, and generate a hash from each file.
    err = filepath.Walk(path, walkFn)

    if err != nil {
        return "", nil
    }

    bytes := hash.Sum(nil)
    encoded := hex.EncodeToString(hashInBytes)
}