dchash

README

dchash

Package dchash implements a configurable variation of Dropbox's Content Hash algorithm in idiomatic Go.

Usage

package checksum

import (
	"crypto/sha512"
	"io"

	"github.com/azazeal/dchash"
)

// Dropbox hashes the data in src as per Dropbox's Content Hash algorithm, using
// SHA256 and over blocks of 4 MiB in size.
func Dropbox(src io.Reader) (sum []byte, err error) {
	h := dchash.New(nil, -1)

	if _, err = io.Copy(h, src); err == nil {
		sum = h.Sum(nil)
	}

	return
}

// SHA512m1 hashes the data in src as per Dropbox's Content Hash algorithm but
// with SHA512 (instead of SHA256) and over blocks of 1 (instead  of 4) MiB in
// size.
func SHA512m1(src io.Reader) (sum []byte, err error) {
	h := dchash.New(sha512.New, 1<<20)

	if _, err = io.Copy(h, src); err == nil {
		sum = h.Sum(nil)
	}

	return
}

Documentation

Overview

Package dchash implements a configurable variation of Dropbox's Content Hash.

Index

• Constants
• func New(newFunc func() hash.Hash, blockSize int) hash.Hash

Constants

const (
	// DefaultHash denotes the default Hash.
	DefaultHash = crypto.SHA256

	// DefaultBlockSize denotes the default block size.
	DefaultBlockSize = 1 << 22
)

Functions

func New

func New(newFunc func() hash.Hash, blockSize int) hash.Hash

New returns a Hash which yields checksums according to Dropbox's Content Hash algorithm, more details on which may be found here:

https://www.dropbox.com/developers/reference/content-hash

Should newFunc be nil, DefaultHash.New will be used in its place.

Should blockSize be less than 1, DefaultBlockSize will be used instead.

Hashes returned by New are NOT safe for concurrent use by multiple goroutines.