quickxorhash

README

quickxorhash

A pure-Go implementation of Microsoft's QuickXorHash, the content hash that SharePoint Online and OneDrive for Business report for every file. It implements the standard library hash.Hash interface and has no dependencies beyond the Go standard library.

Microsoft Graph returns the digest for a file in the file.hashes.quickXorHash field of a driveItem. Computing the same hash locally lets a client tell whether a file already matches the copy stored in a document library without downloading it — the problem this package was written to solve, for an rsync-style SharePoint mirror that could not rely on timestamps surviving an upload.

Install

go get github.com/excelano/quickxorhash

Use

The value returned by New is a hash.Hash, so it streams like crypto/sha1 or hash/crc32. Graph encodes the digest with standard base64, so compare against that:

import (
	"encoding/base64"
	"io"
	"os"

	"github.com/excelano/quickxorhash"
)

func localHash(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()

	h := quickxorhash.New()
	if _, err := io.Copy(h, f); err != nil {
		return "", err
	}
	return base64.StdEncoding.EncodeToString(h.Sum(nil)), nil
}

For a one-shot hash of a byte slice already in memory, quickxorhash.Sum returns the raw 20-byte digest:

sum := quickxorhash.Sum(data) // [20]byte
b64 := base64.StdEncoding.EncodeToString(sum[:])

About the algorithm

QuickXorHash is a 160-bit hash that XORs the input into a rotating bit accumulator and folds the total length into the result. It is defined by Microsoft and described in the OneDrive developer documentation. This is an independent implementation from that description, verified against digests captured directly from Microsoft Graph (see the test vectors).

License

MIT. Built by David M. Anderson with AI assistance (Claude, Anthropic).

Documentation

Overview

Package quickxorhash implements Microsoft's QuickXorHash, the content hash that SharePoint Online and OneDrive for Business report in a driveItem's file.hashes.quickXorHash field over Microsoft Graph. It lets a client decide whether a local file already matches the copy stored in a document library without downloading it — handy for sync, mirroring, and de-duplication.

QuickXorHash is a 160-bit XOR-based hash defined by Microsoft and described in the OneDrive developer documentation. Graph returns the digest base64-encoded, so pair this package with encoding/base64 to compare:

h := quickxorhash.New()
if _, err := io.Copy(h, f); err != nil {
	return err
}
got := base64.StdEncoding.EncodeToString(h.Sum(nil))
// compare got against driveItem.file.hashes.quickXorHash

The value returned by New implements the standard library hash.Hash interface, so it streams and drops in anywhere crypto/sha1 or hash/crc32 would. This is an independent implementation from the published algorithm description and depends only on the standard library.

Index

• Constants
• func New() hash.Hash
• func Sum(data []byte) [Size]byte

Examples

• New

Constants

const (
	// Size is the length in bytes of a QuickXorHash digest.
	Size = 20
	// BlockSize is the hash's block size in bytes. The algorithm imposes no
	// real block size; this is the conventional value reported to callers.
	BlockSize = 64
)

Functions

func New

func New() hash.Hash

New returns a new hash.Hash computing the QuickXorHash digest.

Example

h := New()
h.Write([]byte("hello from xsync repro\n"))
fmt.Println(base64.StdEncoding.EncodeToString(h.Sum(nil)))

Output:
CSQji5vp5jAfdiZvfwMI8DCHPLg=

func Sum

func Sum(data []byte) [Size]byte

Sum returns the QuickXorHash digest of data in a single call.