Add labeled hash helper functions for hashing data

lhash/algs.go

@@ -6,6 +6,7 @@ package lhash
 import (
 	"crypto"
 	"hash"
+	"io"
 
 	// Register SHA2 in Go's internal registry.
 	_ "crypto/sha256"
@@ -83,3 +84,18 @@ func (a Algorithm) new() hash.Hash {
 		return nil
 	}
 }
+
+// Digest creates a new labeled hash and digests the given data.
+func (a Algorithm) Digest(data []byte) *LabeledHash {
+	return Digest(a, data)
+}
+
+// DigestFile creates a new labeled hash and digests the given file.
+func (a Algorithm) DigestFile(pathToFile string) (*LabeledHash, error) {
+	return DigestFile(a, pathToFile)
+}
+
+// DigestFromReader creates a new labeled hash and digests from the given reader.
+func (a Algorithm) DigestFromReader(alg Algorithm, reader io.Reader) (*LabeledHash, error) {
+	return DigestFromReader(a, reader)
+}

lhash/labeledhash.go

@@ -1,11 +1,14 @@
 package lhash
 
 import (
+	"bufio"
 	"crypto/subtle"
 	"encoding/base64"
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"io"
+	"os"
 
 	"github.com/mr-tron/base58"
 
@@ -21,15 +24,43 @@ type LabeledHash struct {
 // Digest creates a new labeled hash and digests the given data.
 func Digest(alg Algorithm, data []byte) *LabeledHash {
 	hasher := alg.new()
-	_, _ = hasher.Write(data) // never returns an error
-	defer hasher.Reset()      // internal state may leak data if kept in memory
+	_, _ = hasher.Write(data) // Never returns an error.
+	defer hasher.Reset()      // Internal state may leak data if kept in memory.
 
 	return &LabeledHash{
 		alg:    alg,
 		digest: hasher.Sum(nil),
 	}
 }
 
+// DigestFile creates a new labeled hash and digests the given file.
+func DigestFile(alg Algorithm, pathToFile string) (*LabeledHash, error) {
+	// Open file that should be hashed.
+	file, err := os.OpenFile(pathToFile, os.O_RDONLY, 0)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open file: %w", err)
+	}
+
+	return DigestFromReader(alg, file)
+}
+
+// DigestFromReader creates a new labeled hash and digests from the given reader.
+func DigestFromReader(alg Algorithm, reader io.Reader) (*LabeledHash, error) {
+	hasher := alg.new()
+	defer hasher.Reset() // Internal state may leak data if kept in memory.
+
+	// Pipe all data directly to the hashing algorithm.
+	_, err := bufio.NewReader(reader).WriteTo(hasher)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read: %w", err)
+	}
+
+	return &LabeledHash{
+		alg:    alg,
+		digest: hasher.Sum(nil),
+	}, nil
+}
+
 // Load loads a labeled hash from the given []byte slice.
 func Load(labeledHash []byte) (*LabeledHash, error) {
 	c := container.New(labeledHash)
@@ -95,6 +126,16 @@ func FromBase58(base58Encoded string) (*LabeledHash, error) {
 	return Load(raw)
 }
 
+// Algorithm returns the algorithm of the labeled hash.
+func (lh *LabeledHash) Algorithm() Algorithm {
+	return lh.alg
+}
+
+// Sum returns the raw calculated hash digest.
+func (lh *LabeledHash) Sum() []byte {
+	return lh.digest
+}
+
 // Bytes return the []byte representation of the labeled hash.
 func (lh *LabeledHash) Bytes() []byte {
 	c := container.New()