feature: added hasher

pkg/io/crypto/hasher/hasher.go

@@ -0,0 +1,72 @@
+package hasher
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"hash"
+	"io"
+	"os"
+)
+
+type Hasher struct {
+	HashSupplier func() hash.Hash
+}
+
+func NewSha256Hasher() *Hasher {
+	return NewHasher(func() hash.Hash {
+		return sha256.New()
+	},
+	)
+}
+
+func NewMd5Hasher() *Hasher {
+	return NewHasher(func() hash.Hash {
+		return md5.New()
+	},
+	)
+}
+
+func NewHasher(hashSupplier func() hash.Hash) *Hasher {
+	return &Hasher{
+		HashSupplier: hashSupplier,
+	}
+}
+
+func (self *Hasher) GetFileHashString(fileLocation string) (string, error) {
+	bytes, err := self.GetFileHashBytes(fileLocation)
+	if err != nil {
+		return "", err
+	}
+
+	return string(bytes), nil
+}
+
+func (self *Hasher) GetFileHashBytes(fileLocation string) ([]byte, error) {
+	file, err := os.Open(fileLocation)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	return self.GetHashBytes(file)
+}
+
+func (self *Hasher) GetHashString(reader io.Reader) (string, error) {
+	bytes, err := self.GetHashBytes(reader)
+	if err != nil {
+		return "", err
+	}
+
+	return string(bytes), nil
+}
+
+func (self *Hasher) GetHashBytes(reader io.Reader) ([]byte, error) {
+	hasher := self.HashSupplier()
+	_, err := io.Copy(hasher, reader)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return hasher.Sum(nil), nil
+}