diff --git a/app/tlsh.go b/app/tlsh.go
index ef59754..f97c533 100644
--- a/app/tlsh.go
+++ b/app/tlsh.go
@@ -3,21 +3,29 @@ package main
 import (
 	"flag"
 	"fmt"
+	"os"
 
 	"github.com/glaslos/tlsh"
 )
 
 func main() {
+	var file = flag.String("f", "", "path to the file to be hashed")
+	var raw = flag.Bool("r", false, "set to get only the hash")
 	flag.Parse()
-	if len(flag.Args()) < 1 {
-		fmt.Println("Please provide a file path: ./tlsh /tmp/file")
+	if *file == "" {
+		fmt.Fprintf(os.Stderr, "Usage of %s [-f <file>]\n\n", os.Args[0])
+		flag.PrintDefaults()
+		fmt.Println()
 		return
 	}
-	fileName := flag.Args()[0]
-	hash, err := tlsh.Hash(fileName)
+	hash, err := tlsh.Hash(*file)
 	if err != nil {
 		fmt.Println(err)
 		return
 	}
-	fmt.Printf("%s  %s\n", hash, fileName)
+	if *raw {
+		fmt.Println(hash)
+	} else {
+		fmt.Printf("%s  %s\n", hash, *file)
+	}
 }
diff --git a/tlsh.go b/tlsh.go
index a58ab7b..23bfc5d 100644
--- a/tlsh.go
+++ b/tlsh.go
@@ -1,9 +1,11 @@
 package tlsh
 
 import (
+	"bufio"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"math"
+	"os"
 )
 
 const (
@@ -215,40 +217,72 @@ func makeStringTLSH(biHash []byte) (hash string) {
 	return
 }
 
-func fillBuckets(data []byte) (buckets [numBuckets]uint, checksum byte) {
-	chunk := [windowLength]byte{}
-	salt := [6]byte{2, 3, 5, 7, 11, 13}
-	sw := 0
-
-	for sw <= len(data)-windowLength {
+func reverse(s [5]byte) [5]byte {
+	for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
+		s[i], s[j] = s[j], s[i]
+	}
+	return s
+}
 
-		for j, x := sw+windowLength-1, 0; j >= sw; j, x = j-1, x+1 {
-			chunk[x] = data[j]
-		}
+func fillBuckets(r fuzzyReader) ([numBuckets]uint, byte, int, error) {
+	buckets := [numBuckets]uint{}
+	chunkSlice := make([]byte, windowLength)
+	chunk := [5]byte{}
+	salt := [6]byte{2, 3, 5, 7, 11, 13}
+	fileSize := 0
+	checksum := byte(0)
 
-		sw++
+	n, err := r.Read(chunkSlice)
+	if err != nil {
+		return [numBuckets]uint{}, 0, 0, err
+	}
+	copy(chunk[:], chunkSlice[0:5])
+	chunk = reverse(chunk)
+	fileSize += n
+	for {
 		triplets := getTriplets(chunk)
-
 		checksumTriplet := [3]byte{chunk[0], chunk[1], checksum}
 		checksum = pearsonHash(0, checksumTriplet)
-
 		for i, triplet := range triplets {
 			buckets[pearsonHash(salt[i], triplet)]++
 		}
+		copy(chunk[1:], chunk[0:4])
+		chunk[0], err = r.ReadByte()
+		if err != nil {
+			if err != io.EOF {
+				return [numBuckets]uint{}, 0, 0, err
+			}
+			break
+		}
+		fileSize++
 	}
-	return buckets, checksum
+	return buckets, checksum, fileSize, nil
 }
 
-//Hash calculates the TLSH for the input file
-func Hash(filename string) (hash string, err error) {
-	data, err := ioutil.ReadFile(filename)
+type fuzzyReader interface {
+	Read([]byte) (int, error)
+	ReadByte() (byte, error)
+}
+
+//HashReader calculates the TLSH for the input reader
+func HashReader(r fuzzyReader) (hash string, err error) {
+	buckets, checksum, fileSize, err := fillBuckets(r)
 	if err != nil {
 		return
 	}
-
-	buckets, checksum := fillBuckets(data)
 	q1, q2, q3 := quartilePoints(buckets)
-	hash = makeStringTLSH(hashTLSH(len(data), buckets, checksum, q1, q2, q3))
+	hash = makeStringTLSH(hashTLSH(fileSize, buckets, checksum, q1, q2, q3))
 
 	return hash, nil
 }
+
+//Hash calculates the TLSH for the input file
+func Hash(filename string) (hash string, err error) {
+	f, err := os.Open(filename)
+	defer f.Close()
+	if err != nil {
+		return
+	}
+	r := bufio.NewReader(f)
+	return HashReader(r)
+}
diff --git a/tlsh_test.go b/tlsh_test.go
index 7143d62..2267358 100644
--- a/tlsh_test.go
+++ b/tlsh_test.go
@@ -1,8 +1,8 @@
 package tlsh
 
 import (
-	"fmt"
-	"io/ioutil"
+	"bufio"
+	"os"
 	"testing"
 )
 
@@ -25,12 +25,11 @@ var (
 
 func TestReal(t *testing.T) {
 	for _, tc := range testCases {
-		if bar, err := Hash(tc.filename); bar != tc.hash {
-			fmt.Printf("%s\n", bar)
+		if hash, err := Hash(tc.filename); hash != tc.hash {
 			if err != nil {
 				t.Error(err)
 			}
-			t.Errorf("\nfilename: %s\n%s\n%s - doesn't match real hash\n", tc.filename, tc.hash, bar)
+			t.Errorf("\nfilename: %s\n%s\n%s - doesn't match real hash\n", tc.filename, tc.hash, hash)
 		}
 	}
 }
@@ -44,21 +43,30 @@ func BenchmarkPearson(b *testing.B) {
 }
 
 func BenchmarkFillBuckets(b *testing.B) {
-	data, err := ioutil.ReadFile("tests/test_file_1")
+	f, err := os.Open("tests/test_file_1")
+	defer f.Close()
 	if err != nil {
 		b.Error(err)
 	}
+	f.Seek(0, 0)
 	for n := 0; n < b.N; n++ {
-		fillBuckets(data)
+		r := bufio.NewReader(f)
+		fillBuckets(r)
+		f.Seek(0, 0)
 	}
 }
 
 func BenchmarkQuartilePoints(b *testing.B) {
-	data, err := ioutil.ReadFile("tests/test_file_1")
+	f, err := os.Open("tests/test_file_1")
+	defer f.Close()
+	if err != nil {
+		b.Error(err)
+	}
+	r := bufio.NewReader(f)
+	buckets, _, _, err := fillBuckets(r)
 	if err != nil {
 		b.Error(err)
 	}
-	buckets, _ := fillBuckets(data)
 	for n := 0; n < b.N; n++ {
 		quartilePoints(buckets)
 	}