From 41a62f783d6751c121710b5249a1b3089613171e Mon Sep 17 00:00:00 2001
From: Christian Uhsat <christian@uhsat.de>
Date: Sat, 18 May 2024 01:42:17 +0200
Subject: [PATCH] version 0.10.2

---
 internal/hash/hash.go      | 66 ++++++++++++++++++++++++++++++++++++++
 internal/hash/hash_test.go | 54 +++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)
 create mode 100644 internal/hash/hash.go
 create mode 100644 internal/hash/hash_test.go

diff --git a/internal/hash/hash.go b/internal/hash/hash.go
new file mode 100644
index 0000000..3f0af21
--- /dev/null
+++ b/internal/hash/hash.go
@@ -0,0 +1,66 @@
+// Hash functions.
+package hash
+
+import (
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"errors"
+	"hash"
+	"hash/crc32"
+	"io"
+	"os"
+	"strings"
+)
+
+const (
+	CRC32  = "crc32"
+	MD5    = "md5"
+	SHA1   = "sha1"
+	SHA256 = "sha256"
+)
+
+var Supported = [...]string{CRC32, MD5, SHA1, SHA256}
+
+func Sum(name, algo string) (b []byte, err error) {
+	h, err := new(algo)
+
+	if err != nil {
+		return
+	}
+
+	f, err := os.Open(name)
+
+	if err != nil {
+		return
+	}
+
+	defer f.Close()
+
+	if _, err = io.Copy(h, f); err != nil {
+		return
+	}
+
+	b = h.Sum(nil)
+
+	return
+}
+
+func new(name string) (h hash.Hash, err error) {
+	switch strings.ToLower(name) {
+	case CRC32:
+		h = crc32.NewIEEE()
+	case MD5:
+		h = md5.New()
+	case SHA1:
+		h = sha1.New()
+	case SHA256:
+		h = sha256.New()
+	default:
+		if len(name) > 0 {
+			err = errors.New("algorithms supported: " + strings.Join(Supported[:], " "))
+		}
+	}
+
+	return
+}
diff --git a/internal/hash/hash_test.go b/internal/hash/hash_test.go
new file mode 100644
index 0000000..1cd0122
--- /dev/null
+++ b/internal/hash/hash_test.go
@@ -0,0 +1,54 @@
+// Hash implementation tests.
+package hash
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/cuhsat/fact/internal/test"
+)
+
+func TestSum(t *testing.T) {
+	cases := []struct {
+		name, file, algo, sum string
+	}{
+		{
+			name: "Test with crc32",
+			file: test.Testdata("mbr"),
+			algo: CRC32,
+			sum:  "14e55a3a",
+		},
+		{
+			name: "Test with md5",
+			file: test.Testdata("mbr"),
+			algo: MD5,
+			sum:  "cb3ca368f5f6514d9a47f3723bddf826",
+		},
+		{
+			name: "Test with sha1",
+			file: test.Testdata("mbr"),
+			algo: SHA1,
+			sum:  "830a4645a04b895eb5e19bfa3eb017423aad9758",
+		},
+		{
+			name: "Test with sha256",
+			file: test.Testdata("mbr"),
+			algo: SHA256,
+			sum:  "f58ca4adc037022d6a00d87f90b9480a580a5af5cac948b28bf7d8e0793107a1",
+		},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.name, func(t *testing.T) {
+			s, err := Sum(tt.file, tt.algo)
+
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if fmt.Sprintf("%x", s) != tt.sum {
+				t.Fatal("Sum mismatch")
+			}
+		})
+	}
+}