From 2a1b44de6c8a4cc891f21ca7d8925980f25f15a9 Mon Sep 17 00:00:00 2001
From: Unbewohnte <unbewohnte@gmail.com>
Date: Fri, 16 Jul 2021 16:29:17 +0300
Subject: [PATCH] =?UTF-8?q?=E1=9F=9Cmall=20code-readability=20improvements?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 util/bits.go      |  2 +-
 util/bits_test.go |  6 +++---
 v2/frame.go       | 22 +++++++++-------------
 v2/header.go      | 32 ++++++++++++++------------------
 4 files changed, 27 insertions(+), 35 deletions(-)

diff --git a/util/bits.go b/util/bits.go
index 115560a..3a363d9 100644
--- a/util/bits.go
+++ b/util/bits.go
@@ -1,6 +1,6 @@
 package util
 
 // Tells if bit is set in given byte
-func IsSet(n byte, bitN int) bool {
+func GetBit(n byte, bitN int) bool {
 	return n&byte(1<<bitN-1) != 0
 }
diff --git a/util/bits_test.go b/util/bits_test.go
index cd96704..470c6f7 100644
--- a/util/bits_test.go
+++ b/util/bits_test.go
@@ -2,13 +2,13 @@ package util
 
 import "testing"
 
-func TestIsSet(t *testing.T) {
+func TestGetBit(t *testing.T) {
 	testBytes := []byte{1 << 0, 1 << 1, 1 << 2, 1 << 3}
 
 	for index, testByte := range testBytes {
-		if !IsSet(testByte, index+1) {
+		if !GetBit(testByte, index+1) {
 			t.Errorf("IsSet failed: expected %dth bit of %d to be %v; got %v",
-				index+1, testByte, true, IsSet(testByte, index+1))
+				index+1, testByte, true, GetBit(testByte, index+1))
 		}
 	}
 }
diff --git a/v2/frame.go b/v2/frame.go
index d7738c9..d46e2b2 100644
--- a/v2/frame.go
+++ b/v2/frame.go
@@ -87,41 +87,37 @@ func getFrameHeader(fHeaderbytes []byte, version string) (FrameHeader, error) {
 		header.Size = framesize
 
 		// Flags
-		frameFlagsByte1 := fHeaderbytes[8]
-		frameFlagsByte2 := fHeaderbytes[9]
+		frameFlags1 := fHeaderbytes[8]
+		frameFlags2 := fHeaderbytes[9]
 
-		// I don`t have enough knowledge to handle this more elegantly
-
-		flagsByte1Bits := fmt.Sprintf("%08b", frameFlagsByte1)
-		flagsByte2Bits := fmt.Sprintf("%08b", frameFlagsByte2)
 		var flags FrameFlags
 
-		if flagsByte1Bits[0] == 1 {
+		if util.GetBit(frameFlags1, 1) {
 			flags.TagAlterPreservation = true
 		} else {
 			flags.TagAlterPreservation = false
 		}
-		if flagsByte1Bits[1] == 1 {
+		if util.GetBit(frameFlags1, 2) {
 			flags.FileAlterPreservation = true
 		} else {
 			flags.FileAlterPreservation = false
 		}
-		if flagsByte1Bits[2] == 1 {
+		if util.GetBit(frameFlags1, 3) {
 			flags.ReadOnly = true
 		} else {
 			flags.ReadOnly = false
 		}
-		if flagsByte2Bits[0] == 1 {
+		if util.GetBit(frameFlags2, 1) {
 			flags.Compressed = true
 		} else {
 			flags.Compressed = false
 		}
-		if flagsByte2Bits[1] == 1 {
+		if util.GetBit(frameFlags2, 1) {
 			flags.Encrypted = true
 		} else {
 			flags.Encrypted = false
 		}
-		if flagsByte2Bits[2] == 1 {
+		if util.GetBit(frameFlags2, 1) {
 			flags.InGroup = true
 		} else {
 			flags.InGroup = false
@@ -179,7 +175,7 @@ func (f *Frame) Text() string {
 }
 
 // Returns bytes of the frame that can be
-// written in a file.
+// written into a file.
 // func (f *Frame) Bytes() ([]byte, error) {
 // 	header := f.Header
 // 	contents := f.Contents
diff --git a/v2/header.go b/v2/header.go
index 6ec1b51..469b7c1 100644
--- a/v2/header.go
+++ b/v2/header.go
@@ -72,8 +72,7 @@ func (h *Header) readExtendedHeader(r io.Reader) error {
 		if err != nil {
 			return fmt.Errorf("could not read from reader: %s", err)
 		}
-		flagbits := fmt.Sprintf("%08b", extendedFlag[0])
-		if flagbits[0] == 1 {
+		if util.GetBit(extendedFlag[0], 1) {
 			extended.Flags.CRCpresent = true
 		} else {
 			extended.Flags.CRCpresent = false
@@ -90,20 +89,19 @@ func (h *Header) readExtendedHeader(r io.Reader) error {
 			return fmt.Errorf("could not read from reader: %s", err)
 		}
 
-		flagBits := fmt.Sprintf("%08b", flagByte[0])
-		if flagBits[1] == 1 {
+		if util.GetBit(flagByte[0], 2) {
 			extended.Flags.UpdateTag = true
 		} else {
 			extended.Flags.UpdateTag = false
 		}
 
-		if flagBits[2] == 1 {
+		if util.GetBit(flagByte[0], 3) {
 			extended.Flags.CRCpresent = true
 		} else {
 			extended.Flags.CRCpresent = false
 		}
 
-		if flagBits[3] == 1 {
+		if util.GetBit(flagByte[0], 4) {
 			extended.Flags.HasRestrictions = true
 		} else {
 			extended.Flags.HasRestrictions = false
@@ -195,7 +193,7 @@ func readHeader(rs io.ReadSeeker) (Header, error) {
 
 	identifier := hBytes[0:3]
 
-	// check if has identifier ID3v2
+	// check if has ID3v2 identifier
 	if !bytes.Equal([]byte(HEADERIDENTIFIER), identifier) {
 		return Header{}, ErrDoesNotUseID3v2
 	}
@@ -219,33 +217,31 @@ func readHeader(rs io.ReadSeeker) (Header, error) {
 	// flags
 	flags := hBytes[5]
 
-	flagBits := fmt.Sprintf("%08b", flags) // 1 byte is 8 bits
-
 	// v3.0 and v4.0 have different amount of flags
 	switch header.Version {
 	case V2_2:
-		if flagBits[0] == 1 {
+		if util.GetBit(flags, 1) {
 			header.Flags.Unsynchronisated = true
 		} else {
 			header.Flags.Unsynchronisated = false
 		}
-		if flagBits[1] == 1 {
+		if util.GetBit(flags, 2) {
 			header.Flags.Compressed = true
 		} else {
 			header.Flags.Compressed = false
 		}
 	case V2_3:
-		if flagBits[0] == 1 {
+		if util.GetBit(flags, 1) {
 			header.Flags.Unsynchronisated = true
 		} else {
 			header.Flags.Unsynchronisated = false
 		}
-		if flagBits[1] == 1 {
+		if util.GetBit(flags, 2) {
 			header.Flags.HasExtendedHeader = true
 		} else {
 			header.Flags.HasExtendedHeader = false
 		}
-		if flagBits[2] == 1 {
+		if util.GetBit(flags, 3) {
 			header.Flags.Experimental = true
 		} else {
 			header.Flags.Experimental = false
@@ -254,22 +250,22 @@ func readHeader(rs io.ReadSeeker) (Header, error) {
 		header.Flags.FooterPresent = false
 
 	case V2_4:
-		if flagBits[0] == 1 {
+		if util.GetBit(flags, 1) {
 			header.Flags.Unsynchronisated = true
 		} else {
 			header.Flags.Unsynchronisated = false
 		}
-		if flagBits[1] == 1 {
+		if util.GetBit(flags, 2) {
 			header.Flags.HasExtendedHeader = true
 		} else {
 			header.Flags.HasExtendedHeader = false
 		}
-		if flagBits[2] == 1 {
+		if util.GetBit(flags, 3) {
 			header.Flags.Experimental = true
 		} else {
 			header.Flags.Experimental = false
 		}
-		if flagBits[3] == 1 {
+		if util.GetBit(flags, 4) {
 			header.Flags.FooterPresent = true
 		} else {
 			header.Flags.FooterPresent = false