Move changes from exp2 to main

This is largely a move to simplify a lot of the readers
Also further breaks out functions.

superblock.go

@@ -1,31 +1,22 @@
 package squashfs
 
-//The types of compression supported by squashfs.
-const (
-	GzipCompression = 1 + iota
-	LzmaCompression
-	LzoCompression
-	XzCompression
-	Lz4Compression
-	ZstdCompression
-)
+import "math"
 
-//Superblock contains important information about a squashfs file. Located at the very front of the archive.
 type superblock struct {
 	Magic            uint32
 	InodeCount       uint32
-	CreationTime     uint32
+	ModTime          uint32
 	BlockSize        uint32
 	FragCount        uint32
-	CompressionType  uint16
+	CompType         uint16
 	BlockLog         uint16
 	Flags            uint16
-	IDCount          uint16
-	MajorVersion     uint16
-	MinorVersion     uint16
+	IdCount          uint16
+	VerMaj           uint16
+	VerMin           uint16
 	RootInodeRef     uint64
-	BytesUsed        uint64
-	IDTableStart     uint64
+	Size             uint64
+	IdTableStart     uint64
 	XattrTableStart  uint64
 	InodeTableStart  uint64
 	DirTableStart    uint64
@@ -33,94 +24,53 @@ type superblock struct {
 	ExportTableStart uint64
 }
 
-//SuperblockFlags is the series of flags describing how a squashfs archive is packed.
-type SuperblockFlags struct {
-	//If true, inodes are stored uncompressed.
-	UncompressedInodes bool
-	//If true, data is stored uncompressed.
-	UncompressedData bool
-	check            bool
-	//If true, fragments are stored uncompressed.
-	UncompressedFragments bool
-	//If true, ALL data is stored in sequential data blocks instead of utilizing fragments.
-	NoFragments bool
-	//If true, the last block of data will always be stored as a fragment if it's less then the block size.
-	AlwaysFragment bool
-	//If true, duplicate files are only stored once. (Currently unsupported)
-	RemoveDuplicates bool
-	//If true, the export table is populated. (Currently unsupported)
-	Exportable bool
-	//If true, the xattr table is uncompressed. (Currently unsupported)
-	UncompressedXattr bool
-	//If true, the xattr table is not populated. (Currently unsupported)
-	NoXattr           bool
-	compressorOptions bool
-	//If true, the UID/GID table is stored uncompressed.
-	UncompressedIDs bool
+func (s superblock) hasMagic() bool {
+	return s.Magic == 0x73717368
 }
 
-//DefaultFlags are the default SuperblockFlags that are used.
-var DefaultFlags = SuperblockFlags{
-	RemoveDuplicates: true,
-	Exportable:       true,
+func (s superblock) checkBlockLog() bool {
+	return s.BlockLog == uint16(math.Log2(float64(s.BlockSize)))
 }
 
-//GetFlags returns a SuperblockFlags for a given superblock.
-func (s *superblock) GetFlags() SuperblockFlags {
-	return SuperblockFlags{
-		UncompressedInodes:    s.Flags&0x1 == 0x1,
-		UncompressedData:      s.Flags&0x2 == 0x2,
-		check:                 s.Flags&0x4 == 0x4,
-		UncompressedFragments: s.Flags&0x8 == 0x8,
-		NoFragments:           s.Flags&0x10 == 0x10,
-		AlwaysFragment:        s.Flags&0x20 == 0x20,
-		RemoveDuplicates:      s.Flags&0x40 == 0x40,
-		Exportable:            s.Flags&0x80 == 0x80,
-		UncompressedXattr:     s.Flags&0x100 == 0x100,
-		NoXattr:               s.Flags&0x200 == 0x200,
-		compressorOptions:     s.Flags&0x400 == 0x400,
-		UncompressedIDs:       s.Flags&0x800 == 0x800,
-	}
+func (s superblock) uncompressedInodes() bool {
+	return s.Flags&0x1 == 0x1
 }
 
-//ToUint returns the uint16 representation of the given SuperblockFlags
-func (s *SuperblockFlags) ToUint() uint16 {
-	var out uint16
-	if s.UncompressedInodes {
-		out = out | 0x1
-	}
-	if s.UncompressedData {
-		out = out | 0x2
-	}
-	if s.check {
-		out = out | 0x4
-	}
-	if s.UncompressedFragments {
-		out = out | 0x8
-	}
-	if s.NoFragments {
-		out = out | 0x10
-	}
-	if s.AlwaysFragment {
-		out = out | 0x20
-	}
-	if s.RemoveDuplicates {
-		out = out | 0x40
-	}
-	if s.Exportable {
-		out = out | 0x80
-	}
-	if s.UncompressedXattr {
-		out = out | 0x100
-	}
-	if s.NoXattr {
-		out = out | 0x200
-	}
-	if s.compressorOptions {
-		out = out | 0x400
-	}
-	if s.UncompressedIDs {
-		out = out | 0x800
-	}
-	return out
+func (s superblock) uncompressedData() bool {
+	return s.Flags&0x2 == 0x2
+}
+func (s superblock) uncompressedFragments() bool {
+	return s.Flags&0x8 == 0x8
+}
+
+func (s superblock) noFragments() bool {
+	return s.Flags&0x10 == 0x10
+}
+
+func (s superblock) alwaysFragment() bool {
+	return s.Flags&0x20 == 0x20
+}
+
+func (s superblock) duplicates() bool {
+	return s.Flags&0x40 == 0x40
+}
+
+func (s superblock) exportable() bool {
+	return s.Flags&0x80 == 0x80
+}
+
+func (s superblock) uncompressedXattrs() bool {
+	return s.Flags&0x100 == 0x100
+}
+
+func (s superblock) noXattrs() bool {
+	return s.Flags&0x200 == 0x200
+}
+
+func (s superblock) compressionOptions() bool {
+	return s.Flags&0x400 == 0x400
+}
+
+func (s superblock) uncompressedIDs() bool {
+	return s.Flags&0x800 == 0x800
 }