Adding struct and func documentation

bmap.go

@@ -21,20 +21,23 @@ import (
 
 const defaultBMAPHash = "0000000000000000000000000000000000000000"
 
-type Block struct {
+// BlockRange represents a range of blocks of written data
+type BlockRange struct {
 	XMLName xml.Name `xml:"Range"`
 	Start   int64
 	End     int64
 	Hash    string `xml:"sha1,attr"`
 }
 
+// Range is an intermediate data type for xml conversion
 type Range struct {
 	XMLName xml.Name `xml:"Range"`
 	Range   string   `xml:",chardata"`
 	Hash    string   `xml:"sha1,attr"`
 }
 
-func (b *Block) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+// MarshalXML is used to convert BlockRange to a Range object for XML output
+func (b *BlockRange) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
 	//fmt.Println(e)
 	//fmt.Println(start)
 
@@ -50,7 +53,8 @@ func (b *Block) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
 	return err
 }
 
-func (b *Block) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+// UnmarshalXML is used to convert a Range object from XML input into a BlockRange object
+func (b *BlockRange) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 
 	r := Range{}
 	err := d.DecodeElement(&r, &start)
@@ -86,10 +90,12 @@ func (b *Block) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 	return nil
 }
 
+// BlockMap represents a list of Block Ranges
 type BlockMap struct {
-	Range []Block
+	Range []BlockRange
 }
 
+// BMap contains all of the information that needs to be represented in the bmap file
 type BMap struct {
 	XMLName           xml.Name `xml:"bmap"`
 	Version           string   `xml:"version,attr"`
@@ -101,19 +107,23 @@ type BMap struct {
 	BlockMap          BlockMap `xml:"BlockMap"`
 }
 
-func NewBMap(filename string) BMap {
+// NewBMap creates a new BMap representation by reading an image file
+func NewBMap(filename string) (BMap, error) {
 	stat := syscall.Stat_t{}
 	syscall.Stat(filename, &stat)
 	blockSize := stat.Blksize
 
-	fd, _ := os.Open(filename)
+	fd, err := os.Open(filename)
-
 	defer fd.Close()
-
+	if err != nil {
-	blockMap, total := getBlockMap(fd, blockSize)
+		return BMap{}, err
-	return BMap{Version: "1.3", ImageSize: stat.Size, BlockSize: blockSize, BlocksCount: stat.Size / blockSize, MappedBlocksCount: total, BmapFileSHA1: defaultBMAPHash, BlockMap: BlockMap{blockMap}}
 	}
 
+	blockMap, total := getBlockMap(fd, blockSize)
+	return BMap{Version: "1.3", ImageSize: stat.Size, BlockSize: blockSize, BlocksCount: stat.Size / blockSize, MappedBlocksCount: total, BmapFileSHA1: defaultBMAPHash, BlockMap: BlockMap{blockMap}}, nil
+}
+
+// XMLOutput converts a BMap object to it's corresponding XML output
 func (b *BMap) XMLOutput() ([]byte, error) {
 	output, err := xml.MarshalIndent(b, "", "    ")
 	if err != nil {
@@ -122,6 +132,7 @@ func (b *BMap) XMLOutput() ([]byte, error) {
 	return append([]byte(xml.Header), output...), err
 }
 
+// Write generates initial XML output, takes the SHA signature, and writes updated XML to file
 func (b *BMap) Write(outputFilename string) error {
 	output, err := b.XMLOutput()
 	if err != nil {
@@ -146,6 +157,7 @@ func (b *BMap) Write(outputFilename string) error {
 	return err
 }
 
+// Load reads and converts a bmap file to a BMap object
 func Load(filename string) (BMap, error) {
 	b := BMap{}
 	data, err := ioutil.ReadFile(filename)
@@ -178,6 +190,7 @@ func Load(filename string) (BMap, error) {
 	return b, err
 }
 
+// Copy copies an input file and uses the BMap data to create a new image file
 func (b *BMap) Copy(input string, output string) error {
 	inFile, err := os.Open(input)
 	defer inFile.Close()
@@ -276,33 +289,35 @@ func getBZReader(reader io.Reader) (io.ReadSeeker, error) {
 	return bytes.NewReader(data), nil
 }
 
-func getBlockMap(fd *os.File, blockSize int64) ([]Block, int64) {
+// getBlockMap finds all of the ranges of written blocks in a file/image
+func getBlockMap(fd *os.File, blockSize int64) ([]BlockRange, int64) {
 	//fd, _ := os.Open(filename)
 	f := fibmap.NewFibmapFile(fd)
 
 	holes := f.SeekDataHole()
-	blockMap := make([]Block, len(holes)/2)
+	blockMap := make([]BlockRange, len(holes)/2)
-	currentBlock := Block{}
+	currentBlockRange := BlockRange{}
 	mappedBlocks := int64(0)
 	for i, v := range holes {
-		if i%2 == 0 { //Block found @
+		if i%2 == 0 { //BlockRange found @
-			currentBlock = Block{Start: v / blockSize}
+			currentBlockRange = BlockRange{Start: v / blockSize}
 		} else { // Length of block
 			length := v / blockSize
-			currentBlock.End = currentBlock.Start + length - 1
+			currentBlockRange.End = currentBlockRange.Start + length - 1
 
 			h := sha1.New()
-			fd.Seek(currentBlock.Start*blockSize, 0)
+			fd.Seek(currentBlockRange.Start*blockSize, 0)
 			io.CopyN(h, fd, v)
-			currentBlock.Hash = hex.EncodeToString(h.Sum(nil))
+			currentBlockRange.Hash = hex.EncodeToString(h.Sum(nil))
 
-			blockMap[i/2] = currentBlock
+			blockMap[i/2] = currentBlockRange
 			mappedBlocks += length
 		}
 	}
 	return blockMap, mappedBlocks
 }
 
+// getSHA1Hash returns a hex encoded hash from an io.Reader
 func getSHA1Hash(r io.Reader) string {
 	h := sha1.New()
 	io.Copy(h, r)