common: improve documentation comments (ethereum#16701)

This commit adds many comments and removes unused code.
It also removes the EmptyHash function, which had some uses
but was silly.

common/bytes.go

@@ -19,15 +19,20 @@ package common
 
 import "encoding/hex"
 
+// ToHex returns the hex representation of b, prefixed with '0x'.
+// For empty slices, the return value is "0x0".
+//
+// Deprecated: use hexutil.Encode instead.
 func ToHex(b []byte) string {
 	hex := Bytes2Hex(b)
-	// Prefer output of "0x0" instead of "0x"
 	if len(hex) == 0 {
 		hex = "0"
 	}
 	return "0x" + hex
 }
 
+// FromHex returns the bytes represented by the hexadecimal string s.
+// s may be prefixed with "0x".
 func FromHex(s string) []byte {
 	if len(s) > 1 {
 		if s[0:2] == "0x" || s[0:2] == "0X" {
@@ -40,9 +45,7 @@ func FromHex(s string) []byte {
 	return Hex2Bytes(s)
 }
 
-// Copy bytes
-//
-// Returns an exact copy of the provided bytes
+// CopyBytes returns an exact copy of the provided bytes.
 func CopyBytes(b []byte) (copiedBytes []byte) {
 	if b == nil {
 		return nil
@@ -53,14 +56,17 @@ func CopyBytes(b []byte) (copiedBytes []byte) {
 	return
 }
 
+// hasHexPrefix validates str begins with '0x' or '0X'.
 func hasHexPrefix(str string) bool {
 	return len(str) >= 2 && str[0] == '0' && (str[1] == 'x' || str[1] == 'X')
 }
 
+// isHexCharacter returns bool of c being a valid hexadecimal.
 func isHexCharacter(c byte) bool {
 	return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F')
 }
 
+// isHex validates whether each byte is valid hexadecimal string.
 func isHex(str string) bool {
 	if len(str)%2 != 0 {
 		return false
@@ -73,16 +79,18 @@ func isHex(str string) bool {
 	return true
 }
 
+// Bytes2Hex returns the hexadecimal encoding of d.
 func Bytes2Hex(d []byte) string {
 	return hex.EncodeToString(d)
 }
 
+// Hex2Bytes returns the bytes represented by the hexadecimal string str.
 func Hex2Bytes(str string) []byte {
 	h, _ := hex.DecodeString(str)
-
 	return h
 }
 
+// Hex2BytesFixed returns bytes of a specified fixed length flen.
 func Hex2BytesFixed(str string, flen int) []byte {
 	h, _ := hex.DecodeString(str)
 	if len(h) == flen {
@@ -96,6 +104,7 @@ func Hex2BytesFixed(str string, flen int) []byte {
 	return hh
 }
 
+// RightPadBytes zero-pads slice to the right up to length l.
 func RightPadBytes(slice []byte, l int) []byte {
 	if l <= len(slice) {
 		return slice
@@ -107,6 +116,7 @@ func RightPadBytes(slice []byte, l int) []byte {
 	return padded
 }
 
+// LeftPadBytes zero-pads slice to the left up to length l.
 func LeftPadBytes(slice []byte, l int) []byte {
 	if l <= len(slice) {
 		return slice

common/math/big.go

@@ -78,7 +78,7 @@ func ParseBig256(s string) (*big.Int, bool) {
 	return bigint, ok
 }
 
-// MustParseBig parses s as a 256 bit big integer and panics if the string is invalid.
+// MustParseBig256 parses s as a 256 bit big integer and panics if the string is invalid.
 func MustParseBig256(s string) *big.Int {
 	v, ok := ParseBig256(s)
 	if !ok {
@@ -186,9 +186,8 @@ func U256(x *big.Int) *big.Int {
 func S256(x *big.Int) *big.Int {
 	if x.Cmp(tt255) < 0 {
 		return x
-	} else {
-		return new(big.Int).Sub(x, tt256)
 	}
+	return new(big.Int).Sub(x, tt256)
 }
 
 // Exp implements exponentiation by squaring.

common/number/int.go

@@ -34,13 +34,12 @@ func limitUnsigned256(x *Number) *Number {
 func limitSigned256(x *Number) *Number {
 	if x.num.Cmp(tt255) < 0 {
 		return x
-	} else {
-		x.num.Sub(x.num, tt256)
-		return x
 	}
+	x.num.Sub(x.num, tt256)
+	return x
 }
 
-// Number function
+// Initialiser is a Number function
 type Initialiser func(n int64) *Number
 
 // A Number represents a generic integer with a bounding function limiter. Limit is called after each operations
@@ -51,79 +50,79 @@ type Number struct {
 	limit func(n *Number) *Number
 }
 
-// Returns a new initialiser for a new *Number without having to expose certain fields
+// NewInitialiser returns a new initialiser for a new *Number without having to expose certain fields
 func NewInitialiser(limiter func(*Number) *Number) Initialiser {
 	return func(n int64) *Number {
 		return &Number{big.NewInt(n), limiter}
 	}
 }
 
-// Return a Number with a UNSIGNED limiter up to 256 bits
+// Uint256 returns a Number with a UNSIGNED limiter up to 256 bits
 func Uint256(n int64) *Number {
 	return &Number{big.NewInt(n), limitUnsigned256}
 }
 
-// Return a Number with a SIGNED limiter up to 256 bits
+// Int256 returns Number with a SIGNED limiter up to 256 bits
 func Int256(n int64) *Number {
 	return &Number{big.NewInt(n), limitSigned256}
 }
 
-// Returns a Number with a SIGNED unlimited size
+// Big returns a Number with a SIGNED unlimited size
 func Big(n int64) *Number {
 	return &Number{big.NewInt(n), func(x *Number) *Number { return x }}
 }
 
-// Sets i to sum of x+y
+// Add sets i to sum of x+y
 func (i *Number) Add(x, y *Number) *Number {
 	i.num.Add(x.num, y.num)
 	return i.limit(i)
 }
 
-// Sets i to difference of x-y
+// Sub sets i to difference of x-y
 func (i *Number) Sub(x, y *Number) *Number {
 	i.num.Sub(x.num, y.num)
 	return i.limit(i)
 }
 
-// Sets i to product of x*y
+// Mul sets i to product of x*y
 func (i *Number) Mul(x, y *Number) *Number {
 	i.num.Mul(x.num, y.num)
 	return i.limit(i)
 }
 
-// Sets i to the quotient prodject of x/y
+// Div sets i to the quotient prodject of x/y
 func (i *Number) Div(x, y *Number) *Number {
 	i.num.Div(x.num, y.num)
 	return i.limit(i)
 }
 
-// Sets i to x % y
+// Mod sets i to x % y
 func (i *Number) Mod(x, y *Number) *Number {
 	i.num.Mod(x.num, y.num)
 	return i.limit(i)
 }
 
-// Sets i to x << s
+// Lsh sets i to x << s
 func (i *Number) Lsh(x *Number, s uint) *Number {
 	i.num.Lsh(x.num, s)
 	return i.limit(i)
 }
 
-// Sets i to x^y
+// Pow sets i to x^y
 func (i *Number) Pow(x, y *Number) *Number {
 	i.num.Exp(x.num, y.num, big.NewInt(0))
 	return i.limit(i)
 }
 
 // Setters
 
-// Set x to i
+// Set sets x to i
 func (i *Number) Set(x *Number) *Number {
 	i.num.Set(x.num)
 	return i.limit(i)
 }
 
-// Set x bytes to i
+// SetBytes sets x bytes to i
 func (i *Number) SetBytes(x []byte) *Number {
 	i.num.SetBytes(x)
 	return i.limit(i)
@@ -140,12 +139,12 @@ func (i *Number) Cmp(x *Number) int {
 
 // Getters
 
-// Returns the string representation of i
+// String returns the string representation of i
 func (i *Number) String() string {
 	return i.num.String()
 }
 
-// Returns the byte representation of i
+// Bytes returns the byte representation of i
 func (i *Number) Bytes() []byte {
 	return i.num.Bytes()
 }
@@ -160,17 +159,17 @@ func (i *Number) Int64() int64 {
 	return i.num.Int64()
 }
 
-// Returns the signed version of i
+// Int256 returns the signed version of i
 func (i *Number) Int256() *Number {
 	return Int(0).Set(i)
 }
 
-// Returns the unsigned version of i
+// Uint256 returns the unsigned version of i
 func (i *Number) Uint256() *Number {
 	return Uint(0).Set(i)
 }
 
-// Returns the index of the first bit that's set to 1
+// FirstBitSet returns the index of the first bit that's set to 1
 func (i *Number) FirstBitSet() int {
 	for j := 0; j < i.num.BitLen(); j++ {
 		if i.num.Bit(j) > 0 {

common/path.go

@@ -30,6 +30,7 @@ func MakeName(name, version string) string {
 	return fmt.Sprintf("%s/v%s/%s/%s", name, version, runtime.GOOS, runtime.Version())
 }
 
+// FileExist checks if a file exists at filePath.
 func FileExist(filePath string) bool {
 	_, err := os.Stat(filePath)
 	if err != nil && os.IsNotExist(err) {
@@ -39,9 +40,10 @@ func FileExist(filePath string) bool {
 	return true
 }
 
-func AbsolutePath(Datadir string, filename string) string {
+// AbsolutePath returns datadir + filename, or filename if it is absolute.
+func AbsolutePath(datadir string, filename string) string {
 	if filepath.IsAbs(filename) {
 		return filename
 	}
-	return filepath.Join(Datadir, filename)
+	return filepath.Join(datadir, filename)
 }