Optimizing crypto/ed25519.go (#21)

* Optimizing `crypto/ed25519.go`

1. Avoid unnecessary copying of byte arrays.
     it is not necessary to make a copy of the byte array in these cases since the byte arrays are the same size and have the same underlying structure. 
2. Use of constants instead of literals `const CompressedPublicKeySize = 33` instead `if len(paddr) != 33`

* Cleaning up after comments

- Moved constant definition top
- Using `PublicKeyLen` instead of `32`

* Reverting back the changes

- Simplifying the function isn't possible, I thought it was but checking it on a text editor, I realized is not possible.

* Added new constant, and fixing naming convention

* Updating `PrivateKeySeedSize` to `...Len`

- Updating naming convention
- Fixing wrong variable naming (`PrivateKeyLen` (64) to `PublicKeyLen` (32))

* Using `Len` instead of `Size`

Consistency

* Adding `PrivateKeySeedLen`

crypto/ed25519.go

@@ -21,9 +21,11 @@ type (
 )
 
 const (
- PublicKeyLen = ed25519.PublicKeySize
- PrivateKeyLen = ed25519.PrivateKeySize
- SignatureLen = ed25519.SignatureSize
+ PublicKeyCompressedLen = 33
+ PublicKeyLen = ed25519.PublicKeySize
+ PrivateKeyLen = ed25519.PrivateKeySize
+ PrivateKeySeedLen = ed25519.SeedSize
+ SignatureLen = ed25519.SignatureSize
 )
 
 var (
@@ -51,11 +53,11 @@ func ParseAddress(hrp, saddr string) (PublicKey, error) {
  if phrp != hrp {
  return EmptyPublicKey, ErrIncorrectHrp
  }
- if len(paddr) != 33 /* compressed public key size */ {
+ if len(paddr) != PublicKeyCompressedLen {
  return EmptyPublicKey, ErrInvalidPublicKey
  }
  var p PublicKey
- copy(p[:], paddr[:32])
+ copy(p[:], paddr[:PublicKeyLen])
  return p, nil
 }
 
@@ -74,7 +76,7 @@ func GeneratePrivateKey() (PrivateKey, error) {
 // PublicKey returns a PublicKey associated with the Ed25519 PrivateKey p.
 // The PublicKey is the last 32 bytes of p.
 func (p PrivateKey) PublicKey() PublicKey {
- rpk := p[32:] // privateKey == private|public
+ rpk := p[PrivateKeySeedLen:] // privateKey == private|public
  var pk PublicKey
  copy(pk[:], rpk)
  return pk