mirror of
https://github.com/rclone/rclone.git
synced 2024-11-27 02:45:16 +01:00
135 lines
3.3 KiB
Go
135 lines
3.3 KiB
Go
// Package mrhash implements the mailru hash, which is a modified SHA1.
|
|
// If file size is less than or equal to the SHA1 block size (20 bytes),
|
|
// its hash is simply its data right-padded with zero bytes.
|
|
// Hash sum of a larger file is computed as a SHA1 sum of the file data
|
|
// bytes concatenated with a decimal representation of the data length.
|
|
package mrhash
|
|
|
|
import (
|
|
"crypto/sha1"
|
|
"encoding"
|
|
"encoding/hex"
|
|
"errors"
|
|
"hash"
|
|
"strconv"
|
|
)
|
|
|
|
const (
|
|
// BlockSize of the checksum in bytes.
|
|
BlockSize = sha1.BlockSize
|
|
// Size of the checksum in bytes.
|
|
Size = sha1.Size
|
|
startString = "mrCloud"
|
|
hashError = "hash function returned error"
|
|
)
|
|
|
|
// Global errors
|
|
var (
|
|
ErrorInvalidHash = errors.New("invalid hash")
|
|
)
|
|
|
|
type digest struct {
|
|
total int // bytes written into hash so far
|
|
sha hash.Hash // underlying SHA1
|
|
small []byte // small content
|
|
}
|
|
|
|
// New returns a new hash.Hash computing the Mailru checksum.
|
|
func New() hash.Hash {
|
|
d := &digest{}
|
|
d.Reset()
|
|
return d
|
|
}
|
|
|
|
// Write writes len(p) bytes from p to the underlying data stream. It returns
|
|
// the number of bytes written from p (0 <= n <= len(p)) and any error
|
|
// encountered that caused the write to stop early. Write must return a non-nil
|
|
// error if it returns n < len(p). Write must not modify the slice data, even
|
|
// temporarily.
|
|
//
|
|
// Implementations must not retain p.
|
|
func (d *digest) Write(p []byte) (n int, err error) {
|
|
n, err = d.sha.Write(p)
|
|
if err != nil {
|
|
panic(hashError)
|
|
}
|
|
d.total += n
|
|
if d.total <= Size {
|
|
d.small = append(d.small, p...)
|
|
}
|
|
return n, nil
|
|
}
|
|
|
|
// Sum appends the current hash to b and returns the resulting slice.
|
|
// It does not change the underlying hash state.
|
|
func (d *digest) Sum(b []byte) []byte {
|
|
// If content is small, return it padded to Size
|
|
if d.total <= Size {
|
|
padded := make([]byte, Size)
|
|
copy(padded, d.small)
|
|
return append(b, padded...)
|
|
}
|
|
endString := strconv.Itoa(d.total)
|
|
copy, err := cloneSHA1(d.sha)
|
|
if err == nil {
|
|
_, err = copy.Write([]byte(endString))
|
|
}
|
|
if err != nil {
|
|
panic(hashError)
|
|
}
|
|
return copy.Sum(b)
|
|
}
|
|
|
|
// cloneSHA1 clones state of SHA1 hash
|
|
func cloneSHA1(orig hash.Hash) (clone hash.Hash, err error) {
|
|
state, err := orig.(encoding.BinaryMarshaler).MarshalBinary()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
clone = sha1.New()
|
|
err = clone.(encoding.BinaryUnmarshaler).UnmarshalBinary(state)
|
|
return
|
|
}
|
|
|
|
// Reset resets the Hash to its initial state.
|
|
func (d *digest) Reset() {
|
|
d.sha = sha1.New()
|
|
_, _ = d.sha.Write([]byte(startString))
|
|
d.total = 0
|
|
}
|
|
|
|
// Size returns the number of bytes Sum will return.
|
|
func (d *digest) Size() int {
|
|
return Size
|
|
}
|
|
|
|
// BlockSize returns the hash's underlying block size.
|
|
// The Write method must be able to accept any amount
|
|
// of data, but it may operate more efficiently if all writes
|
|
// are a multiple of the block size.
|
|
func (d *digest) BlockSize() int {
|
|
return BlockSize
|
|
}
|
|
|
|
// Sum returns the Mailru checksum of the data.
|
|
func Sum(data []byte) []byte {
|
|
var d digest
|
|
d.Reset()
|
|
_, _ = d.Write(data)
|
|
return d.Sum(nil)
|
|
}
|
|
|
|
// DecodeString converts a string to the Mailru hash
|
|
func DecodeString(s string) ([]byte, error) {
|
|
b, err := hex.DecodeString(s)
|
|
if err != nil || len(b) != Size {
|
|
return nil, ErrorInvalidHash
|
|
}
|
|
return b, nil
|
|
}
|
|
|
|
// must implement this interface
|
|
var (
|
|
_ hash.Hash = (*digest)(nil)
|
|
)
|