mirror of
https://gitlab.com/pulsechaincom/prysm-pulse.git
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0ade1f121d
* save stuff * fix in v1 * clean up more * fix bugs * add comments and clean up * add flag + test * add tests * fmt * radek's review * gaz * kasey's review * gaz and new conditional * improve naming
177 lines
5.8 KiB
Go
177 lines
5.8 KiB
Go
// Package ssz defines HashTreeRoot utility functions.
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package ssz
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import (
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"bytes"
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"encoding/binary"
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"github.com/minio/sha256-simd"
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"github.com/pkg/errors"
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"github.com/prysmaticlabs/go-bitfield"
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"github.com/prysmaticlabs/prysm/encoding/bytesutil"
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)
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const bytesPerChunk = 32
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// BitlistRoot returns the mix in length of a bitwise Merkleized bitfield.
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func BitlistRoot(hasher HashFn, bfield bitfield.Bitfield, maxCapacity uint64) ([32]byte, error) {
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limit := (maxCapacity + 255) / 256
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if bfield == nil || bfield.Len() == 0 {
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length := make([]byte, 32)
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root, err := BitwiseMerkleize(hasher, [][]byte{}, 0, limit)
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if err != nil {
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return [32]byte{}, err
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}
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return MixInLength(root, length), nil
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}
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chunks, err := Pack([][]byte{bfield.Bytes()})
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if err != nil {
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return [32]byte{}, err
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}
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buf := new(bytes.Buffer)
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if err := binary.Write(buf, binary.LittleEndian, bfield.Len()); err != nil {
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return [32]byte{}, err
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}
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output := make([]byte, 32)
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copy(output, buf.Bytes())
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root, err := BitwiseMerkleize(hasher, chunks, uint64(len(chunks)), limit)
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if err != nil {
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return [32]byte{}, err
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}
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return MixInLength(root, output), nil
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}
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// BitwiseMerkleize - given ordered BYTES_PER_CHUNK-byte chunks, if necessary utilize
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// zero chunks so that the number of chunks is a power of two, Merkleize the chunks,
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// and return the root.
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// Note that merkleize on a single chunk is simply that chunk, i.e. the identity
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// when the number of chunks is one.
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func BitwiseMerkleize(hasher HashFn, chunks [][]byte, count, limit uint64) ([32]byte, error) {
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if count > limit {
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return [32]byte{}, errors.New("merkleizing list that is too large, over limit")
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}
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hashFn := NewHasherFunc(hasher)
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leafIndexer := func(i uint64) []byte {
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return chunks[i]
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}
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return Merkleize(hashFn, count, limit, leafIndexer), nil
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}
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// BitwiseMerkleizeArrays is used when a set of 32-byte root chunks are provided.
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func BitwiseMerkleizeArrays(hasher HashFn, chunks [][32]byte, count, limit uint64) ([32]byte, error) {
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if count > limit {
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return [32]byte{}, errors.New("merkleizing list that is too large, over limit")
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}
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hashFn := NewHasherFunc(hasher)
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leafIndexer := func(i uint64) []byte {
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return chunks[i][:]
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}
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return Merkleize(hashFn, count, limit, leafIndexer), nil
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}
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// Pack a given byte array's final chunk with zeroes if needed.
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func Pack(serializedItems [][]byte) ([][]byte, error) {
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areAllEmpty := true
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for _, item := range serializedItems {
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if !bytes.Equal(item, []byte{}) {
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areAllEmpty = false
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break
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}
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}
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// If there are no items, we return an empty chunk.
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if len(serializedItems) == 0 || areAllEmpty {
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emptyChunk := make([]byte, bytesPerChunk)
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return [][]byte{emptyChunk}, nil
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} else if len(serializedItems[0]) == bytesPerChunk {
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// If each item has exactly BYTES_PER_CHUNK length, we return the list of serialized items.
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return serializedItems, nil
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}
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// We flatten the list in order to pack its items into byte chunks correctly.
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var orderedItems []byte
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for _, item := range serializedItems {
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orderedItems = append(orderedItems, item...)
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}
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numItems := len(orderedItems)
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var chunks [][]byte
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for i := 0; i < numItems; i += bytesPerChunk {
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j := i + bytesPerChunk
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// We create our upper bound index of the chunk, if it is greater than numItems,
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// we set it as numItems itself.
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if j > numItems {
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j = numItems
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}
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// We create chunks from the list of items based on the
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// indices determined above.
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chunks = append(chunks, orderedItems[i:j])
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}
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// Right-pad the last chunk with zero bytes if it does not
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// have length bytesPerChunk.
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lastChunk := chunks[len(chunks)-1]
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for len(lastChunk) < bytesPerChunk {
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lastChunk = append(lastChunk, 0)
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}
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chunks[len(chunks)-1] = lastChunk
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return chunks, nil
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}
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// PackByChunk a given byte array's final chunk with zeroes if needed.
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func PackByChunk(serializedItems [][]byte) ([][bytesPerChunk]byte, error) {
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emptyChunk := [bytesPerChunk]byte{}
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// If there are no items, we return an empty chunk.
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if len(serializedItems) == 0 {
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return [][bytesPerChunk]byte{emptyChunk}, nil
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} else if len(serializedItems[0]) == bytesPerChunk {
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// If each item has exactly BYTES_PER_CHUNK length, we return the list of serialized items.
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chunks := make([][bytesPerChunk]byte, 0, len(serializedItems))
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for _, c := range serializedItems {
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chunks = append(chunks, bytesutil.ToBytes32(c))
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}
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return chunks, nil
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}
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// We flatten the list in order to pack its items into byte chunks correctly.
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var orderedItems []byte
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for _, item := range serializedItems {
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orderedItems = append(orderedItems, item...)
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}
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// If all our serialized item slices are length zero, we
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// exit early.
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if len(orderedItems) == 0 {
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return [][bytesPerChunk]byte{emptyChunk}, nil
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}
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numItems := len(orderedItems)
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var chunks [][bytesPerChunk]byte
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for i := 0; i < numItems; i += bytesPerChunk {
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j := i + bytesPerChunk
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// We create our upper bound index of the chunk, if it is greater than numItems,
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// we set it as numItems itself.
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if j > numItems {
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j = numItems
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}
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// We create chunks from the list of items based on the
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// indices determined above.
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// Right-pad the last chunk with zero bytes if it does not
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// have length bytesPerChunk from the helper.
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// The ToBytes32 helper allocates a 32-byte array, before
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// copying the ordered items in. This ensures that even if
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// the last chunk is != 32 in length, we will right-pad it with
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// zero bytes.
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chunks = append(chunks, bytesutil.ToBytes32(orderedItems[i:j]))
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}
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return chunks, nil
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}
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// MixInLength appends hash length to root
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func MixInLength(root [32]byte, length []byte) [32]byte {
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var hash [32]byte
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h := sha256.New()
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h.Write(root[:])
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h.Write(length)
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// The hash interface never returns an error, for that reason
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// we are not handling the error below. For reference, it is
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// stated here https://golang.org/pkg/hash/#Hash
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// #nosec G104
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h.Sum(hash[:0])
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return hash
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}
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