6211eef7ee
This commit adds a new function which is similar to the DoubleSha256
function except it returns a ShaHash copy instead of a byte slice. It
also adds a new benchmark for it.
This can be a slight optimization in certain cases where the caller
ultimately wants a ShaHash since it can avoid a heap allocation and
additional copy to convert the result to a ShaHash (the function simply
performs a type cast against the returned array which is not possible
against a []byte).
existing: DoubleSha256 500000 3081 ns/op 32 B/op 1 allocs/op
new: DoubleSha256SH 500000 2939 ns/op 0 B/op 0 allocs/op
The hashing functions for blocks and transactions have also been updated
to make use of the new function since they directly return the ShaHash.
The transaction change in particular is quite useful since transactions
are frequently hashed and this change allows all of those hashes to avoid
an additional heap allocation.
536 lines
12 KiB
Go
536 lines
12 KiB
Go
// Copyright (c) 2013-2015 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package wire
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import (
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"crypto/rand"
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"encoding/binary"
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"fmt"
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"io"
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"math"
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"github.com/btcsuite/fastsha256"
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)
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// Maximum payload size for a variable length integer.
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const MaxVarIntPayload = 9
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// readElement reads the next sequence of bytes from r using little endian
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// depending on the concrete type of element pointed to.
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func readElement(r io.Reader, element interface{}) error {
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var scratch [8]byte
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// Attempt to read the element based on the concrete type via fast
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// type assertions first.
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switch e := element.(type) {
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case *int32:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = int32(binary.LittleEndian.Uint32(b))
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return nil
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case *uint32:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = binary.LittleEndian.Uint32(b)
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return nil
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case *int64:
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b := scratch[0:8]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = int64(binary.LittleEndian.Uint64(b))
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return nil
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case *uint64:
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b := scratch[0:8]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = binary.LittleEndian.Uint64(b)
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return nil
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case *bool:
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b := scratch[0:1]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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if b[0] == 0x00 {
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*e = false
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} else {
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*e = true
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}
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return nil
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// Message header checksum.
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case *[4]byte:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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// Message header command.
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case *[CommandSize]uint8:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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// IP address.
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case *[16]byte:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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case *ShaHash:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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case *ServiceFlag:
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b := scratch[0:8]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = ServiceFlag(binary.LittleEndian.Uint64(b))
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return nil
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case *InvType:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = InvType(binary.LittleEndian.Uint32(b))
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return nil
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case *BitcoinNet:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = BitcoinNet(binary.LittleEndian.Uint32(b))
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return nil
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case *BloomUpdateType:
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b := scratch[0:1]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = BloomUpdateType(b[0])
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return nil
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case *RejectCode:
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b := scratch[0:1]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = RejectCode(b[0])
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return nil
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}
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// Fall back to the slower binary.Read if a fast path was not available
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// above.
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return binary.Read(r, binary.LittleEndian, element)
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}
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// readElements reads multiple items from r. It is equivalent to multiple
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// calls to readElement.
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func readElements(r io.Reader, elements ...interface{}) error {
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for _, element := range elements {
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err := readElement(r, element)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// writeElement writes the little endian representation of element to w.
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func writeElement(w io.Writer, element interface{}) error {
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var scratch [8]byte
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// Attempt to write the element based on the concrete type via fast
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// type assertions first.
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switch e := element.(type) {
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case int32:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, uint32(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case uint32:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, e)
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case int64:
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b := scratch[0:8]
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binary.LittleEndian.PutUint64(b, uint64(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case uint64:
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b := scratch[0:8]
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binary.LittleEndian.PutUint64(b, e)
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case bool:
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b := scratch[0:1]
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if e == true {
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b[0] = 0x01
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} else {
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b[0] = 0x00
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}
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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// Message header checksum.
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case [4]byte:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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// Message header command.
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case [CommandSize]uint8:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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// IP address.
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case [16]byte:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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case *ShaHash:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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case ServiceFlag:
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b := scratch[0:8]
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binary.LittleEndian.PutUint64(b, uint64(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case InvType:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, uint32(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case BitcoinNet:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, uint32(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case BloomUpdateType:
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b := scratch[0:1]
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b[0] = uint8(e)
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case RejectCode:
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b := scratch[0:1]
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b[0] = uint8(e)
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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}
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// Fall back to the slower binary.Write if a fast path was not available
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// above.
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return binary.Write(w, binary.LittleEndian, element)
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}
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// writeElements writes multiple items to w. It is equivalent to multiple
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// calls to writeElement.
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func writeElements(w io.Writer, elements ...interface{}) error {
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for _, element := range elements {
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err := writeElement(w, element)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// readVarInt reads a variable length integer from r and returns it as a uint64.
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func readVarInt(r io.Reader, pver uint32) (uint64, error) {
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var b [8]byte
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_, err := io.ReadFull(r, b[0:1])
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if err != nil {
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return 0, err
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}
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var rv uint64
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discriminant := uint8(b[0])
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switch discriminant {
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case 0xff:
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_, err := io.ReadFull(r, b[:])
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if err != nil {
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return 0, err
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}
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rv = binary.LittleEndian.Uint64(b[:])
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case 0xfe:
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_, err := io.ReadFull(r, b[0:4])
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if err != nil {
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return 0, err
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}
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rv = uint64(binary.LittleEndian.Uint32(b[:]))
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case 0xfd:
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_, err := io.ReadFull(r, b[0:2])
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if err != nil {
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return 0, err
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}
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rv = uint64(binary.LittleEndian.Uint16(b[:]))
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default:
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rv = uint64(discriminant)
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}
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return rv, nil
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}
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// writeVarInt serializes val to w using a variable number of bytes depending
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// on its value.
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func writeVarInt(w io.Writer, pver uint32, val uint64) error {
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if val < 0xfd {
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_, err := w.Write([]byte{uint8(val)})
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return err
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}
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if val <= math.MaxUint16 {
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var buf [3]byte
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buf[0] = 0xfd
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binary.LittleEndian.PutUint16(buf[1:], uint16(val))
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_, err := w.Write(buf[:])
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return err
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}
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if val <= math.MaxUint32 {
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var buf [5]byte
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buf[0] = 0xfe
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binary.LittleEndian.PutUint32(buf[1:], uint32(val))
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_, err := w.Write(buf[:])
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return err
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}
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var buf [9]byte
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buf[0] = 0xff
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binary.LittleEndian.PutUint64(buf[1:], val)
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_, err := w.Write(buf[:])
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return err
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}
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// VarIntSerializeSize returns the number of bytes it would take to serialize
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// val as a variable length integer.
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func VarIntSerializeSize(val uint64) int {
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// The value is small enough to be represented by itself, so it's
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// just 1 byte.
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if val < 0xfd {
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return 1
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}
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// Discriminant 1 byte plus 2 bytes for the uint16.
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if val <= math.MaxUint16 {
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return 3
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}
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// Discriminant 1 byte plus 4 bytes for the uint32.
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if val <= math.MaxUint32 {
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return 5
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}
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// Discriminant 1 byte plus 8 bytes for the uint64.
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return 9
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}
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// readVarString reads a variable length string from r and returns it as a Go
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// string. A varString is encoded as a varInt containing the length of the
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// string, and the bytes that represent the string itself. An error is returned
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// if the length is greater than the maximum block payload size, since it would
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// not be possible to put a varString of that size into a block anyways and it
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// also helps protect against memory exhaustion attacks and forced panics
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// through malformed messages.
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func readVarString(r io.Reader, pver uint32) (string, error) {
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count, err := readVarInt(r, pver)
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if err != nil {
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return "", err
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}
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// Prevent variable length strings that are larger than the maximum
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// message size. It would be possible to cause memory exhaustion and
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// panics without a sane upper bound on this count.
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if count > MaxMessagePayload {
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str := fmt.Sprintf("variable length string is too long "+
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"[count %d, max %d]", count, MaxMessagePayload)
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return "", messageError("readVarString", str)
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}
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buf := make([]byte, count)
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_, err = io.ReadFull(r, buf)
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if err != nil {
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return "", err
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}
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return string(buf), nil
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}
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// writeVarString serializes str to w as a varInt containing the length of the
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// string followed by the bytes that represent the string itself.
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func writeVarString(w io.Writer, pver uint32, str string) error {
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err := writeVarInt(w, pver, uint64(len(str)))
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if err != nil {
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return err
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}
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_, err = w.Write([]byte(str))
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if err != nil {
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return err
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}
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return nil
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}
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// readVarBytes reads a variable length byte array. A byte array is encoded
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// as a varInt containing the length of the array followed by the bytes
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// themselves. An error is returned if the length is greater than the
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// passed maxAllowed parameter which helps protect against memory exhuastion
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// attacks and forced panics thorugh malformed messages. The fieldName
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// parameter is only used for the error message so it provides more context in
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// the error.
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func readVarBytes(r io.Reader, pver uint32, maxAllowed uint32,
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fieldName string) ([]byte, error) {
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count, err := readVarInt(r, pver)
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if err != nil {
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return nil, err
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}
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// Prevent byte array larger than the max message size. It would
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// be possible to cause memory exhaustion and panics without a sane
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// upper bound on this count.
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if count > uint64(maxAllowed) {
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str := fmt.Sprintf("%s is larger than the max allowed size "+
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"[count %d, max %d]", fieldName, count, maxAllowed)
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return nil, messageError("readVarBytes", str)
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}
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b := make([]byte, count)
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_, err = io.ReadFull(r, b)
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if err != nil {
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return nil, err
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}
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return b, nil
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}
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// writeVarInt serializes a variable length byte array to w as a varInt
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// containing the number of bytes, followed by the bytes themselves.
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func writeVarBytes(w io.Writer, pver uint32, bytes []byte) error {
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slen := uint64(len(bytes))
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err := writeVarInt(w, pver, slen)
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if err != nil {
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return err
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}
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_, err = w.Write(bytes)
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if err != nil {
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return err
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}
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return nil
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}
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// randomUint64 returns a cryptographically random uint64 value. This
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// unexported version takes a reader primarily to ensure the error paths
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// can be properly tested by passing a fake reader in the tests.
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func randomUint64(r io.Reader) (uint64, error) {
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var b [8]byte
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_, err := io.ReadFull(r, b[:])
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if err != nil {
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return 0, err
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}
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return binary.BigEndian.Uint64(b[:]), nil
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}
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// RandomUint64 returns a cryptographically random uint64 value.
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func RandomUint64() (uint64, error) {
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return randomUint64(rand.Reader)
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}
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// DoubleSha256 calculates sha256(sha256(b)) and returns the resulting bytes.
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func DoubleSha256(b []byte) []byte {
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first := fastsha256.Sum256(b)
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second := fastsha256.Sum256(first[:])
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return second[:]
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}
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// DoubleSha256SH calculates sha256(sha256(b)) and returns the resulting bytes
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// as a ShaHash.
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func DoubleSha256SH(b []byte) ShaHash {
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first := fastsha256.Sum256(b)
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return ShaHash(fastsha256.Sum256(first[:]))
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}
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