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common.go
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common.go
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// Copyright (c) 2013-2016 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package wire
import (
"crypto/rand"
"encoding/binary"
"fmt"
"io"
"math"
"time"
"github.com/gcash/bchd/chaincfg/chainhash"
)
const (
// MaxVarIntPayload is the maximum payload size for a variable length integer.
MaxVarIntPayload = 9
// binaryFreeListMaxItems is the number of buffers to keep in the free
// list to use for binary serialization and deserialization.
binaryFreeListMaxItems = 1024
)
var (
// littleEndian is a convenience variable since binary.LittleEndian is
// quite long.
littleEndian = binary.LittleEndian
// bigEndian is a convenience variable since binary.BigEndian is quite
// long.
bigEndian = binary.BigEndian
)
// binaryFreeList defines a concurrent safe free list of byte slices (up to the
// maximum number defined by the binaryFreeListMaxItems constant) that have a
// cap of 8 (thus it supports up to a uint64). It is used to provide temporary
// buffers for serializing and deserializing primitive numbers to and from their
// binary encoding in order to greatly reduce the number of allocations
// required.
//
// For convenience, functions are provided for each of the primitive unsigned
// integers that automatically obtain a buffer from the free list, perform the
// necessary binary conversion, read from or write to the given io.Reader or
// io.Writer, and return the buffer to the free list.
type binaryFreeList chan []byte
// Borrow returns a byte slice from the free list with a length of 8. A new
// buffer is allocated if there are not any available on the free list.
func (l binaryFreeList) Borrow() []byte {
var buf []byte
select {
case buf = <-l:
default:
buf = make([]byte, 8)
}
return buf[:8]
}
// Return puts the provided byte slice back on the free list. The buffer MUST
// have been obtained via the Borrow function and therefore have a cap of 8.
func (l binaryFreeList) Return(buf []byte) {
select {
case l <- buf:
default:
// Let it go to the garbage collector.
}
}
// Uint8 reads a single byte from the provided reader using a buffer from the
// free list and returns it as a uint8.
func (l binaryFreeList) Uint8(r io.Reader) (uint8, error) {
buf := l.Borrow()[:1]
if _, err := io.ReadFull(r, buf); err != nil {
l.Return(buf)
return 0, err
}
rv := buf[0]
l.Return(buf)
return rv, nil
}
// Uint16 reads two bytes from the provided reader using a buffer from the
// free list, converts it to a number using the provided byte order, and returns
// the resulting uint16.
func (l binaryFreeList) Uint16(r io.Reader, byteOrder binary.ByteOrder) (uint16, error) {
buf := l.Borrow()[:2]
if _, err := io.ReadFull(r, buf); err != nil {
l.Return(buf)
return 0, err
}
rv := byteOrder.Uint16(buf)
l.Return(buf)
return rv, nil
}
// Uint32 reads four bytes from the provided reader using a buffer from the
// free list, converts it to a number using the provided byte order, and returns
// the resulting uint32.
func (l binaryFreeList) Uint32(r io.Reader, byteOrder binary.ByteOrder) (uint32, error) {
buf := l.Borrow()[:4]
if _, err := io.ReadFull(r, buf); err != nil {
l.Return(buf)
return 0, err
}
rv := byteOrder.Uint32(buf)
l.Return(buf)
return rv, nil
}
// Uint64 reads eight bytes from the provided reader using a buffer from the
// free list, converts it to a number using the provided byte order, and returns
// the resulting uint64.
func (l binaryFreeList) Uint64(r io.Reader, byteOrder binary.ByteOrder) (uint64, error) {
buf := l.Borrow()[:8]
if _, err := io.ReadFull(r, buf); err != nil {
l.Return(buf)
return 0, err
}
rv := byteOrder.Uint64(buf)
l.Return(buf)
return rv, nil
}
// PutUint8 copies the provided uint8 into a buffer from the free list and
// writes the resulting byte to the given writer.
func (l binaryFreeList) PutUint8(w io.Writer, val uint8) error {
buf := l.Borrow()[:1]
buf[0] = val
_, err := w.Write(buf)
l.Return(buf)
return err
}
// PutUint16 serializes the provided uint16 using the given byte order into a
// buffer from the free list and writes the resulting two bytes to the given
// writer.
func (l binaryFreeList) PutUint16(w io.Writer, byteOrder binary.ByteOrder, val uint16) error {
buf := l.Borrow()[:2]
byteOrder.PutUint16(buf, val)
_, err := w.Write(buf)
l.Return(buf)
return err
}
// PutUint32 serializes the provided uint32 using the given byte order into a
// buffer from the free list and writes the resulting four bytes to the given
// writer.
func (l binaryFreeList) PutUint32(w io.Writer, byteOrder binary.ByteOrder, val uint32) error {
buf := l.Borrow()[:4]
byteOrder.PutUint32(buf, val)
_, err := w.Write(buf)
l.Return(buf)
return err
}
// PutUint64 serializes the provided uint64 using the given byte order into a
// buffer from the free list and writes the resulting eight bytes to the given
// writer.
func (l binaryFreeList) PutUint64(w io.Writer, byteOrder binary.ByteOrder, val uint64) error {
buf := l.Borrow()[:8]
byteOrder.PutUint64(buf, val)
_, err := w.Write(buf)
l.Return(buf)
return err
}
// binarySerializer provides a free list of buffers to use for serializing and
// deserializing primitive integer values to and from io.Readers and io.Writers.
var binarySerializer binaryFreeList = make(chan []byte, binaryFreeListMaxItems)
// errNonCanonicalVarInt is the common format string used for non-canonically
// encoded variable length integer errors.
var errNonCanonicalVarInt = "non-canonical varint %x - discriminant %x must " +
"encode a value greater than %x"
// uint32Time represents a unix timestamp encoded with a uint32. It is used as
// a way to signal the readElement function how to decode a timestamp into a Go
// time.Time since it is otherwise ambiguous.
type uint32Time time.Time
// int64Time represents a unix timestamp encoded with an int64. It is used as
// a way to signal the readElement function how to decode a timestamp into a Go
// time.Time since it is otherwise ambiguous.
type int64Time time.Time
// readElement reads the next sequence of bytes from r using little endian
// depending on the concrete type of element pointed to.
func readElement(r io.Reader, element interface{}) error {
// Attempt to read the element based on the concrete type via fast
// type assertions first.
switch e := element.(type) {
case *int32:
rv, err := binarySerializer.Uint32(r, littleEndian)
if err != nil {
return err
}
*e = int32(rv)
return nil
case *uint32:
rv, err := binarySerializer.Uint32(r, littleEndian)
if err != nil {
return err
}
*e = rv
return nil
case *int64:
rv, err := binarySerializer.Uint64(r, littleEndian)
if err != nil {
return err
}
*e = int64(rv)
return nil
case *uint64:
rv, err := binarySerializer.Uint64(r, littleEndian)
if err != nil {
return err
}
*e = rv
return nil
case *bool:
rv, err := binarySerializer.Uint8(r)
if err != nil {
return err
}
if rv == 0x00 {
*e = false
} else {
*e = true
}
return nil
// Unix timestamp encoded as a uint32.
case *uint32Time:
rv, err := binarySerializer.Uint32(r, binary.LittleEndian)
if err != nil {
return err
}
*e = uint32Time(time.Unix(int64(rv), 0))
return nil
// Unix timestamp encoded as an int64.
case *int64Time:
rv, err := binarySerializer.Uint64(r, binary.LittleEndian)
if err != nil {
return err
}
*e = int64Time(time.Unix(int64(rv), 0))
return nil
// Message header checksum.
case *[4]byte:
_, err := io.ReadFull(r, e[:])
if err != nil {
return err
}
return nil
// Message header command.
case *[CommandSize]uint8:
_, err := io.ReadFull(r, e[:])
if err != nil {
return err
}
return nil
// IP address.
case *[16]byte:
_, err := io.ReadFull(r, e[:])
if err != nil {
return err
}
return nil
case *chainhash.Hash:
_, err := io.ReadFull(r, e[:])
if err != nil {
return err
}
return nil
case *ServiceFlag:
rv, err := binarySerializer.Uint64(r, littleEndian)
if err != nil {
return err
}
*e = ServiceFlag(rv)
return nil
case *InvType:
rv, err := binarySerializer.Uint32(r, littleEndian)
if err != nil {
return err
}
*e = InvType(rv)
return nil
case *BitcoinNet:
rv, err := binarySerializer.Uint32(r, littleEndian)
if err != nil {
return err
}
*e = BitcoinNet(rv)
return nil
case *BloomUpdateType:
rv, err := binarySerializer.Uint8(r)
if err != nil {
return err
}
*e = BloomUpdateType(rv)
return nil
case *RejectCode:
rv, err := binarySerializer.Uint8(r)
if err != nil {
return err
}
*e = RejectCode(rv)
return nil
}
// Fall back to the slower binary.Read if a fast path was not available
// above.
return binary.Read(r, littleEndian, element)
}
// readElements reads multiple items from r. It is equivalent to multiple
// calls to readElement.
func readElements(r io.Reader, elements ...interface{}) error {
for _, element := range elements {
err := readElement(r, element)
if err != nil {
return err
}
}
return nil
}
// writeElement writes the little endian representation of element to w.
func writeElement(w io.Writer, element interface{}) error {
// Attempt to write the element based on the concrete type via fast
// type assertions first.
switch e := element.(type) {
case int32:
err := binarySerializer.PutUint32(w, littleEndian, uint32(e))
if err != nil {
return err
}
return nil
case uint32:
err := binarySerializer.PutUint32(w, littleEndian, e)
if err != nil {
return err
}
return nil
case int64:
err := binarySerializer.PutUint64(w, littleEndian, uint64(e))
if err != nil {
return err
}
return nil
case uint64:
err := binarySerializer.PutUint64(w, littleEndian, e)
if err != nil {
return err
}
return nil
case bool:
var err error
if e {
err = binarySerializer.PutUint8(w, 0x01)
} else {
err = binarySerializer.PutUint8(w, 0x00)
}
if err != nil {
return err
}
return nil
// Message header checksum.
case [4]byte:
_, err := w.Write(e[:])
if err != nil {
return err
}
return nil
// Message header command.
case [CommandSize]uint8:
_, err := w.Write(e[:])
if err != nil {
return err
}
return nil
// IP address.
case [16]byte:
_, err := w.Write(e[:])
if err != nil {
return err
}
return nil
case *chainhash.Hash:
_, err := w.Write(e[:])
if err != nil {
return err
}
return nil
case ServiceFlag:
err := binarySerializer.PutUint64(w, littleEndian, uint64(e))
if err != nil {
return err
}
return nil
case InvType:
err := binarySerializer.PutUint32(w, littleEndian, uint32(e))
if err != nil {
return err
}
return nil
case BitcoinNet:
err := binarySerializer.PutUint32(w, littleEndian, uint32(e))
if err != nil {
return err
}
return nil
case BloomUpdateType:
err := binarySerializer.PutUint8(w, uint8(e))
if err != nil {
return err
}
return nil
case RejectCode:
err := binarySerializer.PutUint8(w, uint8(e))
if err != nil {
return err
}
return nil
}
// Fall back to the slower binary.Write if a fast path was not available
// above.
return binary.Write(w, littleEndian, element)
}
// writeElements writes multiple items to w. It is equivalent to multiple
// calls to writeElement.
func writeElements(w io.Writer, elements ...interface{}) error {
for _, element := range elements {
err := writeElement(w, element)
if err != nil {
return err
}
}
return nil
}
// ReadVarInt reads a variable length integer from r and returns it as a uint64.
func ReadVarInt(r io.Reader, pver uint32) (uint64, error) {
discriminant, err := binarySerializer.Uint8(r)
if err != nil {
return 0, err
}
var rv uint64
switch discriminant {
case 0xff:
sv, err := binarySerializer.Uint64(r, littleEndian)
if err != nil {
return 0, err
}
rv = sv
// The encoding is not canonical if the value could have been
// encoded using fewer bytes.
min := uint64(0x100000000)
if rv < min {
return 0, messageError("ReadVarInt", fmt.Sprintf(
errNonCanonicalVarInt, rv, discriminant, min))
}
case 0xfe:
sv, err := binarySerializer.Uint32(r, littleEndian)
if err != nil {
return 0, err
}
rv = uint64(sv)
// The encoding is not canonical if the value could have been
// encoded using fewer bytes.
min := uint64(0x10000)
if rv < min {
return 0, messageError("ReadVarInt", fmt.Sprintf(
errNonCanonicalVarInt, rv, discriminant, min))
}
case 0xfd:
sv, err := binarySerializer.Uint16(r, littleEndian)
if err != nil {
return 0, err
}
rv = uint64(sv)
// The encoding is not canonical if the value could have been
// encoded using fewer bytes.
min := uint64(0xfd)
if rv < min {
return 0, messageError("ReadVarInt", fmt.Sprintf(
errNonCanonicalVarInt, rv, discriminant, min))
}
default:
rv = uint64(discriminant)
}
return rv, nil
}
// WriteVarInt serializes val to w using a variable number of bytes depending
// on its value.
func WriteVarInt(w io.Writer, pver uint32, val uint64) error {
if val < 0xfd {
return binarySerializer.PutUint8(w, uint8(val))
}
if val <= math.MaxUint16 {
err := binarySerializer.PutUint8(w, 0xfd)
if err != nil {
return err
}
return binarySerializer.PutUint16(w, littleEndian, uint16(val))
}
if val <= math.MaxUint32 {
err := binarySerializer.PutUint8(w, 0xfe)
if err != nil {
return err
}
return binarySerializer.PutUint32(w, littleEndian, uint32(val))
}
err := binarySerializer.PutUint8(w, 0xff)
if err != nil {
return err
}
return binarySerializer.PutUint64(w, littleEndian, val)
}
// VarIntSerializeSize returns the number of bytes it would take to serialize
// val as a variable length integer.
func VarIntSerializeSize(val uint64) int {
// The value is small enough to be represented by itself, so it's
// just 1 byte.
if val < 0xfd {
return 1
}
// Discriminant 1 byte plus 2 bytes for the uint16.
if val <= math.MaxUint16 {
return 3
}
// Discriminant 1 byte plus 4 bytes for the uint32.
if val <= math.MaxUint32 {
return 5
}
// Discriminant 1 byte plus 8 bytes for the uint64.
return 9
}
// ReadVarString reads a variable length string from r and returns it as a Go
// string. A variable length string is encoded as a variable length integer
// containing the length of the string followed by the bytes that represent the
// string itself. An error is returned if the length is greater than the
// maximum block payload size since it helps protect against memory exhaustion
// attacks and forced panics through malformed messages.
func ReadVarString(r io.Reader, pver uint32) (string, error) {
count, err := ReadVarInt(r, pver)
if err != nil {
return "", err
}
// Prevent variable length strings that are larger than the maximum
// message size. It would be possible to cause memory exhaustion and
// panics without a sane upper bound on this count.
if count > uint64(maxMessagePayload()) {
str := fmt.Sprintf("variable length string is too long "+
"[count %d, max %d]", count, maxMessagePayload())
return "", messageError("ReadVarString", str)
}
buf := make([]byte, count)
_, err = io.ReadFull(r, buf)
if err != nil {
return "", err
}
return string(buf), nil
}
// WriteVarString serializes str to w as a variable length integer containing
// the length of the string followed by the bytes that represent the string
// itself.
func WriteVarString(w io.Writer, pver uint32, str string) error {
err := WriteVarInt(w, pver, uint64(len(str)))
if err != nil {
return err
}
_, err = w.Write([]byte(str))
return err
}
// ReadVarBytes reads a variable length byte array. A byte array is encoded
// as a varInt containing the length of the array followed by the bytes
// themselves. An error is returned if the length is greater than the
// passed maxAllowed parameter which helps protect against memory exhaustion
// attacks and forced panics through malformed messages. The fieldName
// parameter is only used for the error message so it provides more context in
// the error.
func ReadVarBytes(r io.Reader, pver uint32, maxAllowed uint32,
fieldName string) ([]byte, error) {
count, err := ReadVarInt(r, pver)
if err != nil {
return nil, err
}
// Prevent byte array larger than the max message size. It would
// be possible to cause memory exhaustion and panics without a sane
// upper bound on this count.
if count > uint64(maxAllowed) {
str := fmt.Sprintf("%s is larger than the max allowed size "+
"[count %d, max %d]", fieldName, count, maxAllowed)
return nil, messageError("ReadVarBytes", str)
}
b := make([]byte, count)
_, err = io.ReadFull(r, b)
if err != nil {
return nil, err
}
return b, nil
}
// WriteVarBytes serializes a variable length byte array to w as a varInt
// containing the number of bytes, followed by the bytes themselves.
func WriteVarBytes(w io.Writer, pver uint32, bytes []byte) error {
slen := uint64(len(bytes))
err := WriteVarInt(w, pver, slen)
if err != nil {
return err
}
_, err = w.Write(bytes)
return err
}
// randomUint64 returns a cryptographically random uint64 value. This
// unexported version takes a reader primarily to ensure the error paths
// can be properly tested by passing a fake reader in the tests.
func randomUint64(r io.Reader) (uint64, error) {
rv, err := binarySerializer.Uint64(r, bigEndian)
if err != nil {
return 0, err
}
return rv, nil
}
// RandomUint64 returns a cryptographically random uint64 value.
func RandomUint64() (uint64, error) {
return randomUint64(rand.Reader)
}