mirror of
https://github.com/nspcc-dev/neo-go.git
synced 2024-12-05 03:58:23 +00:00
199 lines
4.4 KiB
Go
199 lines
4.4 KiB
Go
package io
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"io"
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"reflect"
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)
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// MaxArraySize is the maximum size of an array which can be decoded.
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// It is taken from https://github.com/neo-project/neo/blob/master/neo/IO/Helper.cs#L130
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const MaxArraySize = 0x1000000
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// BinReader is a convenient wrapper around a io.Reader and err object.
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// Used to simplify error handling when reading into a struct with many fields.
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type BinReader struct {
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r io.Reader
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u64 []byte
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u32 []byte
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u16 []byte
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u8 []byte
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Err error
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}
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// NewBinReaderFromIO makes a BinReader from io.Reader.
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func NewBinReaderFromIO(ior io.Reader) *BinReader {
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u64 := make([]byte, 8)
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u32 := u64[:4]
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u16 := u64[:2]
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u8 := u64[:1]
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return &BinReader{r: ior, u64: u64, u32: u32, u16: u16, u8: u8}
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}
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// NewBinReaderFromBuf makes a BinReader from byte buffer.
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func NewBinReaderFromBuf(b []byte) *BinReader {
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r := bytes.NewReader(b)
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return NewBinReaderFromIO(r)
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}
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// ReadU64LE reads a little-endian encoded uint64 value from the underlying
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// io.Reader. On read failures it returns zero.
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func (r *BinReader) ReadU64LE() uint64 {
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r.ReadBytes(r.u64)
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if r.Err != nil {
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return 0
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}
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return binary.LittleEndian.Uint64(r.u64)
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}
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// ReadU32LE reads a little-endian encoded uint32 value from the underlying
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// io.Reader. On read failures it returns zero.
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func (r *BinReader) ReadU32LE() uint32 {
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r.ReadBytes(r.u32)
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if r.Err != nil {
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return 0
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}
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return binary.LittleEndian.Uint32(r.u32)
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}
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// ReadU16LE reads a little-endian encoded uint16 value from the underlying
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// io.Reader. On read failures it returns zero.
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func (r *BinReader) ReadU16LE() uint16 {
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r.ReadBytes(r.u16)
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if r.Err != nil {
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return 0
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}
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return binary.LittleEndian.Uint16(r.u16)
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}
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// ReadU16BE reads a big-endian encoded uint16 value from the underlying
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// io.Reader. On read failures it returns zero.
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func (r *BinReader) ReadU16BE() uint16 {
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r.ReadBytes(r.u16)
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if r.Err != nil {
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return 0
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}
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return binary.BigEndian.Uint16(r.u16)
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}
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// ReadB reads a byte from the underlying io.Reader. On read failures it
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// returns zero.
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func (r *BinReader) ReadB() byte {
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r.ReadBytes(r.u8)
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if r.Err != nil {
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return 0
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}
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return r.u8[0]
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}
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// ReadBool reads a boolean value encoded in a zero/non-zero byte from the
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// underlying io.Reader. On read failures it returns false.
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func (r *BinReader) ReadBool() bool {
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return r.ReadB() != 0
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}
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// ReadArray reads array into value which must be
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// a pointer to a slice.
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func (r *BinReader) ReadArray(t interface{}, maxSize ...int) {
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value := reflect.ValueOf(t)
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if value.Kind() != reflect.Ptr || value.Elem().Kind() != reflect.Slice {
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panic(value.Type().String() + " is not a pointer to a slice")
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}
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if r.Err != nil {
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return
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}
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sliceType := value.Elem().Type()
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elemType := sliceType.Elem()
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isPtr := elemType.Kind() == reflect.Ptr
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ms := MaxArraySize
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if len(maxSize) != 0 {
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ms = maxSize[0]
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}
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lu := r.ReadVarUint()
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if lu > uint64(ms) {
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r.Err = fmt.Errorf("array is too big (%d)", lu)
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return
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}
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l := int(lu)
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arr := reflect.MakeSlice(sliceType, l, l)
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for i := 0; i < l; i++ {
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var elem reflect.Value
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if isPtr {
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elem = reflect.New(elemType.Elem())
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arr.Index(i).Set(elem)
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} else {
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elem = arr.Index(i).Addr()
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}
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el, ok := elem.Interface().(decodable)
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if !ok {
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panic(elemType.String() + "is not decodable")
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}
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el.DecodeBinary(r)
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}
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value.Elem().Set(arr)
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}
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// ReadVarUint reads a variable-length-encoded integer from the
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// underlying reader.
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func (r *BinReader) ReadVarUint() uint64 {
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if r.Err != nil {
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return 0
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}
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var b = r.ReadB()
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if b == 0xfd {
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return uint64(r.ReadU16LE())
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}
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if b == 0xfe {
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return uint64(r.ReadU32LE())
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}
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if b == 0xff {
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return r.ReadU64LE()
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}
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return uint64(b)
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}
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// ReadVarBytes reads the next set of bytes from the underlying reader.
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// ReadVarUInt() is used to determine how large that slice is
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func (r *BinReader) ReadVarBytes(maxSize ...int) []byte {
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n := r.ReadVarUint()
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ms := MaxArraySize
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if len(maxSize) != 0 {
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ms = maxSize[0]
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}
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if n > uint64(ms) {
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r.Err = fmt.Errorf("byte-slice is too big (%d)", n)
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return nil
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}
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b := make([]byte, n)
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r.ReadBytes(b)
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return b
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}
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// ReadBytes copies fixed-size buffer from the reader to provided slice.
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func (r *BinReader) ReadBytes(buf []byte) {
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if r.Err != nil {
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return
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}
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_, r.Err = io.ReadFull(r.r, buf)
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}
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// ReadString calls ReadVarBytes and casts the results as a string.
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func (r *BinReader) ReadString() string {
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b := r.ReadVarBytes()
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return string(b)
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}
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