neo-go/pkg/io/binaryReader.go

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