package io import ( "bytes" "encoding/binary" "fmt" "io" "reflect" ) // MaxArraySize is the maximum size of an array which can be decoded. // It is taken from https://github.com/neo-project/neo/blob/master/neo/IO/Helper.cs#L130 const MaxArraySize = 0x1000000 // 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. type BinReader struct { r io.Reader u64 []byte u32 []byte u16 []byte u8 []byte 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. 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 ms := MaxArraySize 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 // underlying reader. func (r *BinReader) ReadVarUint() uint64 { if r.Err != nil { return 0 } var b = r.ReadB() if b == 0xfd { return uint64(r.ReadU16LE()) } if b == 0xfe { return uint64(r.ReadU32LE()) } if b == 0xff { return r.ReadU64LE() } 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() 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 } b := make([]byte, n) r.ReadBytes(b) return b } // 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(maxSize ...int) string { b := r.ReadVarBytes(maxSize...) return string(b) }