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decoder.go
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decoder.go
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// Copyright (c) Roman Atachiants and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for details.
package binary
import (
"encoding/binary"
"errors"
"fmt"
"io"
"math"
"reflect"
"sync"
)
// Reusable long-lived decoder pool.
var decoders = &sync.Pool{New: func() interface{} {
return NewDecoder(newReader(nil))
}}
// Reader represents the interface a reader should implement.
type Reader interface {
io.Reader
io.ByteReader
}
// Unmarshal decodes the payload from the binary format.
func Unmarshal(b []byte, v interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
if je, ok := r.(error); ok {
err = fmt.Errorf("%s, bianay %v, destType %T", je.Error(), b, v)
} else {
err = fmt.Errorf("%v, bianay %v, destType %T", r, b, v)
}
}
}()
// Get the decoder from the pool, reset it
d := decoders.Get().(*Decoder)
d.r.(*reader).Reset(b) // Reset the reader
// Decode and set the buffer if successful and free the decoder
err = d.Decode(v)
decoders.Put(d)
return
}
// Decoder represents a binary decoder.
type Decoder struct {
r Reader
s *reader // Not using the interface for better inlining
scratch [10]byte
}
// NewDecoder creates a binary decoder.
func NewDecoder(r Reader) *Decoder {
var slicer *reader
if s, ok := r.(*reader); ok {
slicer = s
}
return &Decoder{
r: r,
s: slicer,
}
}
// Decode decodes a value by reading from the underlying io.Reader.
func (d *Decoder) Decode(v interface{}) (err error) {
rv := reflect.Indirect(reflect.ValueOf(v))
if !rv.CanAddr() {
return errors.New("binary: can only Decode to pointer type")
}
// Scan the type (this will load from cache)
var c Codec
if c, err = scan(rv.Type()); err == nil {
err = c.DecodeTo(d, rv)
}
return
}
// Read reads a set of bytes
func (d *Decoder) Read(b []byte) (int, error) {
return d.r.Read(b)
}
// ReadUvarint reads a variable-length Uint64 from the buffer.
func (d *Decoder) ReadUvarint() (uint64, error) {
return binary.ReadUvarint(d.r)
}
// ReadVarint reads a variable-length Int64 from the buffer.
func (d *Decoder) ReadVarint() (int64, error) {
return binary.ReadVarint(d.r)
}
// ReadUint16 reads a uint16
func (d *Decoder) ReadUint16() (out uint16, err error) {
var b []byte
if b, err = d.sliceOrScratch(2); err == nil {
_ = b[1] // bounds check hint to compiler
out = (uint16(b[0]) | uint16(b[1])<<8)
}
return
}
// ReadUint32 reads a uint32
func (d *Decoder) ReadUint32() (out uint32, err error) {
var b []byte
if b, err = d.sliceOrScratch(4); err == nil {
_ = b[3] // bounds check hint to compiler
out = (uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24)
}
return
}
// ReadUint64 reads a uint64
func (d *Decoder) ReadUint64() (out uint64, err error) {
var b []byte
if b, err = d.sliceOrScratch(8); err == nil {
_ = b[7] // bounds check hint to compiler
out = (uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56)
}
return
}
// ReadFloat32 reads a float32
func (d *Decoder) ReadFloat32() (out float32, err error) {
var v uint32
if v, err = d.ReadUint32(); err == nil {
out = math.Float32frombits(v)
}
return
}
// ReadFloat64 reads a float64
func (d *Decoder) ReadFloat64() (out float64, err error) {
var v uint64
if v, err = d.ReadUint64(); err == nil {
out = math.Float64frombits(v)
}
return
}
// ReadBool reads a single boolean value from the slice.
func (d *Decoder) ReadBool() (bool, error) {
b, err := d.r.ReadByte()
return b == 1, err
}
// ReadComplex reads a complex64
func (d *Decoder) readComplex64() (out complex64, err error) {
err = binary.Read(d.r, binary.LittleEndian, &out)
return
}
// ReadComplex reads a complex128
func (d *Decoder) readComplex128() (out complex128, err error) {
err = binary.Read(d.r, binary.LittleEndian, &out)
return
}
// sliceOrScratch a slice or reads into as scratch buffer. This is useful for values
// which will get reallocated after this, such as ints, floats, etc.
func (d *Decoder) sliceOrScratch(n int) (buffer []byte, err error) {
if d.s != nil {
return d.s.Slice(n)
}
buffer = d.scratch[:n]
_, err = d.r.Read(buffer)
return
}
// Slice selects a sub-slice of next bytes. This is similar to Read() but does not
// actually perform a copy, but simply uses the underlying slice (if available) and
// returns a sub-slice pointing to the same array. Since this requires access
// to the underlying data, this is only available for our default reader.
func (d *Decoder) Slice(n int) ([]byte, error) {
if d.s != nil {
return d.s.Slice(n)
}
// If we don't have a slicer, we can just allocate and read
buffer := make([]byte, n, n)
if _, err := d.Read(buffer); err != nil {
return nil, err
}
return buffer, nil
}