/
encoding.go
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/
encoding.go
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// Copyright 2018 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package encoding
import (
"encoding/binary"
"hash"
"hash/crc32"
"unsafe"
"github.com/pkg/errors"
)
var (
ErrInvalidSize = errors.New("invalid size")
ErrInvalidChecksum = errors.New("invalid checksum")
)
// Encbuf is a helper type to populate a byte slice with various types.
type Encbuf struct {
B []byte
C [binary.MaxVarintLen64]byte
}
func (e *Encbuf) Reset() { e.B = e.B[:0] }
func (e *Encbuf) Get() []byte { return e.B }
func (e *Encbuf) Len() int { return len(e.B) }
func (e *Encbuf) PutString(s string) { e.B = append(e.B, s...) }
func (e *Encbuf) PutByte(c byte) { e.B = append(e.B, c) }
func (e *Encbuf) PutBE32int(x int) { e.PutBE32(uint32(x)) }
func (e *Encbuf) PutUvarint32(x uint32) { e.PutUvarint64(uint64(x)) }
func (e *Encbuf) PutBE64int64(x int64) { e.PutBE64(uint64(x)) }
func (e *Encbuf) PutUvarint(x int) { e.PutUvarint64(uint64(x)) }
func (e *Encbuf) PutBE32(x uint32) {
binary.BigEndian.PutUint32(e.C[:], x)
e.B = append(e.B, e.C[:4]...)
}
func (e *Encbuf) PutBE64(x uint64) {
binary.BigEndian.PutUint64(e.C[:], x)
e.B = append(e.B, e.C[:8]...)
}
func (e *Encbuf) PutUvarint64(x uint64) {
n := binary.PutUvarint(e.C[:], x)
e.B = append(e.B, e.C[:n]...)
}
func (e *Encbuf) PutVarint64(x int64) {
n := binary.PutVarint(e.C[:], x)
e.B = append(e.B, e.C[:n]...)
}
// PutUvarintStr writes a string to the buffer prefixed by its varint length (in bytes!).
func (e *Encbuf) PutUvarintStr(s string) {
b := *(*[]byte)(unsafe.Pointer(&s))
e.PutUvarint(len(b))
e.PutString(s)
}
// PutHash appends a hash over the buffers current contents to the buffer.
func (e *Encbuf) PutHash(h hash.Hash) {
h.Reset()
e.WriteToHash(h)
e.PutHashSum(h)
}
// WriteToHash writes the current buffer contents to the given hash.
func (e *Encbuf) WriteToHash(h hash.Hash) {
_, err := h.Write(e.B)
if err != nil {
panic(err) // The CRC32 implementation does not error
}
}
// PutHashSum writes the Sum of the given hash to the buffer.
func (e *Encbuf) PutHashSum(h hash.Hash) {
e.B = h.Sum(e.B)
}
// Decbuf provides safe methods to extract data from a byte slice. It does all
// necessary bounds checking and advancing of the byte slice.
// Several datums can be extracted without checking for errors. However, before using
// any datum, the err() method must be checked.
type Decbuf struct {
B []byte
E error
}
// NewDecbufAt returns a new decoding buffer. It expects the first 4 bytes
// after offset to hold the big endian encoded content length, followed by the contents and the expected
// checksum.
func NewDecbufAt(bs ByteSlice, off int, castagnoliTable *crc32.Table) Decbuf {
if bs.Len() < off+4 {
return Decbuf{E: ErrInvalidSize}
}
b := bs.Range(off, off+4)
l := int(binary.BigEndian.Uint32(b))
if bs.Len() < off+4+l+4 {
return Decbuf{E: ErrInvalidSize}
}
// Load bytes holding the contents plus a CRC32 checksum.
b = bs.Range(off+4, off+4+l+4)
dec := Decbuf{B: b[:len(b)-4]}
if castagnoliTable != nil {
if exp := binary.BigEndian.Uint32(b[len(b)-4:]); dec.Crc32(castagnoliTable) != exp {
return Decbuf{E: ErrInvalidChecksum}
}
}
return dec
}
// NewDecbufUvarintAt returns a new decoding buffer. It expects the first bytes
// after offset to hold the uvarint-encoded buffers length, followed by the contents and the expected
// checksum.
func NewDecbufUvarintAt(bs ByteSlice, off int, castagnoliTable *crc32.Table) Decbuf {
// We never have to access this method at the far end of the byte slice. Thus just checking
// against the MaxVarintLen32 is sufficient.
if bs.Len() < off+binary.MaxVarintLen32 {
return Decbuf{E: ErrInvalidSize}
}
b := bs.Range(off, off+binary.MaxVarintLen32)
l, n := binary.Uvarint(b)
if n <= 0 || n > binary.MaxVarintLen32 {
return Decbuf{E: errors.Errorf("invalid uvarint %d", n)}
}
if bs.Len() < off+n+int(l)+4 {
return Decbuf{E: ErrInvalidSize}
}
// Load bytes holding the contents plus a CRC32 checksum.
b = bs.Range(off+n, off+n+int(l)+4)
dec := Decbuf{B: b[:len(b)-4]}
if dec.Crc32(castagnoliTable) != binary.BigEndian.Uint32(b[len(b)-4:]) {
return Decbuf{E: ErrInvalidChecksum}
}
return dec
}
// NewDecbufRaw returns a new decoding buffer of the given length.
func NewDecbufRaw(bs ByteSlice, length int) Decbuf {
if bs.Len() < length {
return Decbuf{E: ErrInvalidSize}
}
return Decbuf{B: bs.Range(0, length)}
}
func (d *Decbuf) Uvarint() int { return int(d.Uvarint64()) }
func (d *Decbuf) Be32int() int { return int(d.Be32()) }
func (d *Decbuf) Be64int64() int64 { return int64(d.Be64()) }
// Crc32 returns a CRC32 checksum over the remaining bytes.
func (d *Decbuf) Crc32(castagnoliTable *crc32.Table) uint32 {
return crc32.Checksum(d.B, castagnoliTable)
}
func (d *Decbuf) Skip(l int) {
if len(d.B) < l {
d.E = ErrInvalidSize
return
}
d.B = d.B[l:]
}
func (d *Decbuf) UvarintStr() string {
return string(d.UvarintBytes())
}
// The return value becomes invalid if the byte slice goes away.
// Compared to UvarintStr, this avoid allocations.
func (d *Decbuf) UvarintBytes() []byte {
l := d.Uvarint64()
if d.E != nil {
return []byte{}
}
if len(d.B) < int(l) {
d.E = ErrInvalidSize
return []byte{}
}
s := d.B[:l]
d.B = d.B[l:]
return s
}
func (d *Decbuf) Varint64() int64 {
if d.E != nil {
return 0
}
x, n := binary.Varint(d.B)
if n < 1 {
d.E = ErrInvalidSize
return 0
}
d.B = d.B[n:]
return x
}
func (d *Decbuf) Uvarint64() uint64 {
if d.E != nil {
return 0
}
x, n := binary.Uvarint(d.B)
if n < 1 {
d.E = ErrInvalidSize
return 0
}
d.B = d.B[n:]
return x
}
func (d *Decbuf) Be64() uint64 {
if d.E != nil {
return 0
}
if len(d.B) < 8 {
d.E = ErrInvalidSize
return 0
}
x := binary.BigEndian.Uint64(d.B)
d.B = d.B[8:]
return x
}
func (d *Decbuf) Be32() uint32 {
if d.E != nil {
return 0
}
if len(d.B) < 4 {
d.E = ErrInvalidSize
return 0
}
x := binary.BigEndian.Uint32(d.B)
d.B = d.B[4:]
return x
}
func (d *Decbuf) Byte() byte {
if d.E != nil {
return 0
}
if len(d.B) < 1 {
d.E = ErrInvalidSize
return 0
}
x := d.B[0]
d.B = d.B[1:]
return x
}
func (d *Decbuf) ConsumePadding() {
if d.E != nil {
return
}
for len(d.B) > 1 && d.B[0] == '\x00' {
d.B = d.B[1:]
}
if len(d.B) < 1 {
d.E = ErrInvalidSize
}
}
func (d *Decbuf) Err() error { return d.E }
func (d *Decbuf) Len() int { return len(d.B) }
func (d *Decbuf) Get() []byte { return d.B }
// ByteSlice abstracts a byte slice.
type ByteSlice interface {
Len() int
Range(start, end int) []byte
}