prometheus/index/encoding_helpers.go

193 lines
4.4 KiB
Go

// 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 index
import (
"encoding/binary"
"hash"
"hash/crc32"
"unsafe"
)
// enbuf 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) putBytes(b []byte) { e.b = append(e.b, b...) }
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) putBE64int(x int) { e.putBE64(uint64(x)) }
func (e *encbuf) putBE64int64(x int64) { e.putBE64(uint64(x)) }
func (e *encbuf) putUvarint32(x uint32) { e.putUvarint64(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]...)
}
// putVarintStr 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()
_, err := h.Write(e.b)
if err != nil {
panic(err) // The CRC32 implementation does not error
}
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
}
func (d *decbuf) uvarint() int { return int(d.uvarint64()) }
func (d *decbuf) uvarint32() uint32 { return uint32(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() uint32 {
return crc32.Checksum(d.b, castagnoliTable)
}
func (d *decbuf) uvarintStr() string {
l := d.uvarint64()
if d.e != nil {
return ""
}
if len(d.b) < int(l) {
d.e = errInvalidSize
return ""
}
s := string(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) < 4 {
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) decbuf(l int) decbuf {
if d.e != nil {
return decbuf{e: d.e}
}
if l > len(d.b) {
return decbuf{e: errInvalidSize}
}
r := decbuf{b: d.b[:l]}
d.b = d.b[l:]
return r
}
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 }