123 lines
3.7 KiB
Go
123 lines
3.7 KiB
Go
// Copyright 2025 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package compression
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import (
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"errors"
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"fmt"
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"github.com/golang/snappy"
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)
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// Type represents a valid compression type supported by this package.
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type Type = string
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const (
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// None represents no compression case.
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// None is the default when Type is empty.
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None Type = "none"
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// Snappy represents snappy block format.
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Snappy Type = "snappy"
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// Zstd represents "speed" mode of Zstd (Zstandard https://facebook.github.io/zstd/).
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// This is roughly equivalent to the default Zstandard mode (level 3).
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Zstd Type = "zstd"
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)
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func Types() []Type { return []Type{None, Snappy, Zstd} }
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// Encode returns the encoded form of src for the given compression type.
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// For None or empty message the encoding is not attempted.
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//
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// The buf allows passing various buffer implementations that make encoding more
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// efficient. See NewSyncEncodeBuffer and NewConcurrentEncodeBuffer for further
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// details. For non-zstd compression types, it is valid to pass nil buf.
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//
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// Encode is concurrency-safe, however note the concurrency limits for the
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// buffer of your choice.
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func Encode(t Type, src []byte, buf EncodeBuffer) (ret []byte, err error) {
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if len(src) == 0 || t == "" || t == None {
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return src, nil
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}
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if t == Snappy {
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// If MaxEncodedLen is less than 0 the record is too large to be compressed.
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if snappy.MaxEncodedLen(len(src)) < 0 {
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return src, fmt.Errorf("compression: Snappy can't encode such a large message: %v", len(src))
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}
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var b []byte
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if buf != nil {
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b = buf.get()
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defer func() {
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buf.set(ret)
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}()
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}
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// The snappy library uses `len` to calculate if we need a new buffer.
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// In order to allocate as few buffers as possible make the length
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// equal to the capacity.
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b = b[:cap(b)]
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return snappy.Encode(b, src), nil
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}
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if t == Zstd {
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if buf == nil {
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return nil, errors.New("zstd requested but EncodeBuffer was not provided")
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}
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b := buf.get()
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defer func() {
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buf.set(ret)
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}()
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return buf.zstdEncBuf().EncodeAll(src, b[:0]), nil
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}
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return nil, fmt.Errorf("unsupported compression type: %s", t)
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}
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// Decode returns the decoded form of src for the given compression type.
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//
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// The buf allows passing various buffer implementations that make decoding more
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// efficient. See NewSyncDecodeBuffer and NewConcurrentDecodeBuffer for further
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// details. For non-zstd compression types, it is valid to pass nil buf.
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//
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// Decode is concurrency-safe, however note the concurrency limits for the
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// buffer of your choice.
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func Decode(t Type, src []byte, buf DecodeBuffer) (ret []byte, err error) {
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if len(src) == 0 || t == "" || t == None {
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return src, nil
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}
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if t == Snappy {
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var b []byte
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if buf != nil {
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b = buf.get()
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defer func() {
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buf.set(ret)
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}()
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}
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// The snappy library uses `len` to calculate if we need a new buffer.
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// In order to allocate as few buffers as possible make the length
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// equal to the capacity.
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b = b[:cap(b)]
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return snappy.Decode(b, src)
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}
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if t == Zstd {
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if buf == nil {
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return nil, errors.New("zstd requested but DecodeBuffer was not provided")
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}
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b := buf.get()
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defer func() {
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buf.set(ret)
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}()
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return buf.zstdDecBuf().DecodeAll(src, b[:0])
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}
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return nil, fmt.Errorf("unsupported compression type: %s", t)
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}
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