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164 lines
3.5 KiB
Go
164 lines
3.5 KiB
Go
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// Copyright 2024 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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// Package zstd provides a high-level API for reading and writing zstd-compressed data.
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// It supports both regular and seekable zstd streams.
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// It's not a new wheel, but a wrapper around the zstd and zstd-seekable-format-go packages.
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package zstd
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import (
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"errors"
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"io"
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seekable "github.com/SaveTheRbtz/zstd-seekable-format-go/pkg"
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"github.com/klauspost/compress/zstd"
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)
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type Writer zstd.Encoder
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var _ io.WriteCloser = (*Writer)(nil)
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// NewWriter returns a new zstd writer.
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func NewWriter(w io.Writer, opts ...WriterOption) (*Writer, error) {
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zstdW, err := zstd.NewWriter(w, opts...)
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if err != nil {
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return nil, err
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}
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return (*Writer)(zstdW), nil
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}
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func (w *Writer) Write(p []byte) (int, error) {
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return (*zstd.Encoder)(w).Write(p)
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}
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func (w *Writer) Close() error {
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return (*zstd.Encoder)(w).Close()
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}
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type Reader zstd.Decoder
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var _ io.ReadCloser = (*Reader)(nil)
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// NewReader returns a new zstd reader.
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func NewReader(r io.Reader, opts ...ReaderOption) (*Reader, error) {
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zstdR, err := zstd.NewReader(r, opts...)
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if err != nil {
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return nil, err
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}
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return (*Reader)(zstdR), nil
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}
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func (r *Reader) Read(p []byte) (int, error) {
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return (*zstd.Decoder)(r).Read(p)
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}
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func (r *Reader) Close() error {
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(*zstd.Decoder)(r).Close() // no error returned
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return nil
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}
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type SeekableWriter struct {
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buf []byte
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n int
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w seekable.Writer
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}
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var _ io.WriteCloser = (*SeekableWriter)(nil)
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// NewSeekableWriter returns a zstd writer to compress data to seekable format.
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// blockSize is an important parameter, it should be decided according to the actual business requirements.
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// If it's too small, the compression ratio could be very bad, even no compression at all.
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// If it's too large, it could cost more traffic when reading the data partially from underlying storage.
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func NewSeekableWriter(w io.Writer, blockSize int, opts ...WriterOption) (*SeekableWriter, error) {
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zstdW, err := zstd.NewWriter(nil, opts...)
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if err != nil {
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return nil, err
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}
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seekableW, err := seekable.NewWriter(w, zstdW)
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if err != nil {
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return nil, err
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}
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return &SeekableWriter{
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buf: make([]byte, blockSize),
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w: seekableW,
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}, nil
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}
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func (w *SeekableWriter) Write(p []byte) (int, error) {
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written := 0
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for len(p) > 0 {
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n := copy(w.buf[w.n:], p)
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w.n += n
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written += n
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p = p[n:]
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if w.n == len(w.buf) {
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if _, err := w.w.Write(w.buf); err != nil {
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return written, err
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}
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w.n = 0
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}
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}
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return written, nil
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}
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func (w *SeekableWriter) Close() error {
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if w.n > 0 {
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if _, err := w.w.Write(w.buf[:w.n]); err != nil {
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return err
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}
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}
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return w.w.Close()
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}
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type SeekableReader struct {
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r seekable.Reader
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c func() error
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}
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var _ io.ReadSeekCloser = (*SeekableReader)(nil)
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// NewSeekableReader returns a zstd reader to decompress data from seekable format.
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func NewSeekableReader(r io.ReadSeeker, opts ...ReaderOption) (*SeekableReader, error) {
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zstdR, err := zstd.NewReader(nil, opts...)
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if err != nil {
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return nil, err
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}
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seekableR, err := seekable.NewReader(r, zstdR)
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if err != nil {
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return nil, err
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}
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ret := &SeekableReader{
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r: seekableR,
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}
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if closer, ok := r.(io.Closer); ok {
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ret.c = closer.Close
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}
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return ret, nil
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}
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func (r *SeekableReader) Read(p []byte) (int, error) {
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return r.r.Read(p)
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}
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func (r *SeekableReader) Seek(offset int64, whence int) (int64, error) {
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return r.r.Seek(offset, whence)
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}
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func (r *SeekableReader) Close() error {
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return errors.Join(
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func() error {
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if r.c != nil {
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return r.c()
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}
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return nil
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}(),
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r.r.Close(),
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)
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}
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