148 lines
2.9 KiB
Go
148 lines
2.9 KiB
Go
/*
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Copyright 2022 Alibaba Group Holding Limited.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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package utils
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import (
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"bufio"
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"hash/crc32"
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"io"
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)
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type SeekableBufferReader struct {
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rd io.ReadSeekCloser
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r *bufio.Reader
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offset int64
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}
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func (r *SeekableBufferReader) Close() error {
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rd := r.rd
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r.r.Reset(nil)
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r.rd = nil
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r.offset = 0
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if rd != nil {
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return rd.Close()
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}
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return nil
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}
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func (r *SeekableBufferReader) Read(p []byte) (n int, err error) {
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n, err = r.r.Read(p)
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r.offset += int64(n)
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return
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}
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func (r *SeekableBufferReader) Seek(offset int64, whence int) (int64, error) {
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if whence == io.SeekStart && offset == r.offset {
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return r.offset, nil
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}
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if whence == io.SeekCurrent {
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if offset == 0 {
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return r.offset, nil
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}
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// If seek relative to current and buffer covers, we skip in buffer.
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// Otherwise, we rewrite the seek.
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if offset > 0 && int64(r.r.Buffered()) >= offset {
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_, _ = r.r.Discard(int(offset))
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r.offset += offset
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return r.offset, nil
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} else {
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offset = r.offset + offset
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whence = io.SeekStart
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}
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}
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off, err := r.rd.Seek(offset, whence)
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if err != nil {
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return off, err
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}
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r.r.Reset(r.rd)
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r.offset = off
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return off, nil
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}
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func NewSeekableBufferReader(rd io.ReadSeekCloser) *SeekableBufferReader {
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return &SeekableBufferReader{
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rd: rd,
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r: bufio.NewReaderSize(rd, 8192),
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}
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}
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func NewSeekableBufferReaderSize(rd io.ReadSeekCloser, size int) *SeekableBufferReader {
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return &SeekableBufferReader{
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rd: rd,
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r: bufio.NewReaderSize(rd, size),
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}
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}
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func SkipBytes(r io.Reader, n int64) error {
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if n == 0 {
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return nil
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}
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if seeker, ok := r.(io.Seeker); ok {
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_, err := seeker.Seek(n, io.SeekCurrent)
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return err
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} else {
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_, err := io.CopyN(io.Discard, r, n)
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return err
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}
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}
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type CountReader struct {
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r io.Reader
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cnt int
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}
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func (r *CountReader) Read(p []byte) (n int, err error) {
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n, err = r.r.Read(p)
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r.cnt += n
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return n, err
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}
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func (r *CountReader) BytesRead() int {
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return r.cnt
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}
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func NewCountReader(r io.Reader) *CountReader {
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return &CountReader{r: r}
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}
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type CRC32Reader struct {
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r io.Reader
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checksum uint32
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}
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func (r *CRC32Reader) Read(p []byte) (n int, err error) {
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n, err = r.r.Read(p)
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if err == nil {
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r.checksum = crc32.Update(r.checksum, crc32.IEEETable, p[:n])
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}
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return
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}
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func (r *CRC32Reader) Checksum() uint32 {
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return r.checksum
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}
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func NewCRC32Reader(r io.Reader, checksum uint32) *CRC32Reader {
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return &CRC32Reader{
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r: r,
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checksum: checksum,
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}
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}
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