141 lines
2.9 KiB
Go
141 lines
2.9 KiB
Go
/*
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* Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
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*
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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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*/
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package ar
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import (
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"io"
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"strconv"
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"strings"
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"unsafe"
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)
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// Provides read access to an ar archive.
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// Call next to skip files
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//
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// Example:
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// reader := NewReader(f)
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// var buf bytes.Buffer
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// for {
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// _, err := reader.Next()
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// if err == io.EOF {
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// break
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// }
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// if err != nil {
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// t.Errorf(err.Error())
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// }
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// io.Copy(&buf, reader)
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// }
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type Reader struct {
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r io.Reader
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nb int64
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pad int64
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}
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// Copies read data to r. Strips the global ar header.
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func NewReader(r io.Reader) (*Reader, error) {
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buf := make([]byte, globalHeaderLen)
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if _, err := io.ReadFull(r, buf); err != nil {
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return nil, err
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}
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if string(buf) != globalHeader {
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return nil, errInvalidHeader
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}
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return &Reader{r: r}, nil
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}
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func stringVal(b []byte) string {
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return strings.TrimRight(string(b), " ")
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}
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func intVal(b []byte) (int64, error) {
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return strconv.ParseInt(stringVal(b), 10, 64)
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}
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func (rd *Reader) skipUnread() error {
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skip := rd.nb + rd.pad
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rd.nb, rd.pad = 0, 0
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if seeker, ok := rd.r.(io.Seeker); ok {
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_, err := seeker.Seek(skip, io.SeekCurrent)
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return err
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}
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_, err := io.CopyN(io.Discard, rd.r, skip)
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return err
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}
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func (rd *Reader) readHeader() (header *Header, err error) {
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var rec recHeader
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var buf = (*[headerByteSize]byte)(unsafe.Pointer(&rec))[:]
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if _, err = io.ReadFull(rd.r, buf); err != nil {
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return
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}
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header = new(Header)
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header.Name = stringVal(rec.name[:])
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if header.Size, err = intVal(rec.size[:]); err != nil {
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return
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}
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if header.Size%2 == 1 {
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rd.pad = 1
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} else {
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rd.pad = 0
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}
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if rec.name[0] == '#' {
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if n, e := strconv.ParseInt(strings.TrimPrefix(header.Name[3:], "#1/"), 10, 64); e == nil {
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name := make([]byte, n)
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if _, err = io.ReadFull(rd.r, name); err != nil {
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return
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}
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header.Name = string(name)
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header.Size -= n
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}
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}
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rd.nb = int64(header.Size)
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return
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}
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// Call Next() to skip to the next file in the archive file.
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// Returns a Header which contains the metadata about the
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// file in the archive.
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func (rd *Reader) Next() (*Header, error) {
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err := rd.skipUnread()
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if err != nil {
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return nil, err
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}
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return rd.readHeader()
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}
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// Read data from the current entry in the archive.
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func (rd *Reader) Read(b []byte) (n int, err error) {
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if rd.nb == 0 {
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return 0, io.EOF
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}
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if int64(len(b)) > rd.nb {
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b = b[0:rd.nb]
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}
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n, err = rd.r.Read(b)
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rd.nb -= int64(n)
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return
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}
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