148 lines
4.4 KiB
Go
148 lines
4.4 KiB
Go
/**
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* The MIT License (MIT)
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*
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* Copyright (c) 2014 Yani Iliev <yani@iliev.me>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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package wpress
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import (
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"bytes"
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"errors"
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"os"
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"path/filepath"
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"strconv"
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)
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const (
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headerSize = 4377 // length of the header
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filenameSize = 255 // maximum number of bytes allowed for filename
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contentSize = 14 // maximum number of bytes allowed for content size
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mtimeSize = 12 // maximum number of bytes allowed for last modified date
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prefixSize = 4096 // maximum number of bytes allowed for prefix
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)
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// Header block format of a file
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// Field Name Offset Length Contents
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// Name 0 255 filename (no path, no slash)
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// Size 255 14 length of file contents
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// Mtime 269 12 last modification date
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// Prefix 281 4096 path name, no trailing slashes
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type Header struct {
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Name []byte
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Size []byte
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Mtime []byte
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Prefix []byte
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}
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// PopulateFromBytes populates header struct from bytes array
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func (h *Header) PopulateFromBytes(block []byte) {
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h.Name = block[0:255]
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h.Size = block[255:269]
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h.Mtime = block[269:281]
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h.Prefix = block[281:4377]
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}
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// PopulateFromFilename populates header struct from passed filename
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func (h *Header) PopulateFromFilename(filename string) error {
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// try to open the file
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file, err := os.Open(filename)
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if err != nil {
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return err
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}
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// get the fileinfo
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fi, err := file.Stat()
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if err != nil {
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return err
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}
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// validate if filename fits the allowed length
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if len(fi.Name()) > filenameSize {
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return errors.New("filename is longer than max allowed")
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}
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// create filename buffer
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h.Name = make([]byte, filenameSize)
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// copy filename to the buffer leaving available space as zero-bytes
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copy(h.Name, fi.Name())
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// get filesize as string
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size := strconv.FormatInt(fi.Size(), 10)
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// validate if filesize fits the allowed length
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if len(size) > contentSize {
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return errors.New("file size is larger than max allowed")
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}
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// create size buffer
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h.Size = make([]byte, contentSize)
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// copy content size length to the buffer
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copy(h.Size, size)
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// get last modified date as string
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unixTime := strconv.FormatInt(fi.ModTime().Unix(), 10)
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if len(unixTime) > mtimeSize {
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return errors.New("last modified date is after than max allowed")
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}
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// create mtime buffer
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h.Mtime = make([]byte, mtimeSize)
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// copy mtime to the buffer
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copy(h.Mtime, unixTime)
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// get the path to the file
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_path := filepath.Dir(filename)
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// validate if path fits the allowed length
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if len(_path) > prefixSize {
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return errors.New("prefix size is longer than max allowed")
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}
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// create buffer to put the prefix in
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h.Prefix = make([]byte, prefixSize)
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// put the prefix in the buffer
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copy(h.Prefix, _path)
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// close the file
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err = file.Close()
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if err != nil {
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return err
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}
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return nil
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}
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// GetHeaderBlock returns byte sequence of header block populated with data
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func (h Header) GetHeaderBlock() []byte {
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block := append(h.Name, h.Size...)
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block = append(block, h.Mtime...)
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block = append(block, h.Prefix...)
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return block
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}
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// GetSize returns content size
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func (h Header) GetSize() (int, error) {
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// remove any trailing zero bytes, convert to string, then convert to integer
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return strconv.Atoi(string(bytes.Trim(h.Size, "\x00")))
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}
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// GetEOFBlock returns byte sequence describing EOF
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func (h Header) GetEOFBlock() []byte {
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// generate zero-byte sequence of length headerSize
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return bytes.Repeat([]byte("\x00"), headerSize)
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}
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