文件壓縮與解壓縮實踐

論文字數:8175,頁數:28

摘    要
隨著人們對數據的大量需求以及計算機使用時間的增加，計算機磁盤上的文件越來越大，越來越多。如何讓有限的磁盤空間容納更多的數據成為需要解決的問題。一方面，高速發展的存儲技術以提高磁盤容量來解決這樣的需求，但隨著網絡環境下數據傳遞的產生以及帶寬的限制，大容量數據問題日益突出。在這兩種需求的推動下，對數據壓縮的需求產生了。人們可以將文件在不改變其本身的條件下，將其以更小的占用空間存儲，并且在需要的時候將文件恢復成原有的樣子，這就是壓縮目的。本論文主要研究文件的無損壓縮技術，并簡要介紹了文件壓縮的分類、幾種常用的無損壓縮格式和常用的壓縮算法。運用LZ77字典算法、懶惰匹配算法和Huffman編碼算法，使用Java語言在Jbuilder2006環境下設計了使用GZIP算法對文件壓縮與解壓縮的實現程序。用戶可以根據自己的需求，使用此程序方便地對文件進行壓縮或者解壓縮操作。

關鍵詞：壓縮；解壓縮；GZIP；Java
Practice of File Compression and Decompression
Abstract
As the great demand for data and the using time of computer are increasing, computer files on the disk grow more and more. How to make the limited disk space to store more data has became a problem crying out for solutions. On one hand, the rapid development of storage technology that can increase the disk capacity, can meet such demand. However, with the emergence of data transmission in a network environment and the bandwidth limitations, the problem of large-capacity data is increasingly prominent. With the promotion of both demands, the need for data compression and decompression is generated. People can store a file with a smaller storage space without changing the file’s own condition, and can restore the file; that is the purpose of data compression and decompression. This treatise principally research file lossless compression, otherwise, briefly introduced classification of file compression, some general lossless compression format and general compression algorithm. A procedure within algorithm called GZIP were designed for file compression and decompression in Java language under the circumstances of Jbuilder2006,which used LZ77 dictionary algorithm, lazy match algorithm and Huffman coding algorithm. Users could use this procedure compress or decompress files expediently according to their demand.

Key words: Compression; Decompression; GZIP; Java

目  錄

1 引言 1
1.1 課題背景 1
1.2 國內外現有的研究成果 1
2 壓縮與解壓縮程序分析 2
2.1 需求分析 2
2.2 使用的算法理論 2
2.2.1 LZ77算法簡介 2
2.2.2 Huffman算法簡介 3
2.2.3 GZIP算法原理分析 4
2.3 開發環境 4
3 總體設計 4
3.1 程序功能模塊 5
3.2 模塊分析與流程圖 5
3.2.1 壓縮模塊 5
3.2.2 解壓縮模塊 6
3.3 程序中各個類的初步定義 7
4 詳細設計和實現 8
4.1 壓縮的程序流程 8
4.2 解壓縮的程序流程 9
4.3 主函數代碼 10
4.3.1 gzip壓縮模塊代碼 10
4.3.2 ungzip解壓縮模塊代碼 11
4.4 程序界面設計 12
5 軟件系統測試 17
5.1 運行環境 17
5.2 測試方法 17
5.3 測試結果 17
5.3.1 使用程序對txt文件壓縮 17
5.3.2 使用程序對bmp圖象文件壓縮 18
5.3.3 使用程序對doc文件壓縮 18
結  論 18
參考文獻 19
致    謝 20
聲    明 21