（信源三）词典压缩器的实现--LZO算法

    LZO 是致力于解压速度的一种数据压缩算法，LZO 是 Lempel-Ziv-Oberhumer 的缩写。这个算法是无损算法，参考实现程序是线程安全的。 实现它的一个自由软件工具是lzop。最初的库是用 ANSI C 编写、并且遵从 GNU通用公共许可证发布的。现在 LZO 有用于 Perl、Python 以及 Java 的各种版本。代码版权的所有者是 Markus F. X. J. Oberhumer

    LZO 库实现了许多有下述特点的算法：

    * 解压简单，速度非常快。
    * 解压不需要内存。
    * 压缩相当地快。
    * 压缩需要 64 kB 的内存。
    * 允许在压缩部分以损失压缩速度为代价提高压缩率，解压速度不会降低。
    * 包括生成预先压缩数据的压缩级别，这样可以得到相当有竞争力的压缩比。
    * 另外还有一个只需要 8 kB 内存的压缩级别。
    * 算法是线程安全的。
    * 算法是无损的。

第一步，实现代码基本调试： 
从网址https://www.oberhumer.com/opensource/lzo/下载miniLZO,解压后会看到其包含如下文件： 

其中，lzoconf.h是LZO数据压缩库的配置，lzodefs.h是对体系结构、操作系统和编译器特定的定义，minilzo.h是迷你LZO实时数据压缩库的子集。minilzo.c是C语言版本的迷你LZO实时数据压缩库的子集，testmini.c是minilzo的测试文件。

（1）选择待压缩文件按钮

 void CcompressDlg::OnBnClickedButton3()
 {
     // TODO: 在此添加控件通知处理程序代码
     CString strFile = _T("");

     CFileDialog    dlgFile(TRUE, NULL, NULL, OFN_HIDEREADONLY, _T("Describe Files (*.cfg)|*.cfg|All Files (*.*)|*.*||"), NULL);

     if (dlgFile.DoModal())
     {
         strFile = dlgFile.GetPathName();
     }

     UpdateData(true);          // 获取数据
     path = strFile;
     UpdateData(false);         // 更新数据
 }

 void CcompressDlg::OnBnClickedButton3()
 {
     // TODO: 在此添加控件通知处理程序代码
     CString strFile = _T("");

     CFileDialog    dlgFile(TRUE, NULL, NULL, OFN_HIDEREADONLY, _T("Describe Files (*.cfg)|*.cfg|All Files (*.*)|*.*||"), NULL);

     if (dlgFile.DoModal())
     {
         strFile = dlgFile.GetPathName();
     }

     UpdateData(true);          // 获取数据
     path = strFile;
     UpdateData(false);         // 更新数据
 }

（2）选择解压缩文件按钮

 void CcompressDlg::OnBnClickedButton4()
 {
     // TODO: 在此添加控件通知处理程序代码
     CString strFile = _T("");

     CFileDialog    dlgFile(TRUE, NULL, NULL, OFN_HIDEREADONLY, _T("Describe Files (*.cfg)|*.cfg|All Files (*.*)|*.*||"), NULL);

     if (dlgFile.DoModal())
     {
         strFile = dlgFile.GetPathName();
     }

     UpdateData(true);          // 获取数据
     path_decompress = strFile;
     UpdateData(false);         // 更新数据
 }

 void CcompressDlg::OnBnClickedButton4()
 {
     // TODO: 在此添加控件通知处理程序代码
     CString strFile = _T("");

     CFileDialog    dlgFile(TRUE, NULL, NULL, OFN_HIDEREADONLY, _T("Describe Files (*.cfg)|*.cfg|All Files (*.*)|*.*||"), NULL);

     if (dlgFile.DoModal())
     {
         strFile = dlgFile.GetPathName();
     }

     UpdateData(true);          // 获取数据
     path_decompress = strFile;
     UpdateData(false);         // 更新数据
 }

（3）压缩按钮

 void CcompressDlg::OnBnClickedButton1()
 {
     // TODO: 在此添加控件通知处理程序代码
 #ifdef _UNICODE
     LONG len1;
     len1 = WideCharToMultiByte(CP_ACP, 0, path, -1, NULL, 0, NULL, NULL);
     char *textPath = (char *)malloc(sizeof(char)*(len1 + 1));
     memset(textPath, 0, len1 + 1);
     WideCharToMultiByte(CP_ACP, 0, path, -1, textPath, len1 + 1, NULL, NULL);
 #else
     ptr = new char[str.GetAllocLength() + 1];
 #endif
     err = fopen_s(&ifp, textPath, "rb");
     if (err == 0)
     {
         printf("Thefile'crt_fopen_s.c'wasopened\n");
     }
     fseek(ifp, 0, SEEK_END);
     unsigned long len = ftell(ifp);
     myInLen = len;
     fseek(ifp, 0, SEEK_SET);
     cpTemp = (char*)malloc(len * sizeof(char));
     fread(cpTemp, sizeof(char), len, ifp);
     char *in = cpTemp;
     char *out = (char*)malloc((len + len / 16 + 64 + 3) * sizeof(char));

     if (lzo_init() != LZO_E_OK)
     {
         printf("internal error - lzo_init() failed !!!\n");
         printf("(this usually indicates a compiler bug - try recompiling\nwithout optimizations, and enable '-DLZO_DEBUG' for diagnostics)\n");

     }

     lzo_uint in_len;
     in_len = len;
     lzo_memset(in, 0, in_len);
     lzo_uint out_len;

     int r;

     r = lzo1x_1_compress((unsigned char*)in, in_len, (unsigned char*)out, &out_len, wrkmem);
     char mess[256];

     if (r == LZO_E_OK)
     {
         sprintf_s(mess, sizeof(mess),  "压缩成功！\n\n原文件大小：%lu bytes\n压缩后大小：%lu bytes\n\n解压得到的文件“compress.txt”保存于工程目录下",
             (unsigned long)in_len, (unsigned long)out_len);
         MessageBox(CString(mess));

     }
     else
     {
         /* this should NEVER happen */
         sprintf_s(mess, sizeof(mess), "压缩失败!\n %d\n", r);
         MessageBox(CString(mess));
     }
     /* check for an incompressible block */
     if (out_len >= in_len)
     {
         sprintf_s(mess, sizeof(mess), "未压缩！\n");
         MessageBox(CString(mess));
     }

     err = fopen_s(&ofp, ".\\compress.txt", "wb");
     fwrite(out, sizeof(char), out_len, ofp);

     fclose(ifp);
     fclose(ofp);
     free(cpTemp);
     free(out);
     free(textPath);

 }

 void CcompressDlg::OnBnClickedButton1()
 {
     // TODO: 在此添加控件通知处理程序代码
 #ifdef _UNICODE
     LONG len1;
     len1 = WideCharToMultiByte(CP_ACP, 0, path, -1, NULL, 0, NULL, NULL);
     char *textPath = (char *)malloc(sizeof(char)*(len1 + 1));
     memset(textPath, 0, len1 + 1);
     WideCharToMultiByte(CP_ACP, 0, path, -1, textPath, len1 + 1, NULL, NULL);
 #else
     ptr = new char[str.GetAllocLength() + 1];
 #endif
     err = fopen_s(&ifp, textPath, "rb");
     if (err == 0)
     {
         printf("Thefile'crt_fopen_s.c'wasopened\n");
     }
     fseek(ifp, 0, SEEK_END);
     unsigned long len = ftell(ifp);
     myInLen = len;
     fseek(ifp, 0, SEEK_SET);
     cpTemp = (char*)malloc(len * sizeof(char));
     fread(cpTemp, sizeof(char), len, ifp);
     char *in = cpTemp;
     char *out = (char*)malloc((len + len / 16 + 64 + 3) * sizeof(char));

     if (lzo_init() != LZO_E_OK)
     {
         printf("internal error - lzo_init() failed !!!\n");
         printf("(this usually indicates a compiler bug - try recompiling\nwithout optimizations, and enable '-DLZO_DEBUG' for diagnostics)\n");

     }

     lzo_uint in_len;
     in_len = len;
     lzo_memset(in, 0, in_len);
     lzo_uint out_len;

     int r;

     r = lzo1x_1_compress((unsigned char*)in, in_len, (unsigned char*)out, &out_len, wrkmem);
     char mess[256];

     if (r == LZO_E_OK)
     {
         sprintf_s(mess, sizeof(mess),  "压缩成功！\n\n原文件大小：%lu bytes\n压缩后大小：%lu bytes\n\n解压得到的文件“compress.txt”保存于工程目录下",
             (unsigned long)in_len, (unsigned long)out_len);
         MessageBox(CString(mess));

     }
     else
     {
         /* this should NEVER happen */
         sprintf_s(mess, sizeof(mess), "压缩失败!\n %d\n", r);
         MessageBox(CString(mess));
     }
     /* check for an incompressible block */
     if (out_len >= in_len)
     {
         sprintf_s(mess, sizeof(mess), "未压缩！\n");
         MessageBox(CString(mess));
     }

     err = fopen_s(&ofp, ".\\compress.txt", "wb");
     fwrite(out, sizeof(char), out_len, ofp);

     fclose(ifp);
     fclose(ofp);
     free(cpTemp);
     free(out);
     free(textPath);

 }

（4）解压缩按钮

 void CcompressDlg::OnBnClickedButton2()
 {
     // TODO: 在此添加控件通知处理程序代码
 #ifdef _UNICODE
     LONG len1;
     len1 = WideCharToMultiByte(CP_ACP, 0, path_decompress, -1, NULL, 0, NULL, NULL);
     char *textPath = (char *)malloc(sizeof(char)*(len1 + 1));
     memset(textPath, 0, len1 + 1);
     WideCharToMultiByte(CP_ACP, 0, path_decompress, -1, textPath, len1 + 1, NULL, NULL);
 #else
     ptr = new char[str.GetAllocLength() + 1];
 #endif
     err = fopen_s(&ifp, textPath, "rb");
     if (err == 0)
     {
         printf("Thefile'crt_fopen_s.c'was opened\n");
     }
     fseek(ifp, 0, SEEK_END);
     unsigned long len = ftell(ifp);
     fseek(ifp, 0, SEEK_SET);
     cpTemp = (char*)malloc(len * sizeof(char));
     fread(cpTemp, sizeof(char), len, ifp);
     char *in = cpTemp;
     char *out = (char *)malloc(len*100* sizeof(char));
     memset(out, 0, len * 100 * sizeof(char));

     int r;
     lzo_uint new_len;
     r = lzo1x_decompress((unsigned char*)in, len, (unsigned char*)out, &new_len, NULL);

     char mess[256];
     if (r == LZO_E_OK && new_len == myInLen)
     {
         sprintf_s(mess, sizeof(mess), "解压成功！\n\n待解压文件大小： %lu bytes\n解压后文件大小： %lu bytes\n\n解压得到的文件“decompress.txt”保存于工程目录下",
             (unsigned long)len, (unsigned long)new_len);
         MessageBox(CString(mess));
     }
     else
     {
         /* this should NEVER happen */
         sprintf_s(mess, sizeof(mess), "解压失败！ %d\n", r);
         MessageBox(CString(mess));
     }
     err = fopen_s(&ofp, ".\\decompress.txt", "wt+");
     fwrite(out, sizeof(char), new_len, ofp);

     fclose(ifp);
     fclose(ofp);
     free(cpTemp);
     free(textPath);
     free(out);
 }

 void CcompressDlg::OnBnClickedButton2()
 {
     // TODO: 在此添加控件通知处理程序代码
 #ifdef _UNICODE
     LONG len1;
     len1 = WideCharToMultiByte(CP_ACP, 0, path_decompress, -1, NULL, 0, NULL, NULL);
     char *textPath = (char *)malloc(sizeof(char)*(len1 + 1));
     memset(textPath, 0, len1 + 1);
     WideCharToMultiByte(CP_ACP, 0, path_decompress, -1, textPath, len1 + 1, NULL, NULL);
 #else
     ptr = new char[str.GetAllocLength() + 1];
 #endif
     err = fopen_s(&ifp, textPath, "rb");
     if (err == 0)
     {
         printf("Thefile'crt_fopen_s.c'was opened\n");
     }
     fseek(ifp, 0, SEEK_END);
     unsigned long len = ftell(ifp);
     fseek(ifp, 0, SEEK_SET);
     cpTemp = (char*)malloc(len * sizeof(char));
     fread(cpTemp, sizeof(char), len, ifp);
     char *in = cpTemp;
     char *out = (char *)malloc(len*100* sizeof(char));
     memset(out, 0, len * 100 * sizeof(char));

     int r;
     lzo_uint new_len;
     r = lzo1x_decompress((unsigned char*)in, len, (unsigned char*)out, &new_len, NULL);

     char mess[256];
     if (r == LZO_E_OK && new_len == myInLen)
     {
         sprintf_s(mess, sizeof(mess), "解压成功！\n\n待解压文件大小： %lu bytes\n解压后文件大小： %lu bytes\n\n解压得到的文件“decompress.txt”保存于工程目录下",
             (unsigned long)len, (unsigned long)new_len);
         MessageBox(CString(mess));
     }
     else
     {
         /* this should NEVER happen */
         sprintf_s(mess, sizeof(mess), "解压失败！ %d\n", r);
         MessageBox(CString(mess));
     }
     err = fopen_s(&ofp, ".\\decompress.txt", "wt+");
     fwrite(out, sizeof(char), new_len, ofp);

     fclose(ifp);
     fclose(ofp);
     free(cpTemp);
     free(textPath);
     free(out);
 }

界面效果如图所示：

之后选择压缩文件路径进行压缩即可得到压缩和解压目的