C中的SQLite及其支持的REGEXP

我正在

C

中使用

sqlite3

，我想添加对

REGEXP

操作符的支持。默认情况下，用户定义的函数

regexp（）

不存在，调用

regexp

通常会导致错误（根据SQLite页面）

如何添加

regexp

函数以支持

regexp

？我大概会通过

sqlite3\u create\u函数

调用来实现这一点，但我不知道应用程序定义的

regexp（）

会是什么样子

我可以将

regex.h

中的函数与

sqlite3\u create\u函数一起使用吗？如何使用？我传递给SQLite的任何函数都必须接受三个类型为sqlite3_context*、int、sqlite3_value**的参数。然而，SQLite文档似乎没有解释这些参数的含义

是否有

C

regexp（）

函数的示例代码

---

我在谷歌或SQLite页面上找不到太多关于这方面的信息。

它看起来像这样：

static void user_regexp(sqlite3_context *context, int argc, sqlite3_value **argv)
{
    struct re_pattern_buffer buffer;
    const char *out;
    char *pattern;
    char *input_string;
    char *result;
    struct re_registers regs;

    if ((sqlite3_value_type(argv[0]) != SQLITE_TEXT )
         || ((sqlite3_value_type(argv[1]) != SQLITE_TEXT ))
    {
        sqlite3_result_err("Improper argument types");
        return;
    }

    re_set_syntax(RE_SYNTAX_POSIX_EGREP);
    memset(&buffer, 0, sizeof (buffer));
    if (!(pattern = strdupa(sqlite3_value_text(argv[0])))
        || !(input_string = strdupa(sqlite3_value_text(argv[1]))))
    {
        sqlite3_result_err_nomem("Could not allocate memory for strings");
        return;
    }

    if ((out = re_compile_pattern(pattern, strlen(pattern), &buffer))
    {
        sqlite3_result_err("Could not compile pattern!");
        return;
    }

    if (re_match(&buffer, input_string, strlen(input_string), 0, &regs) < 0) 
        sqlite3_result_int64(context, 0);
    else 
    {
        result = strndupa(input_string + regs.start[0], regs.end[0] - regs.start[0]);    
        sqlite3_result_text(context, result, NULL, SQLITE_TRANSIENT);
    }
}

static void user\u regexp（sqlite3\u context*context，int argc，sqlite3\u值**argv）
{
结构模式缓冲区；
const char*out；
字符*模式；
字符*输入字符串；
字符*结果；
结构寄存器regs；
如果（（sqlite3值类型（argv[0]）！=SQLITE文本）
||（（sqlite3_值_类型（argv[1]）！=SQLITE_文本））
{
sqlite3_result_err（“不正确的参数类型”）；
返回；
}
re_集合_语法（re_语法_POSIX_EGREP）；
memset（&buffer，0，sizeof（buffer））；
if（！（pattern=strdupa（sqlite3\u value\u text（argv[0]））
||！（输入字符串=strdupa（sqlite3值文本（argv[1]））
{
sqlite3_result_err_nomem（“无法为字符串分配内存”）；
返回；
}
if（（out=re_compile_pattern（pattern，strlen（pattern），&buffer））
{
sqlite3_result_err（“无法编译模式！”）；
返回；
}
if（重新匹配（&buffer，输入字符串，strlen（输入字符串），0，®s）<0）
sqlite3_result_int64（上下文，0）；
其他的
{
结果=strndupa（输入字符串+regs.start[0]，regs.end[0]-regs.start[0]）；
sqlite3_结果_文本（上下文、结果、空、SQLITE_瞬态）；
}
}

您也可以尝试以下方法：

#include <regex.h>

---

好的，对此有点晚了，但是我想把这篇文章发给所有使用C++包装的人，就像我正在使用的C SQLite API一样。这个答案假设你使用SQLITCPP.

• 从安装windows二进制文件的Regex。这将为您提供足够的文件，即

  Regex.h

  包含文件和

  regex2.dll

  。请记住在项目中添加路径Regex.h，并在包含客户端可执行文件的文件夹中保留dll的副本
• 在构建之前，我们需要进行一些更改，将regex功能添加到

  SELECT

  查询中。为此，请从项目中打开

  数据库.cpp

  文件并
  • 包括windows正则表达式中的

    regex.h

    标题
  • 在包含所有内容之后，在下面添加一段代码（当然，您可以自定义以满足您的需要！）

    extern "C" {
    void sqlite_regexp(sqlite3_context* context, int argc, sqlite3_value** values) {
    int ret;
    regex_t regex;
    char regtext[100];
    char* reg = (char*)sqlite3_value_text(values[0]);
    sprintf(regtext, ".*%s.*", reg);
    //printf("Regtext : %s", regtext);
    char* text = (char*)sqlite3_value_text(values[1]);
    /*  printf("Text : %s\n", text);
    printf("Reg : %s\n", reg); */
    if (argc != 2 || reg == 0 || text == 0) {
        sqlite3_result_error(context, "SQL function regexp() called with invalid arguments.\n", -1);
        return;
    }
    
    ret = regcomp(&regex, regtext, REG_EXTENDED | REG_NOSUB | REG_ICASE);
    if (ret != 0) {
        sqlite3_result_error(context, "error compiling regular expression", -1);
        return;
    }
    
    ret = regexec(&regex, text, 0, NULL, 0);
    /*  if (ret == 0) {
    printf("Found a match. Press any key to continue");
    getc(stdin);
    }*/
    regfree(&regex);
    
    sqlite3_result_int(context, (ret != REG_NOMATCH));
    }
    }
    

  • 现在是更改文件中定义的构造函数的时候了

    // Open the provided database UTF-8 filename with SQLite::OPEN_xxx provided flags.
    Database::Database(const char* apFilename,
    const int   aFlags /*= SQLite::OPEN_READONLY*/,
    const int   aBusyTimeoutMs/* = 0 */,
    const char* apVfs/*= NULL*/) :
    mpSQLite(NULL),
    mFilename(apFilename)
    {
    const int ret = sqlite3_open_v2(apFilename, &mpSQLite, aFlags, apVfs);
    //std::cout << "Reached here";
    //sqlite3_create_function_v2(mpSQLite, "REGEXP", 2, SQLITE_ANY,&sqlite_regexp, NULL, NULL, NULL,NULL);
    sqlite3_create_function(mpSQLite, "regexp", 2, SQLITE_ANY, 0, &sqlite_regexp, 0, 0);
    if (SQLITE_OK != ret)
    {
    const SQLite::Exception exception(mpSQLite, ret); // must create before closing
    sqlite3_close(mpSQLite); // close is required even in case of error on opening
    throw exception;
    }
    else {
    
    }
    if (aBusyTimeoutMs > 0)
    {
    setBusyTimeout(aBusyTimeoutMs);
    }
    }
    
    // Open the provided database UTF-8 filename with SQLite::OPEN_xxx provided flags.
    Database::Database(const std::string& aFilename,
    const int          aFlags     /*    = SQLite::OPEN_READONLY*/,
    const int          aBusyTimeoutMs/*  = 0*/,
    const std::string& aVfs/* = "" */) :
    mpSQLite(NULL),
    mFilename(aFilename)
    {
    
    const int ret = sqlite3_open_v2(aFilename.c_str(), &mpSQLite, aFlags, aVfs.empty() ? NULL : aVfs.c_str());
    sqlite3_create_function(mpSQLite, "regexp", 2, SQLITE_ANY, 0, &sqlite_regexp, 0, 0);
    if (SQLITE_OK != ret)
    {
    const SQLite::Exception exception(mpSQLite, ret); // must create before closing
    sqlite3_close(mpSQLite); // close is required even in case of error on opening
    throw exception;
    }
    if (aBusyTimeoutMs > 0)
    {
    setBusyTimeout(aBusyTimeoutMs);
    }
    }
    

  ---

  ---

  注意：这假设数据库与您的cpp在同一个文件夹中
  这里解释了用户函数的内容：@mu：谢谢，这是我第一次去的地方。当您在这里时-用户函数可以返回什么整数值？或者它们必须是空的吗？所有原型都有

  void

  返回，所以可能有这么多告诉我如何报道“真实”通过

  sqlite3\u context

  参数返回值。@mu:谢谢，我可能就快到了。看起来我必须在

  regex

  方法结束时调用

  sqlite3\u result\u int

  来通知

  SQLite

  结果。虽然我可能在这里错了。我刚刚看到这个问题出现，可能对您有用：

  extern "C" {
  void sqlite_regexp(sqlite3_context* context, int argc, sqlite3_value** values) {
  int ret;
  regex_t regex;
  char regtext[100];
  char* reg = (char*)sqlite3_value_text(values[0]);
  sprintf(regtext, ".*%s.*", reg);
  //printf("Regtext : %s", regtext);
  char* text = (char*)sqlite3_value_text(values[1]);
  /*  printf("Text : %s\n", text);
  printf("Reg : %s\n", reg); */
  if (argc != 2 || reg == 0 || text == 0) {
      sqlite3_result_error(context, "SQL function regexp() called with invalid arguments.\n", -1);
      return;
  }
  
  ret = regcomp(&regex, regtext, REG_EXTENDED | REG_NOSUB | REG_ICASE);
  if (ret != 0) {
      sqlite3_result_error(context, "error compiling regular expression", -1);
      return;
  }
  
  ret = regexec(&regex, text, 0, NULL, 0);
  /*  if (ret == 0) {
  printf("Found a match. Press any key to continue");
  getc(stdin);
  }*/
  regfree(&regex);
  
  sqlite3_result_int(context, (ret != REG_NOMATCH));
  }
  }
  

  // Open the provided database UTF-8 filename with SQLite::OPEN_xxx provided flags.
  Database::Database(const char* apFilename,
  const int   aFlags /*= SQLite::OPEN_READONLY*/,
  const int   aBusyTimeoutMs/* = 0 */,
  const char* apVfs/*= NULL*/) :
  mpSQLite(NULL),
  mFilename(apFilename)
  {
  const int ret = sqlite3_open_v2(apFilename, &mpSQLite, aFlags, apVfs);
  //std::cout << "Reached here";
  //sqlite3_create_function_v2(mpSQLite, "REGEXP", 2, SQLITE_ANY,&sqlite_regexp, NULL, NULL, NULL,NULL);
  sqlite3_create_function(mpSQLite, "regexp", 2, SQLITE_ANY, 0, &sqlite_regexp, 0, 0);
  if (SQLITE_OK != ret)
  {
  const SQLite::Exception exception(mpSQLite, ret); // must create before closing
  sqlite3_close(mpSQLite); // close is required even in case of error on opening
  throw exception;
  }
  else {
  
  }
  if (aBusyTimeoutMs > 0)
  {
  setBusyTimeout(aBusyTimeoutMs);
  }
  }
  
  // Open the provided database UTF-8 filename with SQLite::OPEN_xxx provided flags.
  Database::Database(const std::string& aFilename,
  const int          aFlags     /*    = SQLite::OPEN_READONLY*/,
  const int          aBusyTimeoutMs/*  = 0*/,
  const std::string& aVfs/* = "" */) :
  mpSQLite(NULL),
  mFilename(aFilename)
  {
  
  const int ret = sqlite3_open_v2(aFilename.c_str(), &mpSQLite, aFlags, aVfs.empty() ? NULL : aVfs.c_str());
  sqlite3_create_function(mpSQLite, "regexp", 2, SQLITE_ANY, 0, &sqlite_regexp, 0, 0);
  if (SQLITE_OK != ret)
  {
  const SQLite::Exception exception(mpSQLite, ret); // must create before closing
  sqlite3_close(mpSQLite); // close is required even in case of error on opening
  throw exception;
  }
  if (aBusyTimeoutMs > 0)
  {
  setBusyTimeout(aBusyTimeoutMs);
  }
  }
  

  #include <iostream>
  #include <cstdio>
  #include <cstdlib>
  #include <string>
  #include <SQLiteCpp/SQLiteCpp.h>
  #include <SQLiteCpp/VariadicBind.h>
  // Notice no sqlite3.h huh?
  // Well, this is a C++ wrapper for the SQLITE CAPI afterall.
  
  #ifdef SQLITECPP_ENABLE_ASSERT_HANDLER
  namespace SQLite
  {
  /// definition of the assertion handler enabled when SQLITECPP_ENABLE_ASSERT_HANDLER is defined in the project (CMakeList.txt)
  void assertion_failed(const char* apFile, const long apLine, const char* apFunc, const char* apExpr, const char* apMsg)
  {
  // Print a message to the standard error output stream, and abort the program.
  std::cerr << apFile << ":" << apLine << ":" << " error: assertion failed (" << apExpr << ") in " << apFunc << "() with message \"" << apMsg << "\"\n";
  std::abort();
  }
  }
  #endif
  
  /// Get example path
  static inline std::string getExamplePath()
  {
  std::string filePath(__FILE__);
  return filePath.substr(0, filePath.length() - std::string("Client.cpp").length());
  }
  
  /// Example Database
  static const std::string filename_example_db3 = getExamplePath() + "/example.db3";
  /// Image
  static const std::string filename_logo_png = getExamplePath() + "/logo.png";
  
  
  /// Object Oriented Basic example
  class Example
  {
  public:
  //Constructor
  Example() :
  mDb(filename_example_db3),
  // User change the db and tables accordingly
  mQuery(mDb, "SELECT id,name FROM lookup WHERE name REGEXP :keyword")
  // Open a database file in readonly mode
  {       
  }
  virtual ~Example()
  {
  }
  
  /// List the rows where the "weight" column is greater than the provided aParamValue
  void namehaskeyword(const std::string searchfor)
  {
  std::cout << "Matching results for " << searchfor << "\n";
  
  // Bind the integer value provided to the first parameter of the SQL query
  mQuery.bind(1,searchfor); // same as mQuery.bind(1, aParamValue);
  
   // Loop to execute the query step by step, to get one a row of results at a time
  while (mQuery.executeStep())
  {
  std::cout<<mQuery.getColumn(0) << "\t" << mQuery.getColumn(1) << "\n";
  }
  
  // Reset the query to be able to use it again later
  mQuery.reset();
  }
  
  private:
  SQLite::Database    mDb;    ///< Database connection
  SQLite::Statement   mQuery; ///< Database prepared SQL query
  };
  
  int main()
  {
  // Using SQLITE_VERSION would require #include <sqlite3.h> which we want to avoid: use SQLite::VERSION if possible.
  // std::cout << "SQlite3 version " << SQLITE_VERSION << std::endl;
  std::cout << "SQlite3 version " << SQLite::VERSION << " (" << SQLite::getLibVersion() << ")" << std::endl;
  std::cout << "SQliteC++ version " << SQLITECPP_VERSION << std::endl;
  
  try
  {
  // Doing  a regex query.
  Example example;
  char wannaquit = 'n';
  std::string keyword;
  // Deliberate unlimited loop. You implement something sensible here.
  while (wannaquit != 'y') {
  // Demonstrates the way to use the same query with different parameter values
  std::cout << "Enter the keyword to search for : ";
  std::getline(std::cin, keyword);
  example.namehaskeyword(keyword);
  }
  }
  catch (std::exception& e)
  {
  std::cout << "SQLite exception : " << e.what() << std::endl;
  return EXIT_FAILURE; // unexpected error : exit the example program
  }
  return EXIT_SUCCESS;
  }