[C/C++11]_[初级]_[使用正则表达式库进行分组查询]

场景

1.正则表达式在查询替换字符串数据时效率很高, 可以节省很多不必要的查询代码. 特别是对字符串分组的查询, 可以说如果没有正则表达式,查询分组里的字符串需要写很多额外的代码，还不一定准确.

2.查询并替换XML标签是比较常见的需求, 比如过滤掉HTML标签里的标签, 提取字符串内容等.

例子

1.这里举例了C++正则库的分组查询功能, 一个用于提取特定字符串, 一个用于替换字符串.

// test-regexp.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <regex>
#include <iostream>

std::wstring PickLinkShowContent(const wchar_t* buf1){

std::wstring buf(buf1);
std::wregex pattern(L"(<A HREF=\"[^\"]*\">)([^<]*)(</A>)",
std::regex_constants::ECMAScript|std::regex_constants::icase);
auto words_begin =
std::wsregex_iterator(buf.begin(), buf.end(), pattern);
auto words_end = std::wsregex_iterator();

std::wstring result;
int start = 0;
int end = 0;
for (std::wsregex_iterator i = words_begin; i != words_end; ++i)
{
std::wsmatch match = *i;
size_t pos = match.position();
size_t length = match.length();

std::wstring prev = buf.substr(start,pos-start);

result.append(prev);
result.append(match[2]);
end = pos+length;
start = pos+length;
}

if(end+1 != buf.length()){
result.append(buf.substr(end));
}
return result;
}

std::string ReplaceStr(const char* text,const char* old,const char* _new){
std::regex pattern(old);
std::string rep(_new);
std::string text1(text);
std::string tmp = std::regex_replace(text1,pattern,rep);
return tmp;
}

int _tmain(int argc, _TCHAR* argv[])
{
std::cout << "Test regex group 1" << std::endl;
const wchar_t* buf = L"You haven't installed QQPCMgr on this computer. "
L"Please <a HREF=\"http://www.qq.com\">download</A> and install the latest QQPCMgr first, "
L"then reboot the program.";
auto result = PickLinkShowContent(buf);
std::wcout << result << std::endl;

std::cout << "Test regex group 2" << std::endl;
static const char* buf2 = ""
"<key>name</key>"
"<string>百度</string><key>position</key>"
"<string>2</string>"
"</dict>"
"<key>05975BCB-FD95-48A4-A912-37ECACD39871</key>"
"<dict>"
"<key>name</key>"
"<string>必应</string>"
"<key>url</key>"
"<string>http://www.bing.com/</string>"
"<key>position</key>"
"<string>3</string>";

auto result2 = ReplaceStr(buf2,"(<key>position</key>[^<]*)(<string>)([0-9]*)(</string>)",
"$1<integer>$3</integer>");
std::cout << result2 << std::endl;
system("pause");
return 0;
}

````

输出

<div class="se-preview-section-delimiter"></div>

``` XML
Test regex group 1
You haven't installed QQPCMgr on this computer. Please download and install the
latest QQPCMgr first, then reboot the program.
Test regex group 2
<key>name</key><string>百度</string><key>position</key><integer>2</integer></dic
t><key>05975BCB-FD95-48A4-A912-37ECACD39871</key><dict><key>name</key><string>必
应</string><key>url</key><string>http://www.bing.com/</string><key>position</key
><integer>3</integer>

参考

std::regex_replace

使用正则表达式库regex