C++ 使用STL string 实现的split，trim，replace-修订

使用python的时候默认str 对字符串操作支持非常丰富，相信每个C++程序员都自己写过string的strim、split、replace，
写个小工具函数，留着用，以前偷懒，写了好几次，这次总结一下，贴出来。

#include <iostream>
#include <vector>
using namespace std;

namespace strtool {
string trim(const string& str) {
string::size_type pos = str.find_first_not_of(' ');
if (pos == string::npos) {
return str;
}
string::size_type pos2 = str.find_last_not_of(' ');
if (pos2 != string::npos) {
return str.substr(pos, pos2 - pos + 1);
}
return str.substr(pos);
}

int split(const string& str, vector<string>& ret_, string sep = ",") {
if (str.empty()) {
return 0;
}

string tmp;
string::size_type pos_begin = str.find_first_not_of(sep);
string::size_type comma_pos = 0;

while (pos_begin != string::npos) {
comma_pos = str.find(sep, pos_begin);
if (comma_pos != string::npos) {
tmp = str.substr(pos_begin, comma_pos - pos_begin);
pos_begin = comma_pos + sep.length();
} else {
tmp = str.substr(pos_begin);
pos_begin = comma_pos;
}

if (!tmp.empty()) {
ret_.push_back(tmp);
tmp.clear();
}
}
return 0;
}

string replace(const string& str, const string& src, const string& dest) {
string ret;

string::size_type pos_begin = 0;
string::size_type pos = str.find(src);
while (pos != string::npos) {
cout << "replacexxx:" << pos_begin << " " << pos << "\n";
ret.append(str.data() + pos_begin, pos - pos_begin);
ret += dest;
pos_begin = pos + 1;
pos = str.find(src, pos_begin);
}
if (pos_begin < str.length()) {
ret.append(str.begin() + pos_begin, str.end());
}
return ret;
}

}

int main(int argc, char* argv[]) {
cout << strtool::trim(" nihao ") << "\n";

vector<string> vt;
strtool::split(",o h,,,nice,,,,,,,", vt);
for (size_t i = 0; i < vt.size(); ++i) {
cout << "out:" << vt[i] << "\n";
}

string ret = strtool::replace("xxAxxxAxxAxx", "A", "B");
cout << "replace:" << ret << "\n";
return 0;
}