如何提取和删除std::字符串中的字符

"<RGB:255,0,0>this text is colored RED.<RGB:0,255,0> While this text is colored GREEN";

//this function is called after the loop that checks for the existence of '<'
void RGB_ExtractAndDelete(std::string& RGBformat, int index, RGB& rgb)
{
    int i = index + 5; //we are now next to character ':'
    std::string value;
    int toNumber;
    while (RGBformat[i] != ',')
    {
        value += RGBformat[i++];
    }
    ++i;
    std::stringstream(value) >> toNumber;
    rgb.R = toNumber;
    value = "";
    while (RGBformat[i] != ',')
    {
        value += RGBformat[i++];
    }
    ++i;
    std::stringstream(value) >> toNumber;
    value = "";
    rgb.G = toNumber;
    while (RGBformat[i] != '>')
    {
        value += RGBformat[i++];
    }
    ++i;
    std::stringstream(value) >> toNumber;
    value = "";
    rgb.B = toNumber;
    //I got the right result here which is
    //start: <, end: >
    printf("start: %c, end: %cn", RGBformat[index], RGBformat[i]);
    //but fail in this one
    //this one should erase from '<' until it finds '>'
    RGBformat.erase(index, i);
}

1. 使用std::str::find定位<RGB, :, ,和>。
2. 使用std::str::substr "cut out"字符串。
3. 添加if (!std::strinstream(value)>> toNumber) ...检查号码是否被实际接受。

像这样:

std::string::size_type index = std::RGBformat.find("<RGB");
if (index == std::string::npos)
{
    ... no "<RGB" found
}
std::string::size_type endAngle = std::RGBformat::find(">", index);
if (endAngle == std::string::npos)
{
    ... no ">" found... 
}
std::string::size_type comma = std::RGBformat.find(",", index); 
if (comma == std::string::npos && comma < endAngle)
{
    ... no "," found ... 
}
std::string value = RGBformat.substr(index, comma-index-1);
std::stringstream(value) >> toNumber;
value = "";
rgb.R = toNumber;
std::string::size_type comma2 = std::RGBformat.find(",", comma+1); 
if (comma2 == std::string::npos && comma2 < endAngle)
 ...

请注意，这可能看起来比您当前的代码更笨拙，但它的优点是更安全。如果有人将"<RGB:55> .... "传递到你现有的代码中，它就会崩溃，因为它会一直运行，直到你感到无聊并按下一个键来停止它，或者它崩溃，无论哪个先发生……

如果您可以使用Boost或c++ 11，那么这里确实是正则表达式的完美场所。

你可以用"\<RGB:(\d{1,3}),(\d{1,3}),(\d{1,3})\>"来匹配你的颜色说明符——或者如果你有c++ 11的原始字符串文字，你可以把它写成R"rx(<RGB:(d{1,3}),(d{1,3}),(d{1,3})>)rx"。

用

解析

std::getline

http://en.cppreference.com/w/cpp/string/basic_string/getline

此函数接受分隔符(例如:'<'或'>')作为第三个参数。例如:

基本c++程序，getline()/解析文件

这里有一个修改后的代码，当我不能使用regexp时，我使用它从html中提取文本并从html标记中检索数据。否则，我建议你使用正则表达式，它们更容易设置。

在我的代码中，我以"结束我的标签，颜色为"<RGB:255,0,0> my text"。

希望对你有帮助!

#include <iostream>
#include <string>
#include <vector>
#include <cstdlib>

using namespace std;
typedef struct{
    string text;
    uint8_t r;
    uint8_t g;
    uint8_t b;
}TextInfo;
vector<TextInfo> vect;
const vector<TextInfo> & extractInfos(const string & str){
    string newStr = str;
    vect.clear();
    do{
        TextInfo info;
        int index = newStr.find('>');
        if(index != -1 && newStr.find('<') == 0){
            // We get "<RGB:r,g,b>"
            string color = newStr.substr(0,index+1);
            // We extract red color
            string red = color.substr(color.find(':') + 1, color.find(',') - color.find(':') - 1);
            // We get "g,b>"
            color = color.substr(color.find(',') + 1, color.length() - color.find(','));
            // We extract green color
            string green = color.substr(0,color.find(','));
            // We extract "b>"
            color = color.substr(color.find(',') + 1, color.length() - color.find('>'));
            // We get blue color;
            string blue = color.substr(0,color.find('>'));
            // string to int into a uint8_t
            info.r = atoi(red.c_str());
            info.g = atoi(green.c_str());
            info.b = atoi(blue.c_str());
            // We remove the "<RGB:r,g,b>" part from the string
            newStr = newStr.substr(index+1,newStr.length()-index);
            index = newStr.find("</>");
            // We get the text associated to the color just extracted
            info.text = newStr.substr(0,index);
            // We remove the "</>" that ends the color
            newStr = newStr.substr(index+3,newStr.length()-(index+2));
        }else{
            // We extract the string to the next '<' or to the end if no other color is set
            int i = newStr.find('<');
            if(i == -1){
                i=newStr.length();
            }
            info.text = newStr.substr(0,i);
            info.r = 0;
            info.g = 0;
            info.b = 0; // No color then we put default to black
            // We get the new part of the string without the one we just exctacted
            newStr = newStr.substr(i, newStr.length() - i);
        }
        // We put the data into a vector
        vect.push_back(info);
    }while(newStr.length() != 0); // We do it while there is something to extract
    return vect;
}

int main(void){
    vector<TextInfo> myInfos = extractInfos("<RGB:255,0,0>String to red</><RGB:0,255,0>Green string</>Default color string");
    for(vector<TextInfo>::iterator itr = myInfos.begin();itr != myInfos.end();itr++){
        cout << (*itr).text << endl;
    }
    return 0;
}