Utils.h

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#include "../../Scripting.h"
 
namespace Gorgon { namespace Scripting { namespace Compilers {
 
    template<class ...P_>
    int CheckInputFor(const std::string &input, int &ch, P_ ...args) {
        char allowed[] = {args...};
        int elements = sizeof...(args);
        
        auto errstr = [&] ()-> std::string {
            std::string ret = "Expected ";
            for(int i = 0; i < elements; i++) {
                if(i != 0) {
                    ret.push_back('/');
                }
                ret.push_back(allowed[i]);
            }
            
            return ret;
        };
        
        if((int)input.length() <= ch) {
            throw ParseError({ExceptionType::UnexpectedToken, errstr() + ", end of string encountered.", ch, 0});
        }
        
        char c = input[ch++];
        
        for(int i = 0; i < sizeof...(args); i++) {
            if(allowed[i] == c) {
                return i;
            }
        }
        
        ch--;
        throw ParseError({ExceptionType::UnexpectedToken, errstr() + ", found: " + input.substr(ch, 1), ch, 0});
    }
    
    inline std::string ExtractQuotes(const std::string &input, int &ch) {
        std::string ret = "";
        
        int quotes = CheckInputFor(input, ch, '\'', '"') + 1;
        
        int start = ch;
        
        bool escape = false;
        int escapenum = 0;
        Gorgon::Byte num;
        for(; ch < (int)input.size(); ch++) {
            char c = input[ch];
            if(escape) {
                if(c == '"') {
                    ret.push_back('"');
                }
                else if(c == '\'') {
                    ret.push_back('\'');
                }
                else if(c == '\\') {
                    ret.push_back('\\');
                }
                else if(c == 'n') {
                    ret.push_back('\n');
                }
                else if(c == 't') {
                    ret.push_back('\t');
                }
                else if(c >= '0' && c <= '9') {
                    escapenum++;
                    num = (num << 4) + (c - '0');
                }
                else if(tolower(c) >= 'a' && tolower(c) <= 'f') {
                    escapenum++;
                    num = (num << 4) + (tolower(c) - 'a' + 10);
                }
                else {
                    throw ParseError{ExceptionType::UnexpectedToken, "Invalid escape sequence: \\" + input.substr(ch, 1), ch, 0};
                }
                
                if(escapenum != 1) {
                    escape = false;
                }
                if(escapenum == 2) {
                    ret.push_back((char)num);
                    escapenum = 0;
                }
            }
            else {
                if(c == '\\') {
                    escape = true;
                    num = 0;
                }
                else if(c == '"' && quotes == 2) {
                    break;
                }
                else if(c == '\'' && quotes == 1) {
                    break;
                }
                else {
                    ret.push_back(c);
                }
            }
        }
        
        CheckInputFor(input, ch, quotes == 2 ? '"' : '\'');
        
        return ret;
    }
    
} } }