JSONTools.sol

pragma solidity ^0.4.1;

contract JSONTools{ 
 
	//try _extractString("[\"12345678\"]",0): gas usage 5192 
	function _extractString(bytes v, uint _start) constant returns (string val,uint i) {
        	uint start = 0;
        	uint end = 0;
		for (i=0;v.length > i;i++) {
		    if (v[i] == '"'){ //quotation mark   ---------> needed to break to reduce gas
			if(v[i-1] != '\\'){ //not escaped <------
				end = start == 0 ? 0: i;
				start = start == 0? i+1 : start;
				if(end > 0) break; 
			}
		    }
		}
		bytes memory str = new bytes(end-start);
		for(i=0; i<str.length; i++){
		    str[i] = v[start+i];
		}
		for(i=end+1; i<v.length; i++) if (v[i] == ','){ i++; break; } //end
		val = string(str);
	}

	//try _extractString2("[\"12345678\"]",0): gas usage 5405  
	function _extractString2(bytes v, uint _start) constant returns (string val,uint i) {
		uint start = 0;
		uint end = 0;
		for (i=0;v.length > i;i++) {
		    if (v[i] == '"' && (v[i-1] != '\\')){ //quotation mark and is not escaped ---------> consomes more gas
			end = start == 0 ? 0: i;
			start = start == 0? i+1 : start;
			if(end > 0) break; 
		    }
		}
		bytes memory str = new bytes(end-start);
		for(i=0; i<str.length; i++){
		    str[i] = v[start+i];
		}
		for(i=end+1; i<v.length; i++) if (v[i] == ','){ i++; break; } //end
		val = string(str);
	}
}