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StringUtils.sol 3.34 KB
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Robert Muth committed
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pragma solidity >=0.5.0 <0.6.0;

// Source: https://github.com/ethereum/dapp-bin/blob/master/library/stringUtils.sol

/* The MIT License (MIT)

Copyright (c) 2014 

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



Modifications by muth@tu-berlin.de:
- Added function modifiers for Solidity ^0.5 compatibility 

*/

library StringUtils {
    /// @dev Does a byte-by-byte lexicographical comparison of two strings.
    /// @return a negative number if `_a` is smaller, zero if they are equal
    /// and a positive numbe if `_b` is smaller.
    function compare(string memory _a, string memory _b) public pure returns (int) {
        bytes memory a = bytes(_a);
        bytes memory b = bytes(_b);
        uint minLength = a.length;
        if (b.length < minLength) minLength = b.length;
        //@todo unroll the loop into increments of 32 and do full 32 byte comparisons
        for (uint i = 0; i < minLength; i ++)
            if (a[i] < b[i])
                return -1;
            else if (a[i] > b[i])
                return 1;
        if (a.length < b.length)
            return -1;
        else if (a.length > b.length)
            return 1;
        else
            return 0;
    }
    /// @dev Compares two strings and returns true iff they are equal.
    function equal(string memory _a, string memory _b) public pure returns (bool) {
        return compare(_a, _b) == 0;
    }
    /// @dev Finds the index of the first occurrence of _needle in _haystack
    function indexOf(string memory _haystack, string memory _needle) public pure returns (int)
    {
    	bytes memory h = bytes(_haystack);
    	bytes memory n = bytes(_needle);
    	if(h.length < 1 || n.length < 1 || (n.length > h.length)) 
    		return -1;
    	else if(h.length > (2**128 -1)) // since we have to be able to return -1 (if the char isn't found or input error), this function must return an "int" type with a max length of (2^128 - 1)
    		return -1;									
    	else
    	{
    		uint subindex = 0;
    		for (uint i = 0; i < h.length; i ++)
    		{
    			if (h[i] == n[0]) // found the first char of b
    			{
    				subindex = 1;
    				while(subindex < n.length && (i + subindex) < h.length && h[i + subindex] == n[subindex]) // search until the chars don't match or until we reach the end of a or b
    				{
    					subindex++;
    				}	
    				if(subindex == n.length)
    					return int(i);
    			}
    		}
    		return -1;
    	}	
    }
}