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8d054f4 Sep 28, 2015
56 lines (55 sloc) 2 KB
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 _a, string _b) 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 _a, string _b) returns (bool) {
return compare(_a, _b) == 0;
}
/// @dev Finds the index of the first occurrence of _needle in _haystack
function indexOf(string _haystack, string _needle) 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;
}
}
}