1 files changed, 101 insertions, 0 deletions
diff --git a/libdevcore/StringUtils.cpp b/libdevcore/StringUtils.cpp
new file mode 100644
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--- /dev/null
+++ b/libdevcore/StringUtils.cpp
@@ -0,0 +1,101 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/** @file StringUtils.h
+ * @author Balajiganapathi S <balajiganapathi.s@gmail.com>
+ * @date 2017
+ *
+ * String routines
+ */
+
+#include "StringUtils.h"
+#include <algorithm>
+#include <string>
+#include <vector>
+
+using namespace std;
+using namespace dev;
+
+bool dev::stringWithinDistance(string const& _str1, string const& _str2, size_t _maxDistance)
+{
+	if (_str1 == _str2)
+		return true;
+
+	size_t n1 = _str1.size();
+	size_t n2 = _str2.size();
+	size_t distance = stringDistance(_str1, _str2);
+
+	// if distance is not greater than _maxDistance, and distance is strictly less than length of both names, they can be considered similar
+	// this is to avoid irrelevant suggestions
+	return distance <= _maxDistance && distance < n1 && distance < n2;
+}
+
+size_t dev::stringDistance(string const& _str1, string const& _str2)
+{
+	size_t n1 = _str1.size();
+	size_t n2 = _str2.size();
+	// Optimize by storing only last 2 rows and current row. So first index is considered modulo 3
+	// This is a two-dimensional array of size 3 x (n2 + 1).
+	vector<size_t> dp(3 * (n2 + 1));
+
+	// In this dp formulation of Damerau–Levenshtein distance we are assuming that the strings are 1-based to make base case storage easier.
+	// So index accesser to _name1 and _name2 have to be adjusted accordingly
+	for (size_t i1 = 0; i1 <= n1; ++i1)
+		for (size_t i2 = 0; i2 <= n2; ++i2)
+		{
+			size_t x = 0;
+			if (min(i1, i2) == 0) // base case
+				x = max(i1, i2);
+			else
+			{
+				size_t left = dp[(i1 - 1) % 3 + i2 * 3];
+				size_t up = dp[(i1 % 3) + (i2 - 1) * 3];
+				size_t upleft = dp[((i1 - 1) % 3) + (i2 - 1) * 3];
+				// deletion and insertion
+				x = min(left + 1, up + 1);
+				if (_str1[i1-1] == _str2[i2-1])
+					// same chars, can skip
+					x = min(x, upleft);
+				else
+					// different chars so try substitution
+					x = min(x, upleft + 1);
+
+				// transposing
+				if (i1 > 1 && i2 > 1 && _str1[i1 - 1] == _str2[i2 - 2] && _str1[i1 - 2] == _str2[i2 - 1])
+					x = min(x, dp[((i1 - 2) % 3) + (i2 - 2) * 3] + 1);
+			}
+			dp[(i1 % 3) + i2 * 3] = x;
+		}
+
+	return dp[(n1 % 3) + n2 * 3];
+}
+
+string dev::quotedAlternativesList(vector<string> const& suggestions)
+{
+	if (suggestions.empty())
+		return "";
+	if (suggestions.size() == 1)
+		return "\"" + suggestions.front() + "\"";
+
+	string choices = "\"" + suggestions.front() + "\"";
+	for (size_t i = 1; i + 1 < suggestions.size(); ++i)
+		choices += ", \"" + suggestions[i] + "\"";
+
+	choices += " or \"" + suggestions.back() + "\"";
+
+	return choices;
+}
+