add path.relative

lib/path.js

@@ -165,6 +165,64 @@ if (isWindows) {
     return exports.normalize(joined);
   };
 
+  // path.relative(from, to)
+  // it will solve the relative path from 'from' to 'to', for instance:
+  // from = 'C:\\orandea\\test\\aaa'
+  // to = 'C:\\orandea\\impl\\bbb'
+  // The output of the function should be: '..\\..\\impl\\bbb'
+  // windows version
+  exports.relative = function(from, to) {
+    from = exports.resolve(from);
+    to = exports.resolve(to);
+
+    // windows is not case sensitive
+    var lowerFrom = from.toLowerCase();
+    var lowerTo = to.toLowerCase();
+
+    function trim(arr) {
+      var start = 0;
+      for(;start < arr.length; start++) {
+        if (arr[start] !== '') break;
+      }
+
+      var end = arr.length - 1;
+      for(;end >= 0; end--) {
+        if (arr[end] !== '') break;
+      }
+
+      if (start > end) return [];
+      return arr.slice(start, end - start + 1);
+    }
+
+    var fromParts = trim(from.split('\\'));
+    var toParts = trim(to.split('\\'));
+
+    var lowerFromParts = trim(lowerFrom.split('\\'));
+    var lowerToParts = trim(lowerTo.split('\\'));
+
+    var length = Math.min(lowerFromParts.length, lowerToParts.length);
+    var samePartsLength = length;
+    for(var i = 0; i < length; i++) {
+      if (lowerFromParts[i] !== lowerToParts[i]) {
+        samePartsLength = i;
+        break;
+      }
+    }
+
+    if (samePartsLength == 0) {
+      return to;
+    }
+
+    var outputParts = [];
+    for(var i = samePartsLength; i < lowerFromParts.length; i++) {
+      outputParts.push('..');
+    }
+
+    outputParts = outputParts.concat(toParts.slice(samePartsLength));
+
+    return outputParts.join('\\');
+  };
+
 
 } else /* posix */ {
 
@@ -232,6 +290,51 @@ if (isWindows) {
       return p && typeof p === 'string';
     }).join('/'));
   };
+
+
+  // path.relative(from, to)
+  // posix version
+  exports.relative = function(from, to) {
+    from = exports.resolve(from).substr(1);
+    to = exports.resolve(to).substr(1);
+
+    function trim(arr) {
+      var start = 0;
+      for(;start < arr.length; start++) {
+        if (arr[start] !== '') break;
+      }
+
+      var end = arr.length - 1;
+      for(;end >= 0; end--) {
+        if (arr[end] !== '') break;
+      }
+
+      if (start > end) return [];
+      return arr.slice(start, end - start + 1);
+    }
+
+    var fromParts = trim(from.split('/'));
+    var toParts = trim(to.split('/'));
+
+    var length = Math.min(fromParts.length, toParts.length);
+    var samePartsLength = length;
+    for(var i = 0; i < length; i++) {
+      if (fromParts[i] !== toParts[i]) {
+        samePartsLength = i;
+        break;
+      }
+    }
+
+    var outputParts = [];
+    for(var i = samePartsLength; i < fromParts.length; i++) {
+      outputParts.push('..');
+    }
+
+    outputParts = outputParts.concat(toParts.slice(samePartsLength));
+
+    return outputParts.join('/');
+  };
+
 }
 
 

test/simple/test-path.js

@@ -147,3 +147,39 @@ resolveTests.forEach(function(test) {
   // assert.equal(actual, expected, message);
 });
 assert.equal(failures.length, 0, failures.join(''));
+
+// path.relative tests
+if (isWindows) {
+  // windows
+  var relativeTests =
+   // arguments                     result
+   [['c:/blah\\blah', 'd:/games',   'd:\\games'],
+    ['c:/aaaa/bbbb', 'c:/aaaa',     '..'],
+    ['c:/aaaa/bbbb', 'c:/cccc',     '..\\..\\cccc'],
+    ['c:/aaaa/bbbb', 'c:/aaaa/bbbb',''],
+    ['c:/aaaa/bbbb', 'c:/aaaa/cccc','..\\cccc'],
+    ['c:/aaaa/', 'c:/aaaa/cccc',    'cccc'],
+    ['c:/', 'c:\\aaaa\\bbbb',       'aaaa\\bbbb'],
+    ['c:/aaaa/bbbb', 'd:\\',        'd:\\']];
+} else {
+  // posix
+  var relativeTests =
+    // arguments                    result
+    [['/var/lib', '/var',           '..'],
+     ['/var/lib', '/bin',           '../../bin'],
+     ['/var/lib', '/var/lib',       ''],
+     ['/var/lib', '/var/apache',    '../apache'],
+     ['/var/', '/var/lib',          'lib'],
+     ['/', '/var/lib',              'var/lib']];
+}
+var failures = [];
+relativeTests.forEach(function(test) {
+  var actual = path.relative(test[0], test[1]);
+  var expected = test[2];
+  var message = 'path.relative(' + test.slice(0, 2).map(JSON.stringify).join(',') + ')' +
+                '\n  expect=' + JSON.stringify(expected) +
+                '\n  actual=' + JSON.stringify(actual);
+  if (actual !== expected) failures.push('\n' + message);
+});
+assert.equal(failures.length, 0, failures.join(''));
+