Built-in JSON support

src/json-delay.js

+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+var $JSON = global.JSON;
+
+function IsValidJSON(s) {
+  // All empty whitespace is not valid.
+  if (/^\s*$/.test(s))
+    return false;
+ 
+  // This is taken from http://www.json.org/json2.js which is released to the
+  // public domain.
+  // Changes: We dissallow \u2028 Line separator and \u2029 Paragraph separator
+  // inside strings.  We also treat \u2028 and \u2029 as whitespace which they
+  // are in the RFC but IE and Safari does not match \s to these so we need to
+  // include them in the reg exps in all places where whitespace is allowed.

[Lasse Reichstein, 2009/04/23 15:28:49]

Is this our comment? 
Since Irregexp does include \u2028 and \u2029 in \s, we shouldn't need to add it
(as in [\s\u2028\u2029] below).

[Christian Plesner Hansen, 2009/04/24 08:11:22]

Good point.

+
+  var backslashesRe = /\\["\\\/bfnrtu]/g;
+  var simpleValuesRe =
+      /"[^"\\\n\r\u2028\u2029\x00-\x1f\x7f-\x9f]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g;
+  var openBracketsRe = /(?:^|:|,)(?:[\s\u2028\u2029]*\[)+/g;
+  var remainderRe = /^[\],:{}\s\u2028\u2029]*$/;
+
+  return remainderRe.test(s.replace(backslashesRe, '@').
+      replace(simpleValuesRe, ']').
+      replace(openBracketsRe, ''));  
+}
+
+function ParseJSONUnfiltered(text) {
+  var s = $String(text);
+  if (IsValidJSON(s)) {
+    try {
+      return global.eval('(' + s + ')');

[arv (Not doing code reviews), 2009/04/23 21:07:58]

I hope this is just a temporary solution. This solution is necessary in pure JS
but the whole point of moving JSON into the language was to get away from
relying on regualr expressions and eval.

[Christian Plesner Hansen, 2009/04/24 08:11:22]

That's not the reason I'm adding it but more to have JSON available without
having to send the code over the wire.  I didn't have any plans to change this.

I'll submit the code as it is and then I'll take a look at how difficult it
would be to move the critical parts into the vm.  It might just be a matter of
adding a special flavor of global eval that has an extra check that the AST is
benign before executing it that bails out if it isn't.

[Christian Plesner Hansen, 2009/04/24 13:41:11]

Update: it turned out to be straightforward to move parsing and validation into
native code so I've done that.  No more regexps and eval.

+    } catch (e) {
+      // ignore exceptions
+    }
+  }
+  throw MakeSyntaxError('invalid_json', [s]);
+}
+
+function Revive(holder, name, reviver) {
+  var val = holder[name];
+  if (IS_OBJECT(val)) {
+    if (IS_ARRAY(val)) {
+      var length = val.length;
+      for (var i = 0; i < length; i++) {
+        var newElement = Revive(val, $String(i), reviver);
+        val[i] = newElement;
+      }
+    } else {
+      for (var p in val) {
+        if (ObjectHasOwnProperty.call(val, p)) {
+          var newElement = Revive(val, p, reviver);
+          if (IS_UNDEFINED(newElement)) {
+            delete val[p];
+          } else {
+            val[p] = newElement;
+          }
+        }
+      }
+    }
+  }
+  return reviver.call(holder, name, val);
+}
+
+function JSONParse(text, reviver) {
+  var unfiltered = ParseJSONUnfiltered(text);
+  if (IS_FUNCTION(reviver)) {
+    return Revive({'': unfiltered}, '', reviver);
+  } else {
+    return unfiltered;
+  }
+}
+
+var characterQuoteCache = {
+  '\"': '\\"',
+  '\\': '\\\\',
+  '/': '\\/',
+  '\b': '\\b',
+  '\f': '\\f',
+  '\n': '\\n',
+  '\r': '\\r',
+  '\t': '\\t',
+  '\x0B': '\\u000b'
+};
+
+function QuoteSingleJSONCharacter(c) {
+  if (c in characterQuoteCache)
+    return characterQuoteCache[c];
+  var charCode = c.charCodeAt(0);
+  var result;
+  if (charCode < 16) result = '\\u000';
+  else if (charCode < 256) result = '\\u00';
+  else if (charCode < 4096) result = '\\u0';
+  else result = '\\u';
+  result += charCode.toString(16);
+  characterQuoteCache[c] = result;
+  return result;
+}
+
+function QuoteJSONString(str) {
+  var quotable = /[\\\"\x00-\x1f\x80-\uffff]/g;
+  return '"' + str.replace(quotable, QuoteSingleJSONCharacter) + '"';
+}
+
+function StackContains(stack, val) {
+  var length = stack.length;
+  for (var i = 0; i < length; i++) {
+    if (stack[i] === val)
+      return true;
+  }
+  return false;
+}
+
+function SerializeArray(value, replacer, stack, indent, gap) {
+  if (StackContains(stack, value))
+    throw MakeTypeError('circular_structure', []);
+  stack.push(value);
+  var stepback = indent;
+  indent += gap;
+  var partial = [];
+  var len = value.length;
+  for (var i = 0; i < len; i++) {
+    var strP = JSONSerialize($String(i), value, replacer, stack,
+        indent, gap);
+    if (IS_UNDEFINED(strP))
+      strP = "null";
+    partial.push(strP);
+  }
+  var final;
+  if (gap == "") {
+    final = "[" + partial.join(",") + "]";
+  } else if (partial.length > 0) {
+    var separator = ",\n" + indent;
+    final = "[\n" + indent + partial.join(separator) + "\n" +
+        stepback + "]";
+  } else {
+    final = "[]";
+  }
+  stack.pop();
+  indent = stepback;

[Lasse Reichstein, 2009/04/23 15:28:49]

indent is a local variable here, so setting it just before returning won't do
anything. This line can be removed.
The intended behavior is achieved anyway, since the calling function's indent
hasn't been modified.

[Christian Plesner Hansen, 2009/04/24 08:11:22]

Good point.  I was following the spec a bit too closely.

+  return final;
+}
+
+function SerializeObject(value, replacer, stack, indent, gap) {
+  if (StackContains(stack, value))
+    throw MakeTypeError('circular_structure', []);
+  stack.push(value);
+  var stepback = indent;
+  indent += gap;
+  var partial = [];
+  if (IS_ARRAY(replacer)) {
+    var length = replacer.length;
+    for (var i = length - 1; i >= 0; i--) {
+      if (ObjectHasOwnProperty.call(replacer, i)) {

[Lasse Reichstein, 2009/04/23 15:28:49]

The specification says that the properties of replacer must be iterated in
ascending numeric order.
(Actually, it doesn't, but it does explicitly say that the list of elements
should be in ascending order, and then that something must be done for each
element in the list, which suggests that it should be done in the same order).

[Christian Plesner Hansen, 2009/04/24 08:11:22]

I got ascending and descending mixed up.  Even though what I have is called
"right/left confusion" it actually means that I confuse any pair of directions,
as this demonstrates.  Also good and evil.

+        var p = replacer[i];
+        var strP = JSONSerialize(p, value, replacer, stack, indent, gap);
+        if (!IS_UNDEFINED(strP)) {
+          var member = QuoteJSONString(p) + ":";
+          if (gap != "")
+           member += " ";

[Lasse Reichstein, 2009/04/23 15:28:49]

Should be on previous line (or indented and put in squiggly brackets).

[Christian Plesner Hansen, 2009/04/24 08:11:22]

Gah.  But you're right.

+          member += strP;
+          partial.push(member);
+        }
+      }
+    }
+  } else {
+    for (var p in value) {
+      if (ObjectHasOwnProperty.call(value, p)) {
+        var strP = JSONSerialize(p, value, replacer, stack, indent, gap);
+        if (!IS_UNDEFINED(strP)) {
+          var member = QuoteJSONString(p) + ":";
+          if (gap != "")
+           member += " ";

[Mads Ager (chromium), 2009/04/23 19:09:25]

Indentation.

+          member += strP;
+          partial.push(member);
+        }
+      }
+    }
+  }
+  var final;
+  if (gap == "") {
+    final = "{" + partial.join(",") + "}";
+  } else if (partial.length > 0) {
+    var separator = ",\n" + indent;
+    final = "{\n" + indent + partial.join(separator) + "\n" +
+        stepback + "}";
+  } else {
+    final = "{}";
+  }
+  stack.pop();
+  indent = stepback;

[Lasse Reichstein, 2009/04/23 15:28:49]

Again unnecessary.

+  return final;
+}
+
+function JSONSerialize(key, holder, replacer, stack, indent, gap) {
+  var value = holder[key];
+  if (IS_OBJECT(value) && value) {
+    var toJSON = value.toJSON;
+    if (IS_FUNCTION(toJSON))
+      value = toJSON.call(value, key);
+  }
+  if (IS_FUNCTION(replacer))
+    value = replacer.call(holder, key, value);
+  // Unwrap value if necessary
+  if (IS_OBJECT(value)) {
+    if (IS_NUMBER_WRAPPER(value)) {
+      value = $Number(value);
+    } else if (IS_STRING_WRAPPER(value)) {
+      value = $String(value);
+    }
+  }
+  switch (typeof value) {
+    case "string":
+      return QuoteJSONString(value);
+    case "object":
+      if (!value) {
+        return "null";
+      } else if (IS_ARRAY(value)) {
+        return SerializeArray(value, replacer, stack, indent, gap);
+      } else {
+        return SerializeObject(value, replacer, stack, indent, gap);
+      }
+    case "number":
+      return $isFinite(value) ? $String(value) : "null";
+    case "boolean":
+      return value ? "true" : "false";
+  }
+}
+
+function JSONStringify(value, replacer, space) {
+  var stack = [];
+  var indent = "";
+  if (IS_OBJECT(space)) {
+    // Unwrap 'space' if it is wrapped
+    if (IS_NUMBER_WRAPPER(space)) {
+      space = $Number(space);
+    } else if (IS_STRING_WRAPPER(space)) {
+      space = $String(space);
+    }
+  }
+  var gap;
+  if (IS_NUMBER(space)) {
+    space = $Math.min(space, 100);
+    gap = "";
+    for (var i = 0; i < space; i++)
+      gap += " ";
+  } else if (IS_STRING(space)) {
+    gap = space;
+  } else {
+    gap = "";
+  }
+  return JSONSerialize('', {'': value}, replacer, stack, indent, gap);
+}
+
+function SetupJSON() {
+  InstallFunctions($JSON, DONT_ENUM, $Array(
+    "parse", JSONParse,
+    "stringify", JSONStringify
+  ));
+}
+
+SetupJSON();