Rewrite decodeURL as builtin function, remove now unused runtime functions.

src/uri.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/uri.h"
 
 #include "src/char-predicates-inl.h"
 #include "src/handles.h"
 #include "src/isolate-inl.h"
 #include "src/list.h"
@@ skipping 42 matching lines @@
   }
 }
 
 void AddHexEncodedToBuffer(uint8_t octet, List<uint8_t>* buffer) {
   buffer->Add('%');
   buffer->Add(HexCharOfValue(octet >> 4));
   buffer->Add(HexCharOfValue(octet & 0x0F));
 }
 
 void EncodeSingle(uc16 c, List<uint8_t>* buffer) {
-  uint8_t x = (c >> 12) & 0xF;
-  uint8_t y = (c >> 6) & 63;
-  uint8_t z = c & 63;
-  if (c <= 0x007F) {
-    AddHexEncodedToBuffer(c, buffer);
-  } else if (c <= 0x07FF) {
-    AddHexEncodedToBuffer(y + 192, buffer);
-    AddHexEncodedToBuffer(z + 128, buffer);
-  } else {
-    AddHexEncodedToBuffer(x + 224, buffer);
-    AddHexEncodedToBuffer(y + 128, buffer);
-    AddHexEncodedToBuffer(z + 128, buffer);
+  char s[4];
+  int number_of_bytes;
+  number_of_bytes =
+      unibrow::Utf8::Encode(s, c, unibrow::Utf16::kNoPreviousCharacter, false);
+  for (int k = 0; k < number_of_bytes; k++) {
+    AddHexEncodedToBuffer(s[k], buffer);
   }
 }
 
 void EncodePair(uc16 cc1, uc16 cc2, List<uint8_t>* buffer) {
-  uint8_t u = ((cc1 >> 6) & 0xF) + 1;
-  uint8_t w = (cc1 >> 2) & 0xF;
-  uint8_t x = cc1 & 3;
-  uint8_t y = (cc2 >> 6) & 0xF;
-  uint8_t z = cc2 & 63;
-  AddHexEncodedToBuffer((u >> 2) + 240, buffer);
-  AddHexEncodedToBuffer((((u & 3) << 4) | w) + 128, buffer);
-  AddHexEncodedToBuffer(((x << 4) | y) + 128, buffer);
-  AddHexEncodedToBuffer(z + 128, buffer);
+  char s[4];
+  int number_of_bytes =
+      unibrow::Utf8::Encode(s, unibrow::Utf16::CombineSurrogatePair(cc1, cc2),
+                            unibrow::Utf16::kNoPreviousCharacter, false);
+  for (int k = 0; k < number_of_bytes; k++) {
+    AddHexEncodedToBuffer(s[k], buffer);
+  }
 }
 
 }  // anonymous namespace
 
-Object* Uri::Encode(Isolate* isolate, Handle<String> uri, bool is_uri) {
+MaybeHandle<Object> Uri::Encode(Isolate* isolate, Handle<String> uri,
+                                bool is_uri) {
   uri = String::Flatten(uri);
   int uri_length = uri->length();
   List<uint8_t> buffer(uri_length);
 
   {
     DisallowHeapAllocation no_gc;
     String::FlatContent uri_content = uri->GetFlatContent();
 
     for (int k = 0; k < uri_length; k++) {
       uc16 cc1 = uri_content.Get(k);
@@ skipping 10 matching lines @@
         if (IsUnescapePredicateInUriComponent(cc1) ||
             (is_uri && IsUriSeparator(cc1))) {
           buffer.Add(cc1);
         } else {
           EncodeSingle(cc1, &buffer);
         }
         continue;
       }
 
       AllowHeapAllocation allocate_error_and_return;
-      THROW_NEW_ERROR_RETURN_FAILURE(isolate, NewURIError());
+      THROW_NEW_ERROR(isolate, NewURIError(), Object);
     }
   }
 
   Handle<String> result;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+  ASSIGN_RETURN_ON_EXCEPTION(
       isolate, result,
-      isolate->factory()->NewStringFromOneByte(buffer.ToConstVector()));
-  return *result;
+      isolate->factory()->NewStringFromOneByte(buffer.ToConstVector()), Object);
+  return result;
+}
+
+namespace {  // anonymous namespace for DecodeURI helper functions
+
+bool IsReservedPredicate(uc16 c) {
+  switch (c) {
+    case '#':
+    case '$':
+    case '&':
+    case '+':
+    case ',':
+    case '/':
+    case ':':
+    case ';':
+    case '=':
+    case '?':
+    case '@':
+      return true;
+    default:
+      return false;
+  }
+}
+
+bool IsRepalcementCharacter(List<uint8_t>* octets) {

[Yang, 2016/05/23 06:44:32]

typo.

[Franzi, 2016/05/23 08:55:57]

Done.

+  // 0xFFFD is %ef%bf%bd

[Yang, 2016/05/23 06:44:32]

What does this comment mean?

[Franzi, 2016/05/23 08:55:57]

Reworded the comment to clarify why we check for this particular encoding.

+  if (octets->length() != 3 || octets->at(0) != 0xef || octets->at(1) != 0xbf ||
+      octets->at(2) != 0xbd) {
+    return false;
+  }
+  return true;
+}
+
+bool DecodeOctets(List<uint8_t>* octets, List<uc16>* two_byte_buffer) {
+  size_t cursor = 0;
+  uc32 value = unibrow::Utf8::ValueOf(octets->ToConstVector().start(),
+                                      octets->length(), &cursor);
+  // kBadChar is the Replacement Character, which is the decoding of
+  // valid input %ef%bf%bd
+  if (value == unibrow::Utf8::kBadChar && !IsRepalcementCharacter(octets)) {
+    return false;
+  }
+
+  if (value <= unibrow::Utf16::kMaxNonSurrogateCharCode) {
+    two_byte_buffer->Add(value);
+  } else {
+    two_byte_buffer->Add(unibrow::Utf16::LeadSurrogate(value));
+    two_byte_buffer->Add(unibrow::Utf16::TrailSurrogate(value));
+  }
+  return true;
+}
+
+bool TwoDigitHex(uc16& decoded, int k, String::FlatContent* uri_content) {

[Yang, 2016/05/23 06:44:31]

Can we use uc16* as argument type? That way it's easier to understand, from the
call site, that the argument is an output.

Also see https://google.github.io/styleguide/cppguide.html#Reference_Arguments

[Yang, 2016/05/23 06:44:32]

can we call the second argument "index" or something instead of "k"?

[Franzi, 2016/05/23 08:55:57]

Done.

[Franzi, 2016/05/23 08:55:57]

Done.

+  char high = HexValue(uri_content->Get(k + 1));

[Yang, 2016/05/23 06:44:32]

FlatContent::Get returns a uc16. Casting that to signed char and then comparing
that to 0 smells like undefined behavior.

Let's store the result as uc16 and compare to Utf8::kMaxOneByteChar.

[Franzi, 2016/05/23 08:55:57]

Not sure I understand the comment. HexValue takes a uc32 and returns an int
between -1 and 16. Is that not OK to store as a signed char?

[Yang, 2016/05/23 11:24:59]

Ah I see. I misunderstood. Nevermind this comment.

+  char low = HexValue(uri_content->Get(k + 2));
+  if (high < 0 || low < 0) {
+    return false;
+  }
+  decoded = (high << 4) | low;
+  return true;
+}
+
+template <typename T>
+void AddToBuffer(uc16 decoded, String::FlatContent* uri_content, int k,

[Yang, 2016/05/23 06:44:32]

same here, "index" instead of "k".

[Franzi, 2016/05/23 08:55:57]

Done.

+                 bool is_uri, List<T>* buffer) {
+  if (is_uri && IsReservedPredicate(decoded)) {
+    buffer->Add('%');
+    buffer->Add(uri_content->Get(k + 1));
+    buffer->Add(uri_content->Get(k + 2));

[Yang, 2016/05/23 06:44:31]

Can we have a safeguard here that we don't have implicit clamping here? I.e.
that the return value uri_content->Get fits into the buffer type T?

[Franzi, 2016/05/23 08:55:57]

Done. Throwing exception if uri_content->Get() is larger than
numeric_limits::max() for type T. 

+  } else {
+    buffer->Add(decoded);
+  }
+}
+
+bool IntoTwoByte(int index, bool is_uri, int uri_length,
+                 String::FlatContent* uri_content,
+                 List<uc16>* two_byte_buffer) {
+  for (int k = index; k < uri_length; k++) {
+    uc16 code = uri_content->Get(k);
+    if (code == '%') {
+      uc16 decoded;
+      if (k + 2 >= uri_length || !TwoDigitHex(decoded, k, uri_content)) {
+        return false;
+      }
+      k += 2;
+      if (decoded > unibrow::Utf8::kMaxOneByteChar) {
+        int n = 0;
+        while (((decoded << ++n) & 0x80) != 0) {

[Yang, 2016/05/23 06:44:31]

Can we have this as 

do {
  n++;
} while ((decoded << n) & 0x80);

[Franzi, 2016/05/23 08:55:57]

Changed it to a simple while loop:

    int n = 1;
        while((decoded << n) & 0x80) {
          n++;
        }

+        }
+        if (n == 1 || n > 4 || k + 3 * (n - 1) >= uri_length) {
+          return false;
+        }
+        List<uint8_t> octets;

[Yang, 2016/05/23 06:44:31]

octets will at most have the length 4, right? Can we have a simple array and
pass the length to DecodeOctets?

[Franzi, 2016/05/23 08:55:57]

Done. 

+        octets.Add(decoded);
+
+        for (int i = 1; i < n; i++) {
+          uc16 decodedTrail;
+
+          if (uri_content->Get(++k) != '%' || k + 2 >= uri_length ||
+              !TwoDigitHex(decodedTrail, k, uri_content)) {
+            return false;
+          }
+          k += 2;
+          octets.Add(decodedTrail);
+        }
+
+        if (!DecodeOctets(&octets, two_byte_buffer)) {
+          return false;
+        }
+      } else {
+        AddToBuffer(decoded, uri_content, k - 2, is_uri, two_byte_buffer);
+      }
+    } else {
+      two_byte_buffer->Add(code);
+    }
+  }
+  return true;
+}
+
+bool IntoOneAndTwoByte(Handle<String> uri, bool is_uri,
+                       List<uint8_t>* one_byte_buffer,
+                       List<uc16>* two_byte_buffer) {
+  DisallowHeapAllocation no_gc;
+  String::FlatContent uri_content = uri->GetFlatContent();
+
+  int uri_length = uri->length();
+  for (int k = 0; k < uri_length; k++) {
+    uc16 code = uri_content.Get(k);
+    if (code == '%') {
+      uc16 decoded;
+      if (k + 2 >= uri_length || !TwoDigitHex(decoded, k, &uri_content)) {
+        return false;
+      }
+
+      if (decoded > unibrow::Utf8::kMaxOneByteChar) {
+        return IntoTwoByte(k, is_uri, uri_length, &uri_content,
+                           two_byte_buffer);
+      }
+
+      AddToBuffer(decoded, &uri_content, k, is_uri, one_byte_buffer);
+      k += 2;
+    } else {
+      if (code > unibrow::Utf8::kMaxOneByteChar) {
+        return IntoTwoByte(k, is_uri, uri_length, &uri_content,
+                           two_byte_buffer);
+      }
+      one_byte_buffer->Add(code);
+    }
+  }
+  return true;
+}
+
+}  // anonymous namespace
+
+MaybeHandle<Object> Uri::Decode(Isolate* isolate, Handle<String> uri,
+                                bool is_uri) {
+  uri = String::Flatten(uri);
+  List<uint8_t> one_byte_buffer;
+  List<uc16> two_byte_buffer;
+
+  if (!IntoOneAndTwoByte(uri, is_uri, &one_byte_buffer, &two_byte_buffer)) {
+    THROW_NEW_ERROR(isolate, NewURIError(), Object);
+  }
+
+  Handle<String> left = isolate->factory()->InternalizeOneByteString(
+      one_byte_buffer.ToConstVector());
+
+  Handle<String> right = isolate->factory()->InternalizeTwoByteString(
+      two_byte_buffer.ToConstVector());
+
+  Handle<String> result;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, result, isolate->factory()->NewConsString(left, right), Object);

[Yang, 2016/05/23 06:44:32]

Since we are going to copy from list into the heap anyways, can we simply, for
the mixed encoding case, allocate a large raw two-byte string and CopyChar both
lists into it?

[Franzi, 2016/05/23 08:55:57]

Returning sequential one- or two-byte string. 

+
+  return result;
 }
 
 }  // namespace internal
 }  // namespace v8