Specialize JSON parser to only check for SequentialAsciiString once.

src/json-parser.h

Index: src/json-parser.h
===================================================================
--- src/json-parser.h	(revision 8194)
+++ src/json-parser.h	(working copy)
@@ -28,12 +28,19 @@
 #ifndef V8_JSON_PARSER_H_
 #define V8_JSON_PARSER_H_
 
+#include "v8.h"
+
+#include "char-predicates-inl.h"
+#include "conversions.h"
+#include "messages.h"
+#include "spaces-inl.h"
 #include "token.h"
 
 namespace v8 {
 namespace internal {
 
 // A simple json parser.
+template <bool seq_ascii>
 class JsonParser BASE_EMBEDDED {
  public:
   static Handle<Object> Parse(Handle<String> source) {
@@ -50,7 +57,7 @@
     position_++;
     if (position_ > source_length_) {
       c0_ = kEndOfString;
-    } else if (is_sequential_ascii_) {
+    } else if (seq_ascii) {
       c0_ = seq_source_->SeqAsciiStringGet(position_);
     } else {
       c0_ = source_->Get(position_);
@@ -149,7 +156,6 @@
   int source_length_;
   Handle<SeqAsciiString> seq_source_;
 
-  bool is_sequential_ascii_;
   // begin and end position of scanned string or number
   int beg_pos_;
   int end_pos_;
@@ -161,6 +167,381 @@
   double number_;
 };
 
+template <bool seq_ascii>
+Handle<Object> JsonParser<seq_ascii>::ParseJson(Handle<String> source) {
+  isolate_ = source->map()->isolate();
+  source_ = Handle<String>(source->TryFlattenGetString());
+  source_length_ = source_->length() - 1;
+
+  // Optimized fast case where we only have ascii characters.
+  if (seq_ascii) {
+    seq_source_ = Handle<SeqAsciiString>::cast(source_);
+  }
+
+  // Set initial position right before the string.
+  position_ = -1;
+  // Advance to the first character (posibly EOS)
+  AdvanceSkipWhitespace();
+  Handle<Object> result = ParseJsonValue();
+  if (result.is_null() || c0_ != kEndOfString) {
+    // Parse failed. Current character is the unexpected token.
+
+    const char* message;
+    Factory* factory = isolate()->factory();
+    Handle<JSArray> array;
+
+    switch (c0_) {
+      case kEndOfString:
+        message = "unexpected_eos";
+        array = factory->NewJSArray(0);
+        break;
+      case '-':
+      case '0':
+      case '1':
+      case '2':
+      case '3':
+      case '4':
+      case '5':
+      case '6':
+      case '7':
+      case '8':
+      case '9':
+        message = "unexpected_token_number";
+        array = factory->NewJSArray(0);
+        break;
+      case '"':
+        message = "unexpected_token_string";
+        array = factory->NewJSArray(0);
+        break;
+      default:
+        message = "unexpected_token";
+        Handle<Object> name = LookupSingleCharacterStringFromCode(c0_);
+        Handle<FixedArray> element = factory->NewFixedArray(1);
+        element->set(0, *name);
+        array = factory->NewJSArrayWithElements(element);
+        break;
+    }
+
+    MessageLocation location(factory->NewScript(source),
+                             position_,
+                             position_ + 1);
+    Handle<Object> result = factory->NewSyntaxError(message, array);
+    isolate()->Throw(*result, &location);
+    return Handle<Object>::null();
+  }
+  return result;
+}
+
+
+// Parse any JSON value.
+template <bool seq_ascii>
+Handle<Object> JsonParser<seq_ascii>::ParseJsonValue() {
+  switch (c0_) {
+    case '"':
+      return ParseJsonString();
+    case '-':
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+      return ParseJsonNumber();
+    case 'f':
+      if (AdvanceGetChar() == 'a' && AdvanceGetChar() == 'l' &&
+          AdvanceGetChar() == 's' && AdvanceGetChar() == 'e') {
+        AdvanceSkipWhitespace();
+        return isolate()->factory()->false_value();
+      } else {
+        return ReportUnexpectedCharacter();
+      }
+    case 't':
+      if (AdvanceGetChar() == 'r' && AdvanceGetChar() == 'u' &&
+          AdvanceGetChar() == 'e') {
+        AdvanceSkipWhitespace();
+        return isolate()->factory()->true_value();
+      } else {
+        return ReportUnexpectedCharacter();
+      }
+    case 'n':
+      if (AdvanceGetChar() == 'u' && AdvanceGetChar() == 'l' &&
+          AdvanceGetChar() == 'l') {
+        AdvanceSkipWhitespace();
+        return isolate()->factory()->null_value();
+      } else {
+        return ReportUnexpectedCharacter();
+      }
+    case '{':
+      return ParseJsonObject();
+    case '[':
+      return ParseJsonArray();
+    default:
+      return ReportUnexpectedCharacter();
+  }
+}
+
+
+// Parse a JSON object. Position must be right at '{'.
+template <bool seq_ascii>
+Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
+  Handle<JSFunction> object_constructor(
+      isolate()->global_context()->object_function());
+  Handle<JSObject> json_object =
+      isolate()->factory()->NewJSObject(object_constructor);
+  ASSERT_EQ(c0_, '{');
+
+  AdvanceSkipWhitespace();
+  if (c0_ != '}') {
+    do {
+      if (c0_ != '"') return ReportUnexpectedCharacter();
+      Handle<String> key = ParseJsonSymbol();
+      if (key.is_null() || c0_ != ':') return ReportUnexpectedCharacter();
+      AdvanceSkipWhitespace();
+      Handle<Object> value = ParseJsonValue();
+      if (value.is_null()) return ReportUnexpectedCharacter();
+
+      uint32_t index;
+      if (key->AsArrayIndex(&index)) {
+        SetOwnElement(json_object, index, value, kNonStrictMode);
+      } else if (key->Equals(isolate()->heap()->Proto_symbol())) {
+        SetPrototype(json_object, value);
+      } else {
+        SetLocalPropertyIgnoreAttributes(json_object, key, value, NONE);
+      }
+    } while (MatchSkipWhiteSpace(','));
+    if (c0_ != '}') {
+      return ReportUnexpectedCharacter();
+    }
+  }
+  AdvanceSkipWhitespace();
+  return json_object;
+}
+
+// Parse a JSON array. Position must be right at '['.
+template <bool seq_ascii>
+Handle<Object> JsonParser<seq_ascii>::ParseJsonArray() {
+  ZoneScope zone_scope(isolate(), DELETE_ON_EXIT);
+  ZoneList<Handle<Object> > elements(4);
+  ASSERT_EQ(c0_, '[');
+
+  AdvanceSkipWhitespace();
+  if (c0_ != ']') {
+    do {
+      Handle<Object> element = ParseJsonValue();
+      if (element.is_null()) return ReportUnexpectedCharacter();
+      elements.Add(element);
+    } while (MatchSkipWhiteSpace(','));
+    if (c0_ != ']') {
+      return ReportUnexpectedCharacter();
+    }
+  }
+  AdvanceSkipWhitespace();
+  // Allocate a fixed array with all the elements.
+  Handle<FixedArray> fast_elements =
+      isolate()->factory()->NewFixedArray(elements.length());
+  for (int i = 0, n = elements.length(); i < n; i++) {
+    fast_elements->set(i, *elements[i]);
+  }
+  return isolate()->factory()->NewJSArrayWithElements(fast_elements);
+}
+
+
+template <bool seq_ascii>
+Handle<Object> JsonParser<seq_ascii>::ParseJsonNumber() {
+  bool negative = false;
+  beg_pos_ = position_;
+  if (c0_ == '-') {
+    Advance();
+    negative = true;
+  }
+  if (c0_ == '0') {
+    Advance();
+    // Prefix zero is only allowed if it's the only digit before
+    // a decimal point or exponent.
+    if ('0' <= c0_ && c0_ <= '9') return ReportUnexpectedCharacter();
+  } else {
+    int i = 0;
+    int digits = 0;
+    if (c0_ < '1' || c0_ > '9') return ReportUnexpectedCharacter();
+    do {
+      i = i * 10 + c0_ - '0';
+      digits++;
+      Advance();
+    } while (c0_ >= '0' && c0_ <= '9');
+    if (c0_ != '.' && c0_ != 'e' && c0_ != 'E' && digits < 10) {
+      number_ = (negative ? -i : i);
+      SkipWhitespace();
+      return isolate()->factory()->NewNumber(number_);
+    }
+  }
+  if (c0_ == '.') {
+    Advance();
+    if (c0_ < '0' || c0_ > '9') return ReportUnexpectedCharacter();
+    do {
+      Advance();
+    } while (c0_ >= '0' && c0_ <= '9');
+  }
+  if (AsciiAlphaToLower(c0_) == 'e') {
+    Advance();
+    if (c0_ == '-' || c0_ == '+') Advance();
+    if (c0_ < '0' || c0_ > '9') return ReportUnexpectedCharacter();
+    do {
+      Advance();
+    } while (c0_ >= '0' && c0_ <= '9');
+  }
+  int length = position_ - beg_pos_;
+  if (seq_ascii) {
+    Vector<const char> chars(seq_source_->GetChars() +  beg_pos_, length);
+    number_ = StringToDouble(isolate()->unicode_cache(),
+                             chars,
+                             NO_FLAGS,  // Hex, octal or trailing junk.
+                             OS::nan_value());
+  } else {
+    Vector<char> buffer = Vector<char>::New(length);
+    String::WriteToFlat(*source_, buffer.start(), beg_pos_, position_);
+    Vector<const char> result =
+        Vector<const char>(reinterpret_cast<const char*>(buffer.start()),
+        length);
+    number_ = StringToDouble(isolate()->unicode_cache(),
+                             result,
+                             NO_FLAGS,  // Hex, octal or trailing junk.
+                             0.0);
+    buffer.Dispose();
+  }
+  SkipWhitespace();
+  return isolate()->factory()->NewNumber(number_);
+}
+
+template <bool seq_ascii>
+Handle<String> JsonParser<seq_ascii>::SlowScanJsonString() {
+  // The currently scanned ascii characters.
+  Handle<String> ascii(isolate()->factory()->NewSubString(source_,
+                                                          beg_pos_,
+                                                          position_));
+  Handle<String> two_byte =
+      isolate()->factory()->NewRawTwoByteString(kInitialSpecialStringSize,
+                                                NOT_TENURED);
+  Handle<SeqTwoByteString> seq_two_byte =
+      Handle<SeqTwoByteString>::cast(two_byte);
+
+  int allocation_count = 1;
+  int count = 0;
+
+  while (c0_ != '"') {
+    // Create new seq string
+    if (count >= kInitialSpecialStringSize * allocation_count) {
+      allocation_count = allocation_count * 2;
+      int new_size = allocation_count * kInitialSpecialStringSize;
+      Handle<String> new_two_byte =
+          isolate()->factory()->NewRawTwoByteString(new_size,
+                                                    NOT_TENURED);
+      uc16* char_start =
+          Handle<SeqTwoByteString>::cast(new_two_byte)->GetChars();
+      String::WriteToFlat(*seq_two_byte, char_start, 0, count);
+      seq_two_byte = Handle<SeqTwoByteString>::cast(new_two_byte);
+    }
+
+    // Check for control character (0x00-0x1f) or unterminated string (<0).
+    if (c0_ < 0x20) return Handle<String>::null();
+    if (c0_ != '\\') {
+      seq_two_byte->SeqTwoByteStringSet(count++, c0_);
+      Advance();
+    } else {
+      Advance();
+      switch (c0_) {
+        case '"':
+        case '\\':
+        case '/':
+          seq_two_byte->SeqTwoByteStringSet(count++, c0_);
+          break;
+        case 'b':
+          seq_two_byte->SeqTwoByteStringSet(count++, '\x08');
+          break;
+        case 'f':
+          seq_two_byte->SeqTwoByteStringSet(count++, '\x0c');
+          break;
+        case 'n':
+          seq_two_byte->SeqTwoByteStringSet(count++, '\x0a');
+          break;
+        case 'r':
+          seq_two_byte->SeqTwoByteStringSet(count++, '\x0d');
+          break;
+        case 't':
+          seq_two_byte->SeqTwoByteStringSet(count++, '\x09');
+          break;
+        case 'u': {
+          uc32 value = 0;
+          for (int i = 0; i < 4; i++) {
+            Advance();
+            int digit = HexValue(c0_);
+            if (digit < 0) {
+              return Handle<String>::null();
+            }
+            value = value * 16 + digit;
+          }
+          seq_two_byte->SeqTwoByteStringSet(count++, value);
+          break;
+        }
+        default:
+          return Handle<String>::null();
+      }
+      Advance();
+    }
+  }
+  // Advance past the last '"'.
+  ASSERT_EQ('"', c0_);
+  AdvanceSkipWhitespace();
+
+  // Shrink the the string to our length.
+  if (isolate()->heap()->InNewSpace(*seq_two_byte)) {
+    isolate()->heap()->new_space()->
+        template ShrinkStringAtAllocationBoundary<SeqTwoByteString>(
+            *seq_two_byte, count);
+  } else {
+    int string_size = SeqTwoByteString::SizeFor(count);
+    int allocated_string_size =
+        SeqTwoByteString::SizeFor(kInitialSpecialStringSize * allocation_count);
+    int delta = allocated_string_size - string_size;
+    Address start_filler_object = seq_two_byte->address() + string_size;
+    seq_two_byte->set_length(count);
+    isolate()->heap()->CreateFillerObjectAt(start_filler_object, delta);
+  }
+  return isolate()->factory()->NewConsString(ascii, seq_two_byte);
+}
+
+template <bool seq_ascii>
+template <bool is_symbol>
+Handle<String> JsonParser<seq_ascii>::ScanJsonString() {
+  ASSERT_EQ('"', c0_);
+  Advance();
+  beg_pos_ = position_;
+  // Fast case for ascii only without escape characters.
+  while (c0_ != '"') {
+    // Check for control character (0x00-0x1f) or unterminated string (<0).
+    if (c0_ < 0x20) return Handle<String>::null();
+    if (c0_ != '\\' && (seq_ascii || c0_ < kMaxAsciiCharCode)) {
+      Advance();
+    } else {
+      return this->SlowScanJsonString();
+    }
+  }
+  ASSERT_EQ('"', c0_);
+  end_pos_ = position_;
+  // Advance past the last '"'.
+  AdvanceSkipWhitespace();
+  if (seq_ascii && is_symbol) {
+    return isolate()->factory()->LookupAsciiSymbol(seq_source_,
+                                                   beg_pos_,
+                                                   end_pos_ - beg_pos_);
+  } else {
+    return isolate()->factory()->NewSubString(source_, beg_pos_, end_pos_);
+  }
+}
+
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_PARSER_H_