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runtime/vm/json_parser.h

Index: runtime/vm/json_parser.h
diff --git a/runtime/vm/json_parser.h b/runtime/vm/json_parser.h
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+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef RUNTIME_VM_JSON_PARSER_H_
+#define RUNTIME_VM_JSON_PARSER_H_
+
+#include "vm/allocation.h"
+#include "vm/zone.h"
+#include "vm/growable_array.h"
+
+namespace dart {
+
+class ParsedJSONArray;
+
+class ParsedJSONValue : public ZoneAllocated {
+ public:
+  virtual ~ParsedJSONValue() {}
+
+  virtual bool IsObject() const { return false; }
+  virtual bool IsArray() const { return false; }
+  virtual bool IsString() const { return false; }
+  virtual bool IsNumber() const { return false; }
+  virtual bool IsBoolean() const { return false; }
+  virtual bool IsError() const { return false; }
+};
+
+class ParsedJSONString : public ParsedJSONValue {
+ public:
+  explicit ParsedJSONString(const char* value) : value_(value) {}
+  bool Equals(const char* other) { return strcmp(value_, other) == 0; }
+  const char* value() { return value_; }
+  virtual bool IsString() const { return true; }
+
+ private:
+  const char* value_;
+};
+
+class ParsedJSONNumber : public ParsedJSONValue {
+ public:
+  explicit ParsedJSONNumber(int64_t value) : value_(value) {}
+
+  int64_t value() { return value_; }
+  virtual bool IsNumber() const { return true; }
+
+ private:
+  int64_t value_;
+};
+
+class ParsedJSONBoolean : public ParsedJSONValue {
+ public:
+  explicit ParsedJSONBoolean(bool value) : value_(value) {}
+
+  bool value() { return value_; }
+  virtual bool IsBoolean() const { return true; }
+
+ private:
+  bool value_;
+};
+
+class ParsedJSONNull : public ParsedJSONValue {
+ public:
+  virtual bool IsNull() const { return true; }
+};
+
+class ParsedJSONObject : public ParsedJSONValue {
+ public:
+  ParsedJSONObject(intptr_t length, ParsedJSONValue** keys_and_values)
+      : length_(length), keys_and_values_(keys_and_values) {}
+
+  ParsedJSONValue* At(const char* key) const {
+    for (intptr_t i = 0; i < length_; i += 2) {
+      ASSERT(keys_and_values_[i]->IsString());
+      ParsedJSONString* jskey =
+          static_cast<ParsedJSONString*>(keys_and_values_[i]);
+      if (jskey->Equals(key)) {
+        return keys_and_values_[i + 1];
+      }
+    }
+    return NULL;
+  }
+
+  virtual bool IsObject() const { return true; }
+
+  ParsedJSONNumber* NumberAt(const char* key) {
+    ParsedJSONValue* member = At(key);
+    if ((member == NULL) || !member->IsNumber()) {
+      return NULL;
+    }
+    return static_cast<ParsedJSONNumber*>(member);
+  }
+
+  ParsedJSONString* StringAt(const char* key) {
+    ParsedJSONValue* member = At(key);
+    if ((member == NULL) || !member->IsString()) {
+      return NULL;
+    }
+    return static_cast<ParsedJSONString*>(member);
+  }
+
+  ParsedJSONBoolean* BooleanAt(const char* key) {
+    ParsedJSONValue* member = At(key);
+    if ((member == NULL) || !member->IsBoolean()) {
+      return NULL;
+    }
+    return static_cast<ParsedJSONBoolean*>(member);
+  }
+
+  inline ParsedJSONArray* ArrayAt(const char* key);
+
+ private:
+  intptr_t length_;
+  ParsedJSONValue** keys_and_values_;
+};
+
+class ParsedJSONArray : public ParsedJSONValue {
+ public:
+  ParsedJSONArray(intptr_t length, ParsedJSONValue** elements)
+      : length_(length), elements_(elements) {}
+
+  ParsedJSONValue* At(intptr_t index) const {
+    ASSERT(index < length_);
+    return elements_[index];
+  }
+
+  intptr_t Length() const { return length_; }
+
+  virtual bool IsArray() const { return true; }
+
+  ParsedJSONObject* ObjectAt(intptr_t index) {
+    ParsedJSONValue* element = At(index);
+    if ((element == NULL) || !element->IsObject()) {
+      return NULL;
+    }
+    return static_cast<ParsedJSONObject*>(element);
+  }
+
+  ParsedJSONNumber* NumberAt(intptr_t index) {
+    ParsedJSONValue* element = At(index);
+    if ((element == NULL) || !element->IsNumber()) {
+      return NULL;
+    }
+    return static_cast<ParsedJSONNumber*>(element);
+  }
+
+ private:
+  intptr_t length_;
+  ParsedJSONValue** elements_;
+};
+
+class ParsedJSONError : public ParsedJSONValue {
+ public:
+  explicit ParsedJSONError(const char* message, intptr_t position)
+      : message_(message), position_(position) {}
+
+  virtual bool IsError() const { return true; }
+
+  const char* message() const { return message_; }
+  intptr_t position() const { return position_; }
+
+ private:
+  const char* message_;
+  intptr_t position_;
+};
+
+class JSONParser {
+ public:
+  JSONParser(const char* buffer, intptr_t length, Zone* zone)
+      : buffer_(buffer), position_(0), length_(length), zone_(zone) {}
+
+  ParsedJSONValue* ParseValue() {
+    ConsumeWhitespace();
+    if (Peek() == '\"') return ParseString();
+    if (IsDigitOrMinus(Peek())) return ParseNumber();
+    if (Peek() == '{') return ParseObject();
+    if (Peek() == '[') return ParseArray();
+    if (PeekAndConsume("true")) return new (zone_) ParsedJSONBoolean(true);
+    if (PeekAndConsume("false")) return new (zone_) ParsedJSONBoolean(false);
+    if (PeekAndConsume("null")) return new (zone_) ParsedJSONNull();
+    return Error("value expected");
+  }
+
+ private:
+  intptr_t Available() const { return length_ - position_; }
+  char Peek() const {
+    if (position_ < length_) return buffer_[position_];
+    return 0;
+  }
+  char Consume() {
+    ASSERT(position_ < length_);
+    return buffer_[position_++];
+  }
+  bool PeekAndConsume(const char* expected) {
+    intptr_t n = strlen(expected);
+    if (Available() < n) return false;
+    if (strncmp(&buffer_[position_], expected, n) != 0) return false;
+    position_ += n;
+    return true;
+  }
+  void ConsumeWhitespace() {
+    while ((Available() > 0) && (buffer_[position_] < ' '))
+      position_++;
+  }
+  bool IsDigit(char c) { return c >= '0' && c <= '9'; }
+  bool IsDigitOrMinus(char c) { return (c == '-') || (c >= '0' && c <= '9'); }
+
+  ParsedJSONValue* ParseString() {
+    ConsumeWhitespace();
+    if (Peek() != '\"') return Error("string expected");
+    Consume();
+    intptr_t start = position_;
+    for (;;) {
+      if (Available() == 0) return Error("unterminated string");
+      if (Consume() == '\"') break;
+    }
+    intptr_t end = position_ - 1;
+
+    char* cstr = zone_->Alloc<char>(end - start + 1);
+    intptr_t dst_pos = 0;
+    for (intptr_t src_pos = start; src_pos < end; src_pos++) {
+      if (buffer_[src_pos] == '\\') {
+        src_pos++;
+      }
+      cstr[dst_pos++] = buffer_[src_pos];
+    }
+    cstr[dst_pos] = '\0';
+
+    return new (zone_) ParsedJSONString(cstr);
+  }
+
+  ParsedJSONValue* ParseNumber() {
+    ConsumeWhitespace();
+    bool negate = false;
+    if (Peek() == '-') {
+      Consume();
+      negate = true;
+    }
+    if (!IsDigit(Peek())) return Error("number expected");
+    int64_t value = 0;
+    for (;;) {
+      if (!IsDigit(Peek())) break;
+      char c = Consume();
+      value *= 10;
+      value += (c - '0');
+    }
+    if (negate) {
+      value = -value;
+    }
+    return new (zone_) ParsedJSONNumber(value);
+  }
+
+  ParsedJSONValue* ParseObject() {
+    ConsumeWhitespace();
+    if (Peek() != '{') return Error("object expected");
+    Consume();
+    ConsumeWhitespace();
+    if (Peek() == '}') return new (zone_) ParsedJSONObject(0, NULL);
+    ZoneGrowableArray<ParsedJSONValue*>* keys_and_values =
+        new (zone_) ZoneGrowableArray<ParsedJSONValue*>(zone_, 6);
+    for (;;) {
+      ParsedJSONValue* key = ParseString();
+      if (key->IsError()) return key;
+      ConsumeWhitespace();
+      if (Consume() != ':') return Error(": expected");
+      ConsumeWhitespace();
+      ParsedJSONValue* value = ParseValue();
+      if (value->IsError()) return value;
+      ConsumeWhitespace();
+
+      keys_and_values->Add(key);
+      keys_and_values->Add(value);
+
+      char c = Consume();
+      if (c == '}') break;
+      if (c != ',') return Error(", expected (object)");
+      ConsumeWhitespace();
+    }
+
+    return new (zone_)
+        ParsedJSONObject(keys_and_values->length(), keys_and_values->data());
+  }
+
+  ParsedJSONValue* ParseArray() {
+    ConsumeWhitespace();
+    if (Peek() != '[') return Error("array expected");
+    Consume();
+    ConsumeWhitespace();
+    if (Peek() == ']') {
+      Consume();
+      return new (zone_) ParsedJSONArray(0, NULL);
+    }
+    ZoneGrowableArray<ParsedJSONValue*>* elements =
+        new (zone_) ZoneGrowableArray<ParsedJSONValue*>(zone_, 6);
+    for (;;) {
+      ParsedJSONValue* element = ParseValue();
+      if (element->IsError()) return element;
+      ConsumeWhitespace();
+
+      elements->Add(element);
+
+      char c = Consume();
+      if (c == ']') break;
+      if (c != ',') return Error(", expected (array)");
+      ConsumeWhitespace();
+    }
+
+    return new (zone_) ParsedJSONArray(elements->length(), elements->data());
+  }
+
+ private:
+  ParsedJSONError* Error(const char* message) {
+    return new (zone_) ParsedJSONError(message, position_);
+  }
+
+  const char* const buffer_;
+  intptr_t position_;
+  intptr_t length_;
+  Zone* zone_;
+};
+
+ParsedJSONArray* ParsedJSONObject::ArrayAt(const char* key) {
+  ParsedJSONValue* member = At(key);
+  if ((member == NULL) || !member->IsArray()) {
+    return NULL;
+  }
+  return static_cast<ParsedJSONArray*>(member);
+}
+
+}  // namespace dart
+
+#endif  // RUNTIME_VM_JSON_PARSER_H_