Revert "Eliminate all code related to the AutomaticProfileResetter."

chrome/browser/profile_resetter/jtl_interpreter.cc

Index: chrome/browser/profile_resetter/jtl_interpreter.cc
diff --git a/chrome/browser/profile_resetter/jtl_interpreter.cc b/chrome/browser/profile_resetter/jtl_interpreter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e25807818b9adb0c7ff5cac0f174a8a26643eb0a
--- /dev/null
+++ b/chrome/browser/profile_resetter/jtl_interpreter.cc
@@ -0,0 +1,748 @@
+// Copyright 2013 The Chromium 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 "chrome/browser/profile_resetter/jtl_interpreter.h"
+
+#include <numeric>
+
+#include "base/memory/scoped_vector.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "chrome/browser/profile_resetter/jtl_foundation.h"
+#include "crypto/hmac.h"
+#include "crypto/sha2.h"
+#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
+#include "url/gurl.h"
+
+namespace {
+
+class ExecutionContext;
+
+// An operation in an interpreted program.
+class Operation {
+ public:
+  virtual ~Operation() {}
+  // Executes the operation on the specified context and instructs the context
+  // to continue execution with the next instruction if appropriate.
+  // Returns true if we should continue with any potential backtracking that
+  // needs to be done.
+  virtual bool Execute(ExecutionContext* context) = 0;
+};
+
+// An execution context of operations.
+class ExecutionContext {
+ public:
+  // |input| is the root of a dictionary that stores the information the
+  // sentence is evaluated on.
+  ExecutionContext(const jtl_foundation::Hasher* hasher,
+                   const std::vector<Operation*>& sentence,
+                   const base::DictionaryValue* input,
+                   base::DictionaryValue* working_memory)
+      : hasher_(hasher),
+        sentence_(sentence),
+        next_instruction_index_(0u),
+        working_memory_(working_memory),
+        error_(false) {
+    stack_.push_back(input);
+  }
+  ~ExecutionContext() {}
+
+  // Returns true in case of success.
+  bool ContinueExecution() {
+    if (error_ || stack_.empty()) {
+      error_ = true;
+      return false;
+    }
+    if (next_instruction_index_ >= sentence_.size())
+      return true;
+
+    Operation* op = sentence_[next_instruction_index_];
+    next_instruction_index_++;
+    bool continue_traversal = op->Execute(this);
+    next_instruction_index_--;
+    return continue_traversal;
+  }
+
+  std::string GetHash(const std::string& input) {
+    return hasher_->GetHash(input);
+  }
+
+  // Calculates the |hash| of a string, integer or double |value|, and returns
+  // true. Returns false otherwise.
+  bool GetValueHash(const base::Value& value, std::string* hash) {
+    DCHECK(hash);
+    std::string value_as_string;
+    int tmp_int = 0;
+    double tmp_double = 0.0;
+    if (value.GetAsInteger(&tmp_int))
+      value_as_string = base::IntToString(tmp_int);
+    else if (value.GetAsDouble(&tmp_double))
+      value_as_string = base::DoubleToString(tmp_double);
+    else if (!value.GetAsString(&value_as_string))
+      return false;
+    *hash = GetHash(value_as_string);
+    return true;
+  }
+
+  const base::Value* current_node() const { return stack_.back(); }
+  std::vector<const base::Value*>* stack() { return &stack_; }
+  base::DictionaryValue* working_memory() { return working_memory_; }
+  bool error() const { return error_; }
+
+ private:
+  // A hasher used to hash node names in a dictionary.
+  const jtl_foundation::Hasher* hasher_;
+  // The sentence to be executed.
+  const std::vector<Operation*> sentence_;
+  // Position in |sentence_|.
+  size_t next_instruction_index_;
+  // A stack of Values, indicating a navigation path from the root node of
+  // |input| (see constructor) to the current node on which the
+  // sentence_[next_instruction_index_] is evaluated.
+  std::vector<const base::Value*> stack_;
+  // Memory into which values can be stored by the program.
+  base::DictionaryValue* working_memory_;
+  // Whether a runtime error occurred.
+  bool error_;
+  DISALLOW_COPY_AND_ASSIGN(ExecutionContext);
+};
+
+class NavigateOperation : public Operation {
+ public:
+  explicit NavigateOperation(const std::string& hashed_key)
+      : hashed_key_(hashed_key) {}
+  virtual ~NavigateOperation() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    const base::DictionaryValue* dict = NULL;
+    if (!context->current_node()->GetAsDictionary(&dict)) {
+      // Just ignore this node gracefully as this navigation is a dead end.
+      // If this NavigateOperation occurred after a NavigateAny operation, those
+      // may still be fulfillable, so we allow continuing the execution of the
+      // sentence on other nodes.
+      return true;
+    }
+    for (base::DictionaryValue::Iterator i(*dict); !i.IsAtEnd(); i.Advance()) {
+      if (context->GetHash(i.key()) != hashed_key_)
+        continue;
+      context->stack()->push_back(&i.value());
+      bool continue_traversal = context->ContinueExecution();
+      context->stack()->pop_back();
+      if (!continue_traversal)
+        return false;
+    }
+    return true;
+  }
+
+ private:
+  std::string hashed_key_;
+  DISALLOW_COPY_AND_ASSIGN(NavigateOperation);
+};
+
+class NavigateAnyOperation : public Operation {
+ public:
+  NavigateAnyOperation() {}
+  virtual ~NavigateAnyOperation() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    const base::DictionaryValue* dict = NULL;
+    const base::ListValue* list = NULL;
+    if (context->current_node()->GetAsDictionary(&dict)) {
+      for (base::DictionaryValue::Iterator i(*dict);
+           !i.IsAtEnd(); i.Advance()) {
+        context->stack()->push_back(&i.value());
+        bool continue_traversal = context->ContinueExecution();
+        context->stack()->pop_back();
+        if (!continue_traversal)
+          return false;
+      }
+    } else if (context->current_node()->GetAsList(&list)) {
+      for (base::ListValue::const_iterator i = list->begin();
+           i != list->end(); ++i) {
+        context->stack()->push_back(*i);
+        bool continue_traversal = context->ContinueExecution();
+        context->stack()->pop_back();
+        if (!continue_traversal)
+          return false;
+      }
+    } else {
+      // Do nothing, just ignore this node.
+    }
+    return true;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NavigateAnyOperation);
+};
+
+class NavigateBackOperation : public Operation {
+ public:
+  NavigateBackOperation() {}
+  virtual ~NavigateBackOperation() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    const base::Value* current_node = context->current_node();
+    context->stack()->pop_back();
+    bool continue_traversal = context->ContinueExecution();
+    context->stack()->push_back(current_node);
+    return continue_traversal;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NavigateBackOperation);
+};
+
+class StoreValue : public Operation {
+ public:
+  StoreValue(const std::string& hashed_name, scoped_ptr<base::Value> value)
+      : hashed_name_(hashed_name),
+        value_(value.Pass()) {
+    DCHECK(base::IsStringUTF8(hashed_name));
+    DCHECK(value_);
+  }
+  virtual ~StoreValue() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    context->working_memory()->Set(hashed_name_, value_->DeepCopy());
+    return context->ContinueExecution();
+  }
+
+ private:
+  std::string hashed_name_;
+  scoped_ptr<base::Value> value_;
+  DISALLOW_COPY_AND_ASSIGN(StoreValue);
+};
+
+class CompareStoredValue : public Operation {
+ public:
+  CompareStoredValue(const std::string& hashed_name,
+                     scoped_ptr<base::Value> value,
+                     scoped_ptr<base::Value> default_value)
+      : hashed_name_(hashed_name),
+        value_(value.Pass()),
+        default_value_(default_value.Pass()) {
+    DCHECK(base::IsStringUTF8(hashed_name));
+    DCHECK(value_);
+    DCHECK(default_value_);
+  }
+  virtual ~CompareStoredValue() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    const base::Value* actual_value = NULL;
+    if (!context->working_memory()->Get(hashed_name_, &actual_value))
+      actual_value = default_value_.get();
+    if (!value_->Equals(actual_value))
+      return true;
+    return context->ContinueExecution();
+  }
+
+ private:
+  std::string hashed_name_;
+  scoped_ptr<base::Value> value_;
+  scoped_ptr<base::Value> default_value_;
+  DISALLOW_COPY_AND_ASSIGN(CompareStoredValue);
+};
+
+template<bool ExpectedTypeIsBooleanNotHashable>
+class StoreNodeValue : public Operation {
+ public:
+  explicit StoreNodeValue(const std::string& hashed_name)
+      : hashed_name_(hashed_name) {
+    DCHECK(base::IsStringUTF8(hashed_name));
+  }
+  virtual ~StoreNodeValue() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    scoped_ptr<base::Value> value;
+    if (ExpectedTypeIsBooleanNotHashable) {
+      if (!context->current_node()->IsType(base::Value::TYPE_BOOLEAN))
+        return true;
+      value.reset(context->current_node()->DeepCopy());
+    } else {
+      std::string hash;
+      if (!context->GetValueHash(*context->current_node(), &hash))
+        return true;
+      value.reset(new base::StringValue(hash));
+    }
+    context->working_memory()->Set(hashed_name_, value.release());
+    return context->ContinueExecution();
+  }
+
+ private:
+  std::string hashed_name_;
+  DISALLOW_COPY_AND_ASSIGN(StoreNodeValue);
+};
+
+// Stores the hash of the registerable domain name -- as in, the portion of the
+// domain that is registerable, as opposed to controlled by a registrar; without
+// subdomains -- of the URL represented by the current node into working memory.
+class StoreNodeRegisterableDomain : public Operation {
+ public:
+  explicit StoreNodeRegisterableDomain(const std::string& hashed_name)
+      : hashed_name_(hashed_name) {
+    DCHECK(base::IsStringUTF8(hashed_name));
+  }
+  virtual ~StoreNodeRegisterableDomain() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    std::string possibly_invalid_url;
+    std::string domain;
+    if (!context->current_node()->GetAsString(&possibly_invalid_url) ||
+        !GetRegisterableDomain(possibly_invalid_url, &domain))
+      return true;
+    context->working_memory()->Set(
+        hashed_name_, new base::StringValue(context->GetHash(domain)));
+    return context->ContinueExecution();
+  }
+
+ private:
+  // If |possibly_invalid_url| is a valid URL having a registerable domain name
+  // part, outputs that in |registerable_domain| and returns true. Otherwise,
+  // returns false.
+  static bool GetRegisterableDomain(const std::string& possibly_invalid_url,
+                                    std::string* registerable_domain) {
+    namespace domains = net::registry_controlled_domains;
+    DCHECK(registerable_domain);
+    GURL url(possibly_invalid_url);
+    if (!url.is_valid())
+      return false;
+    std::string registry_plus_one = domains::GetDomainAndRegistry(
+        url.host(), domains::INCLUDE_PRIVATE_REGISTRIES);
+    size_t registry_length = domains::GetRegistryLength(
+        url.host(),
+        domains::INCLUDE_UNKNOWN_REGISTRIES,
+        domains::INCLUDE_PRIVATE_REGISTRIES);
+    // Fail unless (1.) the URL has a host part; and (2.) that host part is a
+    // well-formed domain name consisting of at least one subcomponent; followed
+    // by either a recognized registry identifier, or exactly one subcomponent,
+    // which is then assumed to be the unknown registry identifier.
+    if (registry_length == std::string::npos || registry_length == 0)
+      return false;
+    DCHECK_LT(registry_length, registry_plus_one.size());
+    // Subtract one to cut off the dot separating the SLD and the registry.
+    registerable_domain->assign(
+        registry_plus_one, 0, registry_plus_one.size() - registry_length - 1);
+    return true;
+  }
+
+  std::string hashed_name_;
+  DISALLOW_COPY_AND_ASSIGN(StoreNodeRegisterableDomain);
+};
+
+class CompareNodeBool : public Operation {
+ public:
+  explicit CompareNodeBool(bool value) : value_(value) {}
+  virtual ~CompareNodeBool() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    bool actual_value = false;
+    if (!context->current_node()->GetAsBoolean(&actual_value))
+      return true;
+    if (actual_value != value_)
+      return true;
+    return context->ContinueExecution();
+  }
+
+ private:
+  bool value_;
+  DISALLOW_COPY_AND_ASSIGN(CompareNodeBool);
+};
+
+class CompareNodeHash : public Operation {
+ public:
+  explicit CompareNodeHash(const std::string& hashed_value)
+      : hashed_value_(hashed_value) {}
+  virtual ~CompareNodeHash() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    std::string actual_hash;
+    if (!context->GetValueHash(*context->current_node(), &actual_hash) ||
+        actual_hash != hashed_value_)
+      return true;
+    return context->ContinueExecution();
+  }
+
+ private:
+  std::string hashed_value_;
+  DISALLOW_COPY_AND_ASSIGN(CompareNodeHash);
+};
+
+class CompareNodeHashNot : public Operation {
+ public:
+  explicit CompareNodeHashNot(const std::string& hashed_value)
+      : hashed_value_(hashed_value) {}
+  virtual ~CompareNodeHashNot() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    std::string actual_hash;
+    if (context->GetValueHash(*context->current_node(), &actual_hash) &&
+        actual_hash == hashed_value_)
+      return true;
+    return context->ContinueExecution();
+  }
+
+ private:
+  std::string hashed_value_;
+  DISALLOW_COPY_AND_ASSIGN(CompareNodeHashNot);
+};
+
+template<bool ExpectedTypeIsBooleanNotHashable>
+class CompareNodeToStored : public Operation {
+ public:
+  explicit CompareNodeToStored(const std::string& hashed_name)
+      : hashed_name_(hashed_name) {}
+  virtual ~CompareNodeToStored() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    const base::Value* stored_value = NULL;
+    if (!context->working_memory()->Get(hashed_name_, &stored_value))
+      return true;
+    if (ExpectedTypeIsBooleanNotHashable) {
+      if (!context->current_node()->IsType(base::Value::TYPE_BOOLEAN) ||
+          !context->current_node()->Equals(stored_value))
+        return true;
+    } else {
+      std::string actual_hash;
+      std::string stored_hash;
+      if (!context->GetValueHash(*context->current_node(), &actual_hash) ||
+          !stored_value->GetAsString(&stored_hash) ||
+          actual_hash != stored_hash)
+        return true;
+    }
+    return context->ContinueExecution();
+  }
+
+ private:
+  std::string hashed_name_;
+  DISALLOW_COPY_AND_ASSIGN(CompareNodeToStored);
+};
+
+class CompareNodeSubstring : public Operation {
+ public:
+  explicit CompareNodeSubstring(const std::string& hashed_pattern,
+                                size_t pattern_length,
+                                uint32 pattern_sum)
+      : hashed_pattern_(hashed_pattern),
+        pattern_length_(pattern_length),
+        pattern_sum_(pattern_sum) {
+    DCHECK(pattern_length_);
+  }
+  virtual ~CompareNodeSubstring() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    std::string value_as_string;
+    if (!context->current_node()->GetAsString(&value_as_string) ||
+        !pattern_length_ || value_as_string.size() < pattern_length_)
+      return true;
+    // Go over the string with a sliding window. Meanwhile, maintain the sum in
+    // an incremental fashion, and only calculate the SHA-256 hash when the sum
+    // checks out so as to improve performance.
+    std::string::const_iterator window_begin = value_as_string.begin();
+    std::string::const_iterator window_end = window_begin + pattern_length_ - 1;
+    uint32 window_sum =
+        std::accumulate(window_begin, window_end, static_cast<uint32>(0u));
+    while (window_end != value_as_string.end()) {
+      window_sum += *window_end++;
+      if (window_sum == pattern_sum_ && context->GetHash(std::string(
+          window_begin, window_end)) == hashed_pattern_)
+        return context->ContinueExecution();
+      window_sum -= *window_begin++;
+    }
+    return true;
+  }
+
+ private:
+  std::string hashed_pattern_;
+  size_t pattern_length_;
+  uint32 pattern_sum_;
+  DISALLOW_COPY_AND_ASSIGN(CompareNodeSubstring);
+};
+
+class StopExecutingSentenceOperation : public Operation {
+ public:
+  StopExecutingSentenceOperation() {}
+  virtual ~StopExecutingSentenceOperation() {}
+  virtual bool Execute(ExecutionContext* context) OVERRIDE {
+    return false;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(StopExecutingSentenceOperation);
+};
+
+class Parser {
+ public:
+  explicit Parser(const std::string& program)
+      : program_(program),
+        next_instruction_index_(0u) {}
+  ~Parser() {}
+  bool ParseNextSentence(ScopedVector<Operation>* output) {
+    ScopedVector<Operation> operators;
+    bool sentence_ended = false;
+    while (next_instruction_index_ < program_.size() && !sentence_ended) {
+      uint8 op_code = 0;
+      if (!ReadOpCode(&op_code))
+        return false;
+      switch (static_cast<jtl_foundation::OpCodes>(op_code)) {
+        case jtl_foundation::NAVIGATE: {
+          std::string hashed_key;
+          if (!ReadHash(&hashed_key))
+            return false;
+          operators.push_back(new NavigateOperation(hashed_key));
+          break;
+        }
+        case jtl_foundation::NAVIGATE_ANY:
+          operators.push_back(new NavigateAnyOperation);
+          break;
+        case jtl_foundation::NAVIGATE_BACK:
+          operators.push_back(new NavigateBackOperation);
+          break;
+        case jtl_foundation::STORE_BOOL: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          bool value = false;
+          if (!ReadBool(&value))
+            return false;
+          operators.push_back(new StoreValue(
+              hashed_name,
+              scoped_ptr<base::Value>(new base::FundamentalValue(value))));
+          break;
+        }
+        case jtl_foundation::COMPARE_STORED_BOOL: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          bool value = false;
+          if (!ReadBool(&value))
+            return false;
+          bool default_value = false;
+          if (!ReadBool(&default_value))
+            return false;
+          operators.push_back(new CompareStoredValue(
+              hashed_name,
+              scoped_ptr<base::Value>(new base::FundamentalValue(value)),
+              scoped_ptr<base::Value>(
+                  new base::FundamentalValue(default_value))));
+          break;
+        }
+        case jtl_foundation::STORE_HASH: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          std::string hashed_value;
+          if (!ReadHash(&hashed_value))
+            return false;
+          operators.push_back(new StoreValue(
+              hashed_name,
+              scoped_ptr<base::Value>(new base::StringValue(hashed_value))));
+          break;
+        }
+        case jtl_foundation::COMPARE_STORED_HASH: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          std::string hashed_value;
+          if (!ReadHash(&hashed_value))
+            return false;
+          std::string hashed_default_value;
+          if (!ReadHash(&hashed_default_value))
+            return false;
+          operators.push_back(new CompareStoredValue(
+              hashed_name,
+              scoped_ptr<base::Value>(new base::StringValue(hashed_value)),
+              scoped_ptr<base::Value>(
+                  new base::StringValue(hashed_default_value))));
+          break;
+        }
+        case jtl_foundation::STORE_NODE_BOOL: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          operators.push_back(new StoreNodeValue<true>(hashed_name));
+          break;
+        }
+        case jtl_foundation::STORE_NODE_HASH: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          operators.push_back(new StoreNodeValue<false>(hashed_name));
+          break;
+        }
+        case jtl_foundation::STORE_NODE_REGISTERABLE_DOMAIN_HASH: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          operators.push_back(new StoreNodeRegisterableDomain(hashed_name));
+          break;
+        }
+        case jtl_foundation::COMPARE_NODE_BOOL: {
+          bool value = false;
+          if (!ReadBool(&value))
+            return false;
+          operators.push_back(new CompareNodeBool(value));
+          break;
+        }
+        case jtl_foundation::COMPARE_NODE_HASH: {
+          std::string hashed_value;
+          if (!ReadHash(&hashed_value))
+            return false;
+          operators.push_back(new CompareNodeHash(hashed_value));
+          break;
+        }
+        case jtl_foundation::COMPARE_NODE_HASH_NOT: {
+          std::string hashed_value;
+          if (!ReadHash(&hashed_value))
+            return false;
+          operators.push_back(new CompareNodeHashNot(hashed_value));
+          break;
+        }
+        case jtl_foundation::COMPARE_NODE_TO_STORED_BOOL: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          operators.push_back(new CompareNodeToStored<true>(hashed_name));
+          break;
+        }
+        case jtl_foundation::COMPARE_NODE_TO_STORED_HASH: {
+          std::string hashed_name;
+          if (!ReadHash(&hashed_name) || !base::IsStringUTF8(hashed_name))
+            return false;
+          operators.push_back(new CompareNodeToStored<false>(hashed_name));
+          break;
+        }
+        case jtl_foundation::COMPARE_NODE_SUBSTRING: {
+          std::string hashed_pattern;
+          uint32 pattern_length = 0, pattern_sum = 0;
+          if (!ReadHash(&hashed_pattern))
+            return false;
+          if (!ReadUint32(&pattern_length) || pattern_length == 0)
+            return false;
+          if (!ReadUint32(&pattern_sum))
+            return false;
+          operators.push_back(new CompareNodeSubstring(
+              hashed_pattern, pattern_length, pattern_sum));
+          break;
+        }
+        case jtl_foundation::STOP_EXECUTING_SENTENCE:
+          operators.push_back(new StopExecutingSentenceOperation);
+          break;
+        case jtl_foundation::END_OF_SENTENCE:
+          sentence_ended = true;
+          break;
+        default:
+          return false;
+      }
+    }
+    output->swap(operators);
+    return true;
+  }
+
+  bool HasNextSentence() const {
+    return next_instruction_index_ < program_.size();
+  }
+
+ private:
+  // Reads an uint8 and returns whether this operation was successful.
+  bool ReadUint8(uint8* out) {
+    DCHECK(out);
+    if (next_instruction_index_ + 1u > program_.size())
+      return false;
+    *out = static_cast<uint8>(program_[next_instruction_index_]);
+    ++next_instruction_index_;
+    return true;
+  }
+
+  // Reads an uint32 and returns whether this operation was successful.
+  bool ReadUint32(uint32* out) {
+    DCHECK(out);
+    if (next_instruction_index_ + 4u > program_.size())
+      return false;
+    *out = 0u;
+    for (int i = 0; i < 4; ++i) {
+      *out >>= 8;
+      *out |= static_cast<uint8>(program_[next_instruction_index_]) << 24;
+      ++next_instruction_index_;
+    }
+    return true;
+  }
+
+  // Reads an operator code and returns whether this operation was successful.
+  bool ReadOpCode(uint8* out) { return ReadUint8(out); }
+
+  bool ReadHash(std::string* out) {
+    DCHECK(out);
+    if (next_instruction_index_ + jtl_foundation::kHashSizeInBytes >
+        program_.size())
+      return false;
+    *out = program_.substr(next_instruction_index_,
+                           jtl_foundation::kHashSizeInBytes);
+    next_instruction_index_ += jtl_foundation::kHashSizeInBytes;
+    DCHECK(jtl_foundation::Hasher::IsHash(*out));
+    return true;
+  }
+
+  bool ReadBool(bool* out) {
+    DCHECK(out);
+    uint8 value = 0;
+    if (!ReadUint8(&value))
+      return false;
+    if (value == 0)
+      *out = false;
+    else if (value == 1)
+      *out = true;
+    else
+      return false;
+    return true;
+  }
+
+  std::string program_;
+  size_t next_instruction_index_;
+  DISALLOW_COPY_AND_ASSIGN(Parser);
+};
+
+}  // namespace
+
+JtlInterpreter::JtlInterpreter(
+    const std::string& hasher_seed,
+    const std::string& program,
+    const base::DictionaryValue* input)
+    : hasher_seed_(hasher_seed),
+      program_(program),
+      input_(input),
+      working_memory_(new base::DictionaryValue),
+      result_(OK) {
+  DCHECK(input->IsType(base::Value::TYPE_DICTIONARY));
+}
+
+JtlInterpreter::~JtlInterpreter() {}
+
+void JtlInterpreter::Execute() {
+  jtl_foundation::Hasher hasher(hasher_seed_);
+  Parser parser(program_);
+  while (parser.HasNextSentence()) {
+    ScopedVector<Operation> sentence;
+    if (!parser.ParseNextSentence(&sentence)) {
+      result_ = PARSE_ERROR;
+      return;
+    }
+    ExecutionContext context(
+        &hasher, sentence.get(), input_, working_memory_.get());
+    context.ContinueExecution();
+    if (context.error()) {
+      result_ = RUNTIME_ERROR;
+      return;
+    }
+  }
+}
+
+bool JtlInterpreter::GetOutputBoolean(const std::string& unhashed_key,
+                                      bool* output) const {
+  std::string hashed_key =
+      jtl_foundation::Hasher(hasher_seed_).GetHash(unhashed_key);
+  return working_memory_->GetBoolean(hashed_key, output);
+}
+
+bool JtlInterpreter::GetOutputString(const std::string& unhashed_key,
+                                     std::string* output) const {
+  std::string hashed_key =
+      jtl_foundation::Hasher(hasher_seed_).GetHash(unhashed_key);
+  return working_memory_->GetString(hashed_key, output);
+}
+
+int JtlInterpreter::CalculateProgramChecksum() const {
+  uint8 digest[3] = {};
+  crypto::SHA256HashString(program_, digest, arraysize(digest));
+  return static_cast<uint32>(digest[0]) << 16 |
+         static_cast<uint32>(digest[1]) << 8 |
+         static_cast<uint32>(digest[2]);
+}