// Copyright (c) 2013, 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.

// Generate a snapshot file after loading all the scripts specified on the
// command line.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <cstdarg>
#include <memory>

#include "bin/builtin.h"
#include "bin/console.h"
#include "bin/dartutils.h"
#include "bin/dfe.h"
#include "bin/eventhandler.h"
#include "bin/file.h"
#include "bin/loader.h"
#include "bin/log.h"
#include "bin/options.h"
#include "bin/platform.h"
#include "bin/thread.h"
#include "bin/utils.h"
#include "bin/vmservice_impl.h"

#include "include/dart_api.h"
#include "include/dart_tools_api.h"

#include "platform/globals.h"
#include "platform/growable_array.h"
#include "platform/hashmap.h"

namespace dart {
namespace bin {

// Exit code indicating an API error.
static const int kApiErrorExitCode = 253;
// Exit code indicating a compilation error.
static const int kCompilationErrorExitCode = 254;
// Exit code indicating an unhandled error that is not a compilation error.
static const int kErrorExitCode = 255;

#define CHECK_RESULT(result)                                                   \
  if (Dart_IsError(result)) {                                                  \
    intptr_t exit_code = 0;                                                    \
    Log::PrintErr("Error: %s\n", Dart_GetError(result));                       \
    if (Dart_IsCompilationError(result)) {                                     \
      exit_code = kCompilationErrorExitCode;                                   \
    } else if (Dart_IsApiError(result)) {                                      \
      exit_code = kApiErrorExitCode;                                           \
    } else {                                                                   \
      exit_code = kErrorExitCode;                                              \
    }                                                                          \
    Dart_ExitScope();                                                          \
    Dart_ShutdownIsolate();                                                    \
    exit(exit_code);                                                           \
  }

// The core snapshot to use when creating isolates. Normally NULL, but loaded
// from a file when creating script snapshots.
const uint8_t* isolate_snapshot_data = NULL;
const uint8_t* isolate_snapshot_instructions = NULL;

// Global state that indicates whether a snapshot is to be created and
// if so which file to write the snapshot into.
enum SnapshotKind {
  kCore,
  kCoreJIT,
  kScript,
  kAppAOTBlobs,
  kAppAOTAssembly,
  kVMAOTAssembly,
};
static SnapshotKind snapshot_kind = kCore;

// Global state which contains a pointer to the script name for which
// a snapshot needs to be created (NULL would result in the creation
// of a generic snapshot that contains only the corelibs).
static char* app_script_name = NULL;

// Global state that captures the entry point manifest files specified on the
// command line.
static CommandLineOptions* entry_points_files = NULL;

// The environment provided through the command line using -D options.
static dart::SimpleHashMap* environment = NULL;

static bool ProcessEnvironmentOption(const char* arg,
                                     CommandLineOptions* vm_options) {
  return OptionProcessor::ProcessEnvironmentOption(arg, vm_options,
                                                   &environment);
}

static const char* kSnapshotKindNames[] = {
    "core",
    "core-jit",
    "script",
    "app-aot-blobs",
    "app-aot-assembly",
    "vm-aot-assembly",
    NULL,
};

#define STRING_OPTIONS_LIST(V)                                                 \
  V(vm_snapshot_data, vm_snapshot_data_filename)                               \
  V(vm_snapshot_instructions, vm_snapshot_instructions_filename)               \
  V(isolate_snapshot_data, isolate_snapshot_data_filename)                     \
  V(isolate_snapshot_instructions, isolate_snapshot_instructions_filename)     \
  V(shared_data, shared_data_filename)                                         \
  V(shared_instructions, shared_instructions_filename)                         \
  V(assembly, assembly_filename)                                               \
  V(script_snapshot, script_snapshot_filename)                                 \
  V(dependencies, dependencies_filename)                                       \
  V(load_compilation_trace, load_compilation_trace_filename)                   \
  V(package_root, commandline_package_root)                                    \
  V(packages, commandline_packages_file)                                       \
  V(save_obfuscation_map, obfuscation_map_filename)

#define BOOL_OPTIONS_LIST(V)                                                   \
  V(obfuscate, obfuscate)                                                      \
  V(verbose, verbose)                                                          \
  V(version, version)                                                          \
  V(help, help)

#define STRING_OPTION_DEFINITION(flag, variable)                               \
  static const char* variable = NULL;                                          \
  DEFINE_STRING_OPTION(flag, variable)
STRING_OPTIONS_LIST(STRING_OPTION_DEFINITION)
#undef STRING_OPTION_DEFINITION

#define BOOL_OPTION_DEFINITION(flag, variable)                                 \
  static bool variable = false;                                                \
  DEFINE_BOOL_OPTION(flag, variable)
BOOL_OPTIONS_LIST(BOOL_OPTION_DEFINITION)
#undef BOOL_OPTION_DEFINITION

DEFINE_ENUM_OPTION(snapshot_kind, SnapshotKind, snapshot_kind);
DEFINE_STRING_OPTION_CB(embedder_entry_points_manifest,
                        { entry_points_files->AddArgument(value); });
DEFINE_STRING_OPTION_CB(url_mapping,
                        { DartUtils::url_mapping->AddArgument(value); });
DEFINE_CB_OPTION(ProcessEnvironmentOption);

static bool IsSnapshottingForPrecompilation() {
  return (snapshot_kind == kAppAOTBlobs) ||
         (snapshot_kind == kAppAOTAssembly) ||
         (snapshot_kind == kVMAOTAssembly);
}

static bool SnapshotKindAllowedFromKernel() {
  return snapshot_kind != kScript;
}

// clang-format off
static void PrintUsage() {
  Log::PrintErr(
"Usage: gen_snapshot [<vm-flags>] [<options>] [<dart-script-file>]           \n"
"                                                                            \n"
"Common options:                                                             \n"
"--package_root=<path>                                                       \n"
"  Where to find packages, that is, package:...  imports.                    \n"
"--packages=<packages_file>                                                  \n"
"  Where to find a package spec file                                         \n"
"--url_mapping=<mapping>                                                     \n"
"  Uses the URL mapping(s) specified on the command line to load the         \n"
"  libraries.                                                                \n"
"--dependencies=<output-file>                                                \n"
"  Generates a Makefile with snapshot output files as targets and all        \n"
"  transitive imports as sources.                                            \n"
"--help                                                                      \n"
"  Display this message (add --verbose for information about all VM options).\n"
"--version                                                                   \n"
"  Print the VM version.                                                     \n"
"                                                                            \n"
"To create a core snapshot:                                                  \n"
"--snapshot_kind=core                                                        \n"
"--vm_snapshot_data=<output-file>                                            \n"
"--isolate_snapshot_data=<output-file>                                       \n"
"[<dart-script-file>]                                                        \n"
"                                                                            \n"
"Writes a snapshot of <dart-script-file> to the specified snapshot files.    \n"
"If no <dart-script-file> is passed, a generic snapshot of all the corelibs  \n"
"is created.                                                                 \n"
"                                                                            \n"
"To create a script snapshot with respect to a given core snapshot:          \n"
"--snapshot_kind=script                                                      \n"
"--vm_snapshot_data=<input-file>                                             \n"
"--isolate_snapshot_data=<input-file>                                        \n"
"--script_snapshot=<output-file>                                             \n"
"<dart-script-file>                                                          \n"
"                                                                            \n"
"Writes a snapshot of <dart-script-file> to the specified snapshot files.    \n"
"If no <dart-script-file> is passed, a generic snapshot of all the corelibs  \n"
"is created.                                                                 \n"
"                                                                            \n"
"To create an AOT application snapshot as blobs suitable for loading with    \n"
"mmap:                                                                       \n"
"--snapshot_kind=app-aot-blobs                                               \n"
"--vm_snapshot_data=<output-file>                                            \n"
"--vm_snapshot_instructions=<output-file>                                    \n"
"--isolate_snapshot_data=<output-file>                                       \n"
"--isolate_snapshot_instructions=<output-file>                               \n"
"{--embedder_entry_points_manifest=<input-file>}                             \n"
"[--obfuscate]                                                               \n"
"[--save-obfuscation-map=<map-filename>]                                     \n"
" <dart-script-file>                                                         \n"
"                                                                            \n"
"To create an AOT application snapshot as assembly suitable for compilation  \n"
"as a static or dynamic library:                                             \n"
"--snapshot_kind=app-aot-assembly                                            \n"
"--assembly=<output-file>                                                    \n"
"{--embedder_entry_points_manifest=<input-file>}                             \n"
"[--obfuscate]                                                               \n"
"[--save-obfuscation-map=<map-filename>]                                     \n"
"<dart-script-file>                                                          \n"
"                                                                            \n"
"AOT snapshots require entry points manifest files, which list the places    \n"
"in the Dart program the embedder calls from the C API (Dart_Invoke, etc).   \n"
"Not specifying these may cause the tree shaker to remove them from the      \n"
"program. The format of this manifest is as follows. Each line in the        \n"
"manifest is a comma separated list of three elements. The first entry is    \n"
"the library URI, the second entry is the class name and the final entry     \n"
"the function name. The file must be terminated with a newline character.    \n"
"                                                                            \n"
"Example:                                                                    \n"
"    dart:something,SomeClass,doSomething                                    \n"
"                                                                            \n"
"AOT snapshots can be obfuscated: that is all identifiers will be renamed    \n"
"during compilation. This mode is enabled with --obfuscate flag. Mapping     \n"
"between original and obfuscated names can be serialized as a JSON array     \n"
"using --save-obfuscation-map=<filename> option. See dartbug.com/30524       \n"
"for implementation details and limitations of the obfuscation pass.         \n"
"                                                                            \n"
"\n");
  if (verbose) {
    Log::PrintErr(
"The following options are only used for VM development and may\n"
"be changed in any future version:\n");
    const char* print_flags = "--print_flags";
    char* error = Dart_SetVMFlags(1, &print_flags);
    ASSERT(error == NULL);
  }
}
// clang-format on

// Parse out the command line arguments. Returns -1 if the arguments
// are incorrect, 0 otherwise.
static int ParseArguments(int argc,
                          char** argv,
                          CommandLineOptions* vm_options,
                          char** script_name) {
  const char* kPrefix = "-";
  const intptr_t kPrefixLen = strlen(kPrefix);

  // Skip the binary name.
  int i = 1;

  // Parse out the vm options.
  while ((i < argc) &&
         OptionProcessor::IsValidFlag(argv[i], kPrefix, kPrefixLen)) {
    if (OptionProcessor::TryProcess(argv[i], vm_options)) {
      i += 1;
      continue;
    }
    vm_options->AddArgument(argv[i]);
    i += 1;
  }

  // Get the script name.
  if (i < argc) {
    *script_name = argv[i];
    i += 1;
  } else {
    *script_name = NULL;
  }

  if (help) {
    PrintUsage();
    Platform::Exit(0);
  } else if (version) {
    Log::PrintErr("Dart VM version: %s\n", Dart_VersionString());
    Platform::Exit(0);
  }

  // Verify consistency of arguments.
  if ((commandline_package_root != NULL) &&
      (commandline_packages_file != NULL)) {
    Log::PrintErr(
        "Specifying both a packages directory and a packages "
        "file is invalid.\n\n");
    return -1;
  }

  switch (snapshot_kind) {
    case kCore: {
      if ((vm_snapshot_data_filename == NULL) ||
          (isolate_snapshot_data_filename == NULL)) {
        Log::PrintErr(
            "Building a core snapshot requires specifying output files for "
            "--vm_snapshot_data and --isolate_snapshot_data.\n\n");
        return -1;
      }
      break;
    }
    case kCoreJIT: {
      if ((vm_snapshot_data_filename == NULL) ||
          (vm_snapshot_instructions_filename == NULL) ||
          (isolate_snapshot_data_filename == NULL) ||
          (isolate_snapshot_instructions_filename == NULL)) {
        Log::PrintErr(
            "Building a core JIT snapshot requires specifying output "
            "files for --vm_snapshot_data, --vm_snapshot_instructions, "
            "--isolate_snapshot_data and --isolate_snapshot_instructions.\n\n");
        return -1;
      }
      break;
    }
    case kScript: {
      if ((vm_snapshot_data_filename == NULL) ||
          (isolate_snapshot_data_filename == NULL) ||
          (script_snapshot_filename == NULL) || (*script_name == NULL)) {
        Log::PrintErr(
            "Building a script snapshot requires specifying input files for "
            "--vm_snapshot_data and --isolate_snapshot_data, an output file "
            "for --script_snapshot, and a Dart script.\n\n");
        return -1;
      }
      break;
    }
    case kAppAOTBlobs: {
      if ((vm_snapshot_data_filename == NULL) ||
          (vm_snapshot_instructions_filename == NULL) ||
          (isolate_snapshot_data_filename == NULL) ||
          (isolate_snapshot_instructions_filename == NULL) ||
          (*script_name == NULL)) {
        Log::PrintErr(
            "Building an AOT snapshot as blobs requires specifying output "
            "files for --vm_snapshot_data, --vm_snapshot_instructions, "
            "--isolate_snapshot_data and --isolate_snapshot_instructions and a "
            "Dart script.\n\n");
        return -1;
      }
      break;
    }
    case kAppAOTAssembly: {
      if ((assembly_filename == NULL) || (*script_name == NULL)) {
        Log::PrintErr(
            "Building an AOT snapshot as assembly requires specifying "
            "an output file for --assembly and a Dart script.\n\n");
        return -1;
      }
      break;
    }
    case kVMAOTAssembly: {
      if ((assembly_filename == NULL) || (*script_name != NULL)) {
        Log::PrintErr(
            "Building an AOT snapshot as assembly requires specifying "
            "an output file for --assembly and a Dart script.\n\n");
        return -1;
      }
      break;
    }
  }

  if (!obfuscate && obfuscation_map_filename != NULL) {
    Log::PrintErr(
        "--obfuscation_map=<...> should only be specified when obfuscation is "
        "enabled by --obfuscate flag.\n\n");
    return -1;
  }

  if (obfuscate && !IsSnapshottingForPrecompilation()) {
    Log::PrintErr(
        "Obfuscation can only be enabled when building AOT snapshot.\n\n");
    return -1;
  }

  return 0;
}

static File* OpenFile(const char* filename) {
  File* file = File::Open(NULL, filename, File::kWriteTruncate);
  if (file == NULL) {
    Log::PrintErr("Error: Unable to write file: %s\n\n", filename);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
  return file;
}

static void WriteFile(const char* filename,
                      const uint8_t* buffer,
                      const intptr_t size) {
  File* file = OpenFile(filename);
  RefCntReleaseScope<File> rs(file);
  if (!file->WriteFully(buffer, size)) {
    Log::PrintErr("Error: Unable to write file: %s\n\n", filename);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
}

static void ReadFile(const char* filename, uint8_t** buffer, intptr_t* size) {
  File* file = File::Open(NULL, filename, File::kRead);
  if (file == NULL) {
    Log::PrintErr("Unable to open file %s\n", filename);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
  RefCntReleaseScope<File> rs(file);
  *size = file->Length();
  *buffer = reinterpret_cast<uint8_t*>(malloc(*size));
  if (!file->ReadFully(*buffer, *size)) {
    Log::PrintErr("Unable to read file %s\n", filename);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
}

class UriResolverIsolateScope {
 public:
  UriResolverIsolateScope() {
    ASSERT(isolate != NULL);
    snapshotted_isolate_ = Dart_CurrentIsolate();
    Dart_ExitIsolate();
    Dart_EnterIsolate(isolate);
    Dart_EnterScope();
  }

  ~UriResolverIsolateScope() {
    ASSERT(snapshotted_isolate_ != NULL);
    Dart_ExitScope();
    Dart_ExitIsolate();
    Dart_EnterIsolate(snapshotted_isolate_);
  }

  static Dart_Isolate isolate;

 private:
  Dart_Isolate snapshotted_isolate_;

  DISALLOW_COPY_AND_ASSIGN(UriResolverIsolateScope);
};

Dart_Isolate UriResolverIsolateScope::isolate = NULL;

static void AddDependency(const char* uri_string) {
  IsolateData* isolate_data =
      reinterpret_cast<IsolateData*>(Dart_CurrentIsolateData());
  MallocGrowableArray<char*>* dependencies = isolate_data->dependencies();
  if (dependencies != NULL) {
    dependencies->Add(strdup(uri_string));
  }
}

static Dart_Handle LoadUrlContents(const char* uri_string) {
  bool failed = false;
  char* error_string = NULL;
  uint8_t* payload = NULL;
  intptr_t payload_length = 0;
  // Switch to the UriResolver Isolate and load the script.
  {
    UriResolverIsolateScope scope;

    Dart_Handle resolved_uri = Dart_NewStringFromCString(uri_string);
    Dart_Handle result =
        Loader::LoadUrlContents(resolved_uri, &payload, &payload_length);
    if (Dart_IsError(result)) {
      failed = true;
      error_string = strdup(Dart_GetError(result));
    }
  }
  AddDependency(uri_string);
  // Switch back to the isolate from which we generate the snapshot and
  // create the source string for the specified uri.
  Dart_Handle result;
  if (!failed) {
    result = Dart_NewStringFromUTF8(payload, payload_length);
    free(payload);
  } else {
    result = Dart_NewApiError(error_string);
    free(error_string);
  }
  return result;
}

static Dart_Handle ResolveUriInWorkingDirectory(const char* script_uri) {
  bool failed = false;
  char* result_string = NULL;

  {
    UriResolverIsolateScope scope;

    // Run DartUtils::ResolveUriInWorkingDirectory in context of uri resolver
    // isolate.
    Dart_Handle result = DartUtils::ResolveUriInWorkingDirectory(
        DartUtils::NewString(script_uri));
    if (Dart_IsError(result)) {
      failed = true;
      result_string = strdup(Dart_GetError(result));
    } else {
      result_string = strdup(DartUtils::GetStringValue(result));
    }
  }

  Dart_Handle result = failed ? Dart_NewApiError(result_string)
                              : DartUtils::NewString(result_string);
  free(result_string);
  return result;
}

static Dart_Handle LoadSnapshotCreationScript(const char* script_name) {
  // First resolve the specified script uri with respect to the original
  // working directory.
  Dart_Handle resolved_uri = ResolveUriInWorkingDirectory(script_name);
  if (Dart_IsError(resolved_uri)) {
    return resolved_uri;
  }
  // Now load the contents of the specified uri.
  const char* resolved_uri_string = DartUtils::GetStringValue(resolved_uri);
  Dart_Handle source = LoadUrlContents(resolved_uri_string);

  if (Dart_IsError(source)) {
    return source;
  }
  if ((snapshot_kind == kCore) || (snapshot_kind == kCoreJIT)) {
    return Dart_LoadLibrary(resolved_uri, Dart_Null(), source, 0, 0);
  } else {
    return Dart_LoadScript(resolved_uri, Dart_Null(), source, 0, 0);
  }
}

static Builtin::BuiltinLibraryId BuiltinId(const char* url) {
  if (DartUtils::IsDartBuiltinLibURL(url)) {
    return Builtin::kBuiltinLibrary;
  }
  if (DartUtils::IsDartIOLibURL(url)) {
    return Builtin::kIOLibrary;
  }
  if (DartUtils::IsDartHttpLibURL(url)) {
    return Builtin::kHttpLibrary;
  }
  if (DartUtils::IsDartCLILibURL(url)) {
    return Builtin::kCLILibrary;
  }
  return Builtin::kInvalidLibrary;
}

// Generates a depfile like gcc -M -MF. Must be consumable by Ninja.
class DependenciesFileWriter : public ValueObject {
 public:
  DependenciesFileWriter() : dependencies_(NULL), file_(NULL), success_(true) {}

  void WriteDependencies(MallocGrowableArray<char*>* dependencies) {
    dependencies_ = dependencies;

    file_ = File::Open(NULL, dependencies_filename, File::kWriteTruncate);
    if (file_ == NULL) {
      Log::PrintErr("Error: Unable to open dependencies file: %s\n\n",
                    dependencies_filename);
      exit(kErrorExitCode);
    }
    RefCntReleaseScope<File> rs(file_);

    // Write dependencies for one of the output files.
    // TODO(https://github.com/ninja-build/ninja/issues/1184): Do this for all
    // output files.
    switch (snapshot_kind) {
      case kCore:
        WriteDependenciesWithTarget(vm_snapshot_data_filename);
        // WriteDependenciesWithTarget(isolate_snapshot_data_filename);
        break;
      case kScript:
        WriteDependenciesWithTarget(script_snapshot_filename);
        break;
      case kAppAOTAssembly:
        WriteDependenciesWithTarget(assembly_filename);
        break;
      case kCoreJIT:
      case kAppAOTBlobs:
        WriteDependenciesWithTarget(vm_snapshot_data_filename);
        // WriteDependenciesWithTarget(vm_snapshot_instructions_filename);
        // WriteDependenciesWithTarget(isolate_snapshot_data_filename);
        // WriteDependenciesWithTarget(isolate_snapshot_instructions_filename);
        break;
      default:
        UNREACHABLE();
    }

    if (!success_) {
      Log::PrintErr("Error: Unable to write dependencies file: %s\n\n",
                    dependencies_filename);
      exit(kErrorExitCode);
    }
  }

 private:
  void WriteDependenciesWithTarget(const char* target) {
    WritePath(target);
    Write(": ");

    if (snapshot_kind == kScript) {
      if (vm_snapshot_data_filename != NULL) {
        WritePath(vm_snapshot_data_filename);
      }
      if (vm_snapshot_instructions_filename != NULL) {
        WritePath(vm_snapshot_instructions_filename);
      }
      if (isolate_snapshot_data_filename != NULL) {
        WritePath(isolate_snapshot_data_filename);
      }
      if (isolate_snapshot_instructions_filename != NULL) {
        WritePath(isolate_snapshot_instructions_filename);
      }
    }

    for (intptr_t i = 0; i < dependencies_->length(); i++) {
      WritePath(dependencies_->At(i));
    }

    Write("\n");
  }

  char* EscapePath(const char* path) {
    char* escaped_path = reinterpret_cast<char*>(malloc(strlen(path) * 2 + 1));
    const char* read_cursor = path;
    char* write_cursor = escaped_path;
    while (*read_cursor != '\0') {
      if ((*read_cursor == ' ') || (*read_cursor == '\\')) {
        *write_cursor++ = '\\';
      }
      *write_cursor++ = *read_cursor++;
    }
    *write_cursor = '\0';
    return escaped_path;
  }

  void WritePath(const char* path) {
    char* escaped_path = EscapePath(path);
    success_ &= file_->Print("%s ", escaped_path);
    free(escaped_path);
  }

  void Write(const char* string) { success_ &= file_->Print("%s", string); }

  MallocGrowableArray<char*>* dependencies_;
  File* file_;
  bool success_;
};

static void CreateAndWriteDependenciesFile() {
  IsolateData* isolate_data =
      reinterpret_cast<IsolateData*>(Dart_CurrentIsolateData());
  MallocGrowableArray<char*>* dependencies = isolate_data->dependencies();
  if (dependencies == NULL) {
    return;
  }

  Loader::ResolveDependenciesAsFilePaths();

  ASSERT(dependencies_filename != NULL);
  if (dependencies_filename != NULL) {
    DependenciesFileWriter writer;
    writer.WriteDependencies(dependencies);
  }

  for (intptr_t i = 0; i < dependencies->length(); i++) {
    free(dependencies->At(i));
  }
  dependencies->Clear();
}

static Dart_Handle CreateSnapshotLibraryTagHandler(Dart_LibraryTag tag,
                                                   Dart_Handle library,
                                                   Dart_Handle url) {
  if (!Dart_IsLibrary(library)) {
    return Dart_NewApiError("not a library");
  }
  Dart_Handle library_url = Dart_LibraryUrl(library);
  if (Dart_IsError(library_url)) {
    return Dart_NewApiError("accessing library url failed");
  }
  const char* library_url_string = DartUtils::GetStringValue(library_url);
  const char* mapped_library_url_string =
      DartUtils::MapLibraryUrl(library_url_string);
  if (mapped_library_url_string != NULL) {
    library_url = ResolveUriInWorkingDirectory(mapped_library_url_string);
    library_url_string = DartUtils::GetStringValue(library_url);
  }

  if (!Dart_IsString(url)) {
    return Dart_NewApiError("url is not a string");
  }
  const char* url_string = DartUtils::GetStringValue(url);
  const char* mapped_url_string = DartUtils::MapLibraryUrl(url_string);

  Builtin::BuiltinLibraryId libraryBuiltinId = BuiltinId(library_url_string);
  if (tag == Dart_kCanonicalizeUrl) {
    if (mapped_url_string) {
      return url;
    }
    // Parts of internal libraries are handled internally.
    if (libraryBuiltinId != Builtin::kInvalidLibrary) {
      return url;
    }
    return Dart_DefaultCanonicalizeUrl(library_url, url);
  }

  Builtin::BuiltinLibraryId builtinId = BuiltinId(url_string);
  if ((builtinId != Builtin::kInvalidLibrary) && (mapped_url_string == NULL)) {
    // Special case for importing a builtin library that isn't remapped.
    if (tag == Dart_kImportTag) {
      return Builtin::LoadLibrary(url, builtinId);
    }
    ASSERT(tag == Dart_kSourceTag);
    return DartUtils::NewError("Unable to part '%s' ", url_string);
  }

  if (libraryBuiltinId != Builtin::kInvalidLibrary) {
    // Special case for parting sources of a builtin library.
    if (tag == Dart_kSourceTag) {
      intptr_t len = snprintf(NULL, 0, "%s/%s", library_url_string, url_string);
      char* patch_filename = reinterpret_cast<char*>(malloc(len + 1));
      snprintf(patch_filename, len + 1, "%s/%s", library_url_string,
               url_string);
      Dart_Handle prefixed_url = Dart_NewStringFromCString(patch_filename);
      Dart_Handle result = Dart_LoadSource(
          library, prefixed_url, Dart_Null(),
          Builtin::PartSource(libraryBuiltinId, patch_filename), 0, 0);
      free(patch_filename);
      return result;
    }
    ASSERT(tag == Dart_kImportTag);
    return DartUtils::NewError("Unable to import '%s' ", url_string);
  }

  Dart_Handle resolved_url = url;
  if (mapped_url_string != NULL) {
    // Mapped urls are relative to working directory.
    resolved_url = ResolveUriInWorkingDirectory(mapped_url_string);
    if (Dart_IsError(resolved_url)) {
      return resolved_url;
    }
  }
  const char* resolved_uri_string = DartUtils::GetStringValue(resolved_url);
  Dart_Handle source = LoadUrlContents(resolved_uri_string);
  if (Dart_IsError(source)) {
    return source;
  }
  if (tag == Dart_kImportTag) {
    return Dart_LoadLibrary(url, Dart_Null(), source, 0, 0);
  } else {
    ASSERT(tag == Dart_kSourceTag);
    return Dart_LoadSource(library, url, Dart_Null(), source, 0, 0);
  }
}

static Dart_Handle LoadGenericSnapshotCreationScript(
    Builtin::BuiltinLibraryId id) {
  Dart_Handle source = Builtin::Source(id);
  if (Dart_IsError(source)) {
    return source;  // source contains the error string.
  }
  Dart_Handle lib;
  // Load the builtin library to make it available in the snapshot
  // for importing.
  lib = Builtin::LoadAndCheckLibrary(id);
  ASSERT(!Dart_IsError(lib));
  return lib;
}

static void LoadEntryPoint(size_t lib_index,
                           const Dart_QualifiedFunctionName* entry) {
  if (strcmp(entry->library_uri, "::") == 0) {
    return;  // Root library always loaded; can't `import '::';`.
  }

  Dart_Handle library_string = Dart_NewStringFromCString(entry->library_uri);
  DART_CHECK_VALID(library_string);
  Dart_Handle library = Dart_LookupLibrary(library_string);
  // Embedder entry points may be setup in libraries that have not been
  // explicitly loaded by the application script. In such cases, library lookup
  // will fail. Manually load those libraries.
  if (Dart_IsError(library)) {
    static const uint32_t kLoadBufferMaxSize = 128;
    char* load_buffer =
        reinterpret_cast<char*>(calloc(kLoadBufferMaxSize, sizeof(char)));
    snprintf(load_buffer, kLoadBufferMaxSize, "import '%s';",
             DartUtils::GetStringValue(library_string));
    Dart_Handle script_handle = Dart_NewStringFromCString(load_buffer);
    memset(load_buffer, 0, kLoadBufferMaxSize);
    snprintf(load_buffer, kLoadBufferMaxSize, "dart:_snapshot_%zu", lib_index);
    Dart_Handle script_url = Dart_NewStringFromCString(load_buffer);
    free(load_buffer);
    Dart_Handle loaded =
        Dart_LoadLibrary(script_url, Dart_Null(), script_handle, 0, 0);
    DART_CHECK_VALID(loaded);

    // Do a fresh lookup
    library = Dart_LookupLibrary(library_string);
  }

  DART_CHECK_VALID(library);
}

static void ImportNativeEntryPointLibrariesIntoRoot(
    const Dart_QualifiedFunctionName* entries) {
  if (entries == NULL) {
    return;
  }

  size_t index = 0;
  while (true) {
    Dart_QualifiedFunctionName entry = entries[index++];
    if (entry.library_uri == NULL) {
      // The termination sentinel has null members.
      break;
    }
    if (strcmp(entry.library_uri, "::") != 0) {
      Dart_Handle entry_library =
          Dart_LookupLibrary(Dart_NewStringFromCString(entry.library_uri));
      DART_CHECK_VALID(entry_library);
      Dart_Handle import_result = Dart_LibraryImportLibrary(
          entry_library, Dart_RootLibrary(), Dart_EmptyString());
      DART_CHECK_VALID(import_result);
    }
  }
}

static void LoadEntryPoints(const Dart_QualifiedFunctionName* entries) {
  if (entries == NULL) {
    return;
  }

  // Setup native resolvers for all libraries found in the manifest.
  size_t index = 0;
  while (true) {
    Dart_QualifiedFunctionName entry = entries[index++];
    if (entry.library_uri == NULL) {
      // The termination sentinel has null members.
      break;
    }
    // Ensure library named in entry point is loaded.
    LoadEntryPoint(index, &entry);
  }
}

static void CleanupEntryPointItem(const Dart_QualifiedFunctionName* entry) {
  if (entry == NULL) {
    return;
  }
  // The allocation used for these entries is zero'ed. So even in error cases,
  // references to some entries will be null. Calling this on an already cleaned
  // up entry is programmer error.
  free(const_cast<char*>(entry->library_uri));
  free(const_cast<char*>(entry->class_name));
  free(const_cast<char*>(entry->function_name));
}

static void CleanupEntryPointsCollection(Dart_QualifiedFunctionName* entries) {
  if (entries == NULL) {
    return;
  }

  size_t index = 0;
  while (true) {
    Dart_QualifiedFunctionName entry = entries[index++];
    if (entry.library_uri == NULL) {
      break;
    }
    CleanupEntryPointItem(&entry);
  }
  free(entries);
}

char* ParserErrorStringCreate(const char* format, ...) {
  static const size_t kErrorBufferSize = 256;

  char* error_buffer =
      reinterpret_cast<char*>(calloc(kErrorBufferSize, sizeof(char)));
  va_list args;
  va_start(args, format);
  vsnprintf(error_buffer, kErrorBufferSize, format, args);
  va_end(args);

  // In case of error, the buffer is released by the caller
  return error_buffer;
}

const char* ParseEntryNameForIndex(uint8_t index) {
  switch (index) {
    case 0:
      return "Library";
    case 1:
      return "Class";
    case 2:
      return "Function";
    default:
      return "Unknown";
  }
  return NULL;
}

static bool ParseEntryPointsManifestSingleLine(
    const char* line,
    Dart_QualifiedFunctionName* entry,
    char** error) {
  bool success = true;
  size_t offset = 0;
  for (uint8_t i = 0; i < 3; i++) {
    const char* component = strchr(line + offset, i == 2 ? '\n' : ',');
    if (component == NULL) {
      success = false;
      *error = ParserErrorStringCreate(
          "Manifest entries must be comma separated and newline terminated. "
          "Could not parse '%s' on line '%s'",
          ParseEntryNameForIndex(i), line);
      break;
    }

    int64_t chars_read = component - (line + offset);
    if (chars_read <= 0) {
      success = false;
      *error =
          ParserErrorStringCreate("There is no '%s' specified on line '%s'",
                                  ParseEntryNameForIndex(i), line);
      break;
    }

    if (entry != NULL) {
      // These allocations are collected in |CleanupEntryPointsCollection|.
      char* entry_item =
          reinterpret_cast<char*>(calloc(chars_read + 1, sizeof(char)));
      memmove(entry_item, line + offset, chars_read);

      switch (i) {
        case 0:  // library
          entry->library_uri = entry_item;
          break;
        case 1:  // class
          entry->class_name = entry_item;
          break;
        case 2:  // function
          entry->function_name = entry_item;
          break;
        default:
          free(entry_item);
          success = false;
          *error = ParserErrorStringCreate("Internal parser error\n");
          break;
      }
    }

    offset += chars_read + 1;
  }
  return success;
}

int64_t ParseEntryPointsManifestLines(FILE* file,
                                      Dart_QualifiedFunctionName* collection) {
  int64_t entries = 0;

  static const int kManifestMaxLineLength = 1024;
  char* line = reinterpret_cast<char*>(malloc(kManifestMaxLineLength));
  size_t line_number = 0;
  while (true) {
    line_number++;
    char* read_line = fgets(line, kManifestMaxLineLength, file);

    if (read_line == NULL) {
      if ((feof(file) != 0) && (ferror(file) != 0)) {
        Log::PrintErr(
            "Error while reading line number %zu. The manifest must be "
            "terminated by a newline\n",
            line_number);
        entries = -1;
      }
      break;
    }

    if ((read_line[0] == '\n') || (read_line[0] == '#')) {
      // Blank or comment line.
      continue;
    }

    Dart_QualifiedFunctionName* entry =
        collection != NULL ? collection + entries : NULL;

    char* error_buffer = NULL;
    if (!ParseEntryPointsManifestSingleLine(read_line, entry, &error_buffer)) {
      CleanupEntryPointItem(entry);
      Log::PrintErr("Parser error on line %zu: %s\n", line_number,
                    error_buffer);
      free(error_buffer);
      entries = -1;
      break;
    }

    entries++;
  }

  free(line);

  return entries;
}

static Dart_QualifiedFunctionName* ParseEntryPointsManifestFiles() {
  // Total number of entries across all manifest files.
  int64_t entry_count = 0;

  // Parse the files once but don't store the results. This is done to first
  // determine the number of entries in the manifest
  for (intptr_t i = 0; i < entry_points_files->count(); i++) {
    const char* path = entry_points_files->GetArgument(i);

    FILE* file = fopen(path, "r");

    if (file == NULL) {
      Log::PrintErr("Could not open entry points manifest file `%s`\n", path);
      return NULL;
    }

    int64_t entries = ParseEntryPointsManifestLines(file, NULL);
    fclose(file);

    if (entries < 0) {
      Log::PrintErr("Manifest file `%s` specified is invalid\n", path);
      return NULL;
    }

    entry_count += entries;
  }

  // Allocate enough storage for the entries in the file plus a termination
  // sentinel and parse it again to populate the allocation
  Dart_QualifiedFunctionName* entries =
      reinterpret_cast<Dart_QualifiedFunctionName*>(
          calloc(entry_count + 1, sizeof(Dart_QualifiedFunctionName)));

  int64_t parsed_entry_count = 0;
  for (intptr_t i = 0; i < entry_points_files->count(); i++) {
    const char* path = entry_points_files->GetArgument(i);
    FILE* file = fopen(path, "r");
    parsed_entry_count +=
        ParseEntryPointsManifestLines(file, &entries[parsed_entry_count]);
    fclose(file);
  }

  ASSERT(parsed_entry_count == entry_count);

  // The entries allocation must be explicitly cleaned up via
  // |CleanupEntryPointsCollection|
  return entries;
}

static Dart_QualifiedFunctionName* ParseEntryPointsManifestIfPresent() {
  Dart_QualifiedFunctionName* entries = ParseEntryPointsManifestFiles();
  if ((entries == NULL) && IsSnapshottingForPrecompilation()) {
    Log::PrintErr(
        "Could not find native embedder entry points during precompilation\n");
    exit(kErrorExitCode);
  }
  return entries;
}

static void LoadCompilationTrace() {
  if ((load_compilation_trace_filename != NULL) &&
      (snapshot_kind == kCoreJIT)) {
    uint8_t* buffer = NULL;
    intptr_t size = 0;
    ReadFile(load_compilation_trace_filename, &buffer, &size);
    Dart_Handle result = Dart_LoadCompilationTrace(buffer, size);
    CHECK_RESULT(result);
  }
}

static void CreateAndWriteCoreSnapshot() {
  ASSERT(snapshot_kind == kCore);
  ASSERT(vm_snapshot_data_filename != NULL);
  ASSERT(isolate_snapshot_data_filename != NULL);

  Dart_Handle result;
  uint8_t* vm_snapshot_data_buffer = NULL;
  intptr_t vm_snapshot_data_size = 0;
  uint8_t* isolate_snapshot_data_buffer = NULL;
  intptr_t isolate_snapshot_data_size = 0;

  // First create a snapshot.
  result = Dart_CreateSnapshot(&vm_snapshot_data_buffer, &vm_snapshot_data_size,
                               &isolate_snapshot_data_buffer,
                               &isolate_snapshot_data_size);
  CHECK_RESULT(result);

  // Now write the vm isolate and isolate snapshots out to the
  // specified file and exit.
  WriteFile(vm_snapshot_data_filename, vm_snapshot_data_buffer,
            vm_snapshot_data_size);
  if (vm_snapshot_instructions_filename != NULL) {
    WriteFile(vm_snapshot_instructions_filename, NULL, 0);
  }
  WriteFile(isolate_snapshot_data_filename, isolate_snapshot_data_buffer,
            isolate_snapshot_data_size);
  if (isolate_snapshot_instructions_filename != NULL) {
    WriteFile(isolate_snapshot_instructions_filename, NULL, 0);
  }
}

static void CreateAndWriteCoreJITSnapshot() {
  ASSERT(snapshot_kind == kCoreJIT);
  ASSERT(vm_snapshot_data_filename != NULL);
  ASSERT(vm_snapshot_instructions_filename != NULL);
  ASSERT(isolate_snapshot_data_filename != NULL);
  ASSERT(isolate_snapshot_instructions_filename != NULL);

  Dart_Handle result;
  uint8_t* vm_snapshot_data_buffer = NULL;
  intptr_t vm_snapshot_data_size = 0;
  uint8_t* vm_snapshot_instructions_buffer = NULL;
  intptr_t vm_snapshot_instructions_size = 0;
  uint8_t* isolate_snapshot_data_buffer = NULL;
  intptr_t isolate_snapshot_data_size = 0;
  uint8_t* isolate_snapshot_instructions_buffer = NULL;
  intptr_t isolate_snapshot_instructions_size = 0;

  // First create a snapshot.
  result = Dart_CreateCoreJITSnapshotAsBlobs(
      &vm_snapshot_data_buffer, &vm_snapshot_data_size,
      &vm_snapshot_instructions_buffer, &vm_snapshot_instructions_size,
      &isolate_snapshot_data_buffer, &isolate_snapshot_data_size,
      &isolate_snapshot_instructions_buffer,
      &isolate_snapshot_instructions_size);
  CHECK_RESULT(result);

  // Now write the vm isolate and isolate snapshots out to the
  // specified file and exit.
  WriteFile(vm_snapshot_data_filename, vm_snapshot_data_buffer,
            vm_snapshot_data_size);
  WriteFile(vm_snapshot_instructions_filename, vm_snapshot_instructions_buffer,
            vm_snapshot_instructions_size);
  WriteFile(isolate_snapshot_data_filename, isolate_snapshot_data_buffer,
            isolate_snapshot_data_size);
  WriteFile(isolate_snapshot_instructions_filename,
            isolate_snapshot_instructions_buffer,
            isolate_snapshot_instructions_size);
}

static void CreateAndWriteScriptSnapshot() {
  ASSERT(snapshot_kind == kScript);
  ASSERT(script_snapshot_filename != NULL);

  // First create a snapshot.
  uint8_t* buffer = NULL;
  intptr_t size = 0;
  Dart_Handle result = Dart_CreateScriptSnapshot(&buffer, &size);
  CHECK_RESULT(result);

  // Now write it out to the specified file.
  WriteFile(script_snapshot_filename, buffer, size);
}

static void StreamingWriteCallback(void* callback_data,
                                   const uint8_t* buffer,
                                   intptr_t size) {
  File* file = reinterpret_cast<File*>(callback_data);
  if (!file->WriteFully(buffer, size)) {
    Log::PrintErr("Error: Unable to write snapshot file\n\n");
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
}

static std::unique_ptr<MappedMemory> MapFile(const char* filename,
                                             File::MapType type,
                                             const uint8_t** buffer) {
  File* file = File::Open(NULL, filename, File::kRead);
  if (file == NULL) {
    Log::PrintErr("Failed to open: %s\n", filename);
    exit(kErrorExitCode);
  }
  RefCntReleaseScope<File> rs(file);
  intptr_t length = file->Length();
  if (length == 0) {
    // Can't map an empty file.
    *buffer = NULL;
    return NULL;
  }
  MappedMemory* mapping = file->Map(type, 0, length);
  if (mapping == NULL) {
    Log::PrintErr("Failed to read: %s\n", filename);
    exit(kErrorExitCode);
  }
  *buffer = reinterpret_cast<const uint8_t*>(mapping->address());
  return std::unique_ptr<MappedMemory>(mapping);
}

static void CreateAndWritePrecompiledSnapshot(
    Dart_QualifiedFunctionName* standalone_entry_points) {
  ASSERT(IsSnapshottingForPrecompilation());
  Dart_Handle result;

  // Precompile with specified embedder entry points
  result = Dart_Precompile(standalone_entry_points);
  CHECK_RESULT(result);

  // Create a precompiled snapshot.
  bool as_assembly = assembly_filename != NULL;
  if (as_assembly) {
    ASSERT(snapshot_kind == kAppAOTAssembly);
    File* file = OpenFile(assembly_filename);
    RefCntReleaseScope<File> rs(file);
    result = Dart_CreateAppAOTSnapshotAsAssembly(StreamingWriteCallback, file);
    CHECK_RESULT(result);
  } else {
    ASSERT(snapshot_kind == kAppAOTBlobs);

    const uint8_t* shared_data = NULL;
    const uint8_t* shared_instructions = NULL;
    std::unique_ptr<MappedMemory> mapped_shared_data;
    std::unique_ptr<MappedMemory> mapped_shared_instructions;
    if (shared_data_filename != NULL) {
      mapped_shared_data =
          MapFile(shared_data_filename, File::kReadOnly, &shared_data);
    }
    if (shared_instructions_filename != NULL) {
      mapped_shared_instructions = MapFile(
          shared_instructions_filename, File::kReadOnly, &shared_instructions);
    }

    uint8_t* vm_snapshot_data_buffer = NULL;
    intptr_t vm_snapshot_data_size = 0;
    uint8_t* vm_snapshot_instructions_buffer = NULL;
    intptr_t vm_snapshot_instructions_size = 0;
    uint8_t* isolate_snapshot_data_buffer = NULL;
    intptr_t isolate_snapshot_data_size = 0;
    uint8_t* isolate_snapshot_instructions_buffer = NULL;
    intptr_t isolate_snapshot_instructions_size = 0;
    result = Dart_CreateAppAOTSnapshotAsBlobs(
        &vm_snapshot_data_buffer, &vm_snapshot_data_size,
        &vm_snapshot_instructions_buffer, &vm_snapshot_instructions_size,
        &isolate_snapshot_data_buffer, &isolate_snapshot_data_size,
        &isolate_snapshot_instructions_buffer,
        &isolate_snapshot_instructions_size, shared_data, shared_instructions);
    CHECK_RESULT(result);

    WriteFile(vm_snapshot_data_filename, vm_snapshot_data_buffer,
              vm_snapshot_data_size);
    WriteFile(vm_snapshot_instructions_filename,
              vm_snapshot_instructions_buffer, vm_snapshot_instructions_size);
    WriteFile(isolate_snapshot_data_filename, isolate_snapshot_data_buffer,
              isolate_snapshot_data_size);
    WriteFile(isolate_snapshot_instructions_filename,
              isolate_snapshot_instructions_buffer,
              isolate_snapshot_instructions_size);
  }

  // Serialize obfuscation map if requested.
  if (obfuscation_map_filename != NULL) {
    ASSERT(obfuscate);
    uint8_t* buffer = NULL;
    intptr_t size = 0;
    result = Dart_GetObfuscationMap(&buffer, &size);
    CHECK_RESULT(result);
    WriteFile(obfuscation_map_filename, buffer, size);
  }
}

static void SetupForUriResolution() {
  // Set up the library tag handler for this isolate.
  Dart_Handle result = Dart_SetLibraryTagHandler(Loader::LibraryTagHandler);
  if (Dart_IsError(result)) {
    Log::PrintErr("%s\n", Dart_GetError(result));
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
  // This is a generic dart snapshot which needs builtin library setup.
  Dart_Handle library =
      LoadGenericSnapshotCreationScript(Builtin::kBuiltinLibrary);
  CHECK_RESULT(library);
}

static void SetupForGenericSnapshotCreation() {
  SetupForUriResolution();

  Dart_Handle library = LoadGenericSnapshotCreationScript(Builtin::kIOLibrary);
  CHECK_RESULT(library);
  Dart_Handle standalone_library =
      LoadGenericSnapshotCreationScript(Builtin::kCLILibrary);
  CHECK_RESULT(standalone_library);
  Dart_Handle result = Dart_FinalizeLoading(false);
  if (Dart_IsError(result)) {
    const char* err_msg = Dart_GetError(library);
    Log::PrintErr("Errors encountered while loading: %s\n", err_msg);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    exit(kErrorExitCode);
  }
}

static Dart_Isolate CreateServiceIsolate(const char* script_uri,
                                         const char* main,
                                         const char* package_root,
                                         const char* package_config,
                                         Dart_IsolateFlags* flags,
                                         void* data,
                                         char** error) {
  IsolateData* isolate_data =
      new IsolateData(script_uri, package_root, package_config, NULL);
  Dart_Isolate isolate = NULL;
  isolate = Dart_CreateIsolate(script_uri, main, isolate_snapshot_data,
                               isolate_snapshot_instructions, NULL, NULL, flags,
                               isolate_data, error);

  if (isolate == NULL) {
    Log::PrintErr("Error: Could not create service isolate\n");
    return NULL;
  }

  Dart_EnterScope();
  if (!Dart_IsServiceIsolate(isolate)) {
    Log::PrintErr("Error: We only expect to create the service isolate\n");
    return NULL;
  }
  Dart_Handle result = Dart_SetLibraryTagHandler(Loader::LibraryTagHandler);
  if (Dart_IsError(result)) {
    Log::PrintErr("Error: Could not set tag handler for service isolate\n");
    return NULL;
  }
  // Setup the native resolver.
  Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
  Builtin::LoadAndCheckLibrary(Builtin::kIOLibrary);
  Builtin::LoadAndCheckLibrary(Builtin::kCLILibrary);

  ASSERT(Dart_IsServiceIsolate(isolate));
  // Load embedder specific bits and return. Will not start http server.
  if (!VmService::Setup("127.0.0.1", -1, false /* running_precompiled */,
                        false /* server dev mode */, false /* trace_loading */,
                        true /* deterministic */)) {
    *error = strdup(VmService::GetErrorMessage());
    return NULL;
  }
  Dart_ExitScope();
  Dart_ExitIsolate();
  return isolate;
}

static int GenerateSnapshotFromKernel(const uint8_t* kernel_buffer,
                                      intptr_t kernel_buffer_size) {
  ASSERT(SnapshotKindAllowedFromKernel());

  char* error = NULL;
  IsolateData* isolate_data = new IsolateData(NULL, commandline_package_root,
                                              commandline_packages_file, NULL);
  if (dependencies_filename != NULL) {
    isolate_data->set_dependencies(new MallocGrowableArray<char*>());
  }

  Dart_IsolateFlags isolate_flags;
  Dart_IsolateFlagsInitialize(&isolate_flags);

  Dart_QualifiedFunctionName* entry_points = NULL;
  if (IsSnapshottingForPrecompilation()) {
    entry_points = ParseEntryPointsManifestIfPresent();
    isolate_flags.obfuscate = obfuscate;
    isolate_flags.entry_points = entry_points;
  }

  // We need to capture the vmservice library in the core snapshot, so load it
  // in the main isolate as well.
  isolate_flags.load_vmservice_library = true;
  Dart_Isolate isolate = Dart_CreateIsolateFromKernel(
      NULL, NULL, kernel_buffer, kernel_buffer_size, &isolate_flags,
      isolate_data, &error);
  if (isolate == NULL) {
    delete isolate_data;
    Log::PrintErr("%s\n", error);
    free(error);
    return kErrorExitCode;
  }

  Dart_EnterScope();
  Dart_Handle result =
      Dart_SetEnvironmentCallback(DartUtils::EnvironmentCallback);
  CHECK_RESULT(result);

  // The root library has to be set to generate AOT snapshots, and sometimes we
  // set one for the core snapshot too.
  // If the input dill file has a root library, then Dart_LoadScript will
  // ignore this dummy uri and set the root library to the one reported in
  // the dill file. Since dill files are not dart script files,
  // trying to resolve the root library URI based on the dill file name
  // would not help.
  //
  // If the input dill file does not have a root library, then
  // Dart_LoadScript will error.
  //
  // TODO(kernel): Dart_CreateIsolateFromKernel should respect the root library
  // in the kernel file, though this requires auditing the other loading paths
  // in the embedders that had to work around this.
  result = Dart_SetRootLibrary(
      Dart_LoadLibraryFromKernel(kernel_buffer, kernel_buffer_size));
  CHECK_RESULT(result);

  switch (snapshot_kind) {
    case kAppAOTBlobs:
    case kAppAOTAssembly: {
      if (Dart_IsNull(Dart_RootLibrary())) {
        Log::PrintErr(
            "Unable to load root library from the input dill file.\n");
        return kErrorExitCode;
      }

      CreateAndWritePrecompiledSnapshot(entry_points);

      CreateAndWriteDependenciesFile();

      CleanupEntryPointsCollection(entry_points);

      break;
    }
    case kCore:
      CreateAndWriteCoreSnapshot();
      break;
    case kCoreJIT:
      LoadCompilationTrace();
      CreateAndWriteCoreJITSnapshot();
      break;
    default:
      UNREACHABLE();
  }

  Dart_ExitScope();
  Dart_ShutdownIsolate();
  error = Dart_Cleanup();
  if (error != NULL) {
    Log::PrintErr("VM cleanup failed: %s\n", error);
    free(error);
  }
  EventHandler::Stop();
  return 0;
}

int main(int argc, char** argv) {
  const int EXTRA_VM_ARGUMENTS = 4;
  CommandLineOptions vm_options(argc + EXTRA_VM_ARGUMENTS);

  // Initialize the URL mapping array.
  CommandLineOptions cmdline_url_mapping(argc);
  DartUtils::url_mapping = &cmdline_url_mapping;

  // Initialize the entrypoints array.
  CommandLineOptions entry_points_files_array(argc);
  entry_points_files = &entry_points_files_array;

  // When running from the command line we assume that we are optimizing for
  // throughput, and therefore use a larger new gen semi space size and a faster
  // new gen growth factor unless others have been specified.
  if (kWordSize <= 4) {
    vm_options.AddArgument("--new_gen_semi_max_size=16");
  } else {
    vm_options.AddArgument("--new_gen_semi_max_size=32");
  }
  vm_options.AddArgument("--new_gen_growth_factor=4");

  // Parse command line arguments.
  if (ParseArguments(argc, argv, &vm_options, &app_script_name) < 0) {
    PrintUsage();
    return kErrorExitCode;
  }
  DartUtils::SetEnvironment(environment);

  // Sniff the script to check if it is actually a dill file.
  uint8_t* kernel_buffer = NULL;
  intptr_t kernel_buffer_size = NULL;
  if (app_script_name != NULL) {
    dfe.ReadScript(app_script_name, &kernel_buffer, &kernel_buffer_size);
  }
  if (kernel_buffer != NULL) {
    if (!SnapshotKindAllowedFromKernel()) {
      // TODO(sivachandra): Add check for the kernel program format (incremental
      // vs batch).
      Log::PrintErr(
          "Can only generate core or aot snapshots from a kernel file.\n");
      return kErrorExitCode;
    }
    if (dependencies_filename != NULL) {
      Log::PrintErr("Depfiles are not supported in Dart 2.\n");
      return kErrorExitCode;
    }
  }

  if (!Platform::Initialize()) {
    Log::PrintErr("Initialization failed\n");
    return kErrorExitCode;
  }
  Console::SaveConfig();
  Thread::InitOnce();
  Loader::InitOnce();
  DartUtils::SetOriginalWorkingDirectory();
  // Start event handler.
  TimerUtils::InitOnce();
  EventHandler::Start();

#if !defined(PRODUCT)
  // Constant true in PRODUCT mode.
  vm_options.AddArgument("--load_deferred_eagerly");
#endif

  if (IsSnapshottingForPrecompilation()) {
    vm_options.AddArgument("--precompilation");
  }
  if (snapshot_kind == kCoreJIT) {
    vm_options.AddArgument("--fields_may_be_reset");
    vm_options.AddArgument("--link_natives_lazily");
#if !defined(PRODUCT)
    vm_options.AddArgument("--collect_code=false");
#endif
  }

  char* error = Dart_SetVMFlags(vm_options.count(), vm_options.arguments());
  if (error != NULL) {
    Log::PrintErr("Setting VM flags failed: %s\n", error);
    free(error);
    return kErrorExitCode;
  }

  // Initialize the Dart VM.
  // Note: We don't expect isolates to be created from dart code during
  // core library snapshot generation. However for the case when a full
  // snasphot is generated from a script (app_script_name != NULL) we will
  // need the service isolate to resolve URI and load code.

  Dart_InitializeParams init_params;
  memset(&init_params, 0, sizeof(init_params));
  init_params.version = DART_INITIALIZE_PARAMS_CURRENT_VERSION;
  if (app_script_name != NULL && kernel_buffer == NULL) {
    // We need the service isolate to load script files.
    // When generating snapshots from a kernel program, we do not need to load
    // any script files.
    init_params.create = CreateServiceIsolate;
  }
  init_params.file_open = DartUtils::OpenFile;
  init_params.file_read = DartUtils::ReadFile;
  init_params.file_write = DartUtils::WriteFile;
  init_params.file_close = DartUtils::CloseFile;
  init_params.entropy_source = DartUtils::EntropySource;
  init_params.start_kernel_isolate = false;

  std::unique_ptr<MappedMemory> mapped_vm_snapshot_data;
  std::unique_ptr<MappedMemory> mapped_vm_snapshot_instructions;
  std::unique_ptr<MappedMemory> mapped_isolate_snapshot_data;
  std::unique_ptr<MappedMemory> mapped_isolate_snapshot_instructions;
  if (snapshot_kind == kScript) {
    mapped_vm_snapshot_data =
        MapFile(vm_snapshot_data_filename, File::kReadOnly,
                &init_params.vm_snapshot_data);

    if (vm_snapshot_instructions_filename != NULL) {
      mapped_vm_snapshot_instructions =
          MapFile(vm_snapshot_instructions_filename, File::kReadExecute,
                  &init_params.vm_snapshot_instructions);
    }

    mapped_isolate_snapshot_data =
        MapFile(isolate_snapshot_data_filename, File::kReadOnly,
                &isolate_snapshot_data);

    if (isolate_snapshot_instructions_filename != NULL) {
      mapped_isolate_snapshot_instructions =
          MapFile(isolate_snapshot_instructions_filename, File::kReadExecute,
                  &isolate_snapshot_instructions);
    }
  }

  error = Dart_Initialize(&init_params);
  if (error != NULL) {
    Log::PrintErr("VM initialization failed: %s\n", error);
    free(error);
    return kErrorExitCode;
  }

  if (kernel_buffer != NULL) {
    return GenerateSnapshotFromKernel(kernel_buffer, kernel_buffer_size);
  }

  Dart_IsolateFlags flags;
  Dart_IsolateFlagsInitialize(&flags);

  Dart_QualifiedFunctionName* entry_points =
      ParseEntryPointsManifestIfPresent();

  IsolateData* isolate_data = new IsolateData(NULL, commandline_package_root,
                                              commandline_packages_file, NULL);
  Dart_Isolate isolate = Dart_CreateIsolate(NULL, NULL, isolate_snapshot_data,
                                            isolate_snapshot_instructions, NULL,
                                            NULL, NULL, isolate_data, &error);
  if (isolate == NULL) {
    Log::PrintErr("Error: %s\n", error);
    free(error);
    exit(kErrorExitCode);
  }

  Dart_Handle result;
  Dart_Handle library;
  Dart_EnterScope();

  if (snapshot_kind == kVMAOTAssembly) {
    File* file = OpenFile(assembly_filename);
    RefCntReleaseScope<File> rs(file);
    result = Dart_CreateVMAOTSnapshotAsAssembly(StreamingWriteCallback, file);
    CHECK_RESULT(result);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    return 0;
  }

  result = Dart_SetEnvironmentCallback(DartUtils::EnvironmentCallback);
  CHECK_RESULT(result);

  // Load up the script before a snapshot is created.
  if (app_script_name != NULL) {
    // This is the case of a custom embedder (e.g: dartium) trying to
    // create a full snapshot. The current isolate is set up so that we can
    // invoke the dart uri resolution code like _resolveURI. App script is
    // loaded into a separate isolate.
    SetupForUriResolution();

    // Prepare builtin and its dependent libraries for use to resolve URIs.
    // Set up various closures, e.g: printing, timers etc.
    // Set up 'package root' for URI resolution.
    result = DartUtils::PrepareForScriptLoading(false, false);
    CHECK_RESULT(result);

    // Set up the load port provided by the service isolate so that we can
    // load scripts.
    result = DartUtils::SetupServiceLoadPort();
    CHECK_RESULT(result);

    // Setup package root if specified.
    result = DartUtils::SetupPackageRoot(NULL, commandline_packages_file);
    CHECK_RESULT(result);

    UriResolverIsolateScope::isolate = isolate;
    Dart_ExitScope();
    Dart_ExitIsolate();

    // Now we create an isolate into which we load all the code that needs to
    // be in the snapshot.
    isolate_data = new IsolateData(app_script_name, commandline_package_root,
                                   commandline_packages_file, NULL);
    if (dependencies_filename != NULL) {
      isolate_data->set_dependencies(new MallocGrowableArray<char*>());
    }

    if (IsSnapshottingForPrecompilation()) {
      flags.obfuscate = obfuscate;
      flags.entry_points = entry_points;
    }

    Dart_Isolate isolate = NULL;
    isolate = Dart_CreateIsolate(NULL, NULL, isolate_snapshot_data,
                                 isolate_snapshot_instructions, NULL, NULL,
                                 &flags, isolate_data, &error);
    if (isolate == NULL) {
      Log::PrintErr("%s\n", error);
      free(error);
      exit(kErrorExitCode);
    }
    Dart_EnterScope();
    result = Dart_SetEnvironmentCallback(DartUtils::EnvironmentCallback);
    CHECK_RESULT(result);

    // Set up the library tag handler in such a manner that it will use the
    // URL mapping specified on the command line to load the libraries.
    result = Dart_SetLibraryTagHandler(CreateSnapshotLibraryTagHandler);
    CHECK_RESULT(result);

    if (commandline_packages_file != NULL) {
      AddDependency(commandline_packages_file);
    }

    ASSERT(kernel_buffer == NULL);

    // Load any libraries named in the entry points. Do this before loading the
    // user's script to ensure conditional imports see the embedder-specific
    // dart: libraries.
    LoadEntryPoints(entry_points);

    // Load the specified script.
    library = LoadSnapshotCreationScript(app_script_name);
    CHECK_RESULT(library);

    ImportNativeEntryPointLibrariesIntoRoot(entry_points);

    // Ensure that we mark all libraries as loaded.
    result = Dart_FinalizeLoading(false);
    CHECK_RESULT(result);

    LoadCompilationTrace();

    switch (snapshot_kind) {
      case kCore:
        CreateAndWriteCoreSnapshot();
        break;
      case kCoreJIT:
        CreateAndWriteCoreJITSnapshot();
        break;
      case kScript:
        CreateAndWriteScriptSnapshot();
        break;
      case kAppAOTBlobs:
      case kAppAOTAssembly:
        CreateAndWritePrecompiledSnapshot(entry_points);
        break;
      default:
        UNREACHABLE();
    }

    CreateAndWriteDependenciesFile();

    Dart_ExitScope();
    Dart_ShutdownIsolate();

    CleanupEntryPointsCollection(entry_points);

    Dart_EnterIsolate(UriResolverIsolateScope::isolate);
    Dart_ShutdownIsolate();
  } else {
    SetupForGenericSnapshotCreation();
    LoadCompilationTrace();
    switch (snapshot_kind) {
      case kCore:
        CreateAndWriteCoreSnapshot();
        break;
      case kCoreJIT:
        CreateAndWriteCoreJITSnapshot();
        break;
      default:
        UNREACHABLE();
        break;
    }

    Dart_ExitScope();
    Dart_ShutdownIsolate();
  }
  error = Dart_Cleanup();
  if (error != NULL) {
    Log::PrintErr("VM cleanup failed: %s\n", error);
    free(error);
  }
  EventHandler::Stop();
  return 0;
}

}  // namespace bin
}  // namespace dart

int main(int argc, char** argv) {
  return dart::bin::main(argc, argv);
}