CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. All rights reserved.

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// modification, are permitted provided that the following conditions are

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//

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#include <v8.h>

#include <assert.h>

#include <fcntl.h>

#include <string.h>

#include <stdio.h>

#include <stdlib.h>

#ifdef COMPRESS_STARTUP_DATA_BZ2

#error Using compressed startup data is not supported for this sample

#endif

/**

 * This sample program shows how to implement a simple javascript shell

 * based on V8.  This includes initializing V8 with command line options,

 * creating global functions, compiling and executing strings.

 *

 * For a more sophisticated shell, consider using the debug shell D8.

 */

v8::Handle<v8::Context> CreateShellContext(v8::Isolate* isolate);

void RunShell(v8::Handle<v8::Context> context);

int RunMain(v8::Isolate* isolate, int argc, char* argv[]);

bool ExecuteString(v8::Isolate* isolate,

                   v8::Handle<v8::String> source,

                   v8::Handle<v8::Value> name,

                   bool print_result,

                   bool report_exceptions);

void Print(const v8::FunctionCallbackInfo<v8::Value>& args);

void Read(const v8::FunctionCallbackInfo<v8::Value>& args);

void Load(const v8::FunctionCallbackInfo<v8::Value>& args);

void Quit(const v8::FunctionCallbackInfo<v8::Value>& args);

void Version(const v8::FunctionCallbackInfo<v8::Value>& args);

v8::Handle<v8::String> ReadFile(const char* name);

void ReportException(v8::Isolate* isolate, v8::TryCatch* handler);

static bool run_shell;

int main(int argc, char* argv[]) {

  v8::V8::InitializeICU();

  v8::V8::SetFlagsFromCommandLine(&argc, argv, true);

  v8::Isolate* isolate = v8::Isolate::GetCurrent();

  run_shell = (argc == 1);

  int result;

  {

    v8::HandleScope handle_scope(isolate);

    v8::Handle<v8::Context> context = CreateShellContext(isolate);

    if (context.IsEmpty()) {

      fprintf(stderr, "Error creating context\n");

      return 1;

    }

    context->Enter();

    result = RunMain(isolate, argc, argv);

    if (run_shell) RunShell(context);

    context->Exit();

  }

  v8::V8::Dispose();

  return result;

}

// Extracts a C string from a V8 Utf8Value.

const char* ToCString(const v8::String::Utf8Value& value) {

  return *value ? *value : "<string conversion failed>";

}

// Creates a new execution environment containing the built-in

// functions.

v8::Handle<v8::Context> CreateShellContext(v8::Isolate* isolate) {

  // Create a template for the global object.

  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New();

  // Bind the global 'print' function to the C++ Print callback.

  global->Set(v8::String::New("print"), v8::FunctionTemplate::New(Print));

  // Bind the global 'read' function to the C++ Read callback.

  global->Set(v8::String::New("read"), v8::FunctionTemplate::New(Read));

  // Bind the global 'load' function to the C++ Load callback.

  global->Set(v8::String::New("load"), v8::FunctionTemplate::New(Load));

  // Bind the 'quit' function

  global->Set(v8::String::New("quit"), v8::FunctionTemplate::New(Quit));

  // Bind the 'version' function

  global->Set(v8::String::New("version"), v8::FunctionTemplate::New(Version));

  return v8::Context::New(isolate, NULL, global);

}

// The callback that is invoked by v8 whenever the JavaScript 'print'

// function is called.  Prints its arguments on stdout separated by

// spaces and ending with a newline.

void Print(const v8::FunctionCallbackInfo<v8::Value>& args) {

  bool first = true;

  for (int i = 0; i < args.Length(); i++) {

    v8::HandleScope handle_scope(args.GetIsolate());

    if (first) {

      first = false;

    } else {

      printf(" ");

    }

    v8::String::Utf8Value str(args[i]);

    const char* cstr = ToCString(str);

    printf("%s", cstr);

  }

  printf("\n");

  fflush(stdout);

}

// The callback that is invoked by v8 whenever the JavaScript 'read'

// function is called.  This function loads the content of the file named in

// the argument into a JavaScript string.

void Read(const v8::FunctionCallbackInfo<v8::Value>& args) {

  if (args.Length() != 1) {

    args.GetIsolate()->ThrowException(

        v8::String::New("Bad parameters"));

    return;

  }

  v8::String::Utf8Value file(args[0]);

  if (*file == NULL) {

    args.GetIsolate()->ThrowException(

        v8::String::New("Error loading file"));

    return;

  }

  v8::Handle<v8::String> source = ReadFile(*file);

  if (source.IsEmpty()) {

    args.GetIsolate()->ThrowException(

        v8::String::New("Error loading file"));

    return;

  }

  args.GetReturnValue().Set(source);

}

// The callback that is invoked by v8 whenever the JavaScript 'load'

// function is called.  Loads, compiles and executes its argument

// JavaScript file.

void Load(const v8::FunctionCallbackInfo<v8::Value>& args) {

  for (int i = 0; i < args.Length(); i++) {

    v8::HandleScope handle_scope(args.GetIsolate());

    v8::String::Utf8Value file(args[i]);

    if (*file == NULL) {

      args.GetIsolate()->ThrowException(

          v8::String::New("Error loading file"));

      return;

    }

    v8::Handle<v8::String> source = ReadFile(*file);

    if (source.IsEmpty()) {

      args.GetIsolate()->ThrowException(

           v8::String::New("Error loading file"));

      return;

    }

    if (!ExecuteString(args.GetIsolate(),

                       source,

                       v8::String::New(*file),

                       false,

                       false)) {

      args.GetIsolate()->ThrowException(

          v8::String::New("Error executing file"));

      return;

    }

  }

}

// The callback that is invoked by v8 whenever the JavaScript 'quit'

// function is called.  Quits.

void Quit(const v8::FunctionCallbackInfo<v8::Value>& args) {

  // If not arguments are given args[0] will yield undefined which

  // converts to the integer value 0.

  int exit_code = args[0]->Int32Value();

  fflush(stdout);

  fflush(stderr);

  exit(exit_code);

}

void Version(const v8::FunctionCallbackInfo<v8::Value>& args) {

  args.GetReturnValue().Set(v8::String::New(v8::V8::GetVersion()));

}

// Reads a file into a v8 string.

v8::Handle<v8::String> ReadFile(const char* name) {

  FILE* file = fopen(name, "rb");

  if (file == NULL) return v8::Handle<v8::String>();

  fseek(file, 0, SEEK_END);

  int size = ftell(file);

  rewind(file);

  char* chars = new char[size + 1];

  chars[size] = '\0';

  for (int i = 0; i < size;) {

    int read = static_cast<int>(fread(&chars[i], 1, size - i, file));

    i += read;

  }

  fclose(file);

  v8::Handle<v8::String> result = v8::String::New(chars, size);

  delete[] chars;

  return result;

}

// Process remaining command line arguments and execute files

int RunMain(v8::Isolate* isolate, int argc, char* argv[]) {

  for (int i = 1; i < argc; i++) {

    const char* str = argv[i];

    if (strcmp(str, "--shell") == 0) {

      run_shell = true;

    } else if (strcmp(str, "-f") == 0) {

      // Ignore any -f flags for compatibility with the other stand-

      // alone JavaScript engines.

      continue;

    } else if (strncmp(str, "--", 2) == 0) {

      fprintf(stderr,

              "Warning: unknown flag %s.\nTry --help for options\n", str);

    } else if (strcmp(str, "-e") == 0 && i + 1 < argc) {

      // Execute argument given to -e option directly.

      v8::Handle<v8::String> file_name = v8::String::New("unnamed");

      v8::Handle<v8::String> source = v8::String::New(argv[++i]);

      if (!ExecuteString(isolate, source, file_name, false, true)) return 1;

    } else {

      // Use all other arguments as names of files to load and run.

      v8::Handle<v8::String> file_name = v8::String::New(str);

      v8::Handle<v8::String> source = ReadFile(str);

      if (source.IsEmpty()) {

        fprintf(stderr, "Error reading '%s'\n", str);

        continue;

      }

      if (!ExecuteString(isolate, source, file_name, false, true)) return 1;

    }

  }

  return 0;

}

// The read-eval-execute loop of the shell.

void RunShell(v8::Handle<v8::Context> context) {

  fprintf(stderr, "V8 version %s [sample shell]\n", v8::V8::GetVersion());

  static const int kBufferSize = 256;

  // Enter the execution environment before evaluating any code.

  v8::Context::Scope context_scope(context);

  v8::Local<v8::String> name(v8::String::New("(shell)"));

  while (true) {

    char buffer[kBufferSize];

    fprintf(stderr, "> ");

    char* str = fgets(buffer, kBufferSize, stdin);

    if (str == NULL) break;

    v8::HandleScope handle_scope(context->GetIsolate());

    ExecuteString(context->GetIsolate(),

                  v8::String::New(str),

                  name,

                  true,

                  true);

  }

  fprintf(stderr, "\n");

}

// Executes a string within the current v8 context.

bool ExecuteString(v8::Isolate* isolate,

                   v8::Handle<v8::String> source,

                   v8::Handle<v8::Value> name,

                   bool print_result,

                   bool report_exceptions) {

  v8::HandleScope handle_scope(isolate);

  v8::TryCatch try_catch;

  v8::Handle<v8::Script> script = v8::Script::Compile(source, name);

  if (script.IsEmpty()) {

    // Print errors that happened during compilation.

    if (report_exceptions)

      ReportException(isolate, &try_catch);

    return false;

  } else {

    v8::Handle<v8::Value> result = script->Run();

    if (result.IsEmpty()) {

      assert(try_catch.HasCaught());

      // Print errors that happened during execution.

      if (report_exceptions)

        ReportException(isolate, &try_catch);

      return false;

    } else {

      assert(!try_catch.HasCaught());

      if (print_result && !result->IsUndefined()) {

        // If all went well and the result wasn't undefined then print

        // the returned value.

        v8::String::Utf8Value str(result);

        const char* cstr = ToCString(str);

        printf("%s\n", cstr);

      }

      return true;

    }

  }

}

void ReportException(v8::Isolate* isolate, v8::TryCatch* try_catch) {

  v8::HandleScope handle_scope(isolate);

  v8::String::Utf8Value exception(try_catch->Exception());

  const char* exception_string = ToCString(exception);

  v8::Handle<v8::Message> message = try_catch->Message();

  if (message.IsEmpty()) {

    // V8 didn't provide any extra information about this error; just

    // print the exception.

    fprintf(stderr, "%s\n", exception_string);

  } else {

    // Print (filename):(line number): (message).

    v8::String::Utf8Value filename(message->GetScriptResourceName());

    const char* filename_string = ToCString(filename);

    int linenum = message->GetLineNumber();

    fprintf(stderr, "%s:%i: %s\n", filename_string, linenum, exception_string);

    // Print line of source code.

    v8::String::Utf8Value sourceline(message->GetSourceLine());

    const char* sourceline_string = ToCString(sourceline);

    fprintf(stderr, "%s\n", sourceline_string);

    // Print wavy underline (GetUnderline is deprecated).

    int start = message->GetStartColumn();

    for (int i = 0; i < start; i++) {

      fprintf(stderr, " ");

    }

    int end = message->GetEndColumn();

    for (int i = start; i < end; i++) {

      fprintf(stderr, "^");

    }

    fprintf(stderr, "\n");

    v8::String::Utf8Value stack_trace(try_catch->StackTrace());

    if (stack_trace.length() > 0) {

      const char* stack_trace_string = ToCString(stack_trace);

      fprintf(stderr, "%s\n", stack_trace_string);

    }

  }

}