root/samples/shell.cc

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DEFINITIONS

This source file includes following definitions.
  1. main
  2. ToCString
  3. CreateShellContext
  4. Print
  5. Read
  6. Load
  7. Quit
  8. Version
  9. ReadFile
  10. RunMain
  11. RunShell
  12. ExecuteString
  13. ReportException

// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#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::Persistent<v8::Context> CreateShellContext();
void RunShell(v8::Handle<v8::Context> context);
int RunMain(int argc, char* argv[]);
bool ExecuteString(v8::Handle<v8::String> source,
                   v8::Handle<v8::Value> name,
                   bool print_result,
                   bool report_exceptions);
v8::Handle<v8::Value> Print(const v8::Arguments& args);
v8::Handle<v8::Value> Read(const v8::Arguments& args);
v8::Handle<v8::Value> Load(const v8::Arguments& args);
v8::Handle<v8::Value> Quit(const v8::Arguments& args);
v8::Handle<v8::Value> Version(const v8::Arguments& args);
v8::Handle<v8::String> ReadFile(const char* name);
void ReportException(v8::TryCatch* handler);


static bool run_shell;


int main(int argc, char* argv[]) {
  v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
  run_shell = (argc == 1);
  int result;
  {
    v8::HandleScope handle_scope;
    v8::Persistent<v8::Context> context = CreateShellContext();
    if (context.IsEmpty()) {
      printf("Error creating context\n");
      return 1;
    }
    context->Enter();
    result = RunMain(argc, argv);
    if (run_shell) RunShell(context);
    context->Exit();
    context.Dispose();
  }
  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::Persistent<v8::Context> CreateShellContext() {
  // 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(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.
v8::Handle<v8::Value> Print(const v8::Arguments& args) {
  bool first = true;
  for (int i = 0; i < args.Length(); i++) {
    v8::HandleScope handle_scope;
    if (first) {
      first = false;
    } else {
      printf(" ");
    }
    v8::String::Utf8Value str(args[i]);
    const char* cstr = ToCString(str);
    printf("%s", cstr);
  }
  printf("\n");
  fflush(stdout);
  return v8::Undefined();
}


// 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.
v8::Handle<v8::Value> Read(const v8::Arguments& args) {
  if (args.Length() != 1) {
    return v8::ThrowException(v8::String::New("Bad parameters"));
  }
  v8::String::Utf8Value file(args[0]);
  if (*file == NULL) {
    return v8::ThrowException(v8::String::New("Error loading file"));
  }
  v8::Handle<v8::String> source = ReadFile(*file);
  if (source.IsEmpty()) {
    return v8::ThrowException(v8::String::New("Error loading file"));
  }
  return source;
}


// The callback that is invoked by v8 whenever the JavaScript 'load'
// function is called.  Loads, compiles and executes its argument
// JavaScript file.
v8::Handle<v8::Value> Load(const v8::Arguments& args) {
  for (int i = 0; i < args.Length(); i++) {
    v8::HandleScope handle_scope;
    v8::String::Utf8Value file(args[i]);
    if (*file == NULL) {
      return v8::ThrowException(v8::String::New("Error loading file"));
    }
    v8::Handle<v8::String> source = ReadFile(*file);
    if (source.IsEmpty()) {
      return v8::ThrowException(v8::String::New("Error loading file"));
    }
    if (!ExecuteString(source, v8::String::New(*file), false, false)) {
      return v8::ThrowException(v8::String::New("Error executing file"));
    }
  }
  return v8::Undefined();
}


// The callback that is invoked by v8 whenever the JavaScript 'quit'
// function is called.  Quits.
v8::Handle<v8::Value> Quit(const v8::Arguments& 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);
  return v8::Undefined();
}


v8::Handle<v8::Value> Version(const v8::Arguments& args) {
  return 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(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) {
      printf("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(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()) {
        printf("Error reading '%s'\n", str);
        continue;
      }
      if (!ExecuteString(source, file_name, false, true)) return 1;
    }
  }
  return 0;
}


// The read-eval-execute loop of the shell.
void RunShell(v8::Handle<v8::Context> context) {
  printf("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];
    printf("> ");
    char* str = fgets(buffer, kBufferSize, stdin);
    if (str == NULL) break;
    v8::HandleScope handle_scope;
    ExecuteString(v8::String::New(str), name, true, true);
  }
  printf("\n");
}


// Executes a string within the current v8 context.
bool ExecuteString(v8::Handle<v8::String> source,
                   v8::Handle<v8::Value> name,
                   bool print_result,
                   bool report_exceptions) {
  v8::HandleScope handle_scope;
  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(&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(&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::TryCatch* try_catch) {
  v8::HandleScope handle_scope;
  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.
    printf("%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();
    printf("%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);
    printf("%s\n", sourceline_string);
    // Print wavy underline (GetUnderline is deprecated).
    int start = message->GetStartColumn();
    for (int i = 0; i < start; i++) {
      printf(" ");
    }
    int end = message->GetEndColumn();
    for (int i = start; i < end; i++) {
      printf("^");
    }
    printf("\n");
    v8::String::Utf8Value stack_trace(try_catch->StackTrace());
    if (stack_trace.length() > 0) {
      const char* stack_trace_string = ToCString(stack_trace);
      printf("%s\n", stack_trace_string);
    }
  }
}

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