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// Copyright 2009 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.
// This controls whether this sample is compiled with debugger support.
// You may trace its usages in source text to see what parts of program
// are responsible for debugging support.
// Note that V8 itself should be compiled with enabled debugger support
// to have it all working.
#define SUPPORT_DEBUGGING
#include <v8.h>
#ifdef SUPPORT_DEBUGGING
#include <v8-debug.h>
#endif
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
/**
* This sample program should demonstrate certain aspects of debugging
* standalone V8-based application.
*
* The program reads input stream, processes it line by line and print
* the result to output. The actual processing is done by custom JavaScript
* script. The script is specified with command line parameters.
*
* The main cycle of the program will sequentially read lines from standard
* input, process them and print to standard output until input closes.
* There are 2 possible configuration in regard to main cycle.
*
* 1. The main cycle is on C++ side. Program should be run with
* --main-cycle-in-cpp option. Script must declare a function named
* "ProcessLine". The main cycle in C++ reads lines and calls this function
* for processing every time. This is a sample script:
function ProcessLine(input_line) {
return ">>>" + input_line + "<<<";
}
*
* 2. The main cycle is in JavaScript. Program should be run with
* --main-cycle-in-js option. Script gets run one time at all and gets
* API of 2 global functions: "read_line" and "print". It should read input
* and print converted lines to output itself. This a sample script:
while (true) {
var line = read_line();
if (!line) {
break;
}
var res = line + " | " + line;
print(res);
}
*
* When run with "-p" argument, the program starts V8 Debugger Agent and
* allows remote debugger to attach and debug JavaScript code.
*
* Interesting aspects:
* 1. Wait for remote debugger to attach
* Normally the program compiles custom script and immediately runs it.
* If programmer needs to debug script from the very beginning, he should
* run this sample program with "--wait-for-connection" command line parameter.
* This way V8 will suspend on the first statement and wait for
* debugger to attach.
*
* 2. Unresponsive V8
* V8 Debugger Agent holds a connection with remote debugger, but it does
* respond only when V8 is running some script. In particular, when this program
* is waiting for input, all requests from debugger get deferred until V8
* is called again. See how "--callback" command-line parameter in this sample
* fixes this issue.
*/
enum MainCycleType {
CycleInCpp,
CycleInJs
};
const char* ToCString(const v8::String::Utf8Value& value);
void ReportException(v8::TryCatch* handler);
v8::Handle<v8::String> ReadFile(const char* name);
v8::Handle<v8::String> ReadLine();
v8::Handle<v8::Value> Print(const v8::Arguments& args);
v8::Handle<v8::Value> ReadLine(const v8::Arguments& args);
bool RunCppCycle(v8::Handle<v8::Script> script, v8::Local<v8::Context> context,
bool report_exceptions);
#ifdef SUPPORT_DEBUGGING
v8::Persistent<v8::Context> debug_message_context;
void DispatchDebugMessages() {
// We are in some random thread. We should already have v8::Locker acquired
// (we requested this when registered this callback). We was called
// because new debug messages arrived; they may have already been processed,
// but we shouldn't worry about this.
//
// All we have to do is to set context and call ProcessDebugMessages.
//
// We should decide which V8 context to use here. This is important for
// "evaluate" command, because it must be executed some context.
// In our sample we have only one context, so there is nothing really to
// think about.
v8::Context::Scope scope(debug_message_context);
v8::Debug::ProcessDebugMessages();
}
#endif
int RunMain(int argc, char* argv[]) {
v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
v8::HandleScope handle_scope;
v8::Handle<v8::String> script_source(NULL);
v8::Handle<v8::Value> script_name(NULL);
int script_param_counter = 0;
#ifdef SUPPORT_DEBUGGING
int port_number = -1;
bool wait_for_connection = false;
bool support_callback = false;
#endif
MainCycleType cycle_type = CycleInCpp;
for (int i = 1; i < argc; i++) {
const char* str = argv[i];
if (strcmp(str, "-f") == 0) {
// Ignore any -f flags for compatibility with the other stand-
// alone JavaScript engines.
continue;
} else if (strcmp(str, "--main-cycle-in-cpp") == 0) {
cycle_type = CycleInCpp;
} else if (strcmp(str, "--main-cycle-in-js") == 0) {
cycle_type = CycleInJs;
#ifdef SUPPORT_DEBUGGING
} else if (strcmp(str, "--callback") == 0) {
support_callback = true;
} else if (strcmp(str, "--wait-for-connection") == 0) {
wait_for_connection = true;
} else if (strcmp(str, "-p") == 0 && i + 1 < argc) {
port_number = atoi(argv[i + 1]); // NOLINT
i++;
#endif
} 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) {
script_source = v8::String::New(argv[i + 1]);
script_name = v8::String::New("unnamed");
i++;
script_param_counter++;
} else {
// Use argument as a name of file to load.
script_source = ReadFile(str);
script_name = v8::String::New(str);
if (script_source.IsEmpty()) {
printf("Error reading '%s'\n", str);
return 1;
}
script_param_counter++;
}
}
if (script_param_counter == 0) {
printf("Script is not specified\n");
return 1;
}
if (script_param_counter != 1) {
printf("Only one script may be specified\n");
return 1;
}
// 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));
if (cycle_type == CycleInJs) {
// Bind the global 'read_line' function to the C++ Print callback.
global->Set(v8::String::New("read_line"),
v8::FunctionTemplate::New(ReadLine));
}
// Create a new execution environment containing the built-in
// functions
v8::Handle<v8::Context> context = v8::Context::New(NULL, global);
// Enter the newly created execution environment.
v8::Context::Scope context_scope(context);
#ifdef SUPPORT_DEBUGGING
debug_message_context = v8::Persistent<v8::Context>::New(context);
v8::Locker locker;
if (support_callback) {
v8::Debug::SetDebugMessageDispatchHandler(DispatchDebugMessages, true);
}
if (port_number != -1) {
v8::Debug::EnableAgent("lineprocessor", port_number, wait_for_connection);
}
#endif
bool report_exceptions = true;
v8::Handle<v8::Script> script;
{
// Compile script in try/catch context.
v8::TryCatch try_catch;
script = v8::Script::Compile(script_source, script_name);
if (script.IsEmpty()) {
// Print errors that happened during compilation.
if (report_exceptions)
ReportException(&try_catch);
return 1;
}
}
{
v8::TryCatch try_catch;
script->Run();
if (try_catch.HasCaught()) {
if (report_exceptions)
ReportException(&try_catch);
return 1;
}
}
if (cycle_type == CycleInCpp) {
bool res = RunCppCycle(script, v8::Context::GetCurrent(),
report_exceptions);
return !res;
} else {
// All is already done.
}
return 0;
}
bool RunCppCycle(v8::Handle<v8::Script> script, v8::Local<v8::Context> context,
bool report_exceptions) {
#ifdef SUPPORT_DEBUGGING
v8::Locker lock;
#endif
v8::Handle<v8::String> fun_name = v8::String::New("ProcessLine");
v8::Handle<v8::Value> process_val =
v8::Context::GetCurrent()->Global()->Get(fun_name);
// If there is no Process function, or if it is not a function,
// bail out
if (!process_val->IsFunction()) {
printf("Error: Script does not declare 'ProcessLine' global function.\n");
return 1;
}
// It is a function; cast it to a Function
v8::Handle<v8::Function> process_fun =
v8::Handle<v8::Function>::Cast(process_val);
while (!feof(stdin)) {
v8::HandleScope handle_scope;
v8::Handle<v8::String> input_line = ReadLine();
if (input_line == v8::Undefined()) {
continue;
}
const int argc = 1;
v8::Handle<v8::Value> argv[argc] = { input_line };
v8::Handle<v8::Value> result;
{
v8::TryCatch try_catch;
result = process_fun->Call(v8::Context::GetCurrent()->Global(),
argc, argv);
if (try_catch.HasCaught()) {
if (report_exceptions)
ReportException(&try_catch);
return false;
}
}
v8::String::Utf8Value str(result);
const char* cstr = ToCString(str);
printf("%s\n", cstr);
}
return true;
}
int main(int argc, char* argv[]) {
int result = RunMain(argc, argv);
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>";
}
// 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 = 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;
}
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");
}
}
// 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_line'
// function is called. Reads a string from standard input and returns.
v8::Handle<v8::Value> ReadLine(const v8::Arguments& args) {
if (args.Length() > 0) {
return v8::ThrowException(v8::String::New("Unexpected arguments"));
}
return ReadLine();
}
v8::Handle<v8::String> ReadLine() {
const int kBufferSize = 1024 + 1;
char buffer[kBufferSize];
char* res;
{
#ifdef SUPPORT_DEBUGGING
v8::Unlocker unlocker;
#endif
res = fgets(buffer, kBufferSize, stdin);
}
if (res == NULL) {
v8::Handle<v8::Primitive> t = v8::Undefined();
return reinterpret_cast<v8::Handle<v8::String>&>(t);
}
// remove newline char
for (char* pos = buffer; *pos != '\0'; pos++) {
if (*pos == '\n') {
*pos = '\0';
break;
}
}
return v8::String::New(buffer);
}
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