Add "lineprocessor" sample program

Add "lineprocessor" sample program

Committed: http://code.google.com/p/v8/source/detail?r=3637

[Peter Rybin, 2009-12-10 18:47:54]

Hi Sorren

This is a sample of debuggable standalone V8 application. I more-or-less
copy-pasted it from shell.cc, though it contains a piece of new code.

I described everything in heading comment in the source file.

This sample contains couple of TODOs.

Peter

[Søren Thygesen Gjesse, 2009-12-11 11:20:01]

Maybe change the name of this to jsdebugging or something like that.

You should also add the sample to the SConstruct file to make it buildbable, and
maybe also a Visual Studio project file (I can do that afterwards).

http://codereview.chromium.org/491006/diff/3001/3002
File samples/lineprocessor.cc (right):

http://codereview.chromium.org/491006/diff/3001/3002#newcode43
samples/lineprocessor.cc:43: * When program starts, script gets compiled and
run. To this point should
I don't see why this sample should require any specific function to be declared.
How about just run the scripts. You can then define callback functions for feof
and fgets (call them something else though) and then have the suggested
JavaScript code have a top-level loop doing the RunCycle work.

http://codereview.chromium.org/491006/diff/3001/3002#newcode63
samples/lineprocessor.cc:63: * allows remote debugger to attach and debug custom
JavaScript code.
Maybe delete "custom"

http://codereview.chromium.org/491006/diff/3001/3002#newcode66
samples/lineprocessor.cc:66: * 1. Wait for remote debugger to attach
With the forced break in wait for connection the "debugger" statement is no
longer needed.

http://codereview.chromium.org/491006/diff/3001/3002#newcode115
samples/lineprocessor.cc:115: // TODO(peter.rybin): implement this.
Please open a bug on this and change to TODO(bugnumber).

http://codereview.chromium.org/491006/diff/3001/3002#newcode119
samples/lineprocessor.cc:119: // TODO(peter.rybin): implement this.
TODO(bugnumber) here as well.

http://codereview.chromium.org/491006/diff/3001/3002#newcode170
samples/lineprocessor.cc:170: // Run script. As a result the script should
declare "ProcessLine" function
I don't think this sample needs to require specific code in the JavaScript files
processed.

http://codereview.chromium.org/491006/diff/3001/3002#newcode200
samples/lineprocessor.cc:200: bool RunCycle(v8::Handle<v8::Function>
process_fun, bool report_exceptions) {
Remove empty line?

http://codereview.chromium.org/491006/diff/3001/3002#newcode221
samples/lineprocessor.cc:221: v8::Handle<v8::String> input_line =
v8::String::New(buffer);
Remove {}'s?

[Peter Rybin, 2009-12-13 23:18:32]

On 2009/12/11 11:20:01, Søren Gjesse wrote:
> Maybe change the name of this to jsdebugging or something like that.
I don't know. Such name will assume something generic about debugging, while the
program itself has very limited purpose: processing lines.

> You should also add the sample to the SConstruct file to make it buildbable,
and

Done

> maybe also a Visual Studio project file (I can do that afterwards).
I'm not sure we can do this. The program is going to be platform-dependent,
because I need multi-threading. That's why I wanted platform.h to be public.

[Peter Rybin, 2009-12-14 00:39:22]

Hi Soren

Thanks for review.

I redid the program so that it supports both main cycle in C++ part and main
cycle in JS part. This way it still illustrates the case of C++ being busy while
quick cycle of V8 is required to process debugger messages, but now it does it
in 2 different scenarios:
1. Processor is busy with C++ and V8 is not currently running (main cycle in
C++)
2. JS is running, but has called slow C++ function, making processor busy in C++
again. In this case I plan to call "void(0)" in V8 in other thread, while C++ is
doing whatever  it does. I don't know though whether V8 is OK with being blocked
in one thread and then being called in other thread.

http://codereview.chromium.org/491006/diff/3001/3002
File samples/lineprocessor.cc (right):

http://codereview.chromium.org/491006/diff/3001/3002#newcode43
samples/lineprocessor.cc:43: * When program starts, script gets compiled and
run. To this point should
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> I don't see why this sample should require any specific function to be
declared.
> How about just run the scripts. You can then define callback functions for
feof
> and fgets (call them something else though) and then have the suggested
> JavaScript code have a top-level loop doing the RunCycle work.

It was important for me to demonstrate a program, that is running V8 only
part-time and gets occupied most of the time by something else. This way it
needs to give a callback to DebugAgent.

On the other hand you are describing another interesting case: when V8 executes
a long script which passes a control back to C++. C++ call may take long, so it
is important to be able to quickly give control back to V8 to process debugger
messages, while C++ call still goes.

So I redid a program, added CycleType enum and supported 2 modes: main cycle in
C++ and main cycle in JS.

http://codereview.chromium.org/491006/diff/3001/3002#newcode63
samples/lineprocessor.cc:63: * allows remote debugger to attach and debug custom
JavaScript code.
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> Maybe delete "custom"

Done.

http://codereview.chromium.org/491006/diff/3001/3002#newcode66
samples/lineprocessor.cc:66: * 1. Wait for remote debugger to attach
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> With the forced break in wait for connection the "debugger" statement is no
> longer needed.

Done.

http://codereview.chromium.org/491006/diff/3001/3002#newcode115
samples/lineprocessor.cc:115: // TODO(peter.rybin): implement this.
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> Please open a bug on this and change to TODO(bugnumber).

Done.

http://codereview.chromium.org/491006/diff/3001/3002#newcode119
samples/lineprocessor.cc:119: // TODO(peter.rybin): implement this.
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> TODO(bugnumber) here as well.

It is already implemented

http://codereview.chromium.org/491006/diff/3001/3002#newcode170
samples/lineprocessor.cc:170: // Run script. As a result the script should
declare "ProcessLine" function
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> I don't think this sample needs to require specific code in the JavaScript
files
> processed.

I came to this because:
1. I wanted main cycle to be in C++ side, so I needed to call some callback in
JavaScript.
2. I wanted to split script into 2 parts: initialization part (the script itself
does initialization) and callback for each line (ProcessLine function becomes
this callback).

http://codereview.chromium.org/491006/diff/3001/3002#newcode200
samples/lineprocessor.cc:200: bool RunCycle(v8::Handle<v8::Function>
process_fun, bool report_exceptions) {
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> Remove empty line?

Done.

http://codereview.chromium.org/491006/diff/3001/3002#newcode221
samples/lineprocessor.cc:221: v8::Handle<v8::String> input_line =
v8::String::New(buffer);
On 2009/12/11 11:20:01, Søren Gjesse wrote:
> Remove {}'s?

Oops.
Done

[Peter Rybin, 2010-01-17 00:06:45]

Hi Søren

I finally redid sample. It uses feature from Issue #549

Peter

[Søren Thygesen Gjesse, 2010-01-18 11:10:22]

LGTM

http://codereview.chromium.org/491006/diff/9001/9003
File samples/lineprocessor.cc (right):

http://codereview.chromium.org/491006/diff/9001/9003#newcode41
samples/lineprocessor.cc:41: * script. The script is specified in command line
parameters.
in -> with/by?

http://codereview.chromium.org/491006/diff/9001/9003#newcode43
samples/lineprocessor.cc:43: * Main cycle of the program should sequentially
read lines from standard input
Main cycle -> The main cycle

should -> will

http://codereview.chromium.org/491006/diff/9001/9003#newcode44
samples/lineprocessor.cc:44: * and processes them and print to standard output
until input closes.
and processes -> , process

http://codereview.chromium.org/491006/diff/9001/9003#newcode47
samples/lineprocessor.cc:47: * 1. Main cycle is on C++ side. Program should be
run with --main-cycle-in-cpp
Main cycle -> The main cycle

http://codereview.chromium.org/491006/diff/9001/9003#newcode48
samples/lineprocessor.cc:48: * option. Script must declare function named
"ProcessLine". Main cycle in C++
declare function -> declare a function

Main cycle -> The main cycle

http://codereview.chromium.org/491006/diff/9001/9003#newcode49
samples/lineprocessor.cc:49: * reads line and calls this function for processing
every time.
reads line -> read lines

http://codereview.chromium.org/491006/diff/9001/9003#newcode57
samples/lineprocessor.cc:57: * 2. Main cycle is on JavaScript side. Program
should be run with
Main cycle -> The main cycle

on JavaScript side -> in JavaScript

http://codereview.chromium.org/491006/diff/9001/9003#newcode397
samples/lineprocessor.cc:397: // The callback that is invoked by v8 whenever the
JavaScript 'print'
Please change this comment to describe ReadLine.

[Peter Rybin, 2010-01-18 16:44:50]

http://codereview.chromium.org/491006/diff/9001/9003
File samples/lineprocessor.cc (right):

http://codereview.chromium.org/491006/diff/9001/9003#newcode41
samples/lineprocessor.cc:41: * script. The script is specified in command line
parameters.
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> in -> with/by?

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode43
samples/lineprocessor.cc:43: * Main cycle of the program should sequentially
read lines from standard input
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> Main cycle -> The main cycle
> 
> should -> will

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode44
samples/lineprocessor.cc:44: * and processes them and print to standard output
until input closes.
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> and processes -> , process

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode47
samples/lineprocessor.cc:47: * 1. Main cycle is on C++ side. Program should be
run with --main-cycle-in-cpp
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> Main cycle -> The main cycle

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode48
samples/lineprocessor.cc:48: * option. Script must declare function named
"ProcessLine". Main cycle in C++
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> declare function -> declare a function
> 
> Main cycle -> The main cycle

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode49
samples/lineprocessor.cc:49: * reads line and calls this function for processing
every time.
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> reads line -> read lines

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode57
samples/lineprocessor.cc:57: * 2. Main cycle is on JavaScript side. Program
should be run with
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> Main cycle -> The main cycle
> 
> on JavaScript side -> in JavaScript

Done.

http://codereview.chromium.org/491006/diff/9001/9003#newcode397
samples/lineprocessor.cc:397: // The callback that is invoked by v8 whenever the
JavaScript 'print'
On 2010/01/18 11:10:22, Søren Gjesse wrote:
> Please change this comment to describe ReadLine.

Done.