gecko-dev/js/examples/jorendb.js

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JavaScript
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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sw=4 et tw=78:
*
* jorendb - A toy command-line debugger for shell-js programs.
*
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* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
* jorendb is a simple command-line debugger for shell-js programs. It is
* intended as a demo of the Debugger object (as there are no shell js programs to
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* speak of).
*
* To run it: $JS -d path/to/this/file/jorendb.js
* To run some JS code under it, try:
* (jorendb) print load("my-script-to-debug.js")
* Execution will stop at debugger statements and you'll get a jorendb prompt.
*/
(function () {
var debuggerSource = "(" + function () {
// Debugger state.
var focusedFrame = null;
var topFrame = null;
var debuggeeValues = [null];
var lastExc = null;
// Convert a debuggee value v to a string.
function dvToString(v) {
return (typeof v !== 'object' || v === null) ? uneval(v) : "[object " + v.class + "]";
}
function showDebuggeeValue(dv) {
var dvrepr = dvToString(dv);
var i = debuggeeValues.length;
debuggeeValues[i] = dv;
print("$" + i + " = " + dvrepr);
}
Object.defineProperty(Debugger.Frame.prototype, "num", {
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configurable: true,
enumerable: false,
get: function () {
var i = 0;
for (var f = topFrame; f && f !== this; f = f.older)
i++;
return f === null ? undefined : i;
}
});
function framePosition(f) {
if (!f.script)
return f.type + " code";
return (f.script.url || f.type + " code") + ":" + f.script.getOffsetLine(f.offset);
}
function callDescription(f) {
return ((f.callee.name || '<anonymous>') +
"(" + f.arguments.map(dvToString).join(", ") + ")");
}
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function showFrame(f, n) {
if (f === undefined || f === null) {
f = focusedFrame;
if (f === null) {
print("No stack.");
return;
}
}
if (n === undefined) {
n = f.num;
if (n === undefined)
throw new Error("Internal error: frame not on stack");
}
var me = '#' + n;
if (f.type === "call")
me += ' ' + callDescription(f);
me += ' ' + framePosition(f);
print(me);
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}
function saveExcursion(fn) {
var tf = topFrame, ff = focusedFrame;
try {
return fn();
} finally {
topFrame = tf;
focusedFrame = ff;
}
}
function quitCommand() {
dbg.enabled = false;
quit(0);
}
function backtraceCommand() {
if (topFrame === null)
print("No stack.");
for (var i = 0, f = topFrame; f; i++, f = f.older)
showFrame(f, i);
}
function printCommand(rest) {
if (focusedFrame === null) {
// This is super bogus, need a way to create an env wrapping the debuggeeGlobal
// and eval against that.
var nonwrappedValue;
try {
nonwrappedValue = debuggeeGlobal.eval(rest);
} catch (exc) {
print("Exception caught.");
nonwrappedValue = exc;
}
if (typeof nonwrappedValue !== "object" || nonwrappedValue === null) {
// primitive value, no sweat
print(" " + uneval(nonwrappedValue));
} else {
// junk for now
print(" " + Object.prototype.toString.call(nonwrappedValue));
}
} else {
// This is the real deal.
var cv = saveExcursion(function () {
return focusedFrame.eval(rest);
});
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if (cv === null) {
if (!dbg.enabled)
return [cv];
print("Debuggee died.");
} else if ('return' in cv) {
if (!dbg.enabled)
return [undefined];
showDebuggeeValue(cv.return);
} else {
if (!dbg.enabled)
return [cv];
print("Exception caught. (To rethrow it, type 'throw'.)");
lastExc = cv.throw;
showDebuggeeValue(lastExc);
}
}
}
function detachCommand() {
dbg.enabled = false;
return [undefined];
}
function continueCommand() {
if (focusedFrame === null) {
print("No stack.");
return;
}
return [undefined];
}
function throwCommand(rest) {
var v;
if (focusedFrame !== topFrame) {
print("To throw, you must select the newest frame (use 'frame 0').");
return;
} else if (focusedFrame === null) {
print("No stack.");
return;
} else if (rest === '') {
return [{throw: lastExc}];
} else {
var cv = saveExcursion(function () { return focusedFrame.eval(rest); });
if (cv === null) {
if (!dbg.enabled)
return [cv];
print("Debuggee died while determining what to throw. Stopped.");
} else if ('return' in cv) {
return [{throw: cv.return}];
} else {
if (!dbg.enabled)
return [cv];
print("Exception determining what to throw. Stopped.");
showDebuggeeValue(cv.throw);
}
return;
}
}
function frameCommand(rest) {
var n, f;
if (rest.match(/[0-9]+/)) {
n = +rest;
f = topFrame;
if (f === null) {
print("No stack.");
return;
}
for (var i = 0; i < n && f; i++) {
if (!f.older) {
print("There is no frame " + rest + ".");
return;
}
f.older.younger = f;
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f = f.older;
}
focusedFrame = f;
showFrame(f, n);
} else if (rest !== '') {
if (topFrame === null)
print("No stack.");
else
showFrame();
} else {
print("do what now?");
}
}
function debugmeCommand() {
var meta = newGlobal("new-compartment");
meta.debuggeeGlobal = this;
meta.debuggerSource = debuggerSource;
meta.prompt = prompt.replace('(', '(meta-');
meta.eval(debuggerSource);
}
function upCommand() {
if (focusedFrame === null)
print("No stack.");
else if (focusedFrame.older === null)
print("Initial frame selected; you cannot go up.");
else {
focusedFrame.older.younger = focusedFrame;
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focusedFrame = focusedFrame.older;
showFrame();
}
}
function downCommand() {
if (focusedFrame === null)
print("No stack.");
else if (!focusedFrame.younger)
print("Youngest frame selected; you cannot go down.");
else {
focusedFrame = focusedFrame.younger;
showFrame();
}
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}
function forcereturnCommand(rest) {
var v;
var f = focusedFrame;
if (f !== topFrame) {
print("To forcereturn, you must select the newest frame (use 'frame 0').");
} else if (f === null) {
print("Nothing on the stack.");
} else if (rest === '') {
return [{return: undefined}];
} else {
var cv = saveExcursion(function () { return f.eval(rest); });
if (cv === null) {
if (!dbg.enabled)
return [cv];
print("Debuggee died while determining what to forcereturn. Stopped.");
} else if ('return' in cv) {
return [{return: cv.return}];
} else {
if (!dbg.enabled)
return [cv];
print("Error determining what to forcereturn. Stopped.");
showDebuggeeValue(cv.throw);
}
}
}
// Build the table of commands.
var commands = {};
var commandArray = [
backtraceCommand, "bt", "where",
continueCommand, "c",
detachCommand,
debugmeCommand,
downCommand, "d",
forcereturnCommand,
frameCommand, "f",
printCommand, "p",
quitCommand, "q",
throwCommand, "t",
upCommand, "u"
];
var last = null;
for (var i = 0; i < commandArray.length; i++) {
var cmd = commandArray[i];
if (typeof cmd === "string")
commands[cmd] = last;
else
last = commands[cmd.name.replace(/Command$/, '')] = cmd;
}
// Break cmd into two parts: its first word and everything else.
function breakcmd(cmd) {
cmd = cmd.trimLeft();
var m = /\s/.exec(cmd);
if (m === null)
return [cmd, ''];
return [cmd.slice(0, m.index), cmd.slice(m.index).trimLeft()];
}
function runcmd(cmd) {
var pieces = breakcmd(cmd);
if (pieces[0] === "")
return undefined;
var first = pieces[0], rest = pieces[1];
if (!commands.hasOwnProperty(first)) {
print("unrecognized command '" + first + "'");
return undefined;
}
var cmd = commands[first];
if (cmd.length === 0 && rest !== '') {
print("this command cannot take an argument");
return undefined;
}
return cmd(rest);
}
function repl() {
var cmd;
for (;;) {
print("\n" + prompt);
cmd = readline();
if (cmd === null)
break;
try {
var result = runcmd(cmd);
if (result === undefined)
; // do nothing
else if (Array.isArray(result))
return result[0];
else
throw new Error("Internal error: result of runcmd wasn't array or undefined");
} catch (exc) {
print("*** Internal error: exception in the debugger code.");
print(" " + exc);
var me = prompt.replace(/^\((.*)\)$/, function (a, b) { return b; });
print("Debug " + me + "? (y/n)");
if (readline().match(/^\s*y/i) !== null)
debugMe();
else
print("ok, ignoring error");
}
}
}
var dbg = new Debugger(debuggeeGlobal);
dbg.onDebuggerStatement = function (frame) {
return saveExcursion(function () {
topFrame = focusedFrame = frame;
print("'debugger' statement hit.");
showFrame();
return repl();
});
};
dbg.onThrow = function (frame, exc) {
return saveExcursion(function () {
topFrame = focusedFrame = frame;
print("Unwinding due to exception. (Type 'c' to continue unwinding.)");
showFrame();
print("Exception value is:");
showDebuggeeValue(exc);
return repl();
});
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};
repl();
} + ")();"
print("jorendb version -0.0");
var g = newGlobal("new-compartment");
g.debuggeeGlobal = this;
g.prompt = '(jorendb)';
g.debuggerSource = debuggerSource;
g.eval(debuggerSource);
})();