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util: improve typed array formatting
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Pretty-print typed arrays like regular arrays.  Speeds up formatting by
almost 300% because it no longer stringifies the array indices.

Pretty-print ArrayBuffer and DataView as well by including byteLength,
byteOffset and buffer properties in the stringified representation.

PR-URL: #3793
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
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@bnoordhuis
bnoordhuis committed Nov 14, 2015
1 parent 8b57b31 commit 34a3591
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Showing 2 changed files with 121 additions and 9 deletions.
77 changes: 68 additions & 9 deletions lib/util.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -284,10 +284,17 @@ function formatValue(ctx, value, recurseTimes) {
formatted = formatPrimitiveNoColor(ctx, raw);
return ctx.stylize('[Boolean: ' + formatted + ']', 'boolean');
}
// Fast path for ArrayBuffer. Can't do the same for DataView because it
// has a non-primitive .buffer property that we need to recurse for.
if (value instanceof ArrayBuffer) {
return `${getConstructorOf(value).name}` +
` { byteLength: ${formatNumber(ctx, value.byteLength)} }`;
}
}

var constructor = getConstructorOf(value);
var base = '', empty = false, braces, formatter;
var base = '', empty = false, braces;
var formatter = formatObject;

if (Array.isArray(value)) {
// We can't use `constructor === Array` because this could
Expand All @@ -314,6 +321,28 @@ function formatValue(ctx, value, recurseTimes) {
keys.unshift('size');
empty = value.size === 0;
formatter = formatMap;
} else if (value instanceof ArrayBuffer) {
braces = ['{', '}'];
keys.unshift('byteLength');
visibleKeys.byteLength = true;
} else if (value instanceof DataView) {
braces = ['{', '}'];
// .buffer goes last, it's not a primitive like the others.
keys.unshift('byteLength', 'byteOffset', 'buffer');
visibleKeys.byteLength = true;
visibleKeys.byteOffset = true;
visibleKeys.buffer = true;
} else if (isTypedArray(value)) {
braces = ['[', ']'];
formatter = formatTypedArray;
if (ctx.showHidden) {
// .buffer goes last, it's not a primitive like the others.
keys.unshift('BYTES_PER_ELEMENT',
'length',
'byteLength',
'byteOffset',
'buffer');
}
} else {
// Only create a mirror if the object superficially looks like a Promise.
var promiseInternals = value instanceof Promise && inspectPromise(value);
Expand All @@ -336,7 +365,6 @@ function formatValue(ctx, value, recurseTimes) {
constructor = null;
braces = ['{', '}'];
empty = true; // No other data than keys.
formatter = formatObject;
}
}
}
Expand Down Expand Up @@ -408,6 +436,15 @@ function formatValue(ctx, value, recurseTimes) {
}


function formatNumber(ctx, value) {
// Format -0 as '-0'. Strict equality won't distinguish 0 from -0,
// so instead we use the fact that 1 / -0 < 0 whereas 1 / 0 > 0 .
if (value === 0 && 1 / value < 0)
return ctx.stylize('-0', 'number');
return ctx.stylize('' + value, 'number');
}


function formatPrimitive(ctx, value) {
if (value === undefined)
return ctx.stylize('undefined', 'undefined');
Expand All @@ -424,13 +461,8 @@ function formatPrimitive(ctx, value) {
.replace(/\\"/g, '"') + '\'';
return ctx.stylize(simple, 'string');
}
if (type === 'number') {
// Format -0 as '-0'. Strict equality won't distinguish 0 from -0,
// so instead we use the fact that 1 / -0 < 0 whereas 1 / 0 > 0 .
if (value === 0 && 1 / value < 0)
return ctx.stylize('-0', 'number');
return ctx.stylize('' + value, 'number');
}
if (type === 'number')
return formatNumber(ctx, value);
if (type === 'boolean')
return ctx.stylize('' + value, 'boolean');
// es6 symbol primitive
Expand Down Expand Up @@ -480,6 +512,20 @@ function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
}


function formatTypedArray(ctx, value, recurseTimes, visibleKeys, keys) {
var output = new Array(value.length);
for (var i = 0, l = value.length; i < l; ++i)
output[i] = formatNumber(ctx, value[i]);
for (const key of keys) {
if (typeof key === 'symbol' || !key.match(/^\d+$/)) {
output.push(
formatProperty(ctx, value, recurseTimes, visibleKeys, key, true));
}
}
return output;
}


function formatSet(ctx, value, recurseTimes, visibleKeys, keys) {
var output = [];
value.forEach(function(v) {
Expand Down Expand Up @@ -626,6 +672,19 @@ function reduceToSingleString(output, base, braces) {
}


function isTypedArray(value) {
return value instanceof Float32Array ||
value instanceof Float64Array ||
value instanceof Int16Array ||
value instanceof Int32Array ||
value instanceof Int8Array ||
value instanceof Uint16Array ||
value instanceof Uint32Array ||
value instanceof Uint8Array ||
value instanceof Uint8ClampedArray;
}


// NOTE: These type checking functions intentionally don't use `instanceof`
// because it is fragile and can be easily faked with `Object.create()`.
exports.isArray = Array.isArray;
Expand Down
53 changes: 53 additions & 0 deletions test/parallel/test-util-inspect.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,59 @@ assert.equal(util.inspect(Object.create({},
'{ visible: 1 }'
);

for (const showHidden of [true, false]) {
const ab = new ArrayBuffer(4);
const dv = new DataView(ab, 1, 2);
assert.equal(util.inspect(ab, showHidden), 'ArrayBuffer { byteLength: 4 }');
assert.equal(util.inspect(new DataView(ab, 1, 2), showHidden),
'DataView {\n' +
' byteLength: 2,\n' +
' byteOffset: 1,\n' +
' buffer: ArrayBuffer { byteLength: 4 } }');
assert.equal(util.inspect(ab, showHidden), 'ArrayBuffer { byteLength: 4 }');
assert.equal(util.inspect(dv, showHidden),
'DataView {\n' +
' byteLength: 2,\n' +
' byteOffset: 1,\n' +
' buffer: ArrayBuffer { byteLength: 4 } }');
ab.x = 42;
dv.y = 1337;
assert.equal(util.inspect(ab, showHidden),
'ArrayBuffer { byteLength: 4, x: 42 }');
assert.equal(util.inspect(dv, showHidden),
'DataView {\n' +
' byteLength: 2,\n' +
' byteOffset: 1,\n' +
' buffer: ArrayBuffer { byteLength: 4, x: 42 },\n' +
' y: 1337 }');
}

[ Float32Array,
Float64Array,
Int16Array,
Int32Array,
Int8Array,
Uint16Array,
Uint32Array,
Uint8Array,
Uint8ClampedArray ].forEach(constructor => {
const length = 2;
const byteLength = length * constructor.BYTES_PER_ELEMENT;
const array = new constructor(new ArrayBuffer(byteLength), 0, length);
array[0] = 65;
array[1] = 97;
assert.equal(util.inspect(array, true),
`${constructor.name} [\n` +
` 65,\n` +
` 97,\n` +
` [BYTES_PER_ELEMENT]: ${constructor.BYTES_PER_ELEMENT},\n` +
` [length]: ${length},\n` +
` [byteLength]: ${byteLength},\n` +
` [byteOffset]: 0,\n` +
` [buffer]: ArrayBuffer { byteLength: ${byteLength} } ]`);
assert.equal(util.inspect(array, false), `${constructor.name} [ 65, 97 ]`);
});

// Due to the hash seed randomization it's not deterministic the order that
// the following ways this hash is displayed.
// See http://codereview.chromium.org/9124004/
Expand Down

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