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stream: inline needMoreData function

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Inline the needMoreData function since it has only one call place.
Update the related comment.
Add a test for the edge case where HWM=0 and state.length=0.
Add a test for ReadableStream.read(n) method's edge case where
n, HWM and state.length are all zero.
This proves that there is no easy way to simplify the check at
https://github.com/nodejs/node/blob/master/lib/_stream_readable.js#L440

Fixes: https://github.com/nodejs/node/issues/19893
Refs: https://github.com/nodejs/node/pull/19896

PR-URL: https://github.com/nodejs/node/pull/21009
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Lance Ball <lball@redhat.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
This commit is contained in:
Miklos Suveges 2018-05-29 01:47:27 +02:00 committed by Matteo Collina
parent f86e5fc437
commit 1c07ebfd97
2 changed files with 52 additions and 34 deletions
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19
lib/_stream_readable.js
View File

@ -270,7 +270,11 @@ function readableAddChunk(stream, chunk, encoding, addToFront, skipChunkCheck) {
}
}
return needMoreData(state);
// We can push more data if we are below the highWaterMark.
// Also, if we have no data yet, we can stand some more bytes.
// This is to work around cases where hwm=0, such as the repl.
return !state.ended &&
(state.length < state.highWaterMark || state.length === 0);
}
function addChunk(stream, state, chunk, addToFront) {
@ -304,19 +308,6 @@ function chunkInvalid(state, chunk) {
}
// We can push more data if we are below the highWaterMark.
// Also, if we have no data yet, we can stand some
// more bytes. This is to work around cases where hwm=0,
// such as the repl. Also, if the push() triggered a
// readable event, and the user called read(largeNumber) such that
// needReadable was set, then we ought to push more, so that another
// 'readable' event will be triggered.
function needMoreData(state) {
return !state.ended &&
(state.length < state.highWaterMark ||
state.length === 0);
}
Readable.prototype.isPaused = function() {
return this._readableState.flowing === false;
};

67
test/parallel/test-streams-highwatermark.js
View File

@ -1,31 +1,58 @@
'use strict';
const common = require('../common');
// This test ensures that the stream implementation correctly handles values
// for highWaterMark which exceed the range of signed 32 bit integers and
// rejects invalid values.
const assert = require('assert');
const stream = require('stream');
// This number exceeds the range of 32 bit integer arithmetic but should still
// be handled correctly.
const ovfl = Number.MAX_SAFE_INTEGER;
{
// This test ensures that the stream implementation correctly handles values
// for highWaterMark which exceed the range of signed 32 bit integers and
// rejects invalid values.
const readable = stream.Readable({ highWaterMark: ovfl });
assert.strictEqual(readable._readableState.highWaterMark, ovfl);
// This number exceeds the range of 32 bit integer arithmetic but should still
// be handled correctly.
const ovfl = Number.MAX_SAFE_INTEGER;
const writable = stream.Writable({ highWaterMark: ovfl });
assert.strictEqual(writable._writableState.highWaterMark, ovfl);
const readable = stream.Readable({ highWaterMark: ovfl });
assert.strictEqual(readable._readableState.highWaterMark, ovfl);
for (const invalidHwm of [true, false, '5', {}, -5, NaN]) {
for (const type of [stream.Readable, stream.Writable]) {
common.expectsError(() => {
type({ highWaterMark: invalidHwm });
}, {
type: TypeError,
code: 'ERR_INVALID_OPT_VALUE',
message: `The value "${invalidHwm}" is invalid for option "highWaterMark"`
});
const writable = stream.Writable({ highWaterMark: ovfl });
assert.strictEqual(writable._writableState.highWaterMark, ovfl);
for (const invalidHwm of [true, false, '5', {}, -5, NaN]) {
for (const type of [stream.Readable, stream.Writable]) {
common.expectsError(() => {
type({ highWaterMark: invalidHwm });
}, {
type: TypeError,
code: 'ERR_INVALID_OPT_VALUE',
message:
`The value "${invalidHwm}" is invalid for option "highWaterMark"`
});
}
}
}
{
// This test ensures that the push method's implementation
// correctly handles the edge case where the highWaterMark and
// the state.length are both zero
const readable = stream.Readable({ highWaterMark: 0 });
for (let i = 0; i < 3; i++) {
const needMoreData = readable.push();
assert.strictEqual(needMoreData, true);
}
}
{
// This test ensures that the read(n) method's implementation
// correctly handles the edge case where the highWaterMark, state.length
// and n are all zero
const readable = stream.Readable({ highWaterMark: 0 });
readable._read = common.mustCall();
readable.read(0);
}