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'use strict';
const common = require('../common');
const stream = require('stream');
const assert = require('assert');
// A consumer stream with a very low highWaterMark, which starts in a state
// where it buffers the chunk it receives rather than indicating that they
// have been consumed.
const writable = new stream.Writable({
highWaterMark: 5
});
let isCurrentlyBufferingWrites = true;
const queue = [];
writable._write = (chunk, encoding, cb) => {
if (isCurrentlyBufferingWrites)
queue.push({ chunk, cb });
else
cb();
};
const readable = new stream.Readable({
read() {}
});
readable.pipe(writable);
readable.once('pause', common.mustCall(() => {
assert.strictEqual(
readable._readableState.awaitDrainWriters,
writable,
'Expected awaitDrainWriters to be a Writable but instead got ' +
`${readable._readableState.awaitDrainWriters}`
);
// First pause, resume manually. The next write() to writable will still
// return false, because chunks are still being buffered, so it will increase
// the awaitDrain counter again.
process.nextTick(common.mustCall(() => {
readable.resume();
}));
readable.once('pause', common.mustCall(() => {
assert.strictEqual(
readable._readableState.awaitDrainWriters,
writable,
'.resume() should not reset the awaitDrainWriters, but instead got ' +
`${readable._readableState.awaitDrainWriters}`
);
// Second pause, handle all chunks from now on. Once all callbacks that
// are currently queued up are handled, the awaitDrain drain counter should
// fall back to 0 and all chunks that are pending on the readable side
// should be flushed.
isCurrentlyBufferingWrites = false;
for (const queued of queue)
queued.cb();
}));
}));
readable.push(Buffer.alloc(100)); // Fill the writable HWM, first 'pause'.
readable.push(Buffer.alloc(100)); // Second 'pause'.
readable.push(Buffer.alloc(100)); // Should get through to the writable.
readable.push(null);
writable.on('finish', common.mustCall(() => {
assert.strictEqual(
readable._readableState.awaitDrainWriters,
null,
`awaitDrainWriters should be reset to null
after all chunks are written but instead got
${readable._readableState.awaitDrainWriters}`
);
// Everything okay, all chunks were written.
}));
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