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Diffstat (limited to 'lib/internal/streams/from.js')
-rw-r--r-- | lib/internal/streams/from.js | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/lib/internal/streams/from.js b/lib/internal/streams/from.js new file mode 100644 index 0000000000..e809f2658d --- /dev/null +++ b/lib/internal/streams/from.js @@ -0,0 +1,46 @@ +'use strict'; + +const { + ERR_INVALID_ARG_TYPE +} = require('internal/errors').codes; + +function from(Readable, iterable, opts) { + let iterator; + if (iterable && iterable[Symbol.asyncIterator]) + iterator = iterable[Symbol.asyncIterator](); + else if (iterable && iterable[Symbol.iterator]) + iterator = iterable[Symbol.iterator](); + else + throw new ERR_INVALID_ARG_TYPE('iterable', ['Iterable'], iterable); + + const readable = new Readable({ + objectMode: true, + ...opts + }); + // Reading boolean to protect against _read + // being called before last iteration completion. + let reading = false; + readable._read = function() { + if (!reading) { + reading = true; + next(); + } + }; + async function next() { + try { + const { value, done } = await iterator.next(); + if (done) { + readable.push(null); + } else if (readable.push(await value)) { + next(); + } else { + reading = false; + } + } catch (err) { + readable.destroy(err); + } + } + return readable; +} + +module.exports = from; |