time-to-botec

README.md (6820B)

---

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 @license Apache-2.0
 
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 Licensed under the Apache License, Version 2.0 (the "License");
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 See the License for the specific language governing permissions and
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 # Iterator Stream
 
 > Create a [readable stream][readable-stream] from an [iterator][mdn-iterator-protocol].
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var iteratorStream = require( '@stdlib/streams/node/from-iterator' );
 ```
 
 <a name="iterator-stream"></a>
 
 #### iteratorStream( iterator\[, options] )
 
 Returns a [readable stream][readable-stream] from an [iterator][mdn-iterator-protocol].
 
 ```javascript
 var inspectStream = require( '@stdlib/streams/node/inspect-sink' );
 var randu = require( '@stdlib/random/iter/randu' );
 
 var iStream;
 var stream;
 
 function log( chunk, idx ) {
     console.log( chunk.toString() );
     if ( idx === 10 ) {
         stream.destroy();
     }
 }
 
 stream = iteratorStream( randu() );
 iStream = inspectStream( log );
 
 stream.pipe( iStream );
 ```
 
 The function accepts the following `options`:
 
 -   **objectMode**: specifies whether a [stream][stream] should operate in [objectMode][object-mode]. Default: `false`.
 -   **encoding**: specifies how `Buffer` objects should be decoded to `strings`. Default: `null`.
 -   **highWaterMark**: specifies the maximum number of bytes to store in an internal buffer before pausing iteration.
 -   **sep**: separator used to join streamed data. This option is only applicable when a stream is **not** in [objectMode][object-mode]. Default: `'\n'`.
 -   **serialize**: custom serialization function. This option is only applicable when a stream is **not** in [objectMode][object-mode].
 
 To set [stream][stream] `options`,
 
 ```javascript
 var randu = require( '@stdlib/random/iter/randu' );
 
 var opts = {
     'objectMode': true,
     'encoding': 'utf8',
     'highWaterMark': 64
 };
 
 var stream = iteratorStream( randu(), opts );
 ```
 
 By default, when not operating in [objectMode][object-mode], a returned [stream][stream] delineates iterated values using a newline character. To specify an alternative separator, set the `sep` option.
 
 ```javascript
 var inspectStream = require( '@stdlib/streams/node/inspect-sink' );
 var randu = require( '@stdlib/random/iter/randu' );
 
 function log( chunk ) {
     console.log( chunk.toString() );
 }
 
 var it = randu({
     'iter': 10
 });
 
 var stream = iteratorStream( it, {
     'sep': ','
 });
 
 var iStream = inspectStream( log );
 
 stream.pipe( iStream );
 ```
 
 By default, when not operating in [objectMode][object-mode], a returned [stream][stream] serializes iterated values as JSON strings. To specify custom serialization behavior (either to a `string` or `Buffer`), set the `serialize` option.
 
 ```javascript
 var inspectStream = require( '@stdlib/streams/node/inspect-sink' );
 var randu = require( '@stdlib/random/iter/randu' );
 
 function serialize( v ) {
     return 'r::' + v.toString();
 }
 
 function log( chunk ) {
     console.log( chunk.toString() );
 }
 
 var it = randu({
     'iter': 10
 });
 
 var stream = iteratorStream( it, {
     'serialize': serialize
 });
 
 var iStream = inspectStream( log );
 
 stream.pipe( iStream );
 ```
 
 * * *
 
 #### iteratorStream.factory( \[options] )
 
 Returns a `function` for creating [readable streams][readable-stream] from [iterators][mdn-iterator-protocol].
 
 ```javascript
 var randu = require( '@stdlib/random/iter/randu' );
 
 var opts = {
     'objectMode': true,
     'encoding': 'utf8',
     'highWaterMark': 64
 };
 
 var createStream = iteratorStream.factory( opts );
 
 var stream1 = createStream( randu() );
 var stream2 = createStream( randu() );
 // ...
 ```
 
 The method accepts the same `options` as [`iteratorStream()`](#iterator-stream).
 
 * * *
 
 #### iteratorStream.objectMode( iterator\[, options] )
 
 This method is a convenience function to create [streams][stream] which **always** operate in [objectMode][object-mode].
 
 ```javascript
 var inspectStream = require( '@stdlib/streams/node/inspect-sink' );
 var randu = require( '@stdlib/random/iter/randu' );
 
 function log( v ) {
     console.log( v );
 }
 
 var opts = {
     'iter': 10
 };
 var stream = iteratorStream.objectMode( randu( opts ) );
 
 opts = {
     'objectMode': true
 };
 var iStream = inspectStream( opts, log );
 
 stream.pipe( iStream );
 ```
 
 This method accepts the same `options` as [`iteratorStream()`](#iterator-stream); however, the method will **always** override the [`objectMode`][object-mode] option in `options`.
 
 </section>
 
 <!-- /.usage -->
 
 * * *
 
 <section class="notes">
 
 ## Notes
 
 -   In [`objectMode`][object-mode], `null` is a reserved value. If an [iterator][mdn-iterator-protocol] generates `null` values (e.g., as a means to encode missing values), the stream will prematurely end. Consider an alternative encoding or explicitly map `null` values to a different value by wrapping the provided [iterator][mdn-iterator-protocol] with another [iterator][mdn-iterator-protocol].
 -   In binary mode, if an [iterator][mdn-iterator-protocol] generates `undefined` values, the stream will emit an error. Consider providing a custom serialization function or explicitly map `undefined` values to a different value by wrapping the provided [iterator][mdn-iterator-protocol] with another [iterator][mdn-iterator-protocol].
 
 </section>
 
 <!-- /.notes -->
 
 * * *
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var inspectStream = require( '@stdlib/streams/node/inspect-sink' );
 var randu = require( '@stdlib/random/iter/randu' );
 var iteratorStream = require( '@stdlib/streams/node/from-iterator' );
 
 function log( v ) {
     console.log( v.toString() );
 }
 
 // Create an iterator which generates uniformly distributed pseudorandom numbers:
 var opts = {
     'iter': 10
 };
 var it = randu( opts );
 
 // Convert the iterator to a stream:
 opts = {
     'objectMode': true
 };
 var stream = iteratorStream( it, opts );
 
 // Create a writable stream for inspecting stream data:
 opts = {
     'objectMode': true
 };
 var iStream = inspectStream( opts, log );
 
 // Begin data flow:
 stream.pipe( iStream );
 ```
 
 </section>
 
 <!-- /.examples -->
 
 <section class="links">
 
 [stream]: https://nodejs.org/api/stream.html
 
 [object-mode]: https://nodejs.org/api/stream.html#stream_object_mode
 
 [readable-stream]: https://nodejs.org/api/stream.html
 
 [mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol
 
 </section>
 
 <!-- /.links -->