Readme.md (4551B)
1 # combined-stream 2 3 A stream that emits multiple other streams one after another. 4 5 **NB** Currently `combined-stream` works with streams version 1 only. There is ongoing effort to switch this library to streams version 2. Any help is welcome. :) Meanwhile you can explore other libraries that provide streams2 support with more or less compatibility with `combined-stream`. 6 7 - [combined-stream2](https://www.npmjs.com/package/combined-stream2): A drop-in streams2-compatible replacement for the combined-stream module. 8 9 - [multistream](https://www.npmjs.com/package/multistream): A stream that emits multiple other streams one after another. 10 11 ## Installation 12 13 ``` bash 14 npm install combined-stream 15 ``` 16 17 ## Usage 18 19 Here is a simple example that shows how you can use combined-stream to combine 20 two files into one: 21 22 ``` javascript 23 var CombinedStream = require('combined-stream'); 24 var fs = require('fs'); 25 26 var combinedStream = CombinedStream.create(); 27 combinedStream.append(fs.createReadStream('file1.txt')); 28 combinedStream.append(fs.createReadStream('file2.txt')); 29 30 combinedStream.pipe(fs.createWriteStream('combined.txt')); 31 ``` 32 33 While the example above works great, it will pause all source streams until 34 they are needed. If you don't want that to happen, you can set `pauseStreams` 35 to `false`: 36 37 ``` javascript 38 var CombinedStream = require('combined-stream'); 39 var fs = require('fs'); 40 41 var combinedStream = CombinedStream.create({pauseStreams: false}); 42 combinedStream.append(fs.createReadStream('file1.txt')); 43 combinedStream.append(fs.createReadStream('file2.txt')); 44 45 combinedStream.pipe(fs.createWriteStream('combined.txt')); 46 ``` 47 48 However, what if you don't have all the source streams yet, or you don't want 49 to allocate the resources (file descriptors, memory, etc.) for them right away? 50 Well, in that case you can simply provide a callback that supplies the stream 51 by calling a `next()` function: 52 53 ``` javascript 54 var CombinedStream = require('combined-stream'); 55 var fs = require('fs'); 56 57 var combinedStream = CombinedStream.create(); 58 combinedStream.append(function(next) { 59 next(fs.createReadStream('file1.txt')); 60 }); 61 combinedStream.append(function(next) { 62 next(fs.createReadStream('file2.txt')); 63 }); 64 65 combinedStream.pipe(fs.createWriteStream('combined.txt')); 66 ``` 67 68 ## API 69 70 ### CombinedStream.create([options]) 71 72 Returns a new combined stream object. Available options are: 73 74 * `maxDataSize` 75 * `pauseStreams` 76 77 The effect of those options is described below. 78 79 ### combinedStream.pauseStreams = `true` 80 81 Whether to apply back pressure to the underlaying streams. If set to `false`, 82 the underlaying streams will never be paused. If set to `true`, the 83 underlaying streams will be paused right after being appended, as well as when 84 `delayedStream.pipe()` wants to throttle. 85 86 ### combinedStream.maxDataSize = `2 * 1024 * 1024` 87 88 The maximum amount of bytes (or characters) to buffer for all source streams. 89 If this value is exceeded, `combinedStream` emits an `'error'` event. 90 91 ### combinedStream.dataSize = `0` 92 93 The amount of bytes (or characters) currently buffered by `combinedStream`. 94 95 ### combinedStream.append(stream) 96 97 Appends the given `stream` to the combinedStream object. If `pauseStreams` is 98 set to `true, this stream will also be paused right away. 99 100 `streams` can also be a function that takes one parameter called `next`. `next` 101 is a function that must be invoked in order to provide the `next` stream, see 102 example above. 103 104 Regardless of how the `stream` is appended, combined-stream always attaches an 105 `'error'` listener to it, so you don't have to do that manually. 106 107 Special case: `stream` can also be a String or Buffer. 108 109 ### combinedStream.write(data) 110 111 You should not call this, `combinedStream` takes care of piping the appended 112 streams into itself for you. 113 114 ### combinedStream.resume() 115 116 Causes `combinedStream` to start drain the streams it manages. The function is 117 idempotent, and also emits a `'resume'` event each time which usually goes to 118 the stream that is currently being drained. 119 120 ### combinedStream.pause(); 121 122 If `combinedStream.pauseStreams` is set to `false`, this does nothing. 123 Otherwise a `'pause'` event is emitted, this goes to the stream that is 124 currently being drained, so you can use it to apply back pressure. 125 126 ### combinedStream.end(); 127 128 Sets `combinedStream.writable` to false, emits an `'end'` event, and removes 129 all streams from the queue. 130 131 ### combinedStream.destroy(); 132 133 Same as `combinedStream.end()`, except it emits a `'close'` event instead of 134 `'end'`. 135 136 ## License 137 138 combined-stream is licensed under the MIT license.