# sonic-boom

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Extremely fast utf8-only stream implementation to write to files and
file descriptors.

This implementation is partial, but support backpressure and `.pipe()` in is here.
However, it is 2-3x faster than Node Core `fs.createWriteStream()`:

```
benchSonic*1000: 1916.904ms
benchSonicSync*1000: 8605.265ms
benchSonic4k*1000: 1965.231ms
benchSonicSync4k*1000: 1588.224ms
benchCore*1000: 5851.959ms
benchConsole*1000: 7605.713ms
```

Note that sync mode without buffering is _slower_ than a Node Core WritableStream, however
this mode matches the expected behavior of `console.log()`.

Note that if this is used to log to a windows terminal (`cmd.exe` or
powershell), it is needed to run `chcp 65001` in the terminal to
correctly display utf-8 characters, see
[chcp](https://ss64.com/nt/chcp.html) for more details.

## Install

```
npm i sonic-boom
```

## Example

```js
'use strict'

const SonicBoom = require('sonic-boom')
const sonic = new SonicBoom({ fd: process.stdout.fd }) // or { dest: '/path/to/destination' }

for (let i = 0; i < 10; i++) {
  sonic.write('hello sonic\n')
}
```

## API

### SonicBoom(opts)

Creates a new instance of SonicBoom.

The options are:

* `fd`: a file descriptor, something that is returned by `fs.open` or
   `fs.openSync`.
* `dest`: a string that is a path to a file to be written to (mode controlled by the `append` option).
* `minLength`: the minimum length of the internal buffer that is
  required to be full before flushing.
* `maxLength`: the maximum length of the internal buffer. If a write operation would cause the buffer
  to exceed `maxLength`, the data written is dropped and a `drop` event is emitted with the dropped data
* `maxWrite`: the maximum number of bytes that can be written; default: 16384
* `sync`: perform writes synchronously (similar to `console.log`).
* `fsync`: perform a [fsyncSync](https://nodejs.org/api/fs.html#fsfsyncsyncfd) every time a write is completed.
* `append`: appends writes to dest file instead of truncating it (default `true`).
* `mode`: specify the creating file `mode` (see [fs.open()](https://nodejs.org/api/fs.html#fsopenpath-flags-mode-callback) from Node.js core).
* `mkdir`: ensure directory for dest file exists when `true` (default `false`).
* `retryEAGAIN(err, writeBufferLen, remainingBufferLen)`: a function that will be called when sonic-boom
    write/writeSync/flushSync encounters a EAGAIN or EBUSY error. If the return value is
    true sonic-boom will retry the operation, otherwise it will bubble the
    error. `err` is the error that caused this function to be called,
    `writeBufferLen` is the length of the buffer sonic-boom tried to write, and
    `remainingBufferLen` is the length of the remaining buffer sonic-boom didn't try to write.

For `sync:false`  a `SonicBoom` instance will emit the `'ready'` event when a file descriptor is available.
For `sync:true` this is not relevant because the `'ready'` event will be fired when the `SonicBoom` instance is created, before it can be subscribed to.


### SonicBoom#write(string)

Writes the string to the file.
It will return false to signal the producer to slow down.

### SonicBoom#flush([cb])

Writes the current buffer to the file if a write was not in progress.
Do nothing if `minLength` is zero or if it is already writing.

call the callback when the flush operation is completed. when failed the callback is called with an error.

### SonicBoom#reopen([file])

Reopen the file in place, useful for log rotation.

Example:

```js
const stream = new SonicBoom('./my.log')
process.on('SIGUSR2', function () {
  stream.reopen()
})
```

### SonicBoom#flushSync()

Flushes the buffered data synchronously. This is a costly operation.

### SonicBoom#end()

Closes the stream, the data will be flushed down asynchronously

### SonicBoom#destroy()

Closes the stream immediately, the data is not flushed.

### Events


#### SonicBoom#close

See [Stream#close](https://nodejs.org/api/stream.html#event-close). The `'close'` event when the instance has been closed.

#### SonicBoom#drain

See [Stream#drain](https://nodejs.org/api/stream.html#event-drain). The `'drain'` event is emitted when source can resume sending data.

#### SonicBoom#drop <any>

When destination file maximal length is reached, the `'drop'` event is emitted with data that could not be written. 

#### SonicBoom#error <Error>

The `'error'` event is emitted when the destination file can not be opened, or written.

#### SonicBoom#finish

See [Stream#finish](https://nodejs.org/api/stream.html#event-finish). The `'finish'` event after calling `end()` method and when all data was written.

#### SonicBoom#ready

The `'ready'` event occurs when the created instance is ready to process input.

#### SonicBoom#write <number>

The `'write'` event occurs every time data is written to the underlying file. It emits the number of written bytes.

## License

MIT
