Continuous reading or writing to a file using random offsets and lengths
npm install random-access-fileContinuous reading or writing to a file using random offsets and lengths
``
npm install random-access-file
If you are receiving a file in multiple pieces in a distributed system it can be useful to write these pieces to disk one by one in various places throughout the file without having to open and close a file descriptor all the time.
random-access-file allows you to do just this.
` js
const RandomAccessFile = require('random-access-file')
const file = new RandomAccessFile('my-file.txt')
file.write(10, Buffer.from('hello'), function(err) {
// write a buffer to offset 10
file.read(10, 5, function(err, buffer) {
console.log(buffer) // read 5 bytes from offset 10
file.close(function() {
console.log('file is closed')
})
})
})
`
file will use an open file descriptor. When you are done with the file you should call file.close().
#### const file = new RandomAccessFile(filename, [options])
Create a new file. Options include:
` js`
{
truncate: false, // truncate the file before reading / writing
size: someSize, // truncate the file to this size first
readable: true, // should the file be opened as readable?
writable: true, // should the file be opened as writable?
lock: false, // lock the file
sparse: false // mark the file as sparse
}
#### file.write(offset, buffer, [callback])
Write a buffer at a specific offset.
#### file.read(offset, length, callback)
Read a buffer at a specific offset. Callback is called with the buffer read.
#### file.del(offset, length, callback)
Delete a portion of the file. Any partial file blocks in the deleted portion are zeroed and, if the file is sparse, the remaining file blocks unlinked in-place.
#### file.truncate(offset, callback)
Truncate the file length to this offset.
#### file.stat(callback)
Stat the storage. Should return an object with useful information about the underlying storage, including:
`js`
{
size: number // how many bytes of data is stored?
}
#### file.close([callback])
Close the underlying file descriptor.
#### file.unlink([callback])
Unlink the underlying file.
#### file.on('open')
Emitted when the file descriptor has been opened. You can access the fd using file.fd.
You do not need to wait for this event before doing any reads/writes.
#### file.on('close')`
Emitted when the file has been closed.
MIT