A Content Addressable Blob Store for Node.
This implements something similar to the object store from git (the .git/objects folder). By default blobs stored by cabs are sha256 hashed and stored in subdirectories to avoid putting too many files in a single directory. The hashing algorithm and depth of the directories are configurable.
Cabs.write(path[, hashFunction, limit]);Pipe in a blob stream (e.g. fs.createReadStream), get back objects for the various pieces stored. Each object has a hash of the block, as well as the starting and ending locations within the stream. You may optionally pass a string representing the hash function to use (default sha256) and number representing the block size (defaults to 5 MB).
To learn more about hashing algorithm tradeoffs read the comments on this issue.
Cabs.read(path);Pipe in the objects from write, returns a readable stream of the blob.
var fs = require('fs')
var Cabs = require('cabs')
/** stream a movie into cabs, store hashes in hashes.json **/
fs.createReadStream('movie.avi')
.pipe(Cabs.write('./storage'))
.pipe(fs.createWriteStream('hashes.json'));
/** later, to retrieve the movie, stream the hashes into cabs **/
fs.createReadStream('hashes.json')
.pipe(Cabs.read('./storage))
.pipe(fs.createWriteStream('movie-copy.avi'));you also have access to the base Cabs class located at cabs.Cabs, initialize it with a location and optionally an options object wtih a string representing the hash function to use (Defaults to sha256), the block size limit (defaults to 5 MB) and the depth of folders to use.
var store = new Cabs('./location');
// or
var store = new Cabs({
path: './location',
hashFunction: 'sha256',
limit: 5 * 1024 *1024
depth: 3
});
store.write(buffer, callback);
//stores buffer, callback is called with the hash
store.read(hash, callback);
//calls the callback with the blob
store.rm(hash, callback);
//removes the file with the given hash
store.destroy(callback);
//deletes all the files related to the store, just a shortcut to rimraf so beware.
store.readStream();
//same as Cabs.read
store.writeStream();
//same as Cabs.write
store.has(hash, callback);
//calls callback with true if it exists, otherwise false
store.check(hash, callback);
//similar to has but throws an error if the file doesn't exist
//or it's hash doesn't match it's address hash
store.writeFile();
//write to a single file on disc. Will only ever emit a single string
//the hash for the combined file you streamed in.
//unlike writeStream which chunks a big file into multiple smaller ones
//which can be handled in memory, this method buffers to disk.
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