commit | 856c083bbbbe5970df8dd2404578b99c8973dc5c | [log] [tgz] |
---|---|---|
author | Lasse R.H. Nielsen <lrn@google.com> | Tue Apr 17 09:51:16 2018 +0200 |
committer | GitHub <noreply@github.com> | Tue Apr 17 09:51:16 2018 +0200 |
tree | 8508c5c798d9a01151d49f494a89dcccf366cd54 | |
parent | 158826cf138033d5493a6df65675a786ee0a4ef3 [diff] |
Remove upper case constants (#13) Remove usage of upper-case constants. Updates SDK version to 2.0.0-dev.17.0
The pool package exposes a Pool
class which makes it easy to manage a limited pool of resources.
The easiest way to use a pool is by calling withResource
. This runs a callback and returns its result, but only once there aren't too many other callbacks currently running.
// Create a Pool that will only allocate 10 resources at once. After 30 seconds // of inactivity with all resources checked out, the pool will throw an error. final pool = new Pool(10, timeout: new Duration(seconds: 30)); Future<String> readFile(String path) { // Since the call to [File.readAsString] is within [withResource], no more // than ten files will be open at once. return pool.withResource(() => new File(path).readAsString()); }
For more fine-grained control, the user can also explicitly request generic PoolResource
objects that can later be released back into the pool. This is what withResource
does under the covers: requests a resource, then releases it once the callback completes.
Pool
ensures that only a limited number of resources are allocated at once. It‘s the caller’s responsibility to ensure that the corresponding physical resource is only consumed when a PoolResource
is allocated.
class PooledFile implements RandomAccessFile { final RandomAccessFile _file; final PoolResource _resource; static Future<PooledFile> open(String path) { return pool.request().then((resource) { return new File(path).open().then((file) { return new PooledFile._(file, resource); }); }); } PooledFile(this._file, this._resource); // ... Future<RandomAccessFile> close() { return _file.close.then((_) { _resource.release(); return this; }); } }