112 lines
5.1 KiB
Markdown
112 lines
5.1 KiB
Markdown
# file-entry-cache
|
|
> Super simple cache for file metadata, useful for process that work o a given series of files
|
|
> and that only need to repeat the job on the changed ones since the previous run of the process — Edit
|
|
|
|
[](https://npmjs.org/package/file-entry-cache)
|
|
[](https://travis-ci.org/royriojas/file-entry-cache)
|
|
|
|
## install
|
|
|
|
```bash
|
|
npm i --save file-entry-cache
|
|
```
|
|
|
|
## Usage
|
|
|
|
The module exposes two functions `create` and `createFromFile`.
|
|
|
|
## `create(cacheName, [directory, useCheckSum])`
|
|
- **cacheName**: the name of the cache to be created
|
|
- **directory**: Optional the directory to load the cache from
|
|
- **usecheckSum**: Whether to use md5 checksum to verify if file changed. If false the default will be to use the mtime and size of the file.
|
|
|
|
## `createFromFile(pathToCache, [useCheckSum])`
|
|
- **pathToCache**: the path to the cache file (this combines the cache name and directory)
|
|
- **useCheckSum**: Whether to use md5 checksum to verify if file changed. If false the default will be to use the mtime and size of the file.
|
|
|
|
```js
|
|
// loads the cache, if one does not exists for the given
|
|
// Id a new one will be prepared to be created
|
|
var fileEntryCache = require('file-entry-cache');
|
|
|
|
var cache = fileEntryCache.create('testCache');
|
|
|
|
var files = expand('../fixtures/*.txt');
|
|
|
|
// the first time this method is called, will return all the files
|
|
var oFiles = cache.getUpdatedFiles(files);
|
|
|
|
// this will persist this to disk checking each file stats and
|
|
// updating the meta attributes `size` and `mtime`.
|
|
// custom fields could also be added to the meta object and will be persisted
|
|
// in order to retrieve them later
|
|
cache.reconcile();
|
|
|
|
// use this if you want the non visited file entries to be kept in the cache
|
|
// for more than one execution
|
|
//
|
|
// cache.reconcile( true /* noPrune */)
|
|
|
|
// on a second run
|
|
var cache2 = fileEntryCache.create('testCache');
|
|
|
|
// will return now only the files that were modified or none
|
|
// if no files were modified previous to the execution of this function
|
|
var oFiles = cache.getUpdatedFiles(files);
|
|
|
|
// if you want to prevent a file from being considered non modified
|
|
// something useful if a file failed some sort of validation
|
|
// you can then remove the entry from the cache doing
|
|
cache.removeEntry('path/to/file'); // path to file should be the same path of the file received on `getUpdatedFiles`
|
|
// that will effectively make the file to appear again as modified until the validation is passed. In that
|
|
// case you should not remove it from the cache
|
|
|
|
// if you need all the files, so you can determine what to do with the changed ones
|
|
// you can call
|
|
var oFiles = cache.normalizeEntries(files);
|
|
|
|
// oFiles will be an array of objects like the following
|
|
entry = {
|
|
key: 'some/name/file', the path to the file
|
|
changed: true, // if the file was changed since previous run
|
|
meta: {
|
|
size: 3242, // the size of the file
|
|
mtime: 231231231, // the modification time of the file
|
|
data: {} // some extra field stored for this file (useful to save the result of a transformation on the file
|
|
}
|
|
}
|
|
|
|
```
|
|
|
|
## Motivation for this module
|
|
|
|
I needed a super simple and dumb **in-memory cache** with optional disk persistence (write-back cache) in order to make
|
|
a script that will beautify files with `esformatter` to execute only on the files that were changed since the last run.
|
|
|
|
In doing so the process of beautifying files was reduced from several seconds to a small fraction of a second.
|
|
|
|
This module uses [flat-cache](https://www.npmjs.com/package/flat-cache) a super simple `key/value` cache storage with
|
|
optional file persistance.
|
|
|
|
The main idea is to read the files when the task begins, apply the transforms required, and if the process succeed,
|
|
then store the new state of the files. The next time this module request for `getChangedFiles` will return only
|
|
the files that were modified. Making the process to end faster.
|
|
|
|
This module could also be used by processes that modify the files applying a transform, in that case the result of the
|
|
transform could be stored in the `meta` field, of the entries. Anything added to the meta field will be persisted.
|
|
Those processes won't need to call `getChangedFiles` they will instead call `normalizeEntries` that will return the
|
|
entries with a `changed` field that can be used to determine if the file was changed or not. If it was not changed
|
|
the transformed stored data could be used instead of actually applying the transformation, saving time in case of only
|
|
a few files changed.
|
|
|
|
In the worst case scenario all the files will be processed. In the best case scenario only a few of them will be processed.
|
|
|
|
## Important notes
|
|
- The values set on the meta attribute of the entries should be `stringify-able` ones if possible, flat-cache uses `circular-json` to try to persist circular structures, but this should be considered experimental. The best results are always obtained with non circular values
|
|
- All the changes to the cache state are done to memory first and only persisted after reconcile.
|
|
|
|
## License
|
|
|
|
MIT
|
|
|
|
|