A deep dive into Jake Wharton’s DiskLruCache

Rahul Raja
Feb 25, 2017 · 11 min read
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Entry object


class Entry{
String key;
long[] lengths;
boolean readable;
Editor currentEditor;
long sequenceNumber;
File getCleanFile(index);
File getDirtyFile(index);
}

Snapshot object


class Snapshot {
String key;
long sequenceNumber;
InputStream[] ins;
long[] lengths;
}

Editor object


class Editor {
Entry entry;
boolean[] written;
boolean hasErrors;
boolean committed;
InputStream newInputStream(index);
OutputStream newOutputStream(index);
}

Journal file

Initializing the cache


DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize)

Writing into the cache


DiskLruCache.Editor editor = null;
editor = mDiskCache.edit(key);

journalWriter.write(DIRTY + ‘ ‘ + key + ‘\n’);

OutputStream out = new BufferedOutputStream(editor.newOutputStream(0), bufferSize);

journalWriter.write(CLEAN + ‘ ‘ + entry.key + entry.getLengths() + ‘\n’);

Getting data from cache


DiskLruCache.Snapshot snapshot = mDiskCache.get(key);

InputStream in = snapshot.getInputStream(0);
BufferedInputStream buffIn = new BufferedInputStream(in, bufferSize);

journalWriter.append(READ + ‘ ‘ + key + ‘\n’);

Closing the cache

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