/**
* Opens the cache in {@code directory}, creating a cache if none exists there.
*
* @param directory a writable directory
* @param valueCount the number of values per cache entry. Must be positive.
* @param maxSize the maximum number of bytes this cache should use to store
* @param maxFileCount the maximum file count this cache should store
* @throws java.io.IOException if reading or writing the cache directory fails
*/
public static DiskLruCache open(
File directory, int appVersion, int valueCount, long maxSize, int maxFileCount)
throws IOException {
if (maxSize <= 0) {
throw new IllegalArgumentException("maxSize <= 0");
}
if (maxFileCount <= 0) {
throw new IllegalArgumentException("maxFileCount <= 0");
}
if (valueCount <= 0) {
throw new IllegalArgumentException("valueCount <= 0");
}
// If a bkp file exists, use it instead.
File backupFile = new File(directory, JOURNAL_FILE_BACKUP);
if (backupFile.exists()) {
File journalFile = new File(directory, JOURNAL_FILE);
// If journal file also exists just delete backup file.
if (journalFile.exists()) {
backupFile.delete();
} else {
renameTo(backupFile, journalFile, false);
}
}
// Prefer to pick up where we left off.
DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize, maxFileCount);
if (cache.journalFile.exists()) {
try {
cache.readJournal();
cache.processJournal();
cache.journalWriter =
new BufferedWriter(
new OutputStreamWriter(
new FileOutputStream(cache.journalFile, true), Util.US_ASCII));
return cache;
} catch (IOException journalIsCorrupt) {
System.out.println(
"DiskLruCache "
+ directory
+ " is corrupt: "
+ journalIsCorrupt.getMessage()
+ ", removing");
cache.delete();
}
}
// Create a new empty cache.
directory.mkdirs();
cache = new DiskLruCache(directory, appVersion, valueCount, maxSize, maxFileCount);
cache.rebuildJournal();
return cache;
}
/**
* Creates a new journal that omits redundant information. This replaces the current journal if it
* exists.
*/
private synchronized void rebuildJournal() throws IOException {
if (journalWriter != null) {
journalWriter.close();
}
Writer writer =
new BufferedWriter(
new OutputStreamWriter(new FileOutputStream(journalFileTmp), Util.US_ASCII));
try {
writer.write(MAGIC);
writer.write("\n");
writer.write(VERSION_1);
writer.write("\n");
writer.write(Integer.toString(appVersion));
writer.write("\n");
writer.write(Integer.toString(valueCount));
writer.write("\n");
writer.write("\n");
for (Entry entry : lruEntries.values()) {
if (entry.currentEditor != null) {
writer.write(DIRTY + ' ' + entry.key + '\n');
} else {
writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
}
}
} finally {
writer.close();
}
if (journalFile.exists()) {
renameTo(journalFile, journalFileBackup, true);
}
renameTo(journalFileTmp, journalFile, false);
journalFileBackup.delete();
journalWriter =
new BufferedWriter(
new OutputStreamWriter(new FileOutputStream(journalFile, true), Util.US_ASCII));
}