Java tutorial
/* * Copyright (C) 2011 The Android Open Source Project * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * http://www.apache.org/licenses/LICENSE-2.0 * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.baseproject.volley.toolbox; import android.os.SystemClock; import android.text.TextUtils; import com.baseproject.utils.Util; import com.baseproject.volley.Cache; import com.baseproject.volley.VolleyLog; import java.io.EOFException; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.FilterInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.Collections; import java.util.HashMap; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.Map; import org.apache.http.protocol.HTTP; /** * Cache implementation that caches files directly onto the hard disk in the specified * directory. The default disk usage size is 5MB, but is configurable. */ public class LruDiskBasedCache implements Cache { /** Map of the Key, CacheHeader pairs */ private final Map<String, CacheHeader> mEntries = new LinkedHashMap<String, CacheHeader>(16, .75f, true); /** Total amount of space currently used by the cache in bytes. */ private long mTotalSize = 0; /** The root directory to use for the cache. */ private final File mRootDirectory; /** The maximum size of the cache in bytes. */ private long mMaxCacheSizeInBytes; /** Default maximum disk usage in bytes. */ private static final long DEFAULT_DISK_USAGE_BYTES = 10 * 1024 * 1024; /** High water mark percentage for the cache */ private static final float HYSTERESIS_FACTOR = 0.5f; /** Magic number for current version of cache file format. */ private static final int CACHE_MAGIC = 0x20140604; /** The max numbers of cache files */ private int mMaxCacheFileNumbers = 0; /** The numbers had cached */ private int mCacheTotalFiles = 0; /** * Constructs an instance of the DiskBasedCache at the specified directory. * * @param rootDirectory * The root directory of the cache. * @param maxCacheSizeInBytes * The maximum size of the cache in bytes. */ public LruDiskBasedCache(File rootDirectory, long maxCacheSizeInBytes) { mRootDirectory = rootDirectory; mMaxCacheSizeInBytes = maxCacheSizeInBytes; mMaxCacheFileNumbers = 0; } public LruDiskBasedCache(File rootDirectory, long maxCacheSizeInBytes, int maxCacheFileNumbers) { this(rootDirectory, maxCacheSizeInBytes); mMaxCacheFileNumbers = maxCacheFileNumbers; } /** * Constructs an instance of the DiskBasedCache at the specified directory using * the default maximum cache size of 5MB. * * @param rootDirectory * The root directory of the cache. */ public LruDiskBasedCache(File rootDirectory) { this(rootDirectory, DEFAULT_DISK_USAGE_BYTES); } /** * Clears the cache. Deletes all cached files from disk. */ @Override public synchronized void clear() { File[] files = mRootDirectory.listFiles(); if (files != null) { for (File file : files) { file.delete(); } } mEntries.clear(); mTotalSize = 0; mCacheTotalFiles = 0; VolleyLog.d("Cache cleared."); } /** * @return Return true if the cache contain entry with the specified key, false otherwise */ public synchronized boolean isContainValue(String key) { return mEntries.get(key) != null; } /** * Returns the cache entry with the specified key if it exists, null otherwise. */ @Override public synchronized Entry get(String key) { CacheHeader entry = mEntries.get(key); // if the entry does not exist, return. if (entry == null) { return null; } File file = getFileForKey(key); CountingInputStream cis = null; try { cis = new CountingInputStream(new FileInputStream(file)); CacheHeader.readHeader(cis); // eat header byte[] data = streamToBytes(cis, (int) (file.length() - cis.bytesRead)); return entry.toCacheEntry(data); } catch (IOException e) { VolleyLog.d("%s: %s", file.getAbsolutePath(), e.toString()); remove(key); return null; } finally { if (cis != null) { try { cis.close(); } catch (IOException ioe) { return null; } } } } /** * Initializes the DiskBasedCache by scanning for all files currently in the * specified root directory. Creates the root directory if necessary. */ @Override public synchronized void initialize() { if (!mRootDirectory.exists()) { if (!mRootDirectory.mkdirs()) { VolleyLog.e("Unable to create cache dir %s", mRootDirectory.getAbsolutePath()); } if (mRootDirectory.isDirectory() && mRootDirectory.canWrite()) { if (Util.getUsableSpace(mRootDirectory) < mMaxCacheSizeInBytes) { mMaxCacheSizeInBytes = Util.getUsableSpace(mRootDirectory) / 2; } } return; } File[] files = mRootDirectory.listFiles(); if (files == null) { return; } for (File file : files) { FileInputStream fis = null; try { fis = new FileInputStream(file); CacheHeader entry = CacheHeader.readHeader(fis); entry.size = file.length(); putEntry(entry.key, entry); } catch (IOException e) { if (file != null) { file.delete(); } } finally { try { if (fis != null) { fis.close(); } } catch (IOException ignored) { } } } } /** * Invalidates an entry in the cache. * * @param key * Cache key * @param fullExpire * True to fully expire the entry, false to soft expire */ @Override public synchronized void invalidate(String key, boolean fullExpire) { // nothing to do now } /** * Puts the entry with the specified key into the cache. */ @Override public synchronized void put(String key, Entry entry) { pruneFileNumbersIfNeeded(); pruneIfNeeded(entry.data.length); File file = getFileForKey(key); try { FileOutputStream fos = new FileOutputStream(file); CacheHeader e = new CacheHeader(key, entry); e.writeHeader(fos); fos.write(entry.data); fos.close(); putEntry(key, e); return; } catch (IOException e) { } boolean deleted = file.delete(); if (!deleted) { VolleyLog.d("Could not clean up file %s", file.getAbsolutePath()); } } /** * Prunes the cache to fit the numbers of files. */ private void pruneFileNumbersIfNeeded() { if (mMaxCacheFileNumbers <= 0) {// user do not set mMaxCacheFileNumbers,so don't check file numbers return; } if (mCacheTotalFiles < mMaxCacheFileNumbers) { return; } if (VolleyLog.DEBUG) { VolleyLog.v("pruneFileNumbers Pruning extra cache entries."); } int delNumbers = mMaxCacheFileNumbers < 10 ? mMaxCacheFileNumbers : 10;// the numbers of one delete time long before = mTotalSize; int prunedFiles = 0; long startTime = SystemClock.elapsedRealtime(); Iterator<Map.Entry<String, CacheHeader>> iterator = mEntries.entrySet().iterator(); while (iterator.hasNext()) { Map.Entry<String, CacheHeader> entry = iterator.next(); CacheHeader e = entry.getValue(); boolean deleted = getFileForKey(e.key).delete(); if (deleted) { mTotalSize -= e.size; mCacheTotalFiles--; } else { VolleyLog.d("pruneFileNumbersIfNeeded: Could not delete cache entry for key=%s, filename=%s", e.key, getFilenameForKey(e.key)); } iterator.remove(); prunedFiles++; if (prunedFiles == delNumbers) { break; } } if (VolleyLog.DEBUG) { VolleyLog.v("pruneFileNumbersIfNeeded: pruned %d files, %d bytes, %d ms", prunedFiles, (mTotalSize - before), SystemClock.elapsedRealtime() - startTime); } } /** * Removes the specified key from the cache if it exists. */ @Override public synchronized void remove(String key) { boolean deleted = getFileForKey(key).delete(); removeEntry(key); if (!deleted) { VolleyLog.d("Could not delete cache entry for key=%s, filename=%s", key, getFilenameForKey(key)); } } /** * Creates a pseudo-unique filename for the specified cache key. * * @param key * The key to generate a file name for. * @return A pseudo-unique filename. */ private String getFilenameForKey(String key) { return Util.md5(key); // int firstHalfLength = key.length() / 2; // String localFilename = String.valueOf(key.substring(0, firstHalfLength).hashCode()); // localFilename += String.valueOf(key.substring(firstHalfLength).hashCode()); // return localFilename; } /** * Returns a file object for the given cache key. */ public File getFileForKey(String key) { return new File(mRootDirectory, getFilenameForKey(key)); } /** * Prunes the cache to fit the amount of bytes specified. * * @param neededSpace * The amount of bytes we are trying to fit into the cache. */ private void pruneIfNeeded(int neededSpace) { if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes) { return; } if (VolleyLog.DEBUG) { VolleyLog.v("Pruning old cache entries."); } long before = mTotalSize; int prunedFiles = 0; long startTime = SystemClock.elapsedRealtime(); Iterator<Map.Entry<String, CacheHeader>> iterator = mEntries.entrySet().iterator(); while (iterator.hasNext()) { Map.Entry<String, CacheHeader> entry = iterator.next(); CacheHeader e = entry.getValue(); boolean deleted = getFileForKey(e.key).delete(); if (deleted) { mTotalSize -= e.size; } else { VolleyLog.d("Could not delete cache entry for key=%s, filename=%s", e.key, getFilenameForKey(e.key)); } iterator.remove(); prunedFiles++; if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes * HYSTERESIS_FACTOR) { break; } } if (VolleyLog.DEBUG) { VolleyLog.v("pruned %d files, %d bytes, %d ms", prunedFiles, (mTotalSize - before), SystemClock.elapsedRealtime() - startTime); } } /** * Puts the entry with the specified key into the cache. * * @param key * The key to identify the entry by. * @param entry * The entry to cache. */ private void putEntry(String key, CacheHeader entry) { if (!mEntries.containsKey(key)) { mTotalSize += entry.size; mCacheTotalFiles++; } else { CacheHeader oldEntry = mEntries.get(key); mTotalSize += (entry.size - oldEntry.size); } mEntries.put(key, entry); } /** * Removes the entry identified by 'key' from the cache. */ private void removeEntry(String key) { CacheHeader entry = mEntries.get(key); if (entry != null) { mTotalSize -= entry.size; mEntries.remove(key); mCacheTotalFiles--; } } /** * Reads the contents of an InputStream into a byte[]. * */ private static byte[] streamToBytes(InputStream in, int length) throws IOException { byte[] bytes = new byte[length]; int count; int pos = 0; while (pos < length && ((count = in.read(bytes, pos, length - pos)) != -1)) { pos += count; } if (pos != length) { throw new IOException("Expected " + length + " bytes, read " + pos + " bytes"); } return bytes; } /** * Handles holding onto the cache headers for an entry. */ // Visible for testing. static class CacheHeader { /** * The size of the data identified by this CacheHeader. (This is not * serialized to disk. */ public long size; /** The key that identifies the cache entry. */ public String key; /** ETag for cache coherence. */ public String etag; /** Charset read from server headers. */ public String charset; public long ttl; private CacheHeader() { } /** * Instantiates a new CacheHeader object * * @param key * The key that identifies the cache entry * @param entry * The cache entry. */ public CacheHeader(String key, Entry entry) { this.key = key; this.size = entry.data.length; this.etag = entry.etag; this.charset = entry.charset; this.ttl = entry.ttl; } /** * Reads the header off of an InputStream and returns a CacheHeader object. * * @param is * The InputStream to read from. * @throws IOException */ public static CacheHeader readHeader(InputStream is) throws IOException { CacheHeader entry = new CacheHeader(); int magic = readInt(is); if (magic != CACHE_MAGIC) { // don't bother deleting, it'll get pruned eventually throw new IOException(); } entry.key = readString(is); entry.etag = readString(is); if (entry.etag.equals("")) { entry.etag = null; } entry.charset = readString(is); if (TextUtils.isEmpty(entry.charset)) { entry.charset = HTTP.UTF_8; } entry.ttl = readLong(is); return entry; } /** * Creates a cache entry for the specified data. */ public Entry toCacheEntry(byte[] data) { Entry e = new Entry(); e.data = data; e.etag = etag; e.charset = charset; e.ttl = ttl; return e; } /** * Writes the contents of this CacheHeader to the specified OutputStream. */ public boolean writeHeader(OutputStream os) { try { writeInt(os, CACHE_MAGIC); writeString(os, key); writeString(os, etag == null ? "" : etag); writeString(os, charset == null ? HTTP.UTF_8 : charset); writeLong(os, ttl); os.flush(); return true; } catch (IOException e) { VolleyLog.d("%s", e.toString()); return false; } } } private static class CountingInputStream extends FilterInputStream { private int bytesRead = 0; private CountingInputStream(InputStream in) { super(in); } @Override public int read() throws IOException { int result = super.read(); if (result != -1) { bytesRead++; } return result; } @Override public int read(byte[] buffer, int offset, int count) throws IOException { int result = super.read(buffer, offset, count); if (result != -1) { bytesRead += result; } return result; } } /* * Homebrewed simple serialization system used for reading and writing cache * headers on disk. Once upon a time, this used the standard Java * Object{Input,Output}Stream, but the default implementation relies heavily * on reflection (even for standard types) and generates a ton of garbage. */ /** * Simple wrapper around {@link InputStream#read()} that throws EOFException * instead of returning -1. */ private static int read(InputStream is) throws IOException { int b = is.read(); if (b == -1) { throw new EOFException(); } return b; } static void writeInt(OutputStream os, int n) throws IOException { os.write((n >> 0) & 0xff); os.write((n >> 8) & 0xff); os.write((n >> 16) & 0xff); os.write((n >> 24) & 0xff); } static int readInt(InputStream is) throws IOException { int n = 0; n |= (read(is) << 0); n |= (read(is) << 8); n |= (read(is) << 16); n |= (read(is) << 24); return n; } static void writeLong(OutputStream os, long n) throws IOException { os.write((byte) (n >>> 0)); os.write((byte) (n >>> 8)); os.write((byte) (n >>> 16)); os.write((byte) (n >>> 24)); os.write((byte) (n >>> 32)); os.write((byte) (n >>> 40)); os.write((byte) (n >>> 48)); os.write((byte) (n >>> 56)); } static long readLong(InputStream is) throws IOException { long n = 0; n |= ((read(is) & 0xFFL) << 0); n |= ((read(is) & 0xFFL) << 8); n |= ((read(is) & 0xFFL) << 16); n |= ((read(is) & 0xFFL) << 24); n |= ((read(is) & 0xFFL) << 32); n |= ((read(is) & 0xFFL) << 40); n |= ((read(is) & 0xFFL) << 48); n |= ((read(is) & 0xFFL) << 56); return n; } static void writeString(OutputStream os, String s) throws IOException { byte[] b = s.getBytes("UTF-8"); writeLong(os, b.length); os.write(b, 0, b.length); } static String readString(InputStream is) throws IOException { int n = (int) readLong(is); byte[] b = streamToBytes(is, n); return new String(b, "UTF-8"); } static void writeStringStringMap(Map<String, String> map, OutputStream os) throws IOException { if (map != null) { writeInt(os, map.size()); for (Map.Entry<String, String> entry : map.entrySet()) { writeString(os, entry.getKey()); writeString(os, entry.getValue()); } } else { writeInt(os, 0); } } static Map<String, String> readStringStringMap(InputStream is) throws IOException { int size = readInt(is); Map<String, String> result = (size == 0) ? Collections.<String, String>emptyMap() : new HashMap<String, String>(size); for (int i = 0; i < size; i++) { String key = readString(is).intern(); String value = readString(is).intern(); result.put(key, value); } return result; } }