Subversion Repositories SmartDukaan

/*

 * 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.android.volley.toolbox;

import android.os.SystemClock;

import com.android.volley.Cache;

import com.android.volley.VolleyLog;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

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;

/**

 * 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 DiskBasedCache 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 final int mMaxCacheSizeInBytes;

    /** Default maximum disk usage in bytes. */

    private static final int DEFAULT_DISK_USAGE_BYTES = 5 * 1024 * 1024;

    /** High water mark percentage for the cache */

    private static final float HYSTERESIS_FACTOR = 0.9f;

    /** Magic number for current version of cache file format. */

    private static final int CACHE_MAGIC = 0x20150306;

    /**

     * 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 DiskBasedCache(File rootDirectory, int maxCacheSizeInBytes) {

        mRootDirectory = rootDirectory;

        mMaxCacheSizeInBytes = maxCacheSizeInBytes;

    }

    /**

     * 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 DiskBasedCache(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;

        VolleyLog.d("Cache cleared.");

    }

    /**

     * 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 BufferedInputStream(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());

            }

            return;

        }

        File[] files = mRootDirectory.listFiles();

        if (files == null) {

            return;

        }

        for (File file : files) {

            BufferedInputStream fis = null;

            try {

                fis = new BufferedInputStream(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) {

        Entry entry = get(key);

        if (entry != null) {

            entry.softTtl = 0;

            if (fullExpire) {

                entry.ttl = 0;

            }

            put(key, entry);

        }

    }

    /**

     * Puts the entry with the specified key into the cache.

     */

    @Override

    public synchronized void put(String key, Entry entry) {

        pruneIfNeeded(entry.data.length);

        File file = getFileForKey(key);

        try {

            BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(file));

            CacheHeader e = new CacheHeader(key, entry);

            boolean success = e.writeHeader(fos);

            if (!success) {

                fos.close();

                VolleyLog.d("Failed to write header for %s", file.getAbsolutePath());

                throw new IOException();

            }

            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());

        }

    }

    /**

     * 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) {

        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;

        } 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);

        }

    }

    /**

     * 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;

        /** Date of this response as reported by the server. */

        public long serverDate;

        /** The last modified date for the requested object. */

        public long lastModified;

        /** TTL for this record. */

        public long ttl;

        /** Soft TTL for this record. */

        public long softTtl;

        /** Headers from the response resulting in this cache entry. */

        public Map<String, String> responseHeaders;

        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.serverDate = entry.serverDate;

            this.lastModified = entry.lastModified;

            this.ttl = entry.ttl;

            this.softTtl = entry.softTtl;

            this.responseHeaders = entry.responseHeaders;

        }

        /**

         * 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.serverDate = readLong(is);

            entry.lastModified = readLong(is);

            entry.ttl = readLong(is);

            entry.softTtl = readLong(is);

            entry.responseHeaders = readStringStringMap(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.serverDate = serverDate;

            e.lastModified = lastModified;

            e.ttl = ttl;

            e.softTtl = softTtl;

            e.responseHeaders = responseHeaders;

            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);

                writeLong(os, serverDate);

                writeLong(os, lastModified);

                writeLong(os, ttl);

                writeLong(os, softTtl);

                writeStringStringMap(responseHeaders, os);

                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;

    }

}