New API and implementation of DB and memory-backed FDs

This depends on a kernel patch that implements read(2)
in the ashmem driver.

Bug http://b/issue?id=2595601

Change-Id: Ie3b10aa471aada21812b35e63954c1b2f0a7b042

6 files changed, 88 insertions, 266 deletions

diff --git a/core/java/android/content/res/AssetFileDescriptor.java b/core/java/android/content/res/AssetFileDescriptor.java
index ccb8605..01ae1da 100644
--- a/core/java/android/content/res/AssetFileDescriptor.java
+++ b/core/java/android/content/res/AssetFileDescriptor.java
@@ -25,8 +25,6 @@ import java.io.FileDescriptor;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
-import java.io.InputStream;
-import java.nio.channels.FileChannel;
 
 /**
  * File descriptor of an entry in the AssetManager.  This provides your own
@@ -51,7 +49,7 @@ public class AssetFileDescriptor implements Parcelable {
      * @param startOffset The location within the file that the asset starts.
      * This must be 0 if length is UNKNOWN_LENGTH.
      * @param length The number of bytes of the asset, or
-     * {@link #UNKNOWN_LENGTH if it extends to the end of the file.
+     * {@link #UNKNOWN_LENGTH} if it extends to the end of the file.
      */
     public AssetFileDescriptor(ParcelFileDescriptor fd, long startOffset,
             long length) {
@@ -125,17 +123,6 @@ public class AssetFileDescriptor implements Parcelable {
     public void close() throws IOException {
         mFd.close();
     }
-    
-    /**
-     * Checks whether this file descriptor is for a memory file.
-     */
-    private boolean isMemoryFile() {
-        try {
-            return MemoryFile.isMemoryFile(mFd.getFileDescriptor());
-        } catch (IOException e) {
-            return false;
-        }
-    }
 
     /**
      * Create and return a new auto-close input stream for this asset.  This
@@ -146,12 +133,6 @@ public class AssetFileDescriptor implements Parcelable {
      * should only call this once for a particular asset.
      */
     public FileInputStream createInputStream() throws IOException {
-        if (isMemoryFile()) {
-            if (mLength > Integer.MAX_VALUE) {
-                throw new IOException("File length too large for a memory file: " + mLength);
-            }
-            return new AutoCloseMemoryFileInputStream(mFd, (int)mLength);
-        }
         if (mLength < 0) {
             return new ParcelFileDescriptor.AutoCloseInputStream(mFd);
         }
@@ -280,66 +261,6 @@ public class AssetFileDescriptor implements Parcelable {
             super.reset();
         }
     }
-    
-    /**
-     * An input stream that reads from a MemoryFile and closes it when the stream is closed.
-     * This extends FileInputStream just because {@link #createInputStream} returns
-     * a FileInputStream. All the FileInputStream methods are
-     * overridden to use the MemoryFile instead.
-     */
-    private static class AutoCloseMemoryFileInputStream extends FileInputStream {
-        private ParcelFileDescriptor mParcelFd;
-        private MemoryFile mFile;
-        private InputStream mStream;
-
-        public AutoCloseMemoryFileInputStream(ParcelFileDescriptor fd, int length)
-                throws IOException {
-            super(fd.getFileDescriptor());
-            mParcelFd = fd;
-            mFile = new MemoryFile(fd.getFileDescriptor(), length, "r");
-            mStream = mFile.getInputStream();
-        }
-
-        @Override
-        public int available() throws IOException {
-            return mStream.available();
-        }
-
-        @Override
-        public void close() throws IOException {
-            mParcelFd.close();  // must close ParcelFileDescriptor, not just the file descriptor,
-                                // since it could be a subclass of ParcelFileDescriptor.
-                                // E.g. ContentResolver.ParcelFileDescriptorInner.close() releases
-                                // a content provider
-            mFile.close();      // to unmap the memory file from the address space.
-            mStream.close();    // doesn't actually do anything
-        }
-
-        @Override
-        public FileChannel getChannel() {
-            return null;
-        }
-
-        @Override
-        public int read() throws IOException {
-            return mStream.read();
-        }
-
-        @Override
-        public int read(byte[] buffer, int offset, int count) throws IOException {
-            return mStream.read(buffer, offset, count);
-        }
-
-        @Override
-        public int read(byte[] buffer) throws IOException {
-            return mStream.read(buffer);
-        }
-
-        @Override
-        public long skip(long count) throws IOException {
-            return mStream.skip(count);
-        }
-    }
 
     /**
      * An OutputStream you can create on a ParcelFileDescriptor, which will
@@ -426,15 +347,4 @@ public class AssetFileDescriptor implements Parcelable {
         }
     };
 
-    /**
-     * Creates an AssetFileDescriptor from a memory file.
-     *
-     * @hide
-     */
-    public static AssetFileDescriptor fromMemoryFile(MemoryFile memoryFile)
-            throws IOException {
-        ParcelFileDescriptor fd = memoryFile.getParcelFileDescriptor();
-        return new AssetFileDescriptor(fd, 0, memoryFile.length());
-    }
-
 }
diff --git a/core/java/android/database/DatabaseUtils.java b/core/java/android/database/DatabaseUtils.java
index c07c3c6..03aa968 100644
--- a/core/java/android/database/DatabaseUtils.java
+++ b/core/java/android/database/DatabaseUtils.java
@@ -31,6 +31,7 @@ import android.database.sqlite.SQLiteFullException;
 import android.database.sqlite.SQLiteProgram;
 import android.database.sqlite.SQLiteStatement;
 import android.os.Parcel;
+import android.os.ParcelFileDescriptor;
 import android.text.TextUtils;
 import android.util.Config;
 import android.util.Log;
@@ -705,6 +706,34 @@ public class DatabaseUtils {
     }
 
     /**
+     * Utility method to run the query on the db and return the blob value in the
+     * first column of the first row.
+     *
+     * @return A read-only file descriptor for a copy of the blob value.
+     */
+    public static ParcelFileDescriptor blobFileDescriptorForQuery(SQLiteDatabase db,
+            String query, String[] selectionArgs) {
+        SQLiteStatement prog = db.compileStatement(query);
+        try {
+            return blobFileDescriptorForQuery(prog, selectionArgs);
+        } finally {
+            prog.close();
+        }
+    }
+
+    /**
+     * Utility method to run the pre-compiled query and return the blob value in the
+     * first column of the first row.
+     *
+     * @return A read-only file descriptor for a copy of the blob value.
+     */
+    public static ParcelFileDescriptor blobFileDescriptorForQuery(SQLiteStatement prog,
+            String[] selectionArgs) {
+        prog.bindAllArgsAsStrings(selectionArgs);
+        return prog.simpleQueryForBlobFileDescriptor();
+    }
+
+    /**
      * Reads a String out of a column in a Cursor and writes it to a ContentValues.
      * Adds nothing to the ContentValues if the column isn't present or if its value is null.
      *
diff --git a/core/java/android/database/sqlite/SQLiteContentHelper.java b/core/java/android/database/sqlite/SQLiteContentHelper.java
deleted file mode 100644
index 2800d86..0000000
--- a/core/java/android/database/sqlite/SQLiteContentHelper.java
+++ /dev/null
@@ -1,92 +0,0 @@
-/*
- * Copyright (C) 2009 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 android.database.sqlite;
-
-import android.content.res.AssetFileDescriptor;
-import android.database.Cursor;
-import android.os.MemoryFile;
-
-import java.io.FileNotFoundException;
-import java.io.IOException;
-
-/**
- * Some helper functions for using SQLite database to implement content providers.
- *
- * @hide
- */
-public class SQLiteContentHelper {
-
-    /**
-     * Runs an SQLite query and returns an AssetFileDescriptor for the
-     * blob in column 0 of the first row. If the first column does
-     * not contain a blob, an unspecified exception is thrown.
-     *
-     * @param db Handle to a readable database.
-     * @param sql SQL query, possibly with query arguments.
-     * @param selectionArgs Query argument values, or {@code null} for no argument.
-     * @return If no exception is thrown, a non-null AssetFileDescriptor is returned.
-     * @throws FileNotFoundException If the query returns no results or the
-     *         value of column 0 is NULL, or if there is an error creating the
-     *         asset file descriptor.
-     */
-    public static AssetFileDescriptor getBlobColumnAsAssetFile(SQLiteDatabase db, String sql,
-            String[] selectionArgs) throws FileNotFoundException {
-        try {
-            MemoryFile file = simpleQueryForBlobMemoryFile(db, sql, selectionArgs);
-            if (file == null) {
-                throw new FileNotFoundException("No results.");
-            }
-            return AssetFileDescriptor.fromMemoryFile(file);
-        } catch (IOException ex) {
-            throw new FileNotFoundException(ex.toString());
-        }
-    }
-
-    /**
-     * Runs an SQLite query and returns a MemoryFile for the
-     * blob in column 0 of the first row. If the first column does
-     * not contain a blob, an unspecified exception is thrown.
-     *
-     * @return A memory file, or {@code null} if the query returns no results
-     *         or the value column 0 is NULL.
-     * @throws IOException If there is an error creating the memory file.
-     */
-    // TODO: make this native and use the SQLite blob API to reduce copying
-    private static MemoryFile simpleQueryForBlobMemoryFile(SQLiteDatabase db, String sql,
-            String[] selectionArgs) throws IOException {
-        Cursor cursor = db.rawQuery(sql, selectionArgs);
-        if (cursor == null) {
-            return null;
-        }
-        try {
-            if (!cursor.moveToFirst()) {
-                return null;
-            }
-            byte[] bytes = cursor.getBlob(0);
-            if (bytes == null) {
-                return null;
-            }
-            MemoryFile file = new MemoryFile(null, bytes.length);
-            file.writeBytes(bytes, 0, 0, bytes.length);
-            file.deactivate();
-            return file;
-        } finally {
-            cursor.close();
-        }
-    }
-
-}
diff --git a/core/java/android/database/sqlite/SQLiteStatement.java b/core/java/android/database/sqlite/SQLiteStatement.java
index 97e39d6..14de60f 100644
--- a/core/java/android/database/sqlite/SQLiteStatement.java
+++ b/core/java/android/database/sqlite/SQLiteStatement.java
@@ -17,7 +17,11 @@
 package android.database.sqlite;
 
 import android.database.DatabaseUtils;
+import android.os.ParcelFileDescriptor;
 import android.os.SystemClock;
+import android.util.Log;
+
+import java.io.IOException;
 
 import dalvik.system.BlockGuard;
 
@@ -33,6 +37,9 @@ import dalvik.system.BlockGuard;
 @SuppressWarnings("deprecation")
 public class SQLiteStatement extends SQLiteProgram
 {
+
+    private static final String TAG = "SQLiteStatement";
+
     private static final boolean READ = true;
     private static final boolean WRITE = false;
 
@@ -150,6 +157,30 @@ public class SQLiteStatement extends SQLiteProgram
     }
 
     /**
+     * Executes a statement that returns a 1 by 1 table with a blob value.
+     *
+     * @return A read-only file descriptor for a copy of the blob value, or {@code null}
+     *         if the value is null or could not be read for some reason.
+     *
+     * @throws android.database.sqlite.SQLiteDoneException if the query returns zero rows
+     */
+    public ParcelFileDescriptor simpleQueryForBlobFileDescriptor() {
+        synchronized(this) {
+            long timeStart = acquireAndLock(READ);
+            try {
+                ParcelFileDescriptor retValue = native_1x1_blob_ashmem();
+                mDatabase.logTimeStat(mSql, timeStart);
+                return retValue;
+            } catch (IOException ex) {
+                Log.e(TAG, "simpleQueryForBlobFileDescriptor() failed", ex);
+                return null;
+            } finally {
+                releaseAndUnlock();
+            }
+        }
+    }
+
+    /**
      * Called before every method in this class before executing a SQL statement,
      * this method does the following:
      * <ul>
@@ -244,4 +275,5 @@ public class SQLiteStatement extends SQLiteProgram
     private final native long native_executeInsert();
     private final native long native_1x1_long();
     private final native String native_1x1_string();
+    private final native ParcelFileDescriptor native_1x1_blob_ashmem() throws IOException;
 }
diff --git a/core/java/android/os/MemoryFile.java b/core/java/android/os/MemoryFile.java
index a81e16b..f82702a 100644
--- a/core/java/android/os/MemoryFile.java
+++ b/core/java/android/os/MemoryFile.java
@@ -58,7 +58,6 @@ public class MemoryFile
     private int mAddress;   // address of ashmem memory
     private int mLength;    // total length of our ashmem region
     private boolean mAllowPurging = false;  // true if our ashmem region is unpinned
-    private final boolean mOwnsRegion;  // false if this is a ref to an existing ashmem region
 
     /**
      * Allocates a new ashmem region. The region is initially not purgable.
@@ -70,38 +69,11 @@ public class MemoryFile
     public MemoryFile(String name, int length) throws IOException {
         mLength = length;
         mFD = native_open(name, length);
-        mAddress = native_mmap(mFD, length, PROT_READ | PROT_WRITE);
-        mOwnsRegion = true;
-    }
-
-    /**
-     * Creates a reference to an existing memory file. Changes to the original file
-     * will be available through this reference.
-     * Calls to {@link #allowPurging(boolean)} on the returned MemoryFile will fail.
-     *
-     * @param fd File descriptor for an existing memory file, as returned by
-     *        {@link #getFileDescriptor()}. This file descriptor will be closed
-     *        by {@link #close()}.
-     * @param length Length of the memory file in bytes.
-     * @param mode File mode. Currently only "r" for read-only access is supported.
-     * @throws NullPointerException if <code>fd</code> is null.
-     * @throws IOException If <code>fd</code> does not refer to an existing memory file,
-     *         or if the file mode of the existing memory file is more restrictive
-     *         than <code>mode</code>.
-     *
-     * @hide
-     */
-    public MemoryFile(FileDescriptor fd, int length, String mode) throws IOException {
-        if (fd == null) {
-            throw new NullPointerException("File descriptor is null.");
-        }
-        if (!isMemoryFile(fd)) {
-            throw new IllegalArgumentException("Not a memory file.");
+        if (length > 0) {
+            mAddress = native_mmap(mFD, length, PROT_READ | PROT_WRITE);
+        } else {
+            mAddress = 0;
         }
-        mLength = length;
-        mFD = fd;
-        mAddress = native_mmap(mFD, length, modeToProt(mode));
-        mOwnsRegion = false;
     }
 
     /**
@@ -122,7 +94,7 @@ public class MemoryFile
      *
      * @hide
      */
-    public void deactivate() {
+    void deactivate() {
         if (!isDeactivated()) {
             try {
                 native_munmap(mAddress, mLength);
@@ -181,9 +153,6 @@ public class MemoryFile
      * @return previous value of allowPurging
      */
     synchronized public boolean allowPurging(boolean allowPurging) throws IOException {
-        if (!mOwnsRegion) {
-            throw new IOException("Only the owner can make ashmem regions purgable.");
-        }
         boolean oldValue = mAllowPurging;
         if (oldValue != allowPurging) {
             native_pin(mFD, !allowPurging);
@@ -260,28 +229,7 @@ public class MemoryFile
     }
 
     /**
-     * Gets a ParcelFileDescriptor for the memory file. See {@link #getFileDescriptor()}
-     * for caveats. This must be here to allow classes outside <code>android.os</code< to
-     * make ParcelFileDescriptors from MemoryFiles, as
-     * {@link ParcelFileDescriptor#ParcelFileDescriptor(FileDescriptor)} is package private.
-     *
-     *
-     * @return The file descriptor owned by this memory file object.
-     *         The file descriptor is not duplicated.
-     * @throws IOException If the memory file has been closed.
-     *
-     * @hide
-     */
-    public ParcelFileDescriptor getParcelFileDescriptor() throws IOException {
-        FileDescriptor fd = getFileDescriptor();
-        return fd != null ? new ParcelFileDescriptor(fd) : null;
-    }
-
-    /**
-     * Gets a FileDescriptor for the memory file. Note that this file descriptor
-     * is only safe to pass to {@link #MemoryFile(FileDescriptor,int)}). It
-     * should not be used with file descriptor operations that expect a file descriptor
-     * for a normal file.
+     * Gets a FileDescriptor for the memory file.
      *
      * The returned file descriptor is not duplicated.
      *
@@ -294,17 +242,6 @@ public class MemoryFile
     }
 
     /**
-     * Checks whether the given file descriptor refers to a memory file.
-     *
-     * @throws IOException If <code>fd</code> is not a valid file descriptor.
-     *
-     * @hide
-     */
-    public static boolean isMemoryFile(FileDescriptor fd) throws IOException {
-        return (native_get_size(fd) >= 0);
-    }
-
-    /**
      * Returns the size of the memory file that the file descriptor refers to,
      * or -1 if the file descriptor does not refer to a memory file.
      *
@@ -316,20 +253,6 @@ public class MemoryFile
         return native_get_size(fd);
     }
 
-    /**
-     * Converts a file mode string to a <code>prot</code> value as expected by
-     * native_mmap().
-     *
-     * @throws IllegalArgumentException if the file mode is invalid.
-     */
-    private static int modeToProt(String mode) {
-        if ("r".equals(mode)) {
-            return PROT_READ;
-        } else {
-            throw new IllegalArgumentException("Unsupported file mode: '" + mode + "'");
-        }
-    }
-
     private class MemoryInputStream extends InputStream {
 
         private int mMark = 0;
diff --git a/core/java/android/os/ParcelFileDescriptor.java b/core/java/android/os/ParcelFileDescriptor.java
index d853f13..c1a1809 100644
--- a/core/java/android/os/ParcelFileDescriptor.java
+++ b/core/java/android/os/ParcelFileDescriptor.java
@@ -153,6 +153,26 @@ public class ParcelFileDescriptor implements Parcelable {
     private static native int createPipeNative(FileDescriptor[] outFds);
 
     /**
+     * Gets a file descriptor for a read-only copy of the given data.
+     *
+     * @param data Data to copy.
+     * @param name Name for the shared memory area that may back the file descriptor.
+     *        This is purely informative and may be {@code null}.
+     * @return A ParcelFileDescriptor.
+     * @throws IOException if there is an error while creating the shared memory area.
+     */
+    public static ParcelFileDescriptor fromData(byte[] data, String name) throws IOException {
+        if (data == null) return null;
+        MemoryFile file = new MemoryFile(name, data.length);
+        if (data.length > 0) {
+            file.writeBytes(data, 0, 0, data.length);
+        }
+        file.deactivate();
+        FileDescriptor fd = file.getFileDescriptor();
+        return fd != null ? new ParcelFileDescriptor(fd) : null;
+    }
+
+    /**
      * Retrieve the actual FileDescriptor associated with this object.
      * 
      * @return Returns the FileDescriptor associated with this object.