Add different ways of reading the dictionary file.

This change adds basic support for an external dictionary provider.
It adds methods for reading the dictionary itself from an asset in
the dictionary provider package directly, obtaining the file name
through the ContentProvider interface; it also adds a way of getting
the data through an InputStream and copying the file locally.

Incidentally this change also adds the code needed to listen for
updating the dictionary provider package and reloading it in time.

This change also goes hand-in-hand with Iab31db6e, which implements
the small closed part of this.

Issue: 3414944

Change-Id: I5e4fff99a59bb99dbdb002102db6c90e6cb41c8a

1 files changed, 141 insertions, 0 deletions

diff --git a/java/src/com/android/inputmethod/latin/BinaryDictionaryFileDumper.java b/java/src/com/android/inputmethod/latin/BinaryDictionaryFileDumper.java
new file mode 100644
index 000000000..d0464dd94
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/BinaryDictionaryFileDumper.java
@@ -0,0 +1,141 @@
+/*
+ * 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.inputmethod.latin;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.net.Uri;
+import android.text.TextUtils;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+
+/**
+ * Group class for static methods to help with creation and getting of the binary dictionary
+ * file from the dictionary provider
+ */
+public class BinaryDictionaryFileDumper {
+    /**
+     * The size of the temporary buffer to copy files.
+     */
+    static final int FILE_READ_BUFFER_SIZE = 1024;
+
+    // Prevents this class to be accidentally instantiated.
+    private BinaryDictionaryFileDumper() {
+    }
+
+    /**
+     * Generates a file name that matches the locale passed as an argument.
+     * The file name is basically the result of the .toString() method, except we replace
+     * any @File.separator with an underscore to avoid generating a file name that may not
+     * be created.
+     * @param locale the locale for which to get the file name
+     * @param context the context to use for getting the directory
+     * @return the name of the file to be created
+     */
+    private static String getCacheFileNameForLocale(Locale locale, Context context) {
+        // The following assumes two things :
+        // 1. That File.separator is not the same character as "_"
+        //    I don't think any android system will ever use "_" as a path separator
+        // 2. That no two locales differ by only a File.separator versus a "_"
+        //    Since "_" can't be part of locale components this should be safe.
+        // Examples:
+        // en -> en
+        // en_US_POSIX -> en_US_POSIX
+        // en__foo/bar -> en__foo_bar
+        final String[] separator = { File.separator };
+        final String[] empty = { "_" };
+        final CharSequence basename = TextUtils.replace(locale.toString(), separator, empty);
+        return context.getFilesDir() + File.separator + basename;
+    }
+
+    /**
+     * Return for a given locale the provider URI to query to get the dictionary.
+     */
+    public static Uri getProviderUri(Locale locale) {
+        return new Uri.Builder().scheme(ContentResolver.SCHEME_CONTENT)
+                .authority(BinaryDictionary.DICTIONARY_PACK_AUTHORITY).appendPath(
+                        locale.toString()).build();
+    }
+
+    /**
+     * Queries a content provider for dictionary data for some locale and returns it as a file name.
+     *
+     * This will query a content provider for dictionary data for a given locale, and return
+     * the name of a file suitable to be mmap'ed. It will copy it to local storage if needed.
+     * It should also check the dictionary version to avoid unnecessary copies but this is
+     * still in TODO state.
+     * This will make the data from the content provider the cached dictionary for this locale,
+     * overwriting any previous cached data.
+     * @returns the name of the file, or null if no data could be obtained.
+     * @throw FileNotFoundException if the provider returns non-existent data.
+     * @throw IOException if the provider-returned data could not be read.
+     */
+    public static String getDictionaryFileFromContentProvider(Locale locale, Context context)
+            throws FileNotFoundException, IOException {
+        // TODO: check whether the dictionary is the same or not and if it is, return the cached
+        // file.
+        final ContentResolver resolver = context.getContentResolver();
+        final Uri dictionaryPackUri = getProviderUri(locale);
+        final InputStream stream = resolver.openInputStream(dictionaryPackUri);
+        if (null == stream) return null;
+        return copyFileTo(stream, getCacheFileNameForLocale(locale, context));
+    }
+
+    /**
+     * Accepts a file as dictionary data for some locale and returns the name of a file.
+     *
+     * This will make the data in the input file the cached dictionary for this locale, overwriting
+     * any previous cached data.
+     */
+    public static String getDictionaryFileFromFile(String fileName, Locale locale,
+            Context context) throws FileNotFoundException, IOException {
+        return copyFileTo(new FileInputStream(fileName), getCacheFileNameForLocale(locale,
+                context));
+    }
+
+    /**
+     * Accepts a resource number as dictionary data for some locale and returns the name of a file.
+     *
+     * This will make the resource the cached dictionary for this locale, overwriting any previous
+     * cached data.
+     */
+    public static String getDictionaryFileFromResource(int resource, Locale locale,
+            Context context) throws FileNotFoundException, IOException {
+        return copyFileTo(context.getResources().openRawResource(resource),
+                getCacheFileNameForLocale(locale, context));
+    }
+
+    /**
+     * Copies the data in an input stream to a target file, creating the file if necessary and
+     * overwriting it if it already exists.
+     */
+    private static String copyFileTo(final InputStream input, final String outputFileName)
+            throws FileNotFoundException, IOException {
+        final byte[] buffer = new byte[FILE_READ_BUFFER_SIZE];
+        final FileOutputStream output = new FileOutputStream(outputFileName);
+        for (int readBytes = input.read(buffer); readBytes >= 0; readBytes = input.read(buffer))
+            output.write(buffer, 0, readBytes);
+        input.close();
+        return outputFileName;
+    }
+}