Add native C APIs for working with the Asset Manager

Change-Id: I493b142c4b35e5cc1a1e85283bb5dfb306a6d261

4 files changed, 366 insertions, 0 deletions

diff --git a/native/android/Android.mk b/native/android/Android.mk
index 2fe0679..950a1e9 100644
--- a/native/android/Android.mk
+++ b/native/android/Android.mk
@@ -6,6 +6,7 @@ include $(CLEAR_VARS)
 # our source files
 #
 LOCAL_SRC_FILES:= \
+    asset_manager.cpp \
     input.cpp \
     looper.cpp \
     native_activity.cpp \
diff --git a/native/android/asset_manager.cpp b/native/android/asset_manager.cpp
new file mode 100644
index 0000000..36c381e
--- /dev/null
+++ b/native/android/asset_manager.cpp
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2010 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.
+ */
+
+#define LOG_TAG "NAsset"
+#include <utils/Log.h>
+
+#include <android/asset_manager.h>
+#include <utils/AssetManager.h>
+#include <utils/AssetDir.h>
+#include <utils/Asset.h>
+#include <utils/threads.h>
+
+#include "jni.h"
+#include "JNIHelp.h"
+
+using namespace android;
+
+// -------------------- Backing implementation of the public API --------------------
+
+// AAssetManager is actually a secret typedef for an empty base class of AssetManager,
+// but AAssetDir and AAsset are actual wrappers for isolation.
+
+// -----
+struct AAssetDir {
+    AssetDir* mAssetDir;
+    size_t mCurFileIndex;
+    String8 mCachedFileName;
+
+    AAssetDir(AssetDir* dir) : mAssetDir(dir), mCurFileIndex(0) { }
+    ~AAssetDir() { delete mAssetDir; }
+};
+
+
+// -----
+struct AAsset {
+    Asset* mAsset;
+
+    AAsset(Asset* asset) : mAsset(asset) { }
+    ~AAsset() { delete mAsset; }
+};
+
+// -------------------- Public native C API --------------------
+
+/**
+ * Supporting information
+ */
+
+static struct assetmanager_offsets_t
+{
+    jfieldID mObject;
+} gAssetManagerOffsets;
+
+static volatile bool gJNIConfigured = false;
+static Mutex gMutex;
+
+/**
+ * Asset Manager functionality
+ */
+AAssetManager* AAssetManager_fromJava(JNIEnv* env, jobject assetManager)
+{
+    {
+        Mutex::Autolock _l(gMutex);
+
+        if (gJNIConfigured == false) {
+            jclass amClass = env->FindClass("android/content/res/AssetManager");
+            gAssetManagerOffsets.mObject = env->GetFieldID(amClass, "mObject", "I");
+            gJNIConfigured = true;
+        }
+    }
+
+    return (AAssetManager*) env->GetIntField(assetManager, gAssetManagerOffsets.mObject);
+}
+
+AAsset* AAssetManager_open(AAssetManager* amgr, const char* filename, int mode)
+{
+    Asset::AccessMode amMode;
+    switch (mode) {
+    case AASSET_MODE_UNKNOWN:
+        amMode = Asset::ACCESS_UNKNOWN;
+        break;
+    case AASSET_MODE_RANDOM:
+        amMode = Asset::ACCESS_RANDOM;
+        break;
+    case AASSET_MODE_STREAMING:
+        amMode = Asset::ACCESS_STREAMING;
+        break;
+    case AASSET_MODE_BUFFER:
+        amMode = Asset::ACCESS_BUFFER;
+        break;
+    default:
+        return NULL;
+    }
+
+    AssetManager* mgr = static_cast<AssetManager*>(amgr);
+    Asset* asset = mgr->open(filename, amMode);
+    if (asset == NULL) {
+        return NULL;
+    }
+
+    return new AAsset(asset);
+}
+
+AAssetDir* AAssetManager_openDir(AAssetManager* amgr, const char* dirName)
+{
+    AssetManager* mgr = static_cast<AssetManager*>(amgr);
+    return new AAssetDir(mgr->openDir(dirName));
+}
+
+/**
+ * AssetDir functionality
+ */
+
+const char* AAssetDir_getNextFileName(AAssetDir* assetDir)
+{
+    const char* returnName = NULL;
+    size_t index = assetDir->mCurFileIndex;
+    const size_t max = assetDir->mAssetDir->getFileCount();
+
+    // Find the next regular file; explicitly don't report directories even if the
+    // underlying implementation changes to report them.  At that point we can add
+    // a more general iterator to this native interface set if appropriate.
+    while ((index < max) && (assetDir->mAssetDir->getFileType(index) != kFileTypeRegular)) {
+        index++;
+    }
+
+    // still in bounds? then the one at 'index' is the next to be reported; generate
+    // the string to return and advance the iterator for next time.
+    if (index < max) {
+        assetDir->mCachedFileName = assetDir->mAssetDir->getFileName(index);
+        returnName = assetDir->mCachedFileName.string();
+        index++;
+    }
+
+    assetDir->mCurFileIndex = index;
+    return returnName;
+}
+
+void AAssetDir_rewind(AAssetDir* assetDir)
+{
+    assetDir->mCurFileIndex = 0;
+}
+
+const char* AAssetDir_getFileName(AAssetDir* assetDir, int index)
+{
+    assetDir->mCachedFileName = assetDir->mAssetDir->getFileName(index);
+    return assetDir->mCachedFileName.string();
+}
+
+void AAssetDir_close(AAssetDir* assetDir)
+{
+    delete assetDir;
+}
+
+/**
+ * Asset functionality
+ */
+
+int AAsset_read(AAsset* asset, void* buf, size_t count)
+{
+    return asset->mAsset->read(buf, (size_t)count);
+}
+
+off_t AAsset_seek(AAsset* asset, off_t offset, int whence)
+{
+    return asset->mAsset->seek(offset, whence);
+}
+
+void AAsset_close(AAsset* asset)
+{
+    asset->mAsset->close();
+    delete asset;
+}
+
+const void* AAsset_getBuffer(AAsset* asset)
+{
+    return asset->mAsset->getBuffer(false);
+}
+
+off_t AAsset_getLength(AAsset* asset)
+{
+    return asset->mAsset->getLength();
+}
+
+off_t AAsset_getRemainingLength(AAsset* asset)
+{
+    return asset->mAsset->getRemainingLength();
+}
+
+int AAsset_openFileDescriptor(AAsset* asset, off_t* outStart, off_t* outLength)
+{
+    return asset->mAsset->openFileDescriptor(outStart, outLength);
+}
+
+int AAsset_isAllocated(AAsset* asset)
+{
+    return asset->mAsset->isAllocated() ? 1 : 0;
+}
diff --git a/native/include/android/asset_manager.h b/native/include/android/asset_manager.h
new file mode 100644
index 0000000..89989f8
--- /dev/null
+++ b/native/include/android/asset_manager.h
@@ -0,0 +1,148 @@
+/*
+ * Copyright (C) 2010 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.
+ */
+
+
+#ifndef ANDROID_ASSET_MANAGER_H
+#define ANDROID_ASSET_MANAGER_H
+
+#include <jni.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct AAssetManager;
+typedef struct AAssetManager AAssetManager;
+
+struct AAssetDir;
+typedef struct AAssetDir AAssetDir;
+
+struct AAsset;
+typedef struct AAsset AAsset;
+
+/* Available modes for opening assets */
+enum {
+    AASSET_MODE_UNKNOWN      = 0,
+    AASSET_MODE_RANDOM       = 1,
+    AASSET_MODE_STREAMING    = 2,
+    AASSET_MODE_BUFFER       = 3
+};
+
+
+/**
+ * Given a Dalvik AssetManager object, obtain the corresponding native AAssetManager
+ * object.  Note that the caller is responsible for obtaining and holding a VM reference
+ * to the jobject to prevent its being garbage collected while the native object is
+ * in use.
+ */
+AAssetManager* AAssetManager_fromJava(JNIEnv* env, jobject assetManager);
+
+/**
+ * Open the named directory within the asset hierarchy.  The directory can then
+ * be inspected with the AAssetDir functions.  To open the top-level directory,
+ * pass in "" as the dirName.
+ *
+ * The object returned here should be freed by calling AAssetDir_close().
+ */
+AAssetDir* AAssetManager_openDir(AAssetManager* mgr, const char* dirName);
+
+/**
+ * Open an asset.
+ *
+ * The object returned here should be freed by calling AAsset_close().
+ */
+AAsset* AAssetManager_open(AAssetManager* mgr, const char* filename, int mode);
+
+/**
+ * Iterate over the files in an asset directory.  A NULL string is returned
+ * when all the file names have been returned.
+ *
+ * The returned file name is suitable for passing to AAssetManager_open().
+ *
+ * The string returned here is owned by the AssetDir implementation and is not
+ * guaranteed to remain valid if any other calls are made on this AAssetDir
+ * instance.
+ */
+const char* AAssetDir_getNextFileName(AAssetDir* assetDir);
+
+/**
+ * Reset the iteration state of AAssetDir_getNextFileName() to the beginning.
+ */
+void AAssetDir_rewind(AAssetDir* assetDir);
+
+/**
+ * Close an opened AAssetDir, freeing any related resources.
+ */
+void AAssetDir_close(AAssetDir* assetDir);
+
+/**
+ * Attempt to read 'count' bytes of data from the current offset.
+ *
+ * Returns the number of bytes read, zero on EOF, or < 0 on error.
+ */
+int AAsset_read(AAsset* asset, void* buf, size_t count);
+
+/**
+ * Seek to the specified offset within the asset data.  'whence' uses the
+ * same constants as lseek()/fseek().
+ *
+ * Returns the new position on success, or (off_t) -1 on error.
+ */
+off_t AAsset_seek(AAsset* asset, off_t offset, int whence);
+
+/**
+ * Close the asset, freeing all associated resources.
+ */
+void AAsset_close(AAsset* asset);
+
+/**
+ * Get a pointer to a buffer holding the entire contents of the assset.
+ *
+ * Returns NULL on failure.
+ */
+const void* AAsset_getBuffer(AAsset* asset);
+
+/**
+ * Report the total size of the asset data.
+ */
+off_t AAsset_getLength(AAsset* asset);
+
+/**
+ * Report the total amount of asset data that can be read from the current position.
+ */
+off_t AAsset_getRemainingLength(AAsset* asset);
+
+/**
+ * Open a new file descriptor that can be used to read the asset data.
+ *
+ * Returns < 0 if direct fd access is not possible (for example, if the asset is
+ * compressed).
+ */
+int AAsset_openFileDescriptor(AAsset* asset, off_t* outStart, off_t* outLength);
+
+/**
+ * Returns whether this asset's internal buffer is allocated in ordinary RAM (i.e. not
+ * mmapped).
+ */
+int AAsset_isAllocated(AAsset* asset);
+
+
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif      // ANDROID_ASSET_MANAGER_H
diff --git a/native/include/android/native_activity.h b/native/include/android/native_activity.h
index ea6f05f..ee4204d 100644
--- a/native/include/android/native_activity.h
+++ b/native/include/android/native_activity.h
@@ -23,6 +23,7 @@
 
 #include <jni.h>
 
+#include <android/asset_manager.h>
 #include <android/input.h>
 #include <android/native_window.h>
 
@@ -84,6 +85,12 @@ typedef struct ANativeActivity {
      * state.
      */
     void* instance;
+
+    /**
+     * Pointer to the Asset Manager instance for the application.  The application
+     * uses this to access binary assets bundled inside its own .apk file.
+     */
+    AAssetManager* assetManager;
 } ANativeActivity;
 
 /**