ImageReader: Add discardFreeBuffers method

This method (currently @hide) discards all cached buffers for
the ImageReader, which can be useful to free up memory at the
cost of reallocationt time if more buffers are needed later.

It has no effect on acquired Images, filled Images waiting to be
acquired, or buffers being actively used by the source rendering to the
Surface.

Bug: 28695173
Change-Id: I427a8ba4ad73a267083f843dbf228bfc53a730d9

1 files changed, 18 insertions, 0 deletions

diff --git a/media/jni/android_media_ImageReader.cpp b/media/jni/android_media_ImageReader.cpp
index c3993ae20183..724fc02271e3 100644
--- a/media/jni/android_media_ImageReader.cpp
+++ b/media/jni/android_media_ImageReader.cpp
@@ -611,6 +611,23 @@ static jint ImageReader_detachImage(JNIEnv* env, jobject thiz, jobject image) {
     return OK;
 }
 
+static void ImageReader_discardFreeBuffers(JNIEnv* env, jobject thiz) {
+    ALOGV("%s:", __FUNCTION__);
+    JNIImageReaderContext* ctx = ImageReader_getContext(env, thiz);
+    if (ctx == NULL) {
+        jniThrowException(env, "java/lang/IllegalStateException", "ImageReader was already closed");
+        return;
+    }
+
+    BufferItemConsumer* bufferConsumer = ctx->getBufferConsumer();
+    status_t res = bufferConsumer->discardFreeBuffers();
+    if (res != OK) {
+        ALOGE("Buffer discard failed: %s (%d)", strerror(-res), res);
+        jniThrowRuntimeException(env,
+                "nativeDicardFreebuffers failed");
+    }
+}
+
 static jobject ImageReader_getSurface(JNIEnv* env, jobject thiz)
 {
     ALOGV("%s: ", __FUNCTION__);
@@ -773,6 +790,7 @@ static const JNINativeMethod gImageReaderMethods[] = {
     {"nativeImageSetup",       "(Landroid/media/Image;)I",   (void*)ImageReader_imageSetup },
     {"nativeGetSurface",       "()Landroid/view/Surface;",   (void*)ImageReader_getSurface },
     {"nativeDetachImage",      "(Landroid/media/Image;)I",   (void*)ImageReader_detachImage },
+    {"nativeDiscardFreeBuffers", "()V",                      (void*)ImageReader_discardFreeBuffers }
 };
 
 static const JNINativeMethod gImageMethods[] = {