Add (hidden for now) purgeable bitmaps

BitmapFactory::Options now let you specify if the resulting bitmap can be
"purgeable". If so, then its decoded pixels may be purged when not actively
being drawn, freeing up that RAM. When such a bitmap is drawn, it will
automatically be re-decoded on demand. This is done by having the bitmap
keep a reference/copy of the encoded data.

Where it is a reference or a copy is controlled by the "shareable" flag in
Options. If this is true, the implementation *may* just reference the encode
data (e.g. a file descriptor) rathern than making a complete copy of it.

Currently, purgeable is not supported for generic inputstreams, but is
enabled for byte-array, file-descriptor, and assets, though for impl
reasons only file-descripts are currently enabled for "shareable", but that
may change in the future.

1 files changed, 30 insertions, 0 deletions

diff --git a/graphics/java/android/graphics/BitmapFactory.java b/graphics/java/android/graphics/BitmapFactory.java
index 3813d8f..9e88d7e 100644
--- a/graphics/java/android/graphics/BitmapFactory.java
+++ b/graphics/java/android/graphics/BitmapFactory.java
@@ -103,6 +103,36 @@ public class BitmapFactory {
         public boolean inScaled;
 
         /**
+         * If this is set to true, then the resulting bitmap will allocate its
+         * pixels such that they can be purged if the system needs to reclaim
+         * memory. In that instance, when the pixels need to be accessed again
+         * (e.g. the bitmap is drawn, getPixels() is called), they will be
+         * automatically re-decoded.
+         *
+         * For the re-decode to happen, the bitmap must have access to the
+         * encoded data, either by sharing a reference to the input
+         * or by making a copy of it. This distinction is controlled by
+         * inInputShareable. If this is true, then the bitmap may keep a shallow
+         * reference to the input. If this is false, then the bitmap will
+         * explicitly make a copy of the input data, and keep that. Even if
+         * sharing is allowed, the implementation may still decide to make a
+         * deep copy of the input data.
+         *
+         * @hide pending API council approval
+         */
+        public boolean inPurgeable;
+
+        /**
+         * This field works in conjuction with inPurgeable. If inPurgeable is
+         * false, then this field is ignored. If inPurgeable is true, then this
+         * field determines whether the bitmap can share a reference to the
+         * input data (inputstream, array, etc.) or if it must make a deep copy.
+         *
+         * @hide pending API council approval
+         */
+        public boolean inInputShareable;
+
+        /**
          * The resulting width of the bitmap, set independent of the state of
          * inJustDecodeBounds. However, if there is an error trying to decode,
          * outWidth will be set to -1.