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.

2 files changed, 155 insertions, 53 deletions

diff --git a/core/jni/Android.mk b/core/jni/Android.mk
index b37447c..ac35459 100644
--- a/core/jni/Android.mk
+++ b/core/jni/Android.mk
@@ -129,6 +129,7 @@ LOCAL_C_INCLUDES += \
 	external/skia/include/core \
 	external/skia/include/effects \
 	external/skia/include/images \
+	external/skia/src/ports \
 	external/skia/include/utils \
 	external/sqlite/dist \
 	external/sqlite/android \
diff --git a/core/jni/android/graphics/BitmapFactory.cpp b/core/jni/android/graphics/BitmapFactory.cpp
index 4ad2eb0..1fd15d6 100644
--- a/core/jni/android/graphics/BitmapFactory.cpp
+++ b/core/jni/android/graphics/BitmapFactory.cpp
@@ -1,6 +1,8 @@
 #define LOG_TAG "BitmapFactory"
 
 #include "SkImageDecoder.h"
+#include "SkImageRef_ashmem.h"
+#include "SkImageRef_GlobalPool.h"
 #include "SkPixelRef.h"
 #include "SkStream.h"
 #include "GraphicsJNI.h"
@@ -19,6 +21,8 @@ static jfieldID gOptions_justBoundsFieldID;
 static jfieldID gOptions_sampleSizeFieldID;
 static jfieldID gOptions_configFieldID;
 static jfieldID gOptions_ditherFieldID;
+static jfieldID gOptions_purgeableFieldID;
+static jfieldID gOptions_shareableFieldID;
 static jfieldID gOptions_widthFieldID;
 static jfieldID gOptions_heightFieldID;
 static jfieldID gOptions_mimeFieldID;
@@ -33,8 +37,6 @@ static jfieldID gFileDescriptor_descriptor;
     #define TRACE_BITMAP(code)
 #endif
 
-//#define MIN_SIZE_TO_USE_MMAP    (4*1024)
-
 ///////////////////////////////////////////////////////////////////////////////
 
 class AutoDecoderCancel {
@@ -207,7 +209,11 @@ public:
     
     virtual bool rewind() {
         off_t pos = fAsset->seek(0, SEEK_SET);
-        return pos != (off_t)-1;
+        if (pos == (off_t)-1) {
+            SkDebugf("----- fAsset->seek(rewind) failed\n");
+            return false;
+        }
+        return true;
     }
     
     virtual size_t read(void* buffer, size_t size) {
@@ -222,15 +228,20 @@ public:
 
             off_t oldOffset = fAsset->seek(0, SEEK_CUR);
             if (-1 == oldOffset) {
+                SkDebugf("---- fAsset->seek(oldOffset) failed\n");
                 return 0;
             }
             off_t newOffset = fAsset->seek(size, SEEK_CUR);
             if (-1 == newOffset) {
+                SkDebugf("---- fAsset->seek(%d) failed\n", size);
                 return 0;
             }
             amount = newOffset - oldOffset;
         } else {
             amount = fAsset->read(buffer, size);
+            if (amount <= 0) {
+                SkDebugf("---- fAsset->read(%d) returned %d\n", size, amount);
+            }
         }
         
         if (amount < 0) {
@@ -279,13 +290,46 @@ static jstring getMimeTypeString(JNIEnv* env, SkImageDecoder::Format format) {
     return jstr;
 }
 
-static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
-                        jobject options) {
+static bool optionsPurgeable(JNIEnv* env, jobject options) {
+    return options != NULL &&
+            env->GetBooleanField(options, gOptions_purgeableFieldID);
+}
+
+static bool optionsShareable(JNIEnv* env, jobject options) {
+    return options != NULL &&
+            env->GetBooleanField(options, gOptions_shareableFieldID);
+}
+
+static jobject nullObjectReturn(const char msg[]) {
+    if (msg) {
+        SkDebugf("--- %s\n", msg);
+    }
+    return NULL;
+}
+
+static SkPixelRef* installPixelRef(SkBitmap* bitmap, SkStream* stream,
+                                   int sampleSize) {
+    SkPixelRef* pr;
+    // only use ashmem for large images, since mmaps come at a price
+    if (bitmap->getSize() >= 32 * 65536) {
+        pr = new SkImageRef_ashmem(stream, bitmap->config(), sampleSize);
+    } else {
+        pr = new SkImageRef_GlobalPool(stream, bitmap->config(), sampleSize);
+    }
+    bitmap->setPixelRef(pr)->unref();
+    return pr;
+}
 
+// since we "may" create a purgeable imageref, we require the stream be ref'able
+// i.e. dynamically allocated, since its lifetime may exceed the current stack
+// frame.
+static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
+                        jobject options, bool allowPurgeable) {
     int sampleSize = 1;
     SkImageDecoder::Mode mode = SkImageDecoder::kDecodePixels_Mode;
     SkBitmap::Config prefConfig = SkBitmap::kNo_Config;
     bool doDither = true;
+    bool isPurgeable = allowPurgeable && optionsPurgeable(env, options);
     
     if (NULL != options) {
         sampleSize = env->GetIntField(options, gOptions_sampleSizeFieldID);
@@ -304,14 +348,14 @@ static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
 
     SkImageDecoder* decoder = SkImageDecoder::Factory(stream);
     if (NULL == decoder) {
-        return NULL;
+        return nullObjectReturn("SkImageDecoder::Factory returned null");
     }
     
     decoder->setSampleSize(sampleSize);
     decoder->setDitherImage(doDither);
 
     NinePatchPeeker     peeker;
-    JavaPixelAllocator  allocator(env);
+    JavaPixelAllocator  javaAllocator(env);
     SkBitmap*           bitmap = new SkBitmap;
     Res_png_9patch      dummy9Patch;
 
@@ -319,23 +363,27 @@ static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
     SkAutoTDelete<SkBitmap>         adb(bitmap);
 
     decoder->setPeeker(&peeker);
-    decoder->setAllocator(&allocator);
-    
+    if (!isPurgeable) {
+        decoder->setAllocator(&javaAllocator);
+    }
+
     AutoDecoderCancel   adc(options, decoder);
 
     // To fix the race condition in case "requestCancelDecode"
     // happens earlier than AutoDecoderCancel object is added
     // to the gAutoDecoderCancelMutex linked list.
-    if (NULL != options) {
-        if (env->GetBooleanField(options, gOptions_mCancelID)) {
-            return NULL;
-        }
+    if (NULL != options && env->GetBooleanField(options, gOptions_mCancelID)) {
+        return nullObjectReturn("gOptions_mCancelID");;
     }
 
-    if (!decoder->decode(stream, bitmap, prefConfig, mode)) {
-        return NULL;
+    SkImageDecoder::Mode decodeMode = mode;
+    if (isPurgeable) {
+        decodeMode = SkImageDecoder::kDecodeBounds_Mode;
     }
-    
+    if (!decoder->decode(stream, bitmap, prefConfig, decodeMode)) {
+        return nullObjectReturn("decoder->decode returned false");
+    }
+
     // update options (if any)
     if (NULL != options) {
         env->SetIntField(options, gOptions_widthFieldID, bitmap->width());
@@ -346,7 +394,7 @@ static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
         env->SetObjectField(options, gOptions_mimeFieldID,
                             getMimeTypeString(env, decoder->getFormat()));
     }
-    
+
     // if we're in justBounds mode, return now (skip the java bitmap)
     if (SkImageDecoder::kDecodeBounds_Mode == mode) {
         return NULL;
@@ -357,12 +405,12 @@ static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
         size_t ninePatchArraySize = peeker.fPatch->serializedSize();
         ninePatchChunk = env->NewByteArray(ninePatchArraySize);
         if (NULL == ninePatchChunk) {
-            return NULL;
+            return nullObjectReturn("ninePatchChunk == null");
         }
         jbyte* array = (jbyte*)env->GetPrimitiveArrayCritical(ninePatchChunk,
                                                               NULL);
         if (NULL == array) {
-            return NULL;
+            return nullObjectReturn("primitive array == null");
         }
         peeker.fPatch->serialize(array);
         env->ReleasePrimitiveArrayCritical(ninePatchChunk, array, 0);
@@ -382,12 +430,18 @@ static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
             GraphicsJNI::set_jrect(env, padding, -1, -1, -1, -1);
         }
     }
-    
-    // promise we will never change our pixels (great for sharing and pictures)
-    SkPixelRef* ref = bitmap->pixelRef();
-    SkASSERT(ref);
-    ref->setImmutable();
 
+    SkPixelRef* pr;
+    if (isPurgeable) {
+        pr = installPixelRef(bitmap, stream, sampleSize);
+    } else {
+        // if we get here, we're in kDecodePixels_Mode and will therefore
+        // already have a pixelref installed.
+        pr = bitmap->pixelRef();
+    }
+    // promise we will never change our pixels (great for sharing and pictures)
+    pr->setImmutable();
+    // now create the java bitmap
     return GraphicsJNI::createBitmap(env, bitmap, false, ninePatchChunk);
 }
 
@@ -400,7 +454,8 @@ static jobject nativeDecodeStream(JNIEnv* env, jobject clazz,
     SkStream* stream = CreateJavaInputStreamAdaptor(env, is, storage);
 
     if (stream) {
-        bitmap = doDecode(env, stream, padding, options);
+        // for now we don't allow purgeable with java inputstreams
+        bitmap = doDecode(env, stream, padding, options, false);
         stream->unref();
     }
     return bitmap;
@@ -441,52 +496,96 @@ static jobject nativeDecodeFileDescriptor(JNIEnv* env, jobject clazz,
 
     jint descriptor = env->GetIntField(fileDescriptor,
                                        gFileDescriptor_descriptor);
-    
-#ifdef MIN_SIZE_TO_USE_MMAP
-    // First try to use mmap
-    size_t size = getFDSize(descriptor);
-    if (size >= MIN_SIZE_TO_USE_MMAP) {
-        void* addr = mmap(NULL, size, PROT_READ, MAP_PRIVATE, descriptor, 0);
-//        SkDebugf("-------- mmap returned %p %d\n", addr, size);
-        if (MAP_FAILED != addr) {
-            SkMemoryStream strm(addr, size);
-            jobject obj = doDecode(env, &strm, padding, bitmapFactoryOptions);
-            munmap(addr, size);
-            return obj;
+
+    bool isPurgeable = optionsPurgeable(env, bitmapFactoryOptions);
+    bool isShareable = optionsShareable(env, bitmapFactoryOptions);
+    bool weOwnTheFD = false;
+    if (isPurgeable && isShareable) {
+        int newFD = ::dup(descriptor);
+        if (-1 != newFD) {
+            weOwnTheFD = true;
+            descriptor = newFD;
         }
     }
-#endif
 
-    // we pass false for closeWhenDone, since the caller owns the descriptor    
-    SkFDStream file(descriptor, false);
-    if (!file.isValid()) {
+    SkFDStream* stream = new SkFDStream(descriptor, weOwnTheFD);
+    SkAutoUnref aur(stream);
+    if (!stream->isValid()) {
         return NULL;
     }
-    
-    /* Restore our offset when we leave, so the caller doesn't have to.
-       This is a real feature, so we can be called more than once with the
-       same descriptor.
+
+    /* Restore our offset when we leave, so we can be called more than once
+       with the same descriptor. This is only required if we didn't dup the
+       file descriptor, but it is OK to do it all the time.
     */
     AutoFDSeek as(descriptor);
 
-    return doDecode(env, &file, padding, bitmapFactoryOptions);
+    return doDecode(env, stream, padding, bitmapFactoryOptions, true);
+}
+
+/*  make a deep copy of the asset, and return it as a stream, or NULL if there
+    was an error.
+ */
+static SkStream* copyAssetToStream(Asset* asset) {
+    // if we could "ref/reopen" the asset, we may not need to copy it here
+    off_t size = asset->seek(0, SEEK_SET);
+    if ((off_t)-1 == size) {
+        SkDebugf("---- copyAsset: asset rewind failed\n");
+        return NULL;
+    }
+
+    size = asset->getLength();
+    if (size <= 0) {
+        SkDebugf("---- copyAsset: asset->getLength() returned %d\n", size);
+        return NULL;
+    }
+
+    SkStream* stream = new SkMemoryStream(size);
+    void* data = const_cast<void*>(stream->getMemoryBase());
+    off_t len = asset->read(data, size);
+    if (len != size) {
+        SkDebugf("---- copyAsset: asset->read(%d) returned %d\n", size, len);
+        delete stream;
+        stream = NULL;
+    }
+    return stream;
 }
 
 static jobject nativeDecodeAsset(JNIEnv* env, jobject clazz,
                                  jint native_asset,    // Asset
                                  jobject padding,       // Rect
                                  jobject options) { // BitmapFactory$Options
-    AssetStreamAdaptor  mystream((Asset*)native_asset);
-
-    return doDecode(env, &mystream, padding, options);
+    SkStream* stream;
+    Asset* asset = reinterpret_cast<Asset*>(native_asset);
+
+    if (optionsPurgeable(env, options)) {
+        // if we could "ref/reopen" the asset, we may not need to copy it here
+        // and we could assume optionsShareable, since assets are always RO
+        stream = copyAssetToStream(asset);
+        if (NULL == stream) {
+            return NULL;
+        }
+    } else {
+        // since we know we'll be done with the asset when we return, we can
+        // just use a simple wrapper
+        stream = new AssetStreamAdaptor(asset);
+    }
+    SkAutoUnref aur(stream);
+    return doDecode(env, stream, padding, options, true);
 }
 
 static jobject nativeDecodeByteArray(JNIEnv* env, jobject, jbyteArray byteArray,
                                      int offset, int length, jobject options) {
-    AutoJavaByteArray   ar(env, byteArray);
-    SkMemoryStream  stream(ar.ptr() + offset, length);
-
-    return doDecode(env, &stream, NULL, options);
+    /*  If optionsShareable() we could decide to just wrap the java array and
+        share it, but that means adding a globalref to the java array object
+        and managing its lifetime. For now we just always copy the array's data
+        if optionsPurgeable().
+     */
+    AutoJavaByteArray ar(env, byteArray);
+    SkStream* stream = new SkMemoryStream(ar.ptr() + offset, length,
+                                          optionsPurgeable(env, options));
+    SkAutoUnref aur(stream);
+    return doDecode(env, stream, NULL, options, true);
 }
 
 static void nativeRequestCancel(JNIEnv*, jobject joptions) {
@@ -595,6 +694,8 @@ int register_android_graphics_BitmapFactory(JNIEnv* env) {
     gOptions_configFieldID = getFieldIDCheck(env, gOptions_class, "inPreferredConfig",
             "Landroid/graphics/Bitmap$Config;");
     gOptions_ditherFieldID = getFieldIDCheck(env, gOptions_class, "inDither", "Z");
+    gOptions_purgeableFieldID = getFieldIDCheck(env, gOptions_class, "inPurgeable", "Z");
+    gOptions_shareableFieldID = getFieldIDCheck(env, gOptions_class, "inInputShareable", "Z");
     gOptions_widthFieldID = getFieldIDCheck(env, gOptions_class, "outWidth", "I");
     gOptions_heightFieldID = getFieldIDCheck(env, gOptions_class, "outHeight", "I");
     gOptions_mimeFieldID = getFieldIDCheck(env, gOptions_class, "outMimeType", "Ljava/lang/String;");