Transfer large bitmaps using ashmem.

Bug: 5224703

Change-Id: If385a66adf4c6179a0bb49c0e6d09a9567e23808

include/binder/Parcel.h

@@ -38,6 +38,9 @@ struct flat_binder_object;  // defined in support_p/binder_module.h
 class Parcel
 {
 public:
+    class ReadableBlob;
+    class WritableBlob;
+
                         Parcel();
                         ~Parcel();
     
@@ -111,7 +114,13 @@ public:
     // Place a file descriptor into the parcel.  A dup of the fd is made, which
     // will be closed once the parcel is destroyed.
     status_t            writeDupFileDescriptor(int fd);
-    
+
+    // Writes a blob to the parcel.
+    // If the blob is small, then it is stored in-place, otherwise it is
+    // transferred by way of an anonymous shared memory region.
+    // The caller should call release() on the blob after writing its contents.
+    status_t            writeBlob(size_t len, WritableBlob* outBlob);
+
     status_t            writeObject(const flat_binder_object& val, bool nullMetaData);
 
     // Like Parcel.java's writeNoException().  Just writes a zero int32.
@@ -159,7 +168,11 @@ public:
     // Retrieve a file descriptor from the parcel.  This returns the raw fd
     // in the parcel, which you do not own -- use dup() to get your own copy.
     int                 readFileDescriptor() const;
-    
+
+    // Reads a blob from the parcel.
+    // The caller should call release() on the blob after reading its contents.
+    status_t            readBlob(size_t len, ReadableBlob* outBlob) const;
+
     const flat_binder_object* readObject(bool nullMetaData) const;
 
     // Explicitly close all file descriptors in the parcel.
@@ -179,7 +192,7 @@ public:
                                             release_func relFunc, void* relCookie);
     
     void                print(TextOutput& to, uint32_t flags = 0) const;
-        
+
 private:
                         Parcel(const Parcel& o);
     Parcel&             operator=(const Parcel& o);
@@ -218,6 +231,36 @@ private:
     
     release_func        mOwner;
     void*               mOwnerCookie;
+
+    class Blob {
+    public:
+        Blob();
+        ~Blob();
+
+        void release();
+        inline size_t size() const { return mSize; }
+
+    protected:
+        void init(bool mapped, void* data, size_t size);
+        void clear();
+
+        bool mMapped;
+        void* mData;
+        size_t mSize;
+    };
+
+public:
+    class ReadableBlob : public Blob {
+        friend class Parcel;
+    public:
+        inline const void* data() const { return mData; }
+    };
+
+    class WritableBlob : public Blob {
+        friend class Parcel;
+    public:
+        inline void* data() { return mData; }
+    };
 };
 
 // ---------------------------------------------------------------------------

libs/binder/Parcel.cpp

@@ -30,12 +30,14 @@
 #include <utils/TextOutput.h>
 #include <utils/misc.h>
 #include <utils/Flattenable.h>
+#include <cutils/ashmem.h>
 
 #include <private/binder/binder_module.h>
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
+#include <sys/mman.h>
 
 #ifndef INT32_MAX
 #define INT32_MAX ((int32_t)(2147483647))
@@ -54,6 +56,9 @@
 // Note: must be kept in sync with android/os/Parcel.java's EX_HAS_REPLY_HEADER
 #define EX_HAS_REPLY_HEADER -128
 
+// Maximum size of a blob to transfer in-place.
+static const size_t IN_PLACE_BLOB_LIMIT = 40 * 1024;
+
 // XXX This can be made public if we want to provide
 // support for typed data.
 struct small_flat_data
@@ -718,6 +723,54 @@ status_t Parcel::writeDupFileDescriptor(int fd)
     return writeObject(obj, true);
 }
 
+status_t Parcel::writeBlob(size_t len, WritableBlob* outBlob)
+{
+    status_t status;
+
+    if (!mAllowFds || len <= IN_PLACE_BLOB_LIMIT) {
+        LOGV("writeBlob: write in place");
+        status = writeInt32(0);
+        if (status) return status;
+
+        void* ptr = writeInplace(len);
+        if (!ptr) return NO_MEMORY;
+
+        outBlob->init(false /*mapped*/, ptr, len);
+        return NO_ERROR;
+    }
+
+    LOGV("writeBlob: write to ashmem");
+    int fd = ashmem_create_region("Parcel Blob", len);
+    if (fd < 0) return NO_MEMORY;
+
+    int result = ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE);
+    if (result < 0) {
+        status = -result;
+    } else {
+        void* ptr = ::mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+        if (ptr == MAP_FAILED) {
+            status = -errno;
+        } else {
+            result = ashmem_set_prot_region(fd, PROT_READ);
+            if (result < 0) {
+                status = -result;
+            } else {
+                status = writeInt32(1);
+                if (!status) {
+                    status = writeFileDescriptor(fd);
+                    if (!status) {
+                        outBlob->init(true /*mapped*/, ptr, len);
+                        return NO_ERROR;
+                    }
+                }
+            }
+        }
+        ::munmap(ptr, len);
+    }
+    ::close(fd);
+    return status;
+}
+
 status_t Parcel::write(const Flattenable& val)
 {
     status_t err;
@@ -1040,6 +1093,32 @@ int Parcel::readFileDescriptor() const
     return BAD_TYPE;
 }
 
+status_t Parcel::readBlob(size_t len, ReadableBlob* outBlob) const
+{
+    int32_t useAshmem;
+    status_t status = readInt32(&useAshmem);
+    if (status) return status;
+
+    if (!useAshmem) {
+        LOGV("readBlob: read in place");
+        const void* ptr = readInplace(len);
+        if (!ptr) return BAD_VALUE;
+
+        outBlob->init(false /*mapped*/, const_cast<void*>(ptr), len);
+        return NO_ERROR;
+    }
+
+    LOGV("readBlob: read from ashmem");
+    int fd = readFileDescriptor();
+    if (fd == int(BAD_TYPE)) return BAD_VALUE;
+
+    void* ptr = ::mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
+    if (!ptr) return NO_MEMORY;
+
+    outBlob->init(true /*mapped*/, ptr, len);
+    return NO_ERROR;
+}
+
 status_t Parcel::read(Flattenable& val) const
 {
     // size
@@ -1469,4 +1548,33 @@ void Parcel::scanForFds() const
     mFdsKnown = true;
 }
 
+// --- Parcel::Blob ---
+
+Parcel::Blob::Blob() :
+        mMapped(false), mData(NULL), mSize(0) {
+}
+
+Parcel::Blob::~Blob() {
+    release();
+}
+
+void Parcel::Blob::release() {
+    if (mMapped && mData) {
+        ::munmap(mData, mSize);
+    }
+    clear();
+}
+
+void Parcel::Blob::init(bool mapped, void* data, size_t size) {
+    mMapped = mapped;
+    mData = data;
+    mSize = size;
+}
+
+void Parcel::Blob::clear() {
+    mMapped = false;
+    mData = NULL;
+    mSize = 0;
+}
+
 }; // namespace android