Add support for sending and receiving ParcelFileDescriptors from native Binder code

Change-Id: I7f308e28ebac0755628e19c9b4d0d7399341b435

include/binder/Parcel.h

@@ -124,6 +124,11 @@ public:
     // will be closed once the parcel is destroyed.
     status_t            writeDupFileDescriptor(int fd);
 
+    // Writes a raw fd and optional comm channel fd to the parcel as a ParcelFileDescriptor.
+    // A dup's of the fds are made, which will be closed once the parcel is destroyed.
+    // Null values are passed as -1.
+    status_t            writeParcelFileDescriptor(int fd, int commChannel = -1);
+
     // 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.
@@ -183,6 +188,11 @@ public:
     // in the parcel, which you do not own -- use dup() to get your own copy.
     int                 readFileDescriptor() const;
 
+    // Reads a ParcelFileDescriptor from the parcel.  Returns the raw fd as
+    // the result, and the optional comm channel fd in outCommChannel.
+    // Null values are returned as -1.
+    int                 readParcelFileDescriptor(int& outCommChannel) 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;

libs/binder/Parcel.cpp

@@ -750,6 +750,32 @@ status_t Parcel::writeDupFileDescriptor(int fd)
     return err;
 }
 
+// WARNING: This method must stay in sync with
+// Parcelable.Creator<ParcelFileDescriptor> CREATOR
+// in frameworks/base/core/java/android/os/ParcelFileDescriptor.java
+status_t Parcel::writeParcelFileDescriptor(int fd, int commChannel) {
+    status_t status;
+
+    if (fd < 0) {
+        status = writeInt32(0); // ParcelFileDescriptor is null
+        if (status) return status;
+    } else {
+        status = writeInt32(1); // ParcelFileDescriptor is not null
+        if (status) return status;
+        status = writeDupFileDescriptor(fd);
+        if (status) return status;
+        if (commChannel < 0) {
+            status = writeInt32(0); // commChannel is null
+            if (status) return status;
+        } else {
+            status = writeInt32(1); // commChannel is not null
+            if (status) return status;
+            status = writeDupFileDescriptor(commChannel);
+        }
+    }
+    return status;
+}
+
 status_t Parcel::writeBlob(size_t len, WritableBlob* outBlob)
 {
     status_t status;
@@ -1148,6 +1174,23 @@ int Parcel::readFileDescriptor() const
     return BAD_TYPE;
 }
 
+// WARNING: This method must stay in sync with writeToParcel()
+// in frameworks/base/core/java/android/os/ParcelFileDescriptor.java
+int Parcel::readParcelFileDescriptor(int& outCommChannel) const {
+    int fd;
+    outCommChannel = -1;
+
+    if (readInt32() == 0) {
+        fd = -1;
+    } else {
+        fd = readFileDescriptor();
+        if (fd >= 0 && readInt32() != 0) {
+            outCommChannel = readFileDescriptor();
+        }
+    }
+    return fd;
+}
+
 status_t Parcel::readBlob(size_t len, ReadableBlob* outBlob) const
 {
     int32_t useAshmem;