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Clarify the behavior of UsbRequest

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This is obviously just about describing a bad behavior. In the next step
these methods should be deprecated and replaced with versions that deal
with ByteBuffers appropriately.

Bug: 31050148
Test: Test that enshrines the documented behavior is submitted alongside
      this change
Change-Id: If250a8bbd636784355e839a1638d52f3bbe9b83d
This commit is contained in:
Philip P. Moltmann
2016-09-23 15:31:23 -07:00
parent 4b331cc154
commit 5dd4e6cf74
2 changed files with 27 additions and 15 deletions
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19
core/java/android/hardware/usb/UsbDeviceConnection.java
View File

@@ -24,7 +24,7 @@ import android.os.ParcelFileDescriptor;
import dalvik.system.CloseGuard;
import java.io.FileDescriptor;
import java.nio.ByteBuffer;
/**
* This class is used for sending and receiving data and control messages to a USB device.
@@ -257,13 +257,20 @@ public class UsbDeviceConnection {
/**
* Waits for the result of a {@link android.hardware.usb.UsbRequest#queue} operation
* Note that this may return requests queued on multiple
* {@link android.hardware.usb.UsbEndpoint}s.
* When multiple endpoints are in use, {@link android.hardware.usb.UsbRequest#getEndpoint} and
* {@link android.hardware.usb.UsbRequest#getClientData} can be useful in determining
* how to process the result of this function.
* <p>Note that this may return requests queued on multiple
* {@link android.hardware.usb.UsbEndpoint}s. When multiple endpoints are in use,
* {@link android.hardware.usb.UsbRequest#getEndpoint} and {@link
* android.hardware.usb.UsbRequest#getClientData} can be useful in determining how to process
* the result of this function.</p>
* <p>Position and array offset of the request's buffer are ignored and assumed to be 0. The
* position will be set to the number of bytes read/written.</p>
*
* @return a completed USB request, or null if an error occurred
*
* @throws IllegalArgumentException if the number of bytes read or written is more than the
* limit of the request's buffer. The number of bytes is
* determined by the {@code length} parameter of
* {@link UsbRequest#queue(ByteBuffer, int)}
*/
public UsbRequest requestWait() {
UsbRequest request = native_request_wait();

23
core/java/android/hardware/usb/UsbRequest.java
View File

@@ -17,6 +17,7 @@
package android.hardware.usb;
import android.util.Log;
import com.android.internal.util.Preconditions;
import dalvik.system.CloseGuard;
import java.nio.ByteBuffer;
@@ -66,7 +67,7 @@ public class UsbRequest {
*/
public boolean initialize(UsbDeviceConnection connection, UsbEndpoint endpoint) {
mEndpoint = endpoint;
mConnection = connection;
mConnection = Preconditions.checkNotNull(connection);
boolean wasInitialized = native_init(connection, endpoint.getAddress(),
endpoint.getAttributes(), endpoint.getMaxPacketSize(), endpoint.getInterval());
@@ -137,15 +138,16 @@ public class UsbRequest {
/**
* Queues the request to send or receive data on its endpoint.
* For OUT endpoints, the given buffer data will be sent on the endpoint.
* For IN endpoints, the endpoint will attempt to read the given number of bytes
* into the specified buffer.
* If the queueing operation is successful, we return true and the result will be
* returned via {@link android.hardware.usb.UsbDeviceConnection#requestWait}
* <p>For OUT endpoints, the given buffer data will be sent on the endpoint. For IN endpoints,
* the endpoint will attempt to read the given number of bytes into the specified buffer. If the
* queueing operation is successful, we return true and the result will be returned via {@link
* android.hardware.usb.UsbDeviceConnection#requestWait}</p>
*
* @param buffer the buffer containing the bytes to write, or location to store the results of a
* read. Position and array offset will be ignored and assumed to be 0. Limit and
* capacity will be ignored.
* @param length number of bytes to read or write.
*
* @param buffer the buffer containing the bytes to write, or location to store
* the results of a read
* @param length number of bytes to read or write
* @return true if the queueing operation succeeded
*/
public boolean queue(ByteBuffer buffer, int length) {
@@ -155,6 +157,9 @@ public class UsbRequest {
mBuffer = buffer;
mLength = length;
// Note: On a buffer slice we lost the capacity information about the underlying buffer,
// hence we cannot check if the access would be a data leak/memory corruption.
boolean result;
if (buffer.isDirect()) {
result = native_queue_direct(buffer, length, out);