Transfer using devusbfs via JNI rather than Android APIs

The Java methods have significant limitations, such as:
- Totally broken handling > 16KB transfers on Oreo and earlier
- Unable to retrieve the actual error code without horrible hacks

Author: cgutman

app/src/main/java/org/cgutman/usbip/errno/Errno.java

@@ -0,0 +1,12 @@
+package org.cgutman.usbip.jni;
+
+public class UsbLib {
+	static {
+		System.loadLibrary("usblib");
+	}
+
+	public static native int doControlTransfer(int fd, byte requestType, byte request, short value,
+											   short index, byte[] data, int length, int timeout);
+
+	public static native int doBulkTransfer(int fd, int endpoint, byte[] data, int timeout);
+}

app/src/main/java/org/cgutman/usbip/jni/UsbLib.java

@@ -1,65 +1,31 @@
 package org.cgutman.usbip.usb;
 
-import org.cgutman.usbip.errno.Errno;
+import org.cgutman.usbip.jni.UsbLib;
 
-import android.hardware.usb.UsbConstants;
 import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbEndpoint;
 
 public class XferUtils {
 
 	public static int doInterruptTransfer(UsbDeviceConnection devConn, UsbEndpoint endpoint, byte[] buff, int timeout) {
 		// Interrupt transfers are implemented as one-shot bulk transfers
-		int res = devConn.bulkTransfer(endpoint, buff,
-				buff.length, timeout);
-		if (res < 0) {
-			res = -Errno.getErrno();
-			if (res != -110) { 
-				// Don't print for ETIMEDOUT
-				System.err.println("Interrupt Xfer failed: "+res);
-			}
+		int res = UsbLib.doBulkTransfer(devConn.getFileDescriptor(), endpoint.getAddress(), buff, timeout);
+		if (res < 0 && res != -110) {
+			// Don't print for ETIMEDOUT
+			System.err.println("Interrupt Xfer failed: "+res);
 		}
 
 		return res;
 	}
 
 	public static int doBulkTransfer(UsbDeviceConnection devConn, UsbEndpoint endpoint, byte[] buff, int timeout) {
-		int bytesTransferred = 0;
-		while (bytesTransferred < buff.length) {
-			byte[] remainingBuffer = new byte[buff.length - bytesTransferred];
-			
-			if (endpoint.getDirection() == UsbConstants.USB_DIR_OUT) {
-				// Copy input data into the new buffer
-				System.arraycopy(buff, bytesTransferred, remainingBuffer, 0, remainingBuffer.length);
-			}
-			
-			int res = devConn.bulkTransfer(endpoint, remainingBuffer,
-					remainingBuffer.length, timeout);
-			if (res < 0) {
-				// Failed transfer terminates the bulk transfer
-				res = -Errno.getErrno();
-				if (res != -110) { 
-					// Don't print for ETIMEDOUT
-					System.err.println("Bulk Xfer failed: "+res);
-				}
-				return res;
-			}
-			
-			if (endpoint.getDirection() == UsbConstants.USB_DIR_IN) {
-				// Copy output data into the original buffer
-				System.arraycopy(remainingBuffer, 0, buff, bytesTransferred, res);
-			}
-			
-			bytesTransferred += res;
-			
-			if (res < endpoint.getMaxPacketSize()) {
-				// A packet less than the maximum size for this endpoint
-				// indicates the transfer has ended
-				break;
-			}
+		int res = UsbLib.doBulkTransfer(devConn.getFileDescriptor(), endpoint.getAddress(), buff, timeout);
+		if (res < 0 && res != -110) {
+			// Don't print for ETIMEDOUT
+			System.err.println("Bulk Xfer failed: "+res);
 		}
-		
-		return bytesTransferred;
+
+		return res;
 	}
 
 	public static int doControlTransfer(UsbDeviceConnection devConn, int requestType,
@@ -75,14 +41,11 @@ public static int doControlTransfer(UsbDeviceConnection devConn, int requestType
 		System.out.printf("SETUP: %x %x %x %x %x\n",
 				requestType, request, value, index, length);
 
-		int res = devConn.controlTransfer(requestType, request, value,
-				index, buff, length, interval);
-		if (res < 0) {
-			res = -Errno.getErrno();
-			if (res != -110) { 
-				// Don't print for ETIMEDOUT
-				System.err.println("Control Xfer failed: "+res);
-			}
+		int res = UsbLib.doControlTransfer(devConn.getFileDescriptor(), (byte)requestType, (byte)request,
+				(short)value, (short)index, buff, length, interval);
+		if (res < 0 && res != -110) {
+			// Don't print for ETIMEDOUT
+			System.err.println("Control Xfer failed: "+res);
 		}
 
 		return res;

app/src/main/java/org/cgutman/usbip/usb/XferUtils.java

@@ -6,7 +6,7 @@ include $(call all-subdir-makefiles)
 LOCAL_PATH := $(MY_LOCAL_PATH)
 
 include $(CLEAR_VARS)
-LOCAL_MODULE    := errno
-LOCAL_SRC_FILES := errno_jni.c
+LOCAL_MODULE    := usblib
+LOCAL_SRC_FILES := usblib_jni.c
 
 include $(BUILD_SHARED_LIBRARY)

app/src/main/jni/errno/errno_jni.c

@@ -0,0 +1,64 @@
+#include <stdlib.h>
+#include <unistd.h>
+#include <jni.h>
+
+#include <errno.h>
+#include <linux/usbdevice_fs.h>
+#include <sys/ioctl.h>
+
+JNIEXPORT jint JNICALL
+Java_org_cgutman_usbip_jni_UsbLib_doBulkTransfer(
+        JNIEnv *env, jclass clazz, jint fd, jint endpoint, jbyteArray data, jint timeout)
+{
+    jbyte* dataPtr = data ? (jbyte*)(*env)->GetPrimitiveArrayCritical(env, data, NULL) : NULL;
+    jsize dataLen = data ? (*env)->GetArrayLength(env, data) : 0;
+
+    struct usbdevfs_bulktransfer xfer = {
+        .ep = endpoint,
+        .len = dataLen,
+        .timeout = timeout,
+        .data = dataPtr,
+    };
+    jint res = TEMP_FAILURE_RETRY(ioctl(fd, USBDEVFS_BULK, &xfer));
+    if (res < 0) {
+        res = -errno;
+    }
+
+    // If this is an OUT or a failed IN, use JNI_ABORT to avoid a useless memcpy().
+    if (dataPtr) {
+        (*env)->ReleasePrimitiveArrayCritical(env, data, dataPtr,
+                                              ((endpoint & 0x80) && (res > 0)) ? 0 : JNI_ABORT);
+    }
+
+    return res;
+};
+
+JNIEXPORT jint JNICALL
+Java_org_cgutman_usbip_jni_UsbLib_doControlTransfer(
+        JNIEnv *env, jclass clazz, jint fd, jbyte requestType, jbyte request, jshort value,
+        jshort index, jbyteArray data, jint length, jint timeout)
+{
+    jbyte* dataPtr = data ? (jbyte*)(*env)->GetPrimitiveArrayCritical(env, data, NULL) : NULL;
+
+    struct usbdevfs_ctrltransfer xfer = {
+            .bRequestType = requestType,
+            .bRequest = request,
+            .wValue = value,
+            .wIndex = index,
+            .wLength = length,
+            .timeout = timeout,
+            .data = dataPtr,
+    };
+    jint res = TEMP_FAILURE_RETRY(ioctl(fd, USBDEVFS_CONTROL, &xfer));
+    if (res < 0) {
+        res = -errno;
+    }
+
+    // If this is an OUT or a failed IN, use JNI_ABORT to avoid a useless memcpy().
+    if (dataPtr) {
+        (*env)->ReleasePrimitiveArrayCritical(env, data, dataPtr,
+                                              ((requestType & 0x80) && (res > 0)) ? 0 : JNI_ABORT);
+    }
+
+    return res;
+};