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A library jar that provides APIs for Applications written for the Google Android Platform.
/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.hardware;
import android.annotation.IntDef;
import android.os.MemoryFile;
import dalvik.system.CloseGuard;
import java.io.IOException;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.nio.channels.Channel;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Class representing a sensor direct channel. Use
* {@link SensorManager#createDirectChannel(android.os.MemoryFile)} or
* {@link SensorManager#createDirectChannel(android.hardware.HardwareBuffer)}
* to obtain an object. The channel object can be then configured
* (see {@link #configure(Sensor, int)})
* to start delivery of sensor events into shared memory buffer.
*/
public final class SensorDirectChannel implements Channel {
// shared memory types
/** @hide */
@Retention(RetentionPolicy.SOURCE)
@IntDef(flag = true, prefix = { "TYPE_" }, value = {
TYPE_MEMORY_FILE,
TYPE_HARDWARE_BUFFER
})
public @interface MemoryType {}
/**
* Shared memory type ashmem, wrapped in MemoryFile object.
*
* @see SensorManager#createDirectChannel(MemoryFile)
*/
public static final int TYPE_MEMORY_FILE = 1;
/**
* Shared memory type wrapped by HardwareBuffer object.
*
* @see SensorManager#createDirectChannel(HardwareBuffer)
*/
public static final int TYPE_HARDWARE_BUFFER = 2;
// sensor rate levels
/** @hide */
@Retention(RetentionPolicy.SOURCE)
@IntDef(flag = true, prefix = { "RATE_" }, value = {
RATE_STOP,
RATE_NORMAL,
RATE_FAST,
RATE_VERY_FAST
})
public @interface RateLevel {}
/**
* Sensor stopped (no event output).
*
* @see #configure(Sensor, int)
*/
public static final int RATE_STOP = 0;
/**
* Sensor operates at nominal rate of 50Hz.
*
* The actual rate is expected to be between 55% to 220% of nominal rate, thus between 27.5Hz to
* 110Hz.
*
* @see #configure(Sensor, int)
*/
public static final int RATE_NORMAL = 1; //50Hz
/**
* Sensor operates at nominal rate of 200Hz.
*
* The actual rate is expected to be between 55% to 220% of nominal rate, thus between 110Hz to
* 440Hz.
*
* @see #configure(Sensor, int)
*/
public static final int RATE_FAST = 2; // ~200Hz
/**
* Sensor operates at nominal rate of 800Hz.
*
* The actual rate is expected to be between 55% to 220% of nominal rate, thus between 440Hz to
* 1760Hz.
*
* @see #configure(Sensor, int)
*/
public static final int RATE_VERY_FAST = 3; // ~800Hz
/**
* Determine if a channel is still valid. A channel is invalidated after {@link #close()} is
* called.
*
* @return true if channel is valid.
*/
@Override
public boolean isOpen() {
return !mClosed.get();
}
/** @removed */
@Deprecated
public boolean isValid() {
return isOpen();
}
/**
* Close sensor direct channel.
*
* Stop all active sensor in the channel and free sensor system resource related to channel.
* Shared memory used for creating the direct channel need to be closed or freed separately.
*
* @see SensorManager#createDirectChannel(MemoryFile)
* @see SensorManager#createDirectChannel(HardwareBuffer)
*/
@Override
public void close() {
if (mClosed.compareAndSet(false, true)) {
mCloseGuard.close();
// actual close action
mManager.destroyDirectChannel(this);
}
}
/**
* Configure sensor rate or stop sensor report.
*
* To start event report of a sensor, or change rate of existing report, call this function with
* rateLevel other than {@link android.hardware.SensorDirectChannel#RATE_STOP}. Sensor events
* will be added into a queue formed by the shared memory used in creation of direction channel.
* Each element of the queue has size of 104 bytes and represents a sensor event. Data
* structure of an element (all fields in little-endian):
*
*
* offset type name
* ------------------------------------------------------------------------
* 0x0000 int32_t size (always 104)
* 0x0004 int32_t sensor report token
* 0x0008 int32_t type (see SensorType)
* 0x000C uint32_t atomic counter
* 0x0010 int64_t timestamp (see Event)
* 0x0018 float[16]/int64_t[8] data (data type depends on sensor type)
* 0x0058 int32_t[4] reserved (set to zero)
*
*
* There are no head or tail pointers. The sequence and frontier of new sensor events is
* determined by the atomic counter, which counts from 1 after creation of direct channel and
* increments 1 for each new event. Atomic counter will wrap back to 1 after it reaches
* UINT32_MAX, skipping value 0 to avoid confusion with uninitialized memory. The writer in
* sensor system will wrap around from the start of shared memory region when it reaches the
* end. If size of memory region is not a multiple of size of element (104 bytes), the residual
* is not used at the end. Function returns a positive sensor report token on success. This
* token can be used to differentiate sensor events from multiple sensor of the same type. For
* example, if there are two accelerometers in the system A and B, it is guaranteed different
* report tokens will be returned when starting sensor A and B.
*
* To stop a sensor, call this function with rateLevel equal {@link
* android.hardware.SensorDirectChannel#RATE_STOP}. If the sensor parameter is left to be null,
* this will stop all active sensor report associated with the direct channel specified.
* Function return 1 on success or 0 on failure.
*
* @param sensor A {@link android.hardware.Sensor} object to denote sensor to be operated.
* @param rateLevel rate level defined in {@link android.hardware.SensorDirectChannel}.
* @return * starting report or changing rate: positive sensor report token on success,
* 0 on failure;
* * stopping report: 1 on success, 0 on failure.
* @throws NullPointerException when channel is null.
*/
public int configure(Sensor sensor, @RateLevel int rateLevel) {
return mManager.configureDirectChannelImpl(this, sensor, rateLevel);
}
/** @hide */
SensorDirectChannel(SensorManager manager, int id, int type, long size) {
mManager = manager;
mNativeHandle = id;
mType = type;
mSize = size;
mCloseGuard.open("SensorDirectChannel");
}
/** @hide */
int getNativeHandle() {
return mNativeHandle;
}
/**
* This function encode handle information in {@link android.os.MemoryFile} into a long array to
* be passed down to native methods.
*
* @hide */
static long[] encodeData(MemoryFile ashmem) {
int fd;
try {
fd = ashmem.getFileDescriptor().getInt$();
} catch (IOException e) {
fd = -1;
}
return new long[] { 1 /*numFds*/, 0 /*numInts*/, fd };
}
@Override
protected void finalize() throws Throwable {
try {
if (mCloseGuard != null) {
mCloseGuard.warnIfOpen();
}
close();
} finally {
super.finalize();
}
}
private final AtomicBoolean mClosed = new AtomicBoolean();
private final CloseGuard mCloseGuard = CloseGuard.get();
private final SensorManager mManager;
private final int mNativeHandle;
private final long mSize;
private final int mType;
}