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Intern strings used in Sensor information.

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By creating a local 'interning map', Sensor information, such as: name, vendor,
stringType, and requirePermissions; 92 string objects are not needed anymore.
This frees ~6KB of memory in all processes accessing SensorManager.

Change-Id: Idfdc98160363bec844c34fc3b71f5e8d7843a7be
This commit is contained in:
destradaa
2015-02-10 15:04:43 -08:00
parent 4a39e1bb33
commit 9ba7c1c175
2 changed files with 145 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

92
core/java/android/hardware/Sensor.java
View File

@@ -810,4 +810,96 @@ public final class Sensor {
+ ", type=" + mType + ", maxRange=" + mMaxRange + ", resolution=" + mResolution
+ ", power=" + mPower + ", minDelay=" + mMinDelay + "}";
}
/**
* Sets the Type associated with the sensor.
* NOTE: to be used only by native bindings in SensorManager.
*
* This allows interned static strings to be used across all representations of the Sensor. If
* a sensor type is not referenced here, it will still be interned by the native SensorManager.
*
* @return {@code true} if the StringType was successfully set, {@code false} otherwise.
*/
private boolean setType(int value) {
mType = value;
switch (mType) {
case TYPE_ACCELEROMETER:
mStringType = STRING_TYPE_ACCELEROMETER;
return true;
case TYPE_AMBIENT_TEMPERATURE:
mStringType = STRING_TYPE_AMBIENT_TEMPERATURE;
return true;
case TYPE_GAME_ROTATION_VECTOR:
mStringType = STRING_TYPE_GAME_ROTATION_VECTOR;
return true;
case TYPE_GEOMAGNETIC_ROTATION_VECTOR:
mStringType = STRING_TYPE_GEOMAGNETIC_ROTATION_VECTOR;
return true;
case TYPE_GLANCE_GESTURE:
mStringType = STRING_TYPE_GLANCE_GESTURE;
return true;
case TYPE_GRAVITY:
mStringType = STRING_TYPE_GRAVITY;
return true;
case TYPE_GYROSCOPE:
mStringType = STRING_TYPE_GYROSCOPE;
return true;
case TYPE_GYROSCOPE_UNCALIBRATED:
mStringType = STRING_TYPE_GYROSCOPE_UNCALIBRATED;
return true;
case TYPE_HEART_RATE:
mStringType = STRING_TYPE_HEART_RATE;
return true;
case TYPE_LIGHT:
mStringType = STRING_TYPE_LIGHT;
return true;
case TYPE_LINEAR_ACCELERATION:
mStringType = STRING_TYPE_LINEAR_ACCELERATION;
return true;
case TYPE_MAGNETIC_FIELD:
mStringType = STRING_TYPE_MAGNETIC_FIELD;
return true;
case TYPE_MAGNETIC_FIELD_UNCALIBRATED:
mStringType = STRING_TYPE_MAGNETIC_FIELD_UNCALIBRATED;
return true;
case TYPE_PICK_UP_GESTURE:
mStringType = STRING_TYPE_PICK_UP_GESTURE;
return true;
case TYPE_PRESSURE:
mStringType = STRING_TYPE_PRESSURE;
return true;
case TYPE_PROXIMITY:
mStringType = STRING_TYPE_PROXIMITY;
return true;
case TYPE_RELATIVE_HUMIDITY:
mStringType = STRING_TYPE_RELATIVE_HUMIDITY;
return true;
case TYPE_ROTATION_VECTOR:
mStringType = STRING_TYPE_ROTATION_VECTOR;
return true;
case TYPE_SIGNIFICANT_MOTION:
mStringType = STRING_TYPE_SIGNIFICANT_MOTION;
return true;
case TYPE_STEP_COUNTER:
mStringType = STRING_TYPE_STEP_COUNTER;
return true;
case TYPE_STEP_DETECTOR:
mStringType = STRING_TYPE_STEP_DETECTOR;
return true;
case TYPE_TILT_DETECTOR:
mStringType = SENSOR_STRING_TYPE_TILT_DETECTOR;
return true;
case TYPE_WAKE_GESTURE:
mStringType = STRING_TYPE_WAKE_GESTURE;
return true;
case TYPE_ORIENTATION:
mStringType = STRING_TYPE_ORIENTATION;
return true;
case TYPE_TEMPERATURE:
mStringType = STRING_TYPE_TEMPERATURE;
return true;
default:
return false;
}
}
}

62
core/jni/android_hardware_SensorManager.cpp
View File

@@ -16,6 +16,8 @@
#define LOG_TAG "SensorManager"
#include <map>
#include <utils/Log.h>
#include <utils/Looper.h>
@@ -44,7 +46,6 @@ struct SensorOffsets
jfieldID vendor;
jfieldID version;
jfieldID handle;
jfieldID type;
jfieldID range;
jfieldID resolution;
jfieldID power;
@@ -55,6 +56,7 @@ struct SensorOffsets
jfieldID requiredPermission;
jfieldID maxDelay;
jfieldID flags;
jmethodID setType;
} gSensorOffsets;
@@ -71,7 +73,6 @@ nativeClassInit (JNIEnv *_env, jclass _this)
sensorOffsets.vendor = _env->GetFieldID(sensorClass, "mVendor", "Ljava/lang/String;");
sensorOffsets.version = _env->GetFieldID(sensorClass, "mVersion", "I");
sensorOffsets.handle = _env->GetFieldID(sensorClass, "mHandle", "I");
sensorOffsets.type = _env->GetFieldID(sensorClass, "mType", "I");
sensorOffsets.range = _env->GetFieldID(sensorClass, "mMaxRange", "F");
sensorOffsets.resolution = _env->GetFieldID(sensorClass, "mResolution","F");
sensorOffsets.power = _env->GetFieldID(sensorClass, "mPower", "F");
@@ -84,6 +85,47 @@ nativeClassInit (JNIEnv *_env, jclass _this)
"Ljava/lang/String;");
sensorOffsets.maxDelay = _env->GetFieldID(sensorClass, "mMaxDelay", "I");
sensorOffsets.flags = _env->GetFieldID(sensorClass, "mFlags", "I");
sensorOffsets.setType = _env->GetMethodID(sensorClass, "setType", "(I)Z");
}
/**
* A key comparator predicate.
* It is used to intern strings associated with Sensor data.
* It defines a 'Strict weak ordering' for the interned strings.
*/
class InternedStringCompare {
public:
bool operator()(const String8* string1, const String8* string2) const {
if (string1 == NULL) {
return string2 != NULL;
}
return string1->compare(*string2) < 0;
}
};
/**
* A localized interning mechanism for Sensor strings.
* We implement our own interning to avoid the overhead of using java.lang.String#intern().
* It is common that Vendor, StringType, and RequirePermission data is common between many of the
* Sensors, by interning the memory usage to represent Sensors is optimized.
*/
static jstring
getInternedString(JNIEnv *env, const String8* string) {
static std::map<const String8*, jstring, InternedStringCompare> internedStrings;
jstring internedString;
std::map<const String8*, jstring>::iterator iterator = internedStrings.find(string);
if (iterator != internedStrings.end()) {
internedString = iterator->second;
} else {
jstring localString = env->NewStringUTF(string->string());
// we are implementing our own interning so expect these strings to be backed by global refs
internedString = (jstring) env->NewGlobalRef(localString);
internedStrings.insert(std::make_pair(string, internedString));
env->DeleteLocalRef(localString);
}
return internedString;
}
static jint
@@ -93,20 +135,19 @@ nativeGetNextSensor(JNIEnv *env, jclass clazz, jobject sensor, jint next)
Sensor const* const* sensorList;
size_t count = mgr.getSensorList(&sensorList);
if (size_t(next) >= count)
if (size_t(next) >= count) {
return -1;
}
Sensor const* const list = sensorList[next];
const SensorOffsets& sensorOffsets(gSensorOffsets);
jstring name = env->NewStringUTF(list->getName().string());
jstring vendor = env->NewStringUTF(list->getVendor().string());
jstring stringType = env->NewStringUTF(list->getStringType().string());
jstring requiredPermission = env->NewStringUTF(list->getRequiredPermission().string());
jstring name = getInternedString(env, &list->getName());
jstring vendor = getInternedString(env, &list->getVendor());
jstring requiredPermission = getInternedString(env, &list->getRequiredPermission());
env->SetObjectField(sensor, sensorOffsets.name, name);
env->SetObjectField(sensor, sensorOffsets.vendor, vendor);
env->SetIntField(sensor, sensorOffsets.version, list->getVersion());
env->SetIntField(sensor, sensorOffsets.handle, list->getHandle());
env->SetIntField(sensor, sensorOffsets.type, list->getType());
env->SetFloatField(sensor, sensorOffsets.range, list->getMaxValue());
env->SetFloatField(sensor, sensorOffsets.resolution, list->getResolution());
env->SetFloatField(sensor, sensorOffsets.power, list->getPowerUsage());
@@ -115,11 +156,14 @@ nativeGetNextSensor(JNIEnv *env, jclass clazz, jobject sensor, jint next)
list->getFifoReservedEventCount());
env->SetIntField(sensor, sensorOffsets.fifoMaxEventCount,
list->getFifoMaxEventCount());
env->SetObjectField(sensor, sensorOffsets.stringType, stringType);
env->SetObjectField(sensor, sensorOffsets.requiredPermission,
requiredPermission);
env->SetIntField(sensor, sensorOffsets.maxDelay, list->getMaxDelay());
env->SetIntField(sensor, sensorOffsets.flags, list->getFlags());
if (env->CallBooleanMethod(sensor, sensorOffsets.setType, list->getType()) == JNI_FALSE) {
jstring stringType = getInternedString(env, &list->getStringType());
env->SetObjectField(sensor, sensorOffsets.stringType, stringType);
}
next++;
return size_t(next) < count ? next : 0;
}