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/*
* Copyright (C) 2022 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 com.android.net.module.util;
import android.system.ErrnoException;
import androidx.annotation.NonNull;
/**
*
* Generic bitmap class for use with BPF programs. Corresponds to a BpfMap
* array type with key->int and value->uint64_t defined in the bpf program.
*
*/
public class BpfBitmap {
private BpfMap<Struct.S32, Struct.S64> mBpfMap;
/**
* Create a BpfBitmap map wrapper with "path" of filesystem.
*
* @param path The path of the BPF map.
*/
public BpfBitmap(@NonNull String path) throws ErrnoException {
mBpfMap = new BpfMap<Struct.S32, Struct.S64>(path, BpfMap.BPF_F_RDWR,
Struct.S32.class, Struct.S64.class);
}
/**
* Retrieves the value from BpfMap for the given key.
*
* @param key The key in the map corresponding to the value to return.
*/
private long getBpfMapValue(Struct.S32 key) throws ErrnoException {
Struct.S64 curVal = mBpfMap.getValue(key);
if (curVal != null) {
return curVal.val;
} else {
return 0;
}
}
/**
* Retrieves the bit for the given index in the bitmap.
*
* @param index Position in bitmap.
*/
public boolean get(int index) throws ErrnoException {
if (index < 0) return false;
Struct.S32 key = new Struct.S32(index >> 6);
return ((getBpfMapValue(key) >>> (index & 63)) & 1L) != 0;
}
/**
* Set the specified index in the bitmap.
*
* @param index Position to set in bitmap.
*/
public void set(int index) throws ErrnoException {
set(index, true);
}
/**
* Unset the specified index in the bitmap.
*
* @param index Position to unset in bitmap.
*/
public void unset(int index) throws ErrnoException {
set(index, false);
}
/**
* Change the specified index in the bitmap to set value.
*
* @param index Position to unset in bitmap.
* @param set Boolean indicating to set or unset index.
*/
public void set(int index, boolean set) throws ErrnoException {
if (index < 0) throw new IllegalArgumentException("Index out of bounds.");
Struct.S32 key = new Struct.S32(index >> 6);
long mask = (1L << (index & 63));
long val = getBpfMapValue(key);
if (set) val |= mask; else val &= ~mask;
mBpfMap.updateEntry(key, new Struct.S64(val));
}
/**
* Clears the map. The map may already be empty.
*
* @throws ErrnoException if updating entry to 0 fails.
*/
public void clear() throws ErrnoException {
mBpfMap.forEach((key, value) -> {
mBpfMap.updateEntry(key, new Struct.S64(0));
});
}
/**
* Checks if all bitmap values are 0.
*/
public boolean isEmpty() throws ErrnoException {
Struct.S32 key = mBpfMap.getFirstKey();
while (key != null) {
if (getBpfMapValue(key) != 0) {
return false;
}
key = mBpfMap.getNextKey(key);
}
return true;
}
}
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