50 lines
1.5 KiB
Java
50 lines
1.5 KiB
Java
package org.thoughtcrime.securesms.util;
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import androidx.annotation.NonNull;
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import org.thoughtcrime.securesms.recipients.Recipient;
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import java.math.BigInteger;
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import java.nio.ByteBuffer;
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import java.nio.ByteOrder;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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import java.util.Arrays;
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import java.util.UUID;
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/**
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* Logic to bucket a user for a given feature flag based on their UUID.
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*/
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public final class BucketingUtil {
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private BucketingUtil() {}
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/**
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* Calculate a user bucket for a given feature flag, uuid, and part per modulus.
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*
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* @param key Feature flag key (e.g., "research.megaphone.1")
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* @param uuid Current user's UUID (see {@link Recipient#getUuid()})
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* @param modulus Drives the bucketing parts per N (e.g., passing 1,000,000 indicates bucketing into parts per million)
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*/
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public static long bucket(@NonNull String key, @NonNull UUID uuid, long modulus) {
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MessageDigest digest;
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try {
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digest = MessageDigest.getInstance("SHA-256");
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} catch (NoSuchAlgorithmException e) {
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throw new AssertionError(e);
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}
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digest.update(key.getBytes());
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digest.update(".".getBytes());
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ByteBuffer byteBuffer = ByteBuffer.wrap(new byte[16]);
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byteBuffer.order(ByteOrder.BIG_ENDIAN);
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byteBuffer.putLong(uuid.getMostSignificantBits());
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byteBuffer.putLong(uuid.getLeastSignificantBits());
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digest.update(byteBuffer.array());
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return new BigInteger(Arrays.copyOfRange(digest.digest(), 0, 8)).mod(BigInteger.valueOf(modulus)).longValue();
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}
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}
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