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| 1 | +/* |
| 2 | + * Copyright 2026 Google LLC |
| 3 | + * |
| 4 | + * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | + * you may not use this file except in compliance with the License. |
| 6 | + * You may obtain a copy of the License at |
| 7 | + * |
| 8 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | + * |
| 10 | + * Unless required by applicable law or agreed to in writing, software |
| 11 | + * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | + * See the License for the specific language governing permissions and |
| 14 | + * limitations under the License. |
| 15 | + */ |
| 16 | + |
| 17 | +package com.google.cloud.spanner.spi.v1; |
| 18 | + |
| 19 | +import com.google.api.core.InternalApi; |
| 20 | +import java.util.Arrays; |
| 21 | + |
| 22 | +/** |
| 23 | + * A simple, unsynchronized byte array output stream optimized for ssformat key encoding. |
| 24 | + * |
| 25 | + * <p>Unlike {@link java.io.ByteArrayOutputStream}, this class is not thread-safe and does not incur |
| 26 | + * synchronization overhead. This provides better performance for single-threaded key encoding |
| 27 | + * operations in the SpanFE bypass hot path. |
| 28 | + * |
| 29 | + * <p>This class is not intended for general use and should only be used within the ssformat |
| 30 | + * encoding implementation. |
| 31 | + */ |
| 32 | +@InternalApi |
| 33 | +public final class GrowableByteArrayOutputStream { |
| 34 | + |
| 35 | + private byte[] buf; |
| 36 | + private int count; |
| 37 | + |
| 38 | + /** Creates a new output stream with a default initial capacity of 32 bytes. */ |
| 39 | + public GrowableByteArrayOutputStream() { |
| 40 | + this(32); |
| 41 | + } |
| 42 | + |
| 43 | + /** |
| 44 | + * Creates a new output stream with the specified initial capacity. |
| 45 | + * |
| 46 | + * @param initialCapacity the initial buffer size |
| 47 | + * @throws IllegalArgumentException if initialCapacity is negative |
| 48 | + */ |
| 49 | + public GrowableByteArrayOutputStream(int initialCapacity) { |
| 50 | + if (initialCapacity < 0) { |
| 51 | + throw new IllegalArgumentException("Negative initial capacity: " + initialCapacity); |
| 52 | + } |
| 53 | + this.buf = new byte[initialCapacity]; |
| 54 | + } |
| 55 | + |
| 56 | + private void ensureCapacity(int minCapacity) { |
| 57 | + if (minCapacity > buf.length) { |
| 58 | + int newCapacity = Math.max(buf.length << 1, minCapacity); |
| 59 | + buf = Arrays.copyOf(buf, newCapacity); |
| 60 | + } |
| 61 | + } |
| 62 | + |
| 63 | + /** |
| 64 | + * Writes the specified byte to this output stream. |
| 65 | + * |
| 66 | + * @param b the byte to write (only the low 8 bits are used) |
| 67 | + */ |
| 68 | + public void write(int b) { |
| 69 | + ensureCapacity(count + 1); |
| 70 | + buf[count++] = (byte) b; |
| 71 | + } |
| 72 | + |
| 73 | + /** |
| 74 | + * Writes a portion of a byte array to this output stream. |
| 75 | + * |
| 76 | + * @param b the source byte array |
| 77 | + * @param off the start offset in the array |
| 78 | + * @param len the number of bytes to write |
| 79 | + */ |
| 80 | + public void write(byte[] b, int off, int len) { |
| 81 | + ensureCapacity(count + len); |
| 82 | + System.arraycopy(b, off, buf, count, len); |
| 83 | + count += len; |
| 84 | + } |
| 85 | + |
| 86 | + /** |
| 87 | + * Returns a copy of the buffer contents as a new byte array. |
| 88 | + * |
| 89 | + * @return a new byte array containing the written bytes |
| 90 | + */ |
| 91 | + public byte[] toByteArray() { |
| 92 | + return Arrays.copyOf(buf, count); |
| 93 | + } |
| 94 | + |
| 95 | + /** Resets the buffer so that it can be reused. The underlying buffer is retained. */ |
| 96 | + public void reset() { |
| 97 | + count = 0; |
| 98 | + } |
| 99 | + |
| 100 | + /** |
| 101 | + * Returns the current number of bytes written to this stream. |
| 102 | + * |
| 103 | + * @return the number of valid bytes in the buffer |
| 104 | + */ |
| 105 | + public int size() { |
| 106 | + return count; |
| 107 | + } |
| 108 | +} |
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