fadedblack commented on code in PR #422: URL: https://github.com/apache/commons-codec/pull/422#discussion_r2762337497
########## src/main/java/org/apache/commons/codec/binary/Base58.java: ########## @@ -0,0 +1,328 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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 + * + * https://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 org.apache.commons.codec.binary; + +import java.math.BigInteger; +import java.nio.charset.StandardCharsets; +import java.util.Map; +import java.util.WeakHashMap; + +/** + * Provides Base58 encoding and decoding as commonly used in cryptocurrency and blockchain applications. + * <p> + * Base58 is a binary-to-text encoding scheme that uses a 58-character alphabet to encode data. It avoids + * characters that can be confused (0/O, I/l, +/) and is commonly used in Bitcoin and other blockchain systems. + * </p> + * <p> + * This implementation accumulates data internally until EOF is signaled, at which point the entire input is + * converted using BigInteger arithmetic. This is necessary because Base58 encoding/decoding requires access + * to the complete data to properly handle leading zeros. + * </p> + * <p> + * This class is thread-safe for read operations but the Context object used during encoding/decoding should + * not be shared between threads. + * </p> + * <p> + * The Base58 alphabet is: 123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz + * (excludes: 0, I, O, l) + * </p> + * + * @see Base58InputStream + * @see Base58OutputStream + * @since 1.15 + */ +public class Base58 extends BaseNCodec { + + /** + * Base58 alphabet: 123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz + * (excludes: 0, I, O, l) + */ + private static final byte[] ENCODE_TABLE = { + '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', + 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', + 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm', 'n', 'o', 'p', 'q', 'r', 's', + 't', 'u', 'v', 'w', 'x', 'y', 'z' + }; + /** + * This array is a lookup table that translates Unicode characters drawn from the "Base58 Alphabet" + * into their numeric equivalents (0-57). Characters that are not in the Base58 alphabet are marked + * with -1. + */ + private static final byte[] DECODE_TABLE = { + // 0 1 2 3 4 5 6 7 8 9 A B C D E F + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f + -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, -1, -1, -1, -1, -1, // 30-3f '1'-'9' -> 0-8 + -1, 9, 10, 11, 12, 13, 14, 15, 16, -1, 17, 18, 19, 20, 21, -1, // 40-4f 'A'-'N', 'P'-'Z' (skip 'I' and 'O') + 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, // 50-5a 'P'-'Z' + -1, -1, -1, -1, -1, // 5b-5f + -1, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, -1, 44, 45, 46, // 60-6f 'a'-'k', 'm'-'o' (skip 'l') + 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, // 70-7a 'p'-'z' + }; + private final transient Map<Context, byte[]> accumulated = new WeakHashMap<>(); + + /** + * Constructs a Base58 codec used for encoding and decoding. + */ + public Base58() { + this(new Builder()); + } + + /** + * Constructs a Base58 codec used for encoding and decoding with custom configuration. + * + * @param builder the builder with custom configuration + */ + public Base58(final Builder builder) { + super(builder); + } + + /** + * Decodes the given Base58 encoded data. + * <p> + * This implementation accumulates data internally. When length < 0 (EOF), the accumulated + * data is converted from Base58 to binary. + * </p> + * + * @param array the byte array containing Base58 encoded data + * @param offset the offset in the array to start from + * @param length the number of bytes to decode, or negative to signal EOF + * @param context the context for this decoding operation + */ + @Override + void decode(byte[] array, int offset, int length, Context context) { + if (context.eof) { + return; + } + + if (length < 0) { + context.eof = true; + final byte[] accumulate = accumulated.getOrDefault(context, new byte[0]); + if (accumulate.length > 0) { + convertFromBase58(accumulate, context); + } + accumulated.remove(context); + return; + } + + final byte[] accumulate = accumulated.getOrDefault(context, new byte[0]); + final byte[] newAccumulated = new byte[accumulate.length + length]; + if (accumulate.length > 0) { + System.arraycopy(accumulate, 0, newAccumulated, 0, accumulate.length); + } + System.arraycopy(array, offset, newAccumulated, accumulate.length, length); + accumulated.put(context, newAccumulated); + } + + /** + * Encodes the given binary data as Base58. + * <p> + * This implementation accumulates data internally. When length < 0 (EOF), the accumulated + * data is converted to Base58. + * </p> + * + * @param array the byte array containing binary data to encode + * @param offset the offset in the array to start from + * @param length the number of bytes to encode, or negative to signal EOF + * @param context the context for this encoding operation + */ + @Override + void encode(byte[] array, int offset, int length, Context context) { + if (context.eof) { + return; + } + + if (length < 0) { + context.eof = true; + final byte[] accumulate = accumulated.getOrDefault(context, new byte[0]); + convertToBase58(accumulate, context); + accumulated.remove(context); + return; + } + + final byte[] accumulate = accumulated.getOrDefault(context, new byte[0]); + final byte[] newAccumulated = new byte[accumulate.length + length]; + if (accumulate.length > 0) { + System.arraycopy(accumulate, 0, newAccumulated, 0, accumulate.length); + } + System.arraycopy(array, offset, newAccumulated, accumulate.length, length); + accumulated.put(context, newAccumulated); + } + + /** + * Converts accumulated binary data to Base58 encoding. + * <p> + * Uses BigInteger arithmetic to convert the binary data to Base58. Leading zeros in the + * binary data are represented as '1' characters in the Base58 encoding. + * </p> + * + * @param accumulate the binary data to encode + * @param context the context for this encoding operation + * @return the buffer containing the encoded data + */ + private byte[] convertToBase58(byte[] accumulate, Context context) { + final StringBuilder base58 = getStringBuilder(accumulate); + final String encoded = base58.reverse().toString(); + + final byte[] encodedBytes = encoded.getBytes(StandardCharsets.UTF_8); + final byte[] buffer = ensureBufferSize(encodedBytes.length, context); + System.arraycopy(encodedBytes, 0, buffer, context.pos, encodedBytes.length); + context.pos += encodedBytes.length; + return buffer; + } + + /** + * Builds the Base58 string representation of the given binary data. + * <p> + * Converts binary data to a BigInteger and divides by 58 repeatedly to get the Base58 digits. + * Handles leading zeros by counting them and appending '1' for each leading zero byte. + * </p> + * + * @param accumulate the binary data to convert + * @return a StringBuilder with the Base58 representation (not yet reversed) + */ + private StringBuilder getStringBuilder(byte[] accumulate) { + BigInteger value = new BigInteger(1, accumulate); + int leadingZeros = 0; + + for (byte b : accumulate) { + if (b == 0) { + leadingZeros++; + } else { + break; + } + } + + final StringBuilder base58 = new StringBuilder(); + while (value.signum() > 0) { + final BigInteger[] divRem = value.divideAndRemainder(BigInteger.valueOf(58)); + base58.append((char) ENCODE_TABLE[divRem[1].intValue()]); + value = divRem[0]; + } + + for (int i = 0; i < leadingZeros; i++) { + base58.append('1'); + } + return base58; + } + + /** + * Converts Base58 encoded data to binary. + * <p> + * Uses BigInteger arithmetic to convert the Base58 string to binary data. Leading '1' characters + * in the Base58 encoding represent leading zero bytes in the binary data. + * </p> + * + * @param base58Data the Base58 encoded data + * @param context the context for this decoding operation + * @throws IllegalArgumentException if the Base58 data contains invalid characters + */ + private void convertFromBase58(byte[] base58Data, Context context) { + BigInteger value = BigInteger.ZERO; + int leadingOnes = 0; + + for (byte b : base58Data) { + if (b == '1') { + leadingOnes++; + } else { + break; + } + } + + final BigInteger base = BigInteger.valueOf(58); + BigInteger power = BigInteger.ONE; + + for (int i = base58Data.length - 1; i >= leadingOnes; i--) { + final byte b = base58Data[i]; + final int digit = b < DECODE_TABLE.length ? DECODE_TABLE[b] : -1; + + if (digit < 0) { + throw new IllegalArgumentException("Invalid character in Base58 string: " + (char) b); + } + + value = value.add(BigInteger.valueOf(digit).multiply(power)); + power = power.multiply(base); + } + + byte[] decoded = value.toByteArray(); + + if (decoded.length > 1 && decoded[0] == 0) { + final byte[] tmp = new byte[decoded.length - 1]; + System.arraycopy(decoded, 1, tmp, 0, tmp.length); + decoded = tmp; + } + + final byte[] result = new byte[leadingOnes + decoded.length]; + System.arraycopy(decoded, 0, result, leadingOnes, decoded.length); + + final byte[] buffer = ensureBufferSize(result.length, context); + System.arraycopy(result, 0, buffer, context.pos, result.length); + context.pos += result.length; + } + + /** + * Returns whether or not the {@code octet} is in the Base58 alphabet. + * + * @param value The value to test. + * @return {@code true} if the value is defined in the Base58 alphabet {@code false} otherwise. + */ + @Override + protected boolean isInAlphabet(byte value) { + return value >= 0 && value < DECODE_TABLE.length && DECODE_TABLE[value] != -1; + } + + /** + * Builds {@link Base58} instances with custom configuration. + * + * @since 1.20.0 + */ + public static class Builder extends AbstractBuilder<Base58, Base58.Builder> { + + /** + * Constructs a new Base58 builder. + */ + public Builder() { + super(ENCODE_TABLE); + setDecodeTable(DECODE_TABLE); + setEncodeTable(ENCODE_TABLE); + } + + /** + * Builds a new Base58 instance with the configured settings. + * + * @return a new Base58 codec + */ + @Override + public Base58 get() { + return new Base58(this); + } + + /** + * Creates a new Base58 codec instance. + * + * @return a new Base58 codec + */ + @Override + public Base58.Builder setEncodeTable(final byte... encodeTable) { Review Comment: Hey, yeah I missed it. Fixed it in this commit -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
