com.fengwenyi.javalib.third.Base64 Maven / Gradle / Ivy
package com.fengwenyi.javalib.third;
/*
* Copyright 1999-2017 Alibaba Group Holding Ltd.
*
* 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.
*/
/**
* Static methods for translating Base64 encoded strings to byte arrays and vice-versa.
*
* @author Josh Bloch
* @version %I%, %G%
* @since 1.4
*/
public class Base64 {
/**
* Translates the specified byte array into a Base64 string as per Preferences.put(byte[]).
* @param a [ellipsis]
* @return [ellipsis]
*/
public static String byteArrayToBase64(byte[] a) {
return byteArrayToBase64(a, false);
}
/**
* Translates the specified byte array into an "alternate representation" Base64 string. This non-standard variant
* uses an alphabet that does not contain the uppercase alphabetic characters, which makes it suitable for use in
* situations where case-folding occurs.
* @param a [ellipsis]
* @return [ellipsis]
*/
public static String byteArrayToAltBase64(byte[] a) {
return byteArrayToBase64(a, true);
}
/**
*
* @param a [ellipsis]
* @param alternate [ellipsis]
* @return [ellipsis]
*/
private static String byteArrayToBase64(byte[] a, boolean alternate) {
int aLen = a.length;
int numFullGroups = aLen / 3;
int numBytesInPartialGroup = aLen - 3 * numFullGroups;
int resultLen = 4 * ((aLen + 2) / 3);
StringBuilder result = new StringBuilder(resultLen);
char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);
// Translate all full groups from byte array elements to Base64
int inCursor = 0;
for (int i = 0; i < numFullGroups; i++) {
int byte0 = a[inCursor++] & 0xff;
int byte1 = a[inCursor++] & 0xff;
int byte2 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 >> 2]);
result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
result.append(intToAlpha[byte2 & 0x3f]);
}
// Translate partial group if present
if (numBytesInPartialGroup != 0) {
int byte0 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 >> 2]);
if (numBytesInPartialGroup == 1) {
result.append(intToAlpha[(byte0 << 4) & 0x3f]);
result.append("==");
} else {
// assert numBytesInPartialGroup == 2;
int byte1 = a[inCursor++] & 0xff;
result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
result.append(intToAlpha[(byte1 << 2) & 0x3f]);
result.append('=');
}
}
// assert inCursor == a.length;
// assert result.length() == resultLen;
return result.toString();
}
/**
* This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
* equivalents as specified in Table 1 of RFC 2045.
*/
private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2',
'3', '4', '5', '6', '7', '8', '9', '+', '/' };
/**
* This array is a lookup table that translates 6-bit positive integer index values into their
* "Alternate Base64 Alphabet" equivalents. This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045. This
* alternate alphabet does not use the capital letters. It is designed for use in environments where "case folding"
* occurs.
*/
private static final char intToAltBase64[] = { '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',
';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2',
'3', '4', '5', '6', '7', '8', '9', '+', '?' };
/**
* Translates the specified Base64 string (as per Preferences.get(byte[])) into a byte array.
* @param s [ellipsis]
* @return [ellipsis]
*/
public static byte[] base64ToByteArray(String s) {
return base64ToByteArray(s, false);
}
/**
* Translates the specified "alternate representation" Base64 string into a byte array.
* @param s [ellipsis]
* @return [ellipsis]
*/
public static byte[] altBase64ToByteArray(String s) {
return base64ToByteArray(s, true);
}
/**
* Translates the specified "alternate representation" Base64 string into a byte array.
* @param s [ellipsis]
* @param alternate [ellipsis]
* @return [ellipsis]
*/
private static byte[] base64ToByteArray(String s, boolean alternate) {
byte[] alphaToInt = (alternate ? altBase64ToInt : base64ToInt);
int sLen = s.length();
int numGroups = sLen / 4;
if (4 * numGroups != sLen) {
throw new IllegalArgumentException("String length must be a multiple of four.");
}
int missingBytesInLastGroup = 0;
int numFullGroups = numGroups;
if (sLen != 0) {
if (s.charAt(sLen - 1) == '=') {
missingBytesInLastGroup++;
numFullGroups--;
}
if (s.charAt(sLen - 2) == '=') {
missingBytesInLastGroup++;
}
}
byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];
// Translate all full groups from base64 to byte array elements
int inCursor = 0, outCursor = 0;
for (int i = 0; i < numFullGroups; i++) {
int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
result[outCursor++] = (byte) ((ch2 << 6) | ch3);
}
// Translate partial group, if present
if (missingBytesInLastGroup != 0) {
int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
if (missingBytesInLastGroup == 1) {
int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
}
}
// assert inCursor == s.length()-missingBytesInLastGroup;
// assert outCursor == result.length;
return result;
}
/**
* Translates the specified character, which is assumed to be in the "Base 64 Alphabet" into its equivalent 6-bit
* positive integer.
*
* @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not in the Base64 Alphabet.
* @param c [ellipsis]
* @param alphaToInt [ellipsis]
* @return [ellipsis]
*/
private static int base64toInt(char c, byte[] alphaToInt) {
int result = alphaToInt[c];
if (result < 0) {
throw new IllegalArgumentException("Illegal character " + c);
}
return result;
}
/**
* This array is a lookup table that translates unicode characters drawn from the "Base64 Alphabet" (as specified in
* Table 1 of RFC 2045) into their 6-bit positive integer equivalents. Characters that are not in the Base64
* alphabet but fall within the bounds of the array are translated to -1.
*/
private static final byte base64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62,
-1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
/**
* This array is the analogue of base64ToInt, but for the nonstandard variant that avoids the use of uppercase
* alphabetic characters.
*/
private static final byte altBase64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10,
11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28,
29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25 };
}
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