BASE641

最新推荐文章于 2025-04-17 08:51:36 发布

转载最新推荐文章于 2025-04-17 08:51:36 发布 · 781 阅读

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本文介绍了一种Base64和Base32解码算法的实现细节，包括解码表、编码表、解码过程等关键组件。通过对不同场景下解码流程的分析，展示了如何处理各种边界情况，例如填充字符和结束标志。

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import java.math.BigInteger;
import java.util.Arrays;
public class SanyiDecode extends SanyiCodec {
private static final int BITS_PER_ENCODED_BYTE = 6;
private static final int BYTES_PER_UNENCODED_BLOCK = 3;
private static final int BYTES_PER_ENCODED_BLOCK = 4;
static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
private static final byte[] STANDARD_ENCODE_TABLE = {
'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', '+', '/'
};
private static final byte[] URL_SAFE_ENCODE_TABLE = {
'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', '-', '_'
};
private static final byte[] DECODE_TABLE = {
-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, 62, -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, 63, -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
};
private static final int MASK_6BITS = 0x3f;
private final byte[] encodeTable;
private final byte[] decodeTable = DECODE_TABLE;
private final byte[] lineSeparator;
private final int decodeSize;
private final int encodeSize;
public SanyiDecode() {
this(0);
}
public SanyiDecode(final boolean urlSafe) {
this(MIME_CHUNK_SIZE, CHUNK_SEPARATOR, urlSafe);
}
public SanyiDecode(final int lineLength) {
this(lineLength, CHUNK_SEPARATOR);
}
public SanyiDecode(final int lineLength, final byte[] lineSeparator) {
this(lineLength, lineSeparator, false);
}
public SanyiDecode(final int lineLength, final byte[] lineSeparator, final boolean urlSafe) {
super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK,
lineLength,
lineSeparator == null ? 0 : lineSeparator.length);
if (lineSeparator != null) {
if (containsAlphabetOrPad(lineSeparator)) {
final String sep = StringUtils.newStringUtf8(lineSeparator);
throw new IllegalArgumentException("lineSeparator must not contain base64 characters: [" + sep + "]");
}
if (lineLength > 0){ // null line-sep forces no chunking rather than throwing IAE
this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
this.lineSeparator = new byte[lineSeparator.length];
System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
} else {
this.encodeSize = BYTES_PER_ENCODED_BLOCK;
this.lineSeparator = null;
}
} else {
this.encodeSize = BYTES_PER_ENCODED_BLOCK;
this.lineSeparator = null;
}
this.decodeSize = this.encodeSize - 1;
this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE;
}
public boolean isUrlSafe() {
return this.encodeTable == URL_SAFE_ENCODE_TABLE;
}
@Override
void decry(final byte[] in, int inPos, final int inAvail, final Context context) {
if (context.eof) {
return;
}
if (inAvail < 0) {
context.eof = true;
}
for (int i = 0; i < inAvail; i++) {
final byte[] buffer = ensureBufferSize(decodeSize, context);
final byte b = in[inPos++];
if (b == pad) {
// We're done.
context.eof = true;
break;
} else {
if (b >= 0 && b < DECODE_TABLE.length) {
final int result = DECODE_TABLE[b];
if (result >= 0) {
context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
context.ibitWorkArea = (context.ibitWorkArea << BITS_PER_ENCODED_BYTE) + result;
if (context.modulus == 0) {
buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) (context.ibitWorkArea & MASK_8BITS);
}
}
}
}
}
if (context.eof && context.modulus != 0) {
final byte[] buffer = ensureBufferSize(decodeSize, context);
switch (context.modulus) {
// case 0 : // impossible, as excluded above
case 1 : // 6 bits - ignore entirely
// TODO not currently tested; perhaps it is impossible?
break;
case 2 : // 12 bits = 8 + 4
context.ibitWorkArea = context.ibitWorkArea >> 4; // dump the extra 4 bits
buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
break;
case 3 : // 18 bits = 8 + 8 + 2
context.ibitWorkArea = context.ibitWorkArea >> 2; // dump 2 bits
buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
break;
default:
throw new IllegalStateException("Impossible modulus "+context.modulus);
}
}
}
public static byte[] decryData(final String dataString) {
return new SanyiDecode().decode(dataString);
}
public static byte[] decryData(final byte[] data) {
return new SanyiDecode().decode(data);
}
public static BigInteger decryInteger(final byte[] pArray) {
return new BigInteger(1, decryData(pArray));
}
@Override
protected boolean isInAlphabet(final byte octet) {
return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
}
}
abstract class SanyiCodec {
static class Context {
int ibitWorkArea;
long lbitWorkArea;
byte[] buffer;
int pos;
int readPos;
boolean eof;
int currentLinePos;
int modulus;
Context() {
}
@SuppressWarnings("boxing") // OK to ignore boxing here
@Override
public String toString() {
return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
"modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
}
}
static final int EOF = -1;
public static final int MIME_CHUNK_SIZE = 76;
public static final int PEM_CHUNK_SIZE = 64;
private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
private static final int DEFAULT_BUFFER_SIZE = 8192;
protected static final int MASK_8BITS = 0xff;
protected static final byte PAD_DEFAULT = '='; // Allow static access to default
@Deprecated
protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
protected final byte pad; // instance variable just in case it needs to vary later
private final int unencodedBlockSize;
private final int encodedBlockSize;
protected final int lineLength;
private final int chunkSeparatorLength;
protected SanyiCodec(final int unencodedBlockSize, final int encodedBlockSize,
final int lineLength, final int chunkSeparatorLength) {
this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
}
protected SanyiCodec(final int unencodedBlockSize, final int encodedBlockSize,
final int lineLength, final int chunkSeparatorLength, final byte pad) {
this.unencodedBlockSize = unencodedBlockSize;
this.encodedBlockSize = encodedBlockSize;
final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
this.chunkSeparatorLength = chunkSeparatorLength;
this.pad = pad;
}
boolean hasData(final Context context) { // package protected for access from I/O streams
return context.buffer != null;
}
int available(final Context context) { // package protected for access from I/O streams
return context.buffer != null ? context.pos - context.readPos : 0;
}
protected int getDefaultBufferSize() {
return DEFAULT_BUFFER_SIZE;
}
private byte[] resizeBuffer(final Context context) {
if (context.buffer == null) {
context.buffer = new byte[getDefaultBufferSize()];
context.pos = 0;
context.readPos = 0;
} else {
final byte[] b = new byte[context.buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
context.buffer = b;
}
return context.buffer;
}
protected byte[] ensureBufferSize(final int size, final Context context){
if ((context.buffer == null) || (context.buffer.length < context.pos + size)){
return resizeBuffer(context);
}
return context.buffer;
}
int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
if (context.buffer != null) {
final int len = Math.min(available(context), bAvail);
System.arraycopy(context.buffer, context.readPos, b, bPos, len);
context.readPos += len;
if (context.readPos >= context.pos) {
context.buffer = null; // so hasData() will return false, and this method can return -1
}
return len;
}
return context.eof ? EOF : 0;
}
protected static boolean isWhiteSpace(final byte byteToCheck) {
switch (byteToCheck) {
case ' ' :
case '\n' :
case '\r' :
case '\t' :
return true;
default :
return false;
}
}
public Object decode(final Object obj) throws SanyiDecoderException {
if (obj instanceof byte[]) {
return decode((byte[]) obj);
} else if (obj instanceof String) {
return decode((String) obj);
} else {
throw new SanyiDecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
}
}
public byte[] decode(final String pArray) {
return decode(StringUtils.getBytesUtf8(pArray));
}
public byte[] decode(final byte[] pArray) {
if (pArray == null || pArray.length == 0) {
return pArray;
}
final Context context = new Context();
decry(pArray, 0, pArray.length, context);
decry(pArray, 0, EOF, context); // Notify decoder of EOF.
final byte[] result = new byte[context.pos];
readResults(result, 0, result.length, context);
return result;
}
abstract void decry(byte[] pArray, int i, int length, Context context);
protected abstract boolean isInAlphabet(byte value);
public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
for (int i = 0; i < arrayOctet.length; i++) {
if (!isInAlphabet(arrayOctet[i]) &&
(!allowWSPad || (arrayOctet[i] != pad) && !isWhiteSpace(arrayOctet[i]))) {
return false;
}
}
return true;
}
public boolean isInAlphabet(final String basen) {
return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
}
protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
if (arrayOctet == null) {
return false;
}
for (final byte element : arrayOctet) {
if (pad == element || isInAlphabet(element)) {
return true;
}
}
return false;
}
public long getEncodedLength(final byte[] pArray) {
long len = ((pArray.length + unencodedBlockSize-1) / unencodedBlockSize) * (long) encodedBlockSize;
if (lineLength > 0) { // We're using chunking
len += ((len + lineLength-1) / lineLength) * chunkSeparatorLength;
}
return len;
}
}
class SanyiDecoderException extends Exception {
private static final long serialVersionUID = 1L;
public SanyiDecoderException() {
super();
}
public SanyiDecoderException(String message) {
super(message);
}
public SanyiDecoderException(String message, Throwable cause) {
super(message, cause);
}
public SanyiDecoderException(Throwable cause) {
super(cause);
}
}
class SanyiCode32 extends SanyiCodec {
private static final int BITS_PER_ENCODED_BYTE = 5;
private static final int BYTES_PER_ENCODED_BLOCK = 8;
private static final int BYTES_PER_UNENCODED_BLOCK = 5;
private static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
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, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, // 30-3f 2-7
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, // 40-4f A-N
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // 50-5a O-Z
};
private static final byte[] ENCODE_TABLE = {
'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',
'2', '3', '4', '5', '6', '7',
};
private static final byte[] HEX_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
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, // 30-3f 2-7
-1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 40-4f A-N
25, 26, 27, 28, 29, 30, 31, 32, // 50-57 O-V
};
private static final byte[] HEX_ENCODE_TABLE = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
};
private static final int MASK_5BITS = 0x1f;
private final int decodeSize;
private final byte[] decodeTable;
private final int encodeSize;
private final byte[] encodeTable;
private final byte[] lineSeparator;
public SanyiCode32() {
this(false);
}
public SanyiCode32(final byte pad) {
this(false, pad);
}
public SanyiCode32(final boolean useHex) {
this(0, null, useHex, PAD_DEFAULT);
}
public SanyiCode32(final boolean useHex, final byte pad) {
this(0, null, useHex, pad);
}
public SanyiCode32(final int lineLength) {
this(lineLength, CHUNK_SEPARATOR);
}
public SanyiCode32(final int lineLength, final byte[] lineSeparator) {
this(lineLength, lineSeparator, false, PAD_DEFAULT);
}
public SanyiCode32(final int lineLength, final byte[] lineSeparator, final boolean useHex) {
this(lineLength, lineSeparator, useHex, PAD_DEFAULT);
}
public SanyiCode32(final int lineLength, final byte[] lineSeparator, final boolean useHex, final byte pad) {
super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, lineLength,
lineSeparator == null ? 0 : lineSeparator.length, pad);
if (useHex) {
this.encodeTable = HEX_ENCODE_TABLE;
this.decodeTable = HEX_DECODE_TABLE;
} else {
this.encodeTable = ENCODE_TABLE;
this.decodeTable = DECODE_TABLE;
}
if (lineLength > 0) {
if (lineSeparator == null) {
throw new IllegalArgumentException("lineLength " + lineLength + " > 0, but lineSeparator is null");
}
// Must be done after initializing the tables
if (containsAlphabetOrPad(lineSeparator)) {
final String sep = StringUtils.newStringUtf8(lineSeparator);
throw new IllegalArgumentException("lineSeparator must not contain Base32 characters: [" + sep + "]");
}
this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
this.lineSeparator = new byte[lineSeparator.length];
System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
} else {
this.encodeSize = BYTES_PER_ENCODED_BLOCK;
this.lineSeparator = null;
}
this.decodeSize = this.encodeSize - 1;
if (isInAlphabet(pad) || isWhiteSpace(pad)) {
throw new IllegalArgumentException("pad must not be in alphabet or whitespace");
}
}
@Override
void decry(final byte[] in, int inPos, final int inAvail, final Context context) {
// package protected for access from I/O streams
if (context.eof) {
return;
}
if (inAvail < 0) {
context.eof = true;
}
for (int i = 0; i < inAvail; i++) {
final byte b = in[inPos++];
if (b == pad) {
// We're done.
context.eof = true;
break;
} else {
final byte[] buffer = ensureBufferSize(decodeSize, context);
if (b >= 0 && b < this.decodeTable.length) {
final int result = this.decodeTable[b];
if (result >= 0) {
context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
// collect decoded bytes
context.lbitWorkArea = (context.lbitWorkArea << BITS_PER_ENCODED_BYTE) + result;
if (context.modulus == 0) { // we can output the 5 bytes
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 32) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 24) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
}
}
}
}
}
if (context.eof && context.modulus >= 2) { // if modulus < 2, nothing to do
final byte[] buffer = ensureBufferSize(decodeSize, context);
// we ignore partial bytes, i.e. only multiples of 8 count
switch (context.modulus) {
case 2 : // 10 bits, drop 2 and output one byte
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 2) & MASK_8BITS);
break;
case 3 : // 15 bits, drop 7 and output 1 byte
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 7) & MASK_8BITS);
break;
case 4 : // 20 bits = 2*8 + 4
context.lbitWorkArea = context.lbitWorkArea >> 4; // drop 4 bits
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
case 5 : // 25bits = 3*8 + 1
context.lbitWorkArea = context.lbitWorkArea >> 1;
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
case 6 : // 30bits = 3*8 + 6
context.lbitWorkArea = context.lbitWorkArea >> 6;
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
case 7 : // 35 = 4*8 +3
context.lbitWorkArea = context.lbitWorkArea >> 3;
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 24) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
default:
// modulus can be 0-7, and we excluded 0,1 already
throw new IllegalStateException("Impossible modulus "+context.modulus);
}
}
}
@Override
public boolean isInAlphabet(final byte octet) {
return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
}
}
class SanyiCode64 extends SanyiCodec {
private static final int BITS_PER_ENCODED_BYTE = 6;
private static final int BYTES_PER_UNENCODED_BLOCK = 3;
private static final int BYTES_PER_ENCODED_BLOCK = 4;
static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
private static final byte[] STANDARD_ENCODE_TABLE = {
'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', '+', '/'
};
private static final byte[] URL_SAFE_ENCODE_TABLE = {
'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', '-', '_'
};
private static final byte[] DECODE_TABLE = {
-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, 62, -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, 63, -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
};
private static final int MASK_6BITS = 0x3f;
private final byte[] encodeTable;
private final byte[] decodeTable = DECODE_TABLE;
private final byte[] lineSeparator;
private final int decodeSize;
private final int encodeSize;
public SanyiCode64() {
this(0);
}
public SanyiCode64(final boolean urlSafe) {
this(MIME_CHUNK_SIZE, CHUNK_SEPARATOR, urlSafe);
}
public SanyiCode64(final int lineLength) {
this(lineLength, CHUNK_SEPARATOR);
}
public SanyiCode64(final int lineLength, final byte[] lineSeparator) {
this(lineLength, lineSeparator, false);
}
public SanyiCode64(final int lineLength, final byte[] lineSeparator, final boolean urlSafe) {
super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK,
lineLength,
lineSeparator == null ? 0 : lineSeparator.length);
// TODO could be simplified if there is no requirement to reject invalid line sep when length <=0
// @see test case Base64Test.testConstructors()
if (lineSeparator != null) {
if (containsAlphabetOrPad(lineSeparator)) {
final String sep = StringUtils.newStringUtf8(lineSeparator);
throw new IllegalArgumentException("lineSeparator must not contain base64 characters: [" + sep + "]");
}
if (lineLength > 0){ // null line-sep forces no chunking rather than throwing IAE
this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
this.lineSeparator = new byte[lineSeparator.length];
System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
} else {
this.encodeSize = BYTES_PER_ENCODED_BLOCK;
this.lineSeparator = null;
}
} else {
this.encodeSize = BYTES_PER_ENCODED_BLOCK;
this.lineSeparator = null;
}
this.decodeSize = this.encodeSize - 1;
this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE;
}
public boolean isUrlSafe() {
return this.encodeTable == URL_SAFE_ENCODE_TABLE;
}
@Override
void decry(final byte[] in, int inPos, final int inAvail, final Context context) {
if (context.eof) {
return;
}
if (inAvail < 0) {
context.eof = true;
}
for (int i = 0; i < inAvail; i++) {
final byte[] buffer = ensureBufferSize(decodeSize, context);
final byte b = in[inPos++];
if (b == pad) {
// We're done.
context.eof = true;
break;
} else {
if (b >= 0 && b < DECODE_TABLE.length) {
final int result = DECODE_TABLE[b];
if (result >= 0) {
context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
context.ibitWorkArea = (context.ibitWorkArea << BITS_PER_ENCODED_BYTE) + result;
if (context.modulus == 0) {
buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) (context.ibitWorkArea & MASK_8BITS);
}
}
}
}
}
// Two forms of EOF as far as base64 decoder is concerned: actual
// EOF (-1) and first time '=' character is encountered in stream.
// This approach makes the '=' padding characters completely optional.
if (context.eof && context.modulus != 0) {
final byte[] buffer = ensureBufferSize(decodeSize, context);
// We have some spare bits remaining
// Output all whole multiples of 8 bits and ignore the rest
switch (context.modulus) {
// case 0 : // impossible, as excluded above
case 1 : // 6 bits - ignore entirely
// TODO not currently tested; perhaps it is impossible?
break;
case 2 : // 12 bits = 8 + 4
context.ibitWorkArea = context.ibitWorkArea >> 4; // dump the extra 4 bits
buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
break;
case 3 : // 18 bits = 8 + 8 + 2
context.ibitWorkArea = context.ibitWorkArea >> 2; // dump 2 bits
buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
break;
default:
throw new IllegalStateException("Impossible modulus "+context.modulus);
}
}
}
@Deprecated
public static boolean isArrayByteBase64(final byte[] arrayOctet) {
return isCode(arrayOctet);
}
public static boolean isCode(final byte octet) {
return octet == PAD_DEFAULT || (octet >= 0 && octet < DECODE_TABLE.length && DECODE_TABLE[octet] != -1);
}
public static boolean isCode(final String base64) {
return isCode(StringUtils.getBytesUtf8(base64));
}
public static boolean isCode(final byte[] arrayOctet) {
for (int i = 0; i < arrayOctet.length; i++) {
if (!isCode(arrayOctet[i]) && !isWhiteSpace(arrayOctet[i])) {
return false;
}
}
return true;
}
public static byte[] decryData(final String dataring) {
return new SanyiCode64().decode(dataring);
}
public static byte[] decryData(final byte[] data) {
return new SanyiCode64().decode(data);
}
public static BigInteger decryInteger(final byte[] pArray) {
return new BigInteger(1, decryData(pArray));
}
static byte[] toIntegerBytes(final BigInteger bigInt) {
int bitlen = bigInt.bitLength();
// round bitlen
bitlen = ((bitlen + 7) >> 3) << 3;
final byte[] bigBytes = bigInt.toByteArray();
if (((bigInt.bitLength() % 8) != 0) && (((bigInt.bitLength() / 8) + 1) == (bitlen / 8))) {
return bigBytes;
}
// set up params for copying everything but sign bit
int startSrc = 0;
int len = bigBytes.length;
// if bigInt is exactly byte-aligned, just skip signbit in copy
if ((bigInt.bitLength() % 8) == 0) {
startSrc = 1;
len--;
}
final int startDst = bitlen / 8 - len; // to pad w/ nulls as per spec
final byte[] resizedBytes = new byte[bitlen / 8];
System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, len);
return resizedBytes;
}
@Override
protected boolean isInAlphabet(final byte octet) {
return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
}
}