public class Base64 
{
private static final char[] S_BASE64CHAR = {
'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 char S_BASE64PAD = '=';
private static final byte[] S_DECODETABLE = new byte[128];
static {
for (int i = 0; i < S_DECODETABLE.length; i ++)
S_DECODETABLE[i] = Byte.MAX_VALUE; // 127
for (int i = 0; i < S_BASE64CHAR.length; i ++) // 0 to 63
S_DECODETABLE[S_BASE64CHAR[i]] = (byte)i;
}
private static int decode0(char[] ibuf, byte[] obuf, int wp) {
int outlen = 3;
if (ibuf[3] == S_BASE64PAD) outlen = 2;
if (ibuf[2] == S_BASE64PAD) outlen = 1;
int b0 = S_DECODETABLE[ibuf[0]];
int b1 = S_DECODETABLE[ibuf[1]];
int b2 = S_DECODETABLE[ibuf[2]];
int b3 = S_DECODETABLE[ibuf[3]];
switch (outlen) {
case 1:
obuf[wp] = (byte)(b0 << 2 & 0xfc | b1 >> 4 & 0x3);
return 1;
case 2:
obuf[wp++] = (byte)(b0 << 2 & 0xfc | b1 >> 4 & 0x3);
obuf[wp] = (byte)(b1 << 4 & 0xf0 | b2 >> 2 & 0xf);
return 2;
case 3:
obuf[wp++] = (byte)(b0 << 2 & 0xfc | b1 >> 4 & 0x3);
obuf[wp++] = (byte)(b1 << 4 & 0xf0 | b2 >> 2 & 0xf);
obuf[wp] = (byte)(b2 << 6 & 0xc0 | b3 & 0x3f);
return 3;
default:
throw new RuntimeException("Internal Errror");
}
}
/** *//**
* Decode the base64 data.
* @param data The base64 encoded data to be decoded
* @param off The offset within the encoded data at which to start decoding
* @param len The length of data to decode
* @return The decoded data
*/
public static byte[] decode(char[] data, int off, int len) {
char[] ibuf = new char[4];
int ibufcount = 0;
byte[] obuf = new byte[len/4*3+3];
int obufcount = 0;
for (int i = off; i < off+len; i ++) {
char ch = data[i];
if (ch == S_BASE64PAD
|| ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
ibuf[ibufcount++] = ch;
if (ibufcount == ibuf.length) {
ibufcount = 0;
obufcount += decode0(ibuf, obuf, obufcount);
}
}
}
if (obufcount == obuf.length)
return obuf;
byte[] ret = new byte[obufcount];
System.arraycopy(obuf, 0, ret, 0, obufcount);
return ret;
}
/** *//**
* Decode the base64 data.
* @param data The base64 encoded data to be decoded
* @return The decoded data
*/
public static byte[] decode(String data) {
char[] ibuf = new char[4];
int ibufcount = 0;
byte[] obuf = new byte[data.length()/4*3+3];
int obufcount = 0;
for (int i = 0; i < data.length(); i ++) {
char ch = data.charAt(i);
if (ch == S_BASE64PAD
|| ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
ibuf[ibufcount++] = ch;
if (ibufcount == ibuf.length) {
ibufcount = 0;
obufcount += decode0(ibuf, obuf, obufcount);
}
}
}
if (obufcount == obuf.length)
return obuf;
byte[] ret = new byte[obufcount];
System.arraycopy(obuf, 0, ret, 0, obufcount);
return ret;
}
/** *//**
* Decode the base64 data.
* @param data The base64 encoded data to be decoded
* @param off The offset within the encoded data at which to start decoding
* @param len The length of data to decode
* @param ostream The OutputStream to which the decoded data should be
* written
*/
public static void decode(char[] data, int off, int len, OutputStream ostream) throws IOException {
char[] ibuf = new char[4];
int ibufcount = 0;
byte[] obuf = new byte[3];
for (int i = off; i < off+len; i ++) {
char ch = data[i];
if (ch == S_BASE64PAD
|| ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
ibuf[ibufcount++] = ch;
if (ibufcount == ibuf.length) {
ibufcount = 0;
int obufcount = decode0(ibuf, obuf, 0);
ostream.write(obuf, 0, obufcount);
}
}
}
}
/** *//**
* Decode the base64 data.
* @param data The base64 encoded data to be decoded
* @param ostream The OutputStream to which the decoded data should be
* written
*/
public static void decode(String data, OutputStream ostream) throws IOException {
char[] ibuf = new char[4];
int ibufcount = 0;
byte[] obuf = new byte[3];
for (int i = 0; i < data.length(); i ++) {
char ch = data.charAt(i);
if (ch == S_BASE64PAD
|| ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
ibuf[ibufcount++] = ch;
if (ibufcount == ibuf.length) {
ibufcount = 0;
int obufcount = decode0(ibuf, obuf, 0);
ostream.write(obuf, 0, obufcount);
}
}
}
}
/** *//**
* Returns base64 representation of specified byte array.
* @param data The data to be encoded
* @return The base64 encoded data
*/
public static String encode(byte[] data) {
return encode(data, 0, data.length);
}
/** *//**
* Returns base64 representation of specified byte array.
* @param data The data to be encoded
* @param off The offset within the data at which to start encoding
* @param len The length of the data to encode
* @return The base64 encoded data
*/
public static String encode(byte[] data, int off, int len) {
if (len <= 0) return "";
char[] out = new char[len/3*4+4];
int rindex = off;
int windex = 0;
int rest = len;
while (rest >= 3) {
int i = ((data[rindex]&0xff)<<16)
+((data[rindex+1]&0xff)<<8)
+(data[rindex+2]&0xff);
out[windex++] = S_BASE64CHAR[i>>18];
out[windex++] = S_BASE64CHAR[(i>>12)&0x3f];
out[windex++] = S_BASE64CHAR[(i>>6)&0x3f];
out[windex++] = S_BASE64CHAR[i&0x3f];
rindex += 3;
rest -= 3;
}
if (rest == 1) {
int i = data[rindex]&0xff;
out[windex++] = S_BASE64CHAR[i>>2];
out[windex++] = S_BASE64CHAR[(i<<4)&0x3f];
out[windex++] = S_BASE64PAD;
out[windex++] = S_BASE64PAD;
} else if (rest == 2) {
int i = ((data[rindex]&0xff)<<8)+(data[rindex+1]&0xff);
out[windex++] = S_BASE64CHAR[i>>10];
out[windex++] = S_BASE64CHAR[(i>>4)&0x3f];
out[windex++] = S_BASE64CHAR[(i<<2)&0x3f];
out[windex++] = S_BASE64PAD;
}
return new String(out, 0, windex);
}
/** *//**
* Outputs base64 representation of the specified byte array to a byte stream.
* @param data The data to be encoded
* @param off The offset within the data at which to start encoding
* @param len The length of the data to encode
* @param ostream The OutputStream to which the encoded data should be
* written
*/
public static void encode(byte[] data, int off, int len, OutputStream ostream) throws IOException {
if (len <= 0) return;
byte[] out = new byte[4];
int rindex = off;
int rest = len;
while (rest >= 3) {
int i = ((data[rindex]&0xff)<<16)
+((data[rindex+1]&0xff)<<8)
+(data[rindex+2]&0xff);
out[0] = (byte)S_BASE64CHAR[i>>18];
out[1] = (byte)S_BASE64CHAR[(i>>12)&0x3f];
out[2] = (byte)S_BASE64CHAR[(i>>6)&0x3f];
out[3] = (byte)S_BASE64CHAR[i&0x3f];
ostream.write(out, 0, 4);
rindex += 3;
rest -= 3;
}
if (rest == 1) {
int i = data[rindex]&0xff;
out[0] = (byte)S_BASE64CHAR[i>>2];
out[1] = (byte)S_BASE64CHAR[(i<<4)&0x3f];
out[2] = (byte)S_BASE64PAD;
out[3] = (byte)S_BASE64PAD;
ostream.write(out, 0, 4);
} else if (rest == 2) {
int i = ((data[rindex]&0xff)<<8)+(data[rindex+1]&0xff);
out[0] = (byte)S_BASE64CHAR[i>>10];
out[1] = (byte)S_BASE64CHAR[(i>>4)&0x3f];
out[2] = (byte)S_BASE64CHAR[(i<<2)&0x3f];
out[3] = (byte)S_BASE64PAD;
ostream.write(out, 0, 4);
}
}
/** *//**
* Outputs base64 representation of the specified byte array to a character stream.
* @param data The data to be encoded
* @param off The offset within the data at which to start encoding
* @param len The length of the data to encode
* @param writer The Writer to which the encoded data should be
* written
*/
public static void encode(byte[] data, int off, int len, Writer writer) throws IOException {
if (len <= 0) return;
char[] out = new char[4];
int rindex = off;
int rest = len;
int output = 0;
while (rest >= 3) {
int i = ((data[rindex]&0xff)<<16)
+((data[rindex+1]&0xff)<<8)
+(data[rindex+2]&0xff);
out[0] = S_BASE64CHAR[i>>18];
out[1] = S_BASE64CHAR[(i>>12)&0x3f];
out[2] = S_BASE64CHAR[(i>>6)&0x3f];
out[3] = S_BASE64CHAR[i&0x3f];
writer.write(out, 0, 4);
rindex += 3;
rest -= 3;
output += 4;
if (output % 76 == 0)
writer.write("\n");
}
if (rest == 1) {
int i = data[rindex]&0xff;
out[0] = S_BASE64CHAR[i>>2];
out[1] = S_BASE64CHAR[(i<<4)&0x3f];
out[2] = S_BASE64PAD;
out[3] = S_BASE64PAD;
writer.write(out, 0, 4);
} else if (rest == 2) {
int i = ((data[rindex]&0xff)<<8)+(data[rindex+1]&0xff);
out[0] = S_BASE64CHAR[i>>10];
out[1] = S_BASE64CHAR[(i>>4)&0x3f];
out[2] = S_BASE64CHAR[(i<<2)&0x3f];
out[3] = S_BASE64PAD;
writer.write(out, 0, 4);
}
}
}
posted on 2008-09-17 11:44
忆风 阅读(455)
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数据结构与算法