标签：int chars Base64 write 自用 lookup Android bits out
/**
* Created by tab on 2017/10/10
*/
public class Base64Encoder extends FilterOutputStream {
private static final char[] chars = {'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 int charCount;
private int carryOver;
/***
* Constructs a new Base64 encoder that writes output to the given
* OutputStream.
*
* @param out the output stream
*/
public Base64Encoder(OutputStream out) {
super(out);
}
/***
* Writes the given byte to the output stream in an encoded form.
*
* @throws IOException if an I/O error occurs
*/
public void write(int b) throws IOException {
// Take 24-bits from three octets, translate into four encoded chars
// Break lines at 76 chars
// If necessary, pad with 0 bits on the right at the end
// Use = signs as padding at the end to ensure encodedLength % 4 == 0
// Remove the sign bit,
// thanks to Christian Schweingruber <chrigu@lorraine.ch>
if (b < 0) {
b += 256;
}
// First byte use first six bits, save last two bits
if (charCount % 3 == 0) {
int lookup = b >> 2;
carryOver = b & 3; // last two bits
out.write(chars[lookup]);
}
// Second byte use previous two bits and first four new bits,
// save last four bits
else if (charCount % 3 == 1) {
int lookup = ((carryOver << 4) + (b >> 4)) & 63;
carryOver = b & 15; // last four bits
out.write(chars[lookup]);
}
// Third byte use previous four bits and first two new bits,
// then use last six new bits
else if (charCount % 3 == 2) {
int lookup = ((carryOver << 2) + (b >> 6)) & 63;
out.write(chars[lookup]);
lookup = b & 63; // last six bits
out.write(chars[lookup]);
carryOver = 0;
}
charCount++;
// Add newline every 76 output chars (that's 57 input chars)
if (charCount % 57 == 0) {
out.write('\n');
}
}
/***
* Writes the given byte array to the output stream in an encoded form.
*
* @param buf the data to be written
* @param off the start offset of the data
* @param len the length of the data
* @throws IOException if an I/O error occurs
*/
public void write(byte[] buf, int off, int len) throws IOException {
// This could of course be optimized
for (int i = 0; i < len; i++) {
write(buf[off + i]);
}
}
/***
* Closes the stream, this MUST be called to ensure proper padding is
* written to the end of the output stream.
*
* @throws IOException if an I/O error occurs
*/
public void close() throws IOException {
// Handle leftover bytes
if (charCount % 3 == 1) { // one leftover
int lookup = (carryOver << 4) & 63;
out.write(chars[lookup]);
out.write('=');
out.write('=');
} else if (charCount % 3 == 2) { // two leftovers
int lookup = (carryOver << 2) & 63;
out.write(chars[lookup]);
out.write('=');
}
super.close();
}
/***
* Returns the encoded form of the given unencoded string. The encoder uses
* the ISO-8859-1 (Latin-1) encoding to convert the string to bytes. For
* greater control over the encoding, encode the string to bytes yourself
* and use encode(byte[]).
*
* @param unencoded the string to encode
* @return the encoded form of the unencoded string
*/
public static String encode(String unencoded) {
byte[] bytes = null;
try {
bytes = unencoded.getBytes("UTF-8");
} catch (UnsupportedEncodingException ignored) {
}
return encode(bytes);
}
/***
* Returns the encoded form of the given unencoded string.
*
* @param bytes the bytes to encode
* @return the encoded form of the unencoded string
*/
public static String encode(byte[] bytes) {
ByteArrayOutputStream out = new ByteArrayOutputStream(
(int) (bytes.length * 1.37));
Base64Encoder encodedOut = new Base64Encoder(out);
try {
encodedOut.write(bytes);
encodedOut.close();
return out.toString("UTF-8");
} catch (IOException ignored) {
return null;
}
}
/**
* file 2 base64
*
* @param filename filename
* @return base64 string
*/
public static String file2Base64(String filename) {
File file = new File(filename);
ULogger.d("filename=" + file.getAbsolutePath());
FileInputStream fileInputStream = null;
if (file.exists()) {
try {
fileInputStream = new FileInputStream(file);
int len = (int) file.length();
byte bytes[] = new byte[len];
int count, total = 0;
while ((count = fileInputStream.read(bytes, total, len - total)) > 0) {
total += count;
}
return Base64.encodeToString(bytes, Base64.DEFAULT);
} catch (Exception ex) {
ex.printStackTrace();
} finally {
if (fileInputStream != null) {
try {
fileInputStream.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
return null;
}
public static void main(String[] args) throws Exception {
if (args.length != 1) {
System.err
.println("Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
return;
}
Base64Encoder encoder = null;
BufferedInputStream in = null;
try {
encoder = new Base64Encoder(System.out);
in = new BufferedInputStream(new FileInputStream(args[0]));
byte[] buf = new byte[4 * 1024]; // 4K buffer
int bytesRead;
while ((bytesRead = in.read(buf)) != -1) {
encoder.write(buf, 0, bytesRead);
}
} finally {
if (in != null)
in.close();
if (encoder != null)
encoder.close();
}
}
}
标签：int,chars,Base64,write,自用,lookup,Android,bits,out 来源： https://www.cnblogs.com/bg-tab/p/16319238.html
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