forked from fanruan/design
李攀
8 years ago
3 changed files with 5 additions and 258 deletions
@ -1,256 +0,0 @@
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package com.fr.design.extra.ucenter; |
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import java.io.*; |
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/** |
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* Created by lp on 2016/9/9. |
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*/ |
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public class Base64 { |
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/** |
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* returns an array of base64-encoded characters to represent the |
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* passed data array. |
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* |
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* @param data the array of bytes to encode |
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* @return base64-coded character array. |
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*/ |
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public static char[] encode(byte[] data) { |
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char[] out = new char[((data.length + 2) / 3) * 4]; |
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//
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// 3 bytes encode to 4 chars. Output is always an even
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// multiple of 4 characters.
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//
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for (int i = 0, index = 0; i < data.length; i += 3, index += 4) { |
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boolean quad = false; |
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boolean trip = false; |
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int val = (0xFF & data[i]); |
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val <<= 8; |
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if ((i + 1) < data.length) { |
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val |= (0xFF & data[i + 1]); |
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trip = true; |
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} |
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val <<= 8; |
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if ((i + 2) < data.length) { |
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val |= (0xFF & data[i + 2]); |
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quad = true; |
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} |
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out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)]; |
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val >>= 6; |
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out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)]; |
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val >>= 6; |
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out[index + 1] = alphabet[val & 0x3F]; |
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val >>= 6; |
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out[index + 0] = alphabet[val & 0x3F]; |
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} |
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return out; |
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} |
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/** |
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* Decodes a BASE-64 encoded stream to recover the original |
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* data. White space before and after will be trimmed away, |
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* but no other manipulation of the input will be performed. |
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* |
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* As of version 1.2 this method will properly handle input |
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* containing junk characters (newlines and the like) rather |
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* than throwing an error. It does this by pre-parsing the |
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* input and generating from that a count of VALID input |
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* characters. |
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**/ |
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public static byte[] decode(char[] data) { |
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// as our input could contain non-BASE64 data (newlines,
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// whitespace of any sort, whatever) we must first adjust
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// our count of USABLE data so that...
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// (a) we don't misallocate the output array, and
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// (b) think that we miscalculated our data length
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// just because of extraneous throw-away junk
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int tempLen = data.length; |
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for (int ix = 0; ix < data.length; ix++) { |
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if ((data[ix] > 255) || codes[data[ix]] < 0) |
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--tempLen; // ignore non-valid chars and padding
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} |
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// calculate required length:
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// -- 3 bytes for every 4 valid base64 chars
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// -- plus 2 bytes if there are 3 extra base64 chars,
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// or plus 1 byte if there are 2 extra.
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int len = (tempLen / 4) * 3; |
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if ((tempLen % 4) == 3) |
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len += 2; |
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if ((tempLen % 4) == 2) |
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len += 1; |
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byte[] out = new byte[len]; |
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int shift = 0; // # of excess bits stored in accum
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int accum = 0; // excess bits
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int index = 0; |
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// we now go through the entire array (NOT using the 'tempLen' value)
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for (int ix = 0; ix < data.length; ix++) { |
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int value = (data[ix] > 255) ? -1 : codes[data[ix]]; |
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if (value >= 0)// skip over non-code
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{ |
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accum <<= 6; // bits shift up by 6 each time thru
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shift += 6; // loop, with new bits being put in
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accum |= value; // at the bottom.
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if (shift >= 8)// whenever there are 8 or more shifted in,
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{ |
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shift -= 8; // write them out (from the top, leaving any
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out[index++] = // excess at the bottom for next iteration.
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(byte) ((accum >> shift) & 0xff); |
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} |
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} |
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// we will also have skipped processing a padding null byte ('=') here;
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// these are used ONLY for padding to an even length and do not legally
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// occur as encoded data. for this reason we can ignore the fact that
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// no index++ operation occurs in that special case: the out[] array is
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// initialized to all-zero bytes to start with and that works to our
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// advantage in this combination.
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} |
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// if there is STILL something wrong we just have to throw up now!
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if (index != out.length) { |
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throw new Error("Miscalculated data length (wrote " + |
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index + " instead of " + out.length + ")"); |
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} |
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return out; |
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} |
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//
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// code characters for values 0..63
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//
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private static char[] alphabet = |
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray(); |
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//
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// lookup table for converting base64 characters to value in range 0..63
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//
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private static byte[] codes = new byte[256]; |
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static { |
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for (int i = 0; i < 256; i++) |
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codes[i] = -1; |
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for (int i = 'A'; i <= 'Z'; i++) |
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codes[i] = (byte) (i - 'A'); |
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for (int i = 'a'; i <= 'z'; i++) |
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codes[i] = (byte) (26 + i - 'a'); |
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for (int i = '0'; i <= '9'; i++) |
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codes[i] = (byte) (52 + i - '0'); |
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codes['+'] = 62; |
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codes['/'] = 63; |
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} |
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///////////////////////////////////////////////////
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// remainder (main method and helper functions) is
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// for testing purposes only, feel free to clip it.
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///////////////////////////////////////////////////
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public static void main(String[] args) { |
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boolean decode = false; |
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if (args.length == 0) { |
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System.out.println("usage: java Base64 [-d[ecode]] filename"); |
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System.exit(0); |
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} |
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for (int i = 0; i < args.length; i++) { |
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if ("-decode".equalsIgnoreCase(args[i])) |
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decode = true; |
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else if ("-d".equalsIgnoreCase(args[i])) |
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decode = true; |
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} |
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String filename = args[args.length - 1]; |
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File file = new File(filename); |
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if (!file.exists()) { |
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System.out.println("Error: file '" + filename + "' doesn't exist!"); |
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System.exit(0); |
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} |
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if (decode) { |
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char[] encoded = readChars(file); |
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byte[] decoded = decode(encoded); |
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writeBytes(file, decoded); |
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} |
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else { |
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byte[] decoded = readBytes(file); |
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char[] encoded = encode(decoded); |
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writeChars(file, encoded); |
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} |
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} |
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private static byte[] readBytes(File file) { |
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ByteArrayOutputStream baos = new ByteArrayOutputStream(); |
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try { |
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InputStream fis = new FileInputStream(file); |
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InputStream is = new BufferedInputStream(fis); |
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int count = 0; |
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byte[] buf = new byte[16384]; |
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while ((count = is.read(buf)) != -1) { |
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if (count > 0) |
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baos.write(buf, 0, count); |
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} |
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is.close(); |
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} |
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catch (Exception e) { |
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e.printStackTrace(); |
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} |
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return baos.toByteArray(); |
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} |
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private static char[] readChars(File file) { |
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CharArrayWriter caw = new CharArrayWriter(); |
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try { |
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Reader fr = new FileReader(file); |
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Reader in = new BufferedReader(fr); |
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int count = 0; |
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char[] buf = new char[16384]; |
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while ((count = in.read(buf)) != -1) { |
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if (count > 0) |
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caw.write(buf, 0, count); |
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} |
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in.close(); |
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} |
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catch (Exception e) { |
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e.printStackTrace(); |
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} |
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return caw.toCharArray(); |
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} |
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private static void writeBytes(File file, byte[] data) { |
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try { |
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OutputStream fos = new FileOutputStream(file); |
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OutputStream os = new BufferedOutputStream(fos); |
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os.write(data); |
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os.close(); |
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} |
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catch (Exception e) { |
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e.printStackTrace(); |
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} |
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} |
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private static void writeChars(File file, char[] data) { |
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try { |
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Writer fos = new FileWriter(file); |
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Writer os = new BufferedWriter(fos); |
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os.write(data); |
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os.close(); |
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} |
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catch (Exception e) { |
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e.printStackTrace(); |
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} |
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} |
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///////////////////////////////////////////////////
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// end of test code.
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///////////////////////////////////////////////////
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} |
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