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With inspiration from other libraries
// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
/*
*******************************************************************************
* Copyright (C) 1996-2016, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*/
package com.ibm.icu.text;
/**
* A decompression engine implementing the Standard Compression Scheme
* for Unicode (SCSU) as outlined in Unicode Technical
* Report #6.
*
* USAGE
*
* The static methods on UnicodeDecompressor may be used in a
* straightforward manner to decompress simple strings:
*
*
* byte [] compressed = ... ; // get compressed bytes from somewhere
* String result = UnicodeDecompressor.decompress(compressed);
*
*
* The static methods have a fairly large memory footprint.
* For finer-grained control over memory usage,
* UnicodeDecompressor offers more powerful APIs allowing
* iterative decompression:
*
*
* // Decompress an array "bytes" of length "len" using a buffer of 512 chars
* // to the Writer "out"
*
* UnicodeDecompressor myDecompressor = new UnicodeDecompressor();
* final static int BUFSIZE = 512;
* char [] charBuffer = new char [ BUFSIZE ];
* int charsWritten = 0;
* int [] bytesRead = new int [1];
* int totalBytesDecompressed = 0;
* int totalCharsWritten = 0;
*
* do {
* // do the decompression
* charsWritten = myDecompressor.decompress(bytes, totalBytesDecompressed,
* len, bytesRead,
* charBuffer, 0, BUFSIZE);
*
* // do something with the current set of chars
* out.write(charBuffer, 0, charsWritten);
*
* // update the no. of bytes decompressed
* totalBytesDecompressed += bytesRead[0];
*
* // update the no. of chars written
* totalCharsWritten += charsWritten;
*
* } while(totalBytesDecompressed < len);
*
* myDecompressor.reset(); // reuse decompressor
*
*
* Decompression is performed according to the standard set forth in
* Unicode Technical
* Report #6
*
* @see UnicodeCompressor
*
* @author Stephen F. Booth
* @stable ICU 2.4
*/
public final class UnicodeDecompressor implements SCSU
{
//==========================
// Instance variables
//==========================
/** Alias to current dynamic window */
private int fCurrentWindow = 0;
/** Dynamic compression window offsets */
private int [] fOffsets = new int [ NUMWINDOWS ];
/** Current compression mode */
private int fMode = SINGLEBYTEMODE;
/** Size of our internal buffer */
private final static int BUFSIZE = 3;
/** Internal buffer for saving state */
private byte [] fBuffer = new byte [BUFSIZE];
/** Number of characters in our internal buffer */
private int fBufferLength = 0;
/**
* Create a UnicodeDecompressor.
* Sets all windows to their default values.
* @see #reset
* @stable ICU 2.4
*/
public UnicodeDecompressor(){
reset(); // initialize to defaults
}
/**
* Decompress a byte array into a String.
* @param buffer The byte array to decompress.
* @return A String containing the decompressed characters.
* @see #decompress(byte [], int, int)
* @stable ICU 2.4
*/
public static String decompress(byte [] buffer){
char [] buf = decompress(buffer, 0, buffer.length);
return new String(buf);
}
/**
* Decompress a byte array into a Unicode character array.
* @param buffer The byte array to decompress.
* @param start The start of the byte run to decompress.
* @param limit The limit of the byte run to decompress.
* @return A character array containing the decompressed bytes.
* @see #decompress(byte [])
* @stable ICU 2.4
*/
public static char [] decompress(byte [] buffer, int start, int limit) {
UnicodeDecompressor comp = new UnicodeDecompressor();
// use a buffer we know will never overflow
// in the worst case, each byte will decompress
// to a surrogate pair (buffer must be at least 2 chars)
int len = Math.max(2, 2 * (limit - start));
char [] temp = new char [len];
int charCount = comp.decompress(buffer, start, limit, null,
temp, 0, len);
char [] result = new char [charCount];
System.arraycopy(temp, 0, result, 0, charCount);
return result;
}
/**
* Decompress a byte array into a Unicode character array.
*
* This function will either completely fill the output buffer,
* or consume the entire input.
*
* @param byteBuffer The byte buffer to decompress.
* @param byteBufferStart The start of the byte run to decompress.
* @param byteBufferLimit The limit of the byte run to decompress.
* @param bytesRead A one-element array. If not null, on return
* the number of bytes read from byteBuffer.
* @param charBuffer A buffer to receive the decompressed data.
* This buffer must be at minimum two characters in size.
* @param charBufferStart The starting offset to which to write
* decompressed data.
* @param charBufferLimit The limiting offset for writing
* decompressed data.
* @return The number of Unicode characters written to charBuffer.
* @stable ICU 2.4
*/
public int decompress(byte [] byteBuffer,
int byteBufferStart,
int byteBufferLimit,
int [] bytesRead,
char [] charBuffer,
int charBufferStart,
int charBufferLimit)
{
// the current position in the source byte buffer
int bytePos = byteBufferStart;
// the current position in the target char buffer
int ucPos = charBufferStart;
// the current byte from the source buffer
int aByte = 0x00;
// charBuffer must be at least 2 chars in size
if(charBuffer.length < 2 || (charBufferLimit - charBufferStart) < 2)
throw new IllegalArgumentException("charBuffer.length < 2");
// if our internal buffer isn't empty, flush its contents
// to the output buffer before doing any more decompression
if(fBufferLength > 0) {
int newBytes = 0;
// fill the buffer completely, to guarantee one full character
if(fBufferLength != BUFSIZE) {
newBytes = fBuffer.length - fBufferLength;
// verify there are newBytes bytes in byteBuffer
if(byteBufferLimit - byteBufferStart < newBytes)
newBytes = byteBufferLimit - byteBufferStart;
System.arraycopy(byteBuffer, byteBufferStart,
fBuffer, fBufferLength, newBytes);
}
// reset buffer length to 0 before recursive call
fBufferLength = 0;
// call self recursively to decompress the buffer
int count = decompress(fBuffer, 0, fBuffer.length, null,
charBuffer, charBufferStart,
charBufferLimit);
// update the positions into the arrays
ucPos += count;
bytePos += newBytes;
}
// the main decompression loop
mainLoop:
while(bytePos < byteBufferLimit && ucPos < charBufferLimit) {
switch(fMode) {
case SINGLEBYTEMODE:
// single-byte mode decompression loop
singleByteModeLoop:
while(bytePos < byteBufferLimit && ucPos < charBufferLimit) {
aByte = byteBuffer[bytePos++] & 0xFF;
switch(aByte) {
// All bytes from 0x80 through 0xFF are remapped
// to chars or surrogate pairs according to the
// currently active window
case 0x80: case 0x81: case 0x82: case 0x83: case 0x84:
case 0x85: case 0x86: case 0x87: case 0x88: case 0x89:
case 0x8A: case 0x8B: case 0x8C: case 0x8D: case 0x8E:
case 0x8F: case 0x90: case 0x91: case 0x92: case 0x93:
case 0x94: case 0x95: case 0x96: case 0x97: case 0x98:
case 0x99: case 0x9A: case 0x9B: case 0x9C: case 0x9D:
case 0x9E: case 0x9F: case 0xA0: case 0xA1: case 0xA2:
case 0xA3: case 0xA4: case 0xA5: case 0xA6: case 0xA7:
case 0xA8: case 0xA9: case 0xAA: case 0xAB: case 0xAC:
case 0xAD: case 0xAE: case 0xAF: case 0xB0: case 0xB1:
case 0xB2: case 0xB3: case 0xB4: case 0xB5: case 0xB6:
case 0xB7: case 0xB8: case 0xB9: case 0xBA: case 0xBB:
case 0xBC: case 0xBD: case 0xBE: case 0xBF: case 0xC0:
case 0xC1: case 0xC2: case 0xC3: case 0xC4: case 0xC5:
case 0xC6: case 0xC7: case 0xC8: case 0xC9: case 0xCA:
case 0xCB: case 0xCC: case 0xCD: case 0xCE: case 0xCF:
case 0xD0: case 0xD1: case 0xD2: case 0xD3: case 0xD4:
case 0xD5: case 0xD6: case 0xD7: case 0xD8: case 0xD9:
case 0xDA: case 0xDB: case 0xDC: case 0xDD: case 0xDE:
case 0xDF: case 0xE0: case 0xE1: case 0xE2: case 0xE3:
case 0xE4: case 0xE5: case 0xE6: case 0xE7: case 0xE8:
case 0xE9: case 0xEA: case 0xEB: case 0xEC: case 0xED:
case 0xEE: case 0xEF: case 0xF0: case 0xF1: case 0xF2:
case 0xF3: case 0xF4: case 0xF5: case 0xF6: case 0xF7:
case 0xF8: case 0xF9: case 0xFA: case 0xFB: case 0xFC:
case 0xFD: case 0xFE: case 0xFF:
// For offsets <= 0xFFFF, convert to a single char
// by adding the window's offset and subtracting
// the generic compression offset
if(fOffsets[ fCurrentWindow ] <= 0xFFFF) {
charBuffer[ucPos++] = (char)
(aByte + fOffsets[ fCurrentWindow ]
- COMPRESSIONOFFSET);
}
// For offsets > 0x10000, convert to a surrogate pair by
// normBase = window's offset - 0x10000
// high surr. = 0xD800 + (normBase >> 10)
// low surr. = 0xDC00 + (normBase & 0x3FF) + (byte & 0x7F)
else {
// make sure there is enough room to write
// both characters
// if not, save state and break out
if((ucPos + 1) >= charBufferLimit) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
int normalizedBase = fOffsets[ fCurrentWindow ]
- 0x10000;
charBuffer[ucPos++] = (char)
(0xD800 + (normalizedBase >> 10));
charBuffer[ucPos++] = (char)
(0xDC00 + (normalizedBase & 0x3FF)+(aByte & 0x7F));
}
break;
// bytes from 0x20 through 0x7F are treated as ASCII and
// are remapped to chars by padding the high byte
// (this is the same as quoting from static window 0)
// NUL (0x00), HT (0x09), CR (0x0A), LF (0x0D)
// are treated as ASCII as well
case 0x00: case 0x09: case 0x0A: case 0x0D:
case 0x20: case 0x21: case 0x22: case 0x23: case 0x24:
case 0x25: case 0x26: case 0x27: case 0x28: case 0x29:
case 0x2A: case 0x2B: case 0x2C: case 0x2D: case 0x2E:
case 0x2F: case 0x30: case 0x31: case 0x32: case 0x33:
case 0x34: case 0x35: case 0x36: case 0x37: case 0x38:
case 0x39: case 0x3A: case 0x3B: case 0x3C: case 0x3D:
case 0x3E: case 0x3F: case 0x40: case 0x41: case 0x42:
case 0x43: case 0x44: case 0x45: case 0x46: case 0x47:
case 0x48: case 0x49: case 0x4A: case 0x4B: case 0x4C:
case 0x4D: case 0x4E: case 0x4F: case 0x50: case 0x51:
case 0x52: case 0x53: case 0x54: case 0x55: case 0x56:
case 0x57: case 0x58: case 0x59: case 0x5A: case 0x5B:
case 0x5C: case 0x5D: case 0x5E: case 0x5F: case 0x60:
case 0x61: case 0x62: case 0x63: case 0x64: case 0x65:
case 0x66: case 0x67: case 0x68: case 0x69: case 0x6A:
case 0x6B: case 0x6C: case 0x6D: case 0x6E: case 0x6F:
case 0x70: case 0x71: case 0x72: case 0x73: case 0x74:
case 0x75: case 0x76: case 0x77: case 0x78: case 0x79:
case 0x7A: case 0x7B: case 0x7C: case 0x7D: case 0x7E:
case 0x7F:
charBuffer[ucPos++] = (char) aByte;
break;
// quote unicode
case SQUOTEU:
// verify we have two bytes following tag
// if not, save state and break out
if( (bytePos + 1) >= byteBufferLimit ) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
aByte = byteBuffer[bytePos++];
charBuffer[ucPos++] = (char)
(aByte << 8 | (byteBuffer[bytePos++] & 0xFF));
break;
// switch to Unicode mode
case SCHANGEU:
fMode = UNICODEMODE;
break singleByteModeLoop;
//break;
// handle all quote tags
case SQUOTE0: case SQUOTE1: case SQUOTE2: case SQUOTE3:
case SQUOTE4: case SQUOTE5: case SQUOTE6: case SQUOTE7:
// verify there is a byte following the tag
// if not, save state and break out
if(bytePos >= byteBufferLimit) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
// if the byte is in the range 0x00 - 0x7F, use
// static window n otherwise, use dynamic window n
int dByte = byteBuffer[bytePos++] & 0xFF;
charBuffer[ucPos++] = (char)
(dByte+ (dByte >= 0x00 && dByte < 0x80
? sOffsets[aByte - SQUOTE0]
: (fOffsets[aByte - SQUOTE0]
- COMPRESSIONOFFSET)));
break;
// handle all change tags
case SCHANGE0: case SCHANGE1: case SCHANGE2: case SCHANGE3:
case SCHANGE4: case SCHANGE5: case SCHANGE6: case SCHANGE7:
fCurrentWindow = aByte - SCHANGE0;
break;
// handle all define tags
case SDEFINE0: case SDEFINE1: case SDEFINE2: case SDEFINE3:
case SDEFINE4: case SDEFINE5: case SDEFINE6: case SDEFINE7:
// verify there is a byte following the tag
// if not, save state and break out
if(bytePos >= byteBufferLimit) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
fCurrentWindow = aByte - SDEFINE0;
fOffsets[fCurrentWindow] =
sOffsetTable[byteBuffer[bytePos++] & 0xFF];
break;
// handle define extended tag
case SDEFINEX:
// verify we have two bytes following tag
// if not, save state and break out
if((bytePos + 1) >= byteBufferLimit ) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
aByte = byteBuffer[bytePos++] & 0xFF;
fCurrentWindow = (aByte & 0xE0) >> 5;
fOffsets[fCurrentWindow] = 0x10000 +
(0x80 * (((aByte & 0x1F) << 8)
| (byteBuffer[bytePos++] & 0xFF)));
break;
// reserved, shouldn't happen
case SRESERVED:
break;
} // end switch
} // end while
break;
case UNICODEMODE:
// unicode mode decompression loop
unicodeModeLoop:
while(bytePos < byteBufferLimit && ucPos < charBufferLimit) {
aByte = byteBuffer[bytePos++] & 0xFF;
switch(aByte) {
// handle all define tags
case UDEFINE0: case UDEFINE1: case UDEFINE2: case UDEFINE3:
case UDEFINE4: case UDEFINE5: case UDEFINE6: case UDEFINE7:
// verify there is a byte following tag
// if not, save state and break out
if(bytePos >= byteBufferLimit ) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
fCurrentWindow = aByte - UDEFINE0;
fOffsets[fCurrentWindow] =
sOffsetTable[byteBuffer[bytePos++] & 0xFF];
fMode = SINGLEBYTEMODE;
break unicodeModeLoop;
//break;
// handle define extended tag
case UDEFINEX:
// verify we have two bytes following tag
// if not, save state and break out
if((bytePos + 1) >= byteBufferLimit ) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
aByte = byteBuffer[bytePos++] & 0xFF;
fCurrentWindow = (aByte & 0xE0) >> 5;
fOffsets[fCurrentWindow] = 0x10000 +
(0x80 * (((aByte & 0x1F) << 8)
| (byteBuffer[bytePos++] & 0xFF)));
fMode = SINGLEBYTEMODE;
break unicodeModeLoop;
//break;
// handle all change tags
case UCHANGE0: case UCHANGE1: case UCHANGE2: case UCHANGE3:
case UCHANGE4: case UCHANGE5: case UCHANGE6: case UCHANGE7:
fCurrentWindow = aByte - UCHANGE0;
fMode = SINGLEBYTEMODE;
break unicodeModeLoop;
//break;
// quote unicode
case UQUOTEU:
// verify we have two bytes following tag
// if not, save state and break out
if(bytePos >= byteBufferLimit - 1) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
aByte = byteBuffer[bytePos++];
charBuffer[ucPos++] = (char)
(aByte << 8 | (byteBuffer[bytePos++] & 0xFF));
break;
default:
// verify there is a byte following tag
// if not, save state and break out
if(bytePos >= byteBufferLimit ) {
--bytePos;
System.arraycopy(byteBuffer, bytePos,
fBuffer, 0,
byteBufferLimit - bytePos);
fBufferLength = byteBufferLimit - bytePos;
bytePos += fBufferLength;
break mainLoop;
}
charBuffer[ucPos++] = (char)
(aByte << 8 | (byteBuffer[bytePos++] & 0xFF));
break;
} // end switch
} // end while
break;
} // end switch( fMode )
} // end while
// fill in output parameter
if(bytesRead != null)
bytesRead [0] = (bytePos - byteBufferStart);
// return # of chars written
return (ucPos - charBufferStart);
}
/**
* Reset the decompressor to its initial state.
* @stable ICU 2.4
*/
public void reset()
{
// reset dynamic windows
fOffsets[0] = 0x0080; // Latin-1
fOffsets[1] = 0x00C0; // Latin-1 Supplement + Latin Extended-A
fOffsets[2] = 0x0400; // Cyrillic
fOffsets[3] = 0x0600; // Arabic
fOffsets[4] = 0x0900; // Devanagari
fOffsets[5] = 0x3040; // Hiragana
fOffsets[6] = 0x30A0; // Katakana
fOffsets[7] = 0xFF00; // Fullwidth ASCII
fCurrentWindow = 0; // Make current window Latin-1
fMode = SINGLEBYTEMODE; // Always start in single-byte mode
fBufferLength = 0; // Empty buffer
}
}