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SquidLib platform-independent logic and utility code. Please refer to
https://github.com/SquidPony/SquidLib .
/*
* LZString4Java By Rufus Huang
* https://github.com/rufushuang/lz-string4java
* MIT License
*
* Port from original JavaScript version by pieroxy
* https://github.com/pieroxy/lz-string
*/
package squidpony;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
/**
* LZ-String compression; wrapped by {@link LZSPlus} for convenience, but extended functionality is available here.
* You can compress a String to a smaller, technically-invalid UTF-16 String with {@link #compress(String)}, and undo
* that with {@link #decompress(String)}. Compress to a valid UTF-16 String with {@link #compressToUTF16(String)},
* decompress such a String with {@link #decompressFromUTF16(String)} (LZSPlus uses these). Compress to Base64 with
* {@link #compressToBase64(String)}, decompress Base64 with {@link #decompressFromBase64(String)}. Compress to
* URI-encoded Strings with {@link #compressToEncodedURIComponent(String)}, decompress those with
* {@link #decompressFromEncodedURIComponent(String)}. This class is super-sourced with a compatible alternative
* implementation on GWT for performance, and a main goal is to provide UTF-16 Strings that can be stored in a browser's
* LocalStorage on GWT. This class is also sometimes used internally when a large compressed String in Java source code
* makes more sense than an even larger resource file.
*/
public final class LZSEncoding {
private LZSEncoding() {};
private static final char[] keyStrBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray(),
keyStrUriSafe = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-$".toCharArray(),
valStrBase64 = new char[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
62, 0, 0, 0, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 64, 0, 0, 0, 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,
0, 0, 0, 0, 0, 0, 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},
valStrUriSafe = new char[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 0, 0, 0, 62, 0, 63, 0, 0,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 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,
0, 0, 0, 0, 0, 0, 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};
/**
* Compress a String using LZ-String encoding but only using Base64 characters ('A'-'Z', 'a'-'z', '0'-'9', '+', '/',
* and '=' for Base64 validity).
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compressToBase64(String uncompressed) {
if (uncompressed == null)
return null;
String res = _compress(uncompressed, 6, keyStrBase64, 0);
switch (res.length() & 3) { // To produce valid Base64
default: // When could this happen ?
case 0:
return res;
case 1:
return res + "===";
case 2:
return res + "==";
case 3:
return res + "=";
}
}
/**
* Decompresses a String that had been compressed with {@link #compressToBase64(String)}.
* @param compressed a Base64-encoded, compressed String
* @return the original uncompressed version of the String
*/
public static String decompressFromBase64(String compressed) {
if (compressed == null)
return null;
if (compressed.isEmpty())
return "";
final char[] input = compressed.toCharArray();
return _decompress(input.length, 32, input, valStrBase64, 0);
}
/**
* Compresses a String using the properties of UTF-16 encoding to store approximately 15 bits of LZW-compressed text
* in each 2-byte Unicode character, which does particularly well with ASCII text and can be smaller than UTF-8 in
* some cases, especially where each char must be stored as UTF-16, e.g. Java Strings or browser-based LocalStorage.
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compressToUTF16(String uncompressed) {
if (uncompressed == null)
return null;
return _compress(uncompressed, 15, null, 32) + " ";
}
/**
* Decompresses a String that had been compressed with {@link #compressToUTF16(String)}.
* @param compressed a UTF16-encoded (as by {@link #compressToUTF16(String)}), compressed String
* @return the original uncompressed version of the String
*/
public static String decompressFromUTF16(String compressed) {
if (compressed == null)
return null;
if (compressed.isEmpty())
return "";
final char[] comp = compressed.toCharArray();
return _decompress(comp.length, 16384, comp, null, -32);
}
/**
* Compress a String using LZ-String encoding but only using valid URI component characters ('A'-'Z', 'a'-'z',
* '0'-'9', '+', '-', and possibly '$').
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compressToEncodedURIComponent(String uncompressed) {
if (uncompressed == null)
return null;
return _compress(uncompressed, 6, keyStrUriSafe, 0) + '+';
}
/**
* Decompresses a String that had been compressed with {@link #compressToEncodedURIComponent(String)}.
* @param compressed a URI-encoded, compressed String
* @return the original uncompressed version of the String
*/
public static String decompressFromEncodedURIComponent(String compressed) {
if (compressed == null) return null;
if (compressed.isEmpty()) return "";
final char[] input = compressed.toCharArray();
return _decompress(input.length, 32, input, valStrUriSafe, 0);
}
/**
* Compresses a String as tightly as possible by using 16 bits of each 16-bit character, which can infrequently
* result in invalid UTF-16 codepoints, but that may not matter for all applications.
* @param uncompressed an uncompressed String to encode
* @return the encoded, compressed String
*/
public static String compress(String uncompressed) {
return _compress(uncompressed, 16, null, 0);
}
private static String _compress(String uncompressedStr, int bitsPerChar, char[] getCharFromInt, int offset) {
if (uncompressedStr == null) return null;
if (uncompressedStr.isEmpty()) return "";
int i, value;
HashMap context_dictionary = new HashMap<>();
HashSet context_dictionaryToCreate = new HashSet<>();
String context_c;
String context_wc;
String context_w = "";
int context_enlargeIn = 2; // Compensate for the first entry which should not count
int context_dictSize = 3;
int context_numBits = 2;
StringBuilder context_data = new StringBuilder(uncompressedStr.length() >>> 1);
int context_data_val = 0;
int context_data_position = 0;
int ii;
char[] uncompressed = uncompressedStr.toCharArray();
for (ii = 0; ii < uncompressed.length; ii++) {
context_c = String.valueOf(uncompressed[ii]);
if (!context_dictionary.containsKey(context_c)) {
context_dictionary.put(context_c, context_dictSize++);
context_dictionaryToCreate.add(context_c);
}
context_wc = context_w + context_c;
if (context_dictionary.containsKey(context_wc)) {
context_w = context_wc;
} else {
if (context_dictionaryToCreate.contains(context_w)) {
if ((value = context_w.charAt(0)) < 256) {
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
}
for (i = 0; i < 8; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
} else {
value = 1;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | value;
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value = 0;
}
value = context_w.charAt(0);
for (i = 0; i < 16; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_enlargeIn--;
if (context_enlargeIn == 0) {
context_enlargeIn = 1 << context_numBits++;
}
context_dictionaryToCreate.remove(context_w);
} else {
value = context_dictionary.get(context_w);
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_enlargeIn--;
if (context_enlargeIn == 0) {
context_enlargeIn = 1 << context_numBits++;
}
// Add wc to the dictionary.
context_dictionary.put(context_wc, context_dictSize++);
context_w = context_c;
}
}
// Output the code for w.
if (!context_w.isEmpty()) {
if (context_dictionaryToCreate.contains(context_w)) {
if (context_w.charAt(0) < 256) {
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
}
value = context_w.charAt(0);
for (i = 0; i < 8; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
} else {
value = 1;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | value;
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value = 0;
}
value = context_w.charAt(0);
for (i = 0; i < 16; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
context_dictionaryToCreate.remove(context_w);
} else {
value = context_dictionary.get(context_w);
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
}
}
// Mark the end of the stream
value = 2;
for (i = 0; i < context_numBits; i++) {
context_data_val = (context_data_val << 1) | (value & 1);
if (context_data_position == bitsPerChar - 1) {
context_data_position = 0;
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
context_data_val = 0;
} else {
context_data_position++;
}
value >>= 1;
}
// Flush the last char
while (true) {
context_data_val = (context_data_val << 1);
if (context_data_position == bitsPerChar - 1) {
context_data.append((char) (((getCharFromInt == null) ? context_data_val : getCharFromInt[context_data_val]) + offset));
break;
} else
context_data_position++;
}
return context_data.toString();
}
/**
* Decompresses a String that had been compressed with {@link #compress(String)}.
* @param compressed a compressed String using the default encoding from {@link #compress(String)}
* @return the original uncompressed version of the String
*/
public static String decompress(final String compressed) {
if (compressed == null)
return null;
if (compressed.isEmpty())
return "";
return _decompress(compressed.length(), 32768, compressed.toCharArray(), null, 0);
}
private static String _decompress(int length, int resetValue, char[] getNextValue, char[] modify, int offset) {
if(getNextValue == null)
return null;
if(getNextValue.length == 0)
return "";
ArrayList dictionary = new ArrayList<>();
int enlargeIn = 4, dictSize = 4, numBits = 3, position = resetValue, index = 1, resb, maxpower, power;
String entry, w, c;
ArrayList result = new ArrayList<>();
char bits, val = (modify == null) ? (char) (getNextValue[0] + offset) : modify[getNextValue[0]];
for (char i = 0; i < 3; i++) {
dictionary.add(i, String.valueOf(i));
}
bits = 0;
maxpower = 2;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (modify == null) ? (char) (getNextValue[index++] + offset) : modify[getNextValue[index++]];
}
bits |= (resb > 0 ? 1 : 0) << power++;
}
switch (bits) {
case 0:
bits = 0;
maxpower = 8;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (modify == null) ? (char) (getNextValue[index++] + offset) : modify[getNextValue[index++]];
}
bits |= (resb > 0 ? 1 : 0) << power++;
}
c = String.valueOf(bits);
break;
case 1:
bits = 0;
maxpower = 16;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (modify == null) ? (char) (getNextValue[index++] + offset) : modify[getNextValue[index++]];
}
bits |= (resb > 0 ? 1 : 0) << power++;
}
c = String.valueOf(bits);
break;
default:
return "";
}
dictionary.add(c);
w = c;
result.add(w);
while (true) {
if (index > length) {
return "";
}
int cc = 0;
maxpower = numBits;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (modify == null) ? (char) (getNextValue[index++] + offset) : modify[getNextValue[index++]];
}
cc |= (resb > 0 ? 1 : 0) << power++;
}
switch (cc) {
case 0:
bits = 0;
maxpower = 8;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (modify == null) ? (char) (getNextValue[index++] + offset) : modify[getNextValue[index++]];
}
bits |= (resb > 0 ? 1 : 0) << power++;
}
dictionary.add(String.valueOf(bits));
cc = dictSize++;
enlargeIn--;
break;
case 1:
bits = 0;
maxpower = 16;
power = 0;
while (power != maxpower) {
resb = val & position;
position >>= 1;
if (position == 0) {
position = resetValue;
val = (modify == null) ? (char) (getNextValue[index++] + offset) : modify[getNextValue[index++]];
}
bits |= (resb > 0 ? 1 : 0) << power++;
}
dictionary.add(String.valueOf(bits));
cc = dictSize++;
enlargeIn--;
break;
case 2:
StringBuilder sb = new StringBuilder(result.size());
for (String s : result)
sb.append(s);
return sb.toString();
}
if (enlargeIn == 0) {
enlargeIn = 1 << numBits;
numBits++;
}
if (cc < dictionary.size() && dictionary.get(cc) != null) {
entry = dictionary.get(cc);
} else {
if (cc == dictSize) {
entry = w + w.charAt(0);
} else {
return "";
}
}
result.add(entry);
// Add w+entry[0] to the dictionary.
dictionary.add(w + entry.charAt(0));
dictSize++;
enlargeIn--;
w = entry;
if (enlargeIn == 0) {
enlargeIn = 1 << numBits;
numBits++;
}
}
}
}