erik/JSON-java
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Java 1.8.

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Douglas Crockford 2014-05-05 15:09:32 -07:00
parent 48d31b7f5c
commit a9a0762383
26 changed files with 747 additions and 819 deletions
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47
zip/Huff.java
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@ -29,7 +29,7 @@ import org.json.JSONException;
/**
* JSONzip is a compression scheme for JSON text.
* @author JSON.org
* @version 2013-04-18
* @version 2014-05-03
*/
/**
@ -42,6 +42,9 @@ import org.json.JSONException;
* symbol is incremented by the tick method. The generate method is used to
* generate the encoding table. The table must be generated before encoding or
* decoding. You may regenerate the table with the latest weights at any time.
*
* After a million ticks, it is assumed that the distribution is well
* understood and that no more regeneration will be required.
*/
public class Huff implements None, PostMortem {
@ -60,6 +63,11 @@ public class Huff implements None, PostMortem {
*/
private Symbol table;
/**
* The number of characters left to learn to adapt the coding table.
*/
private int toLearn;
/**
* Have any weights changed since the table was last generated?
*/
@ -100,7 +108,7 @@ public class Huff implements None, PostMortem {
if (this.integer != that.integer || this.weight != that.weight) {
return false;
}
if ((this.back != null) != (that.back != null)) {
if ((this.back == null) != (that.back == null)) {
return false;
}
Symbol zero = this.zero;
@ -132,6 +140,7 @@ public class Huff implements None, PostMortem {
*/
public Huff(int domain) {
this.domain = domain;
this.toLearn = 1000000;
int length = domain * 2 - 1;
this.symbols = new Symbol[length];
@ -141,7 +150,7 @@ public class Huff implements None, PostMortem {
symbols[i] = new Symbol(i);
}
// SMake the links.
// Make the links.
for (int i = domain; i < length; i += 1) {
symbols[i] = new Symbol(none);
@ -151,8 +160,6 @@ public class Huff implements None, PostMortem {
/**
* Generate the encoding/decoding table. The table determines the bit
* sequences used by the read and write methods.
*
* @return this
*/
public void generate() {
if (!this.upToDate) {
@ -176,8 +183,8 @@ public class Huff implements None, PostMortem {
head = symbol;
} else {
// To save time, we will start the search from the previous symbol instead
// of the head unless the current symbol weights less than the previous symbol.
// We will start the search from the previous symbol instead of the head unless
// the current symbol weights less than the previous symbol.
if (symbol.weight < previous.weight) {
previous = head;
@ -290,7 +297,7 @@ public class Huff implements None, PostMortem {
public boolean postMortem(PostMortem pm) {
// Go through every integer in the domain, generating its bit sequence, and
// then proving that that bit sequence produces the same integer.
// then prove that that bit sequence produces the same integer.
for (int integer = 0; integer < this.domain; integer += 1) {
if (!postMortem(integer)) {
@ -330,29 +337,16 @@ public class Huff implements None, PostMortem {
}
/**
* Increase by 1 the weight associated with a value.
* Increase the weight associated with a value by 1.
*
* @param value
* The number of the symbol to tick
* @return this
*/
public void tick(int value) {
this.symbols[value].weight += 1;
this.upToDate = false;
}
/**
* Increase by 1 the weight associated with a range of values.
*
* @param from
* The first symbol to tick
* @param to
* The last symbol to tick
* @return this
*/
public void tick(int from, int to) {
for (int value = from; value <= to; value += 1) {
tick(value);
if (this.toLearn > 0) {
this.toLearn -= 1;
this.symbols[value].weight += 1;
this.upToDate = false;
}
}
@ -392,7 +386,6 @@ public class Huff implements None, PostMortem {
* The number of the symbol to write
* @param bitwriter
* The destination of the bits.
* @return this
* @throws JSONException
*/
public void write(int value, BitWriter bitwriter) throws JSONException {