com.squarespace.less.jsonast.AstOptimizer Maven / Gradle / Ivy
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/**
* Copyright (c) 2018 SQUARESPACE, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.squarespace.less.jsonast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import com.squarespace.less.core.Pair;
public class AstOptimizer extends AstBuffer {
/** Map from original string to index of triple */
private final Map entryMap = new HashMap<>();
/** List of triples (original, escaped, score) */
private final List entries = new ArrayList<>();
/** Reusable temporary buffer for string escaping */
private final StringBuilder tmp = new StringBuilder();
public Pair, List> noOptimize() {
List table = entries.stream().map(e -> e.escaped).collect(Collectors.toList());
return Pair.of(entryMap, table);
}
public Pair, List> optimize() {
// Sort by frequency descending
entries.sort((a, b) -> Integer.compare(b.freq, a.freq));
List table = new ArrayList<>();
Map index = new HashMap<>();
int size = entries.size();
for (int i = 0; i < size; i++) {
Entry entry = entries.get(i);
int offset = table.size();
index.put(entry.original, offset);
table.add(entry.escaped);
}
return Pair.of(index, table);
}
public String stats() {
// Sort by frequency descending
entries.sort((a, b) -> Integer.compare(b.freq, a.freq));
StringBuilder buf = new StringBuilder();
int size = entries.size();
for (int i = 0; i < size; i++) {
Entry entry = entries.get(i);
if (entry.freq > 1) {
String s = entry.escaped;
String row = String.format("%10d %s\n", entry.freq,
s == null ? "null" : s.substring(0, Math.min(s.length(), 40)));
buf.append(row);
}
}
return buf.toString();
}
/**
* Add a string to the entry map, escaping it, or updating its frequency.
*/
@Override
public void string(String original) {
Integer id = entryMap.get(original);
if (id == null) {
id = entries.size();
String escaped = escape(original);
entryMap.put(original, id);
entries.add(new Entry(original, escaped));
} else {
entries.get(id).freq++;
}
}
// Mandatory escaped characters per JSON RFC 7159
private static final String[] REPLACEMENTS = new String[0x1f];
{
// Quick-replace ASCII C0 controls
for (int i = 0; i < 0x1f; i++) {
REPLACEMENTS[i] = String.format("\\u%04x", i);
}
}
/**
* Escape a string for appending to a JSON stream.
*/
private String escape(String s) {
if (s == null) {
return null;
}
tmp.setLength(0);
int len = s.length();
for (int i = 0; i < len; i++) {
char c = s.charAt(i);
switch (c) {
case '"': tmp.append("\\\""); break;
case '\\': tmp.append("\\\\"); break;
case '\t': tmp.append("\\t"); break;
case '\b': tmp.append("\\b"); break;
case '\n': tmp.append("\\n"); break;
case '\r': tmp.append("\\r"); break;
case '\f': tmp.append("\\f"); break;
// Fixes for eval(json) per https://github.com/google/gson/issues/341
case '\u2028': tmp.append("\\u2028"); break;
case '\u2029': tmp.append("\\u2029"); break;
default:
if (c < 0x20) {
tmp.append(REPLACEMENTS[c]);
} else {
tmp.append(c);
}
break;
}
}
return tmp.toString();
}
private static class Entry {
public final String original;
public final String escaped;
/** Records frequency of occurrence of original string */
public int freq;
public Entry(String original, String escaped) {
this.original = original;
this.escaped = escaped;
this.freq = 1;
}
}
}