org.apache.avro.io.parsing.ValidatingGrammarGenerator Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.avro.io.parsing;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.avro.Schema;
import org.apache.avro.Schema.Field;
/**
* The class that generates validating grammar.
*/
public class ValidatingGrammarGenerator {
/**
* Returns the non-terminal that is the start symbol
* for the grammar for the given schema sc.
*/
public Symbol generate(Schema schema) {
return Symbol.root(generate(schema, new HashMap()));
}
/**
* Returns the non-terminal that is the start symbol
* for the grammar for the given schema sc. If there is already an entry
* for the given schema in the given map seen then
* that entry is returned. Otherwise a new symbol is generated and
* an entry is inserted into the map.
* @param sc The schema for which the start symbol is required
* @param seen A map of schema to symbol mapping done so far.
* @return The start symbol for the schema
*/
public Symbol generate(Schema sc, Map seen) {
switch (sc.getType()) {
case NULL:
return Symbol.NULL;
case BOOLEAN:
return Symbol.BOOLEAN;
case INT:
return Symbol.INT;
case LONG:
return Symbol.LONG;
case FLOAT:
return Symbol.FLOAT;
case DOUBLE:
return Symbol.DOUBLE;
case STRING:
return Symbol.STRING;
case BYTES:
return Symbol.BYTES;
case FIXED:
return Symbol.seq(new Symbol.IntCheckAction(sc.getFixedSize()),
Symbol.FIXED);
case ENUM:
return Symbol.seq(new Symbol.IntCheckAction(sc.getEnumSymbols().size()),
Symbol.ENUM);
case ARRAY:
return Symbol.seq(Symbol.repeat(Symbol.ARRAY_END, generate(sc.getElementType(), seen)),
Symbol.ARRAY_START);
case MAP:
return Symbol.seq(Symbol.repeat(Symbol.MAP_END,
generate(sc.getValueType(), seen), Symbol.STRING),
Symbol.MAP_START);
case RECORD: {
LitS wsc = new LitS(sc);
Symbol rresult = seen.get(wsc);
if (rresult == null) {
Symbol[] production = new Symbol[sc.getFields().size()];
/**
* We construct a symbol without filling the array. Please see
* {@link Symbol#production} for the reason.
*/
rresult = Symbol.seq(production);
seen.put(wsc, rresult);
int i = production.length;
for (Field f : sc.getFields()) {
production[--i] = generate(f.schema(), seen);
}
}
return rresult;
}
case UNION:
List subs = sc.getTypes();
Symbol[] symbols = new Symbol[subs.size()];
String[] labels = new String[subs.size()];
int i = 0;
for (Schema b : sc.getTypes()) {
symbols[i] = generate(b, seen);
labels[i] = b.getFullName();
i++;
}
return Symbol.seq(Symbol.alt(symbols, labels), Symbol.UNION);
default:
throw new RuntimeException("Unexpected schema type");
}
}
/** A wrapper around Schema that does "==" equality. */
static class LitS {
public final Schema actual;
public LitS(Schema actual) { this.actual = actual; }
/**
* Two LitS are equal if and only if their underlying schema is
* the same (not merely equal).
*/
public boolean equals(Object o) {
if (! (o instanceof LitS)) return false;
return actual == ((LitS)o).actual;
}
public int hashCode() {
return actual.hashCode();
}
}
}