159 lines
4.8 KiB
Java
159 lines
4.8 KiB
Java
/*
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* Copyright (C) 2010 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.gson.internal;
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import com.google.gson.JsonElement;
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import com.google.gson.JsonIOException;
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import com.google.gson.JsonNull;
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import com.google.gson.JsonParseException;
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import com.google.gson.JsonSyntaxException;
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import com.google.gson.internal.bind.TypeAdapters;
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import com.google.gson.stream.JsonReader;
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import com.google.gson.stream.JsonToken;
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import com.google.gson.stream.JsonWriter;
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import com.google.gson.stream.MalformedJsonException;
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import java.io.EOFException;
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import java.io.IOException;
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import java.io.Writer;
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import java.util.Objects;
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/** Reads and writes GSON parse trees over streams. */
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public final class Streams {
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private Streams() {
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throw new UnsupportedOperationException();
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}
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/** Takes a reader in any state and returns the next value as a JsonElement. */
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public static JsonElement parse(JsonReader reader) throws JsonParseException {
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boolean isEmpty = true;
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try {
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JsonToken unused = reader.peek();
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isEmpty = false;
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return TypeAdapters.JSON_ELEMENT.read(reader);
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} catch (EOFException e) {
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/*
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* For compatibility with JSON 1.5 and earlier, we return a JsonNull for
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* empty documents instead of throwing.
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*/
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if (isEmpty) {
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return JsonNull.INSTANCE;
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}
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// The stream ended prematurely so it is likely a syntax error.
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throw new JsonSyntaxException(e);
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} catch (MalformedJsonException e) {
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throw new JsonSyntaxException(e);
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} catch (IOException e) {
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throw new JsonIOException(e);
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} catch (NumberFormatException e) {
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throw new JsonSyntaxException(e);
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}
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}
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/** Writes the JSON element to the writer, recursively. */
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public static void write(JsonElement element, JsonWriter writer) throws IOException {
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TypeAdapters.JSON_ELEMENT.write(writer, element);
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}
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public static Writer writerForAppendable(Appendable appendable) {
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return appendable instanceof Writer ? (Writer) appendable : new AppendableWriter(appendable);
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}
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/** Adapts an {@link Appendable} so it can be passed anywhere a {@link Writer} is used. */
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private static final class AppendableWriter extends Writer {
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private final Appendable appendable;
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private final CurrentWrite currentWrite = new CurrentWrite();
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AppendableWriter(Appendable appendable) {
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this.appendable = appendable;
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}
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@Override
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public void write(char[] chars, int offset, int length) throws IOException {
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currentWrite.setChars(chars);
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appendable.append(currentWrite, offset, offset + length);
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}
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@Override
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public void flush() {}
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@Override
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public void close() {}
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// Override these methods for better performance
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// They would otherwise unnecessarily create Strings or char arrays
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@Override
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public void write(int i) throws IOException {
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appendable.append((char) i);
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}
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@Override
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public void write(String str, int off, int len) throws IOException {
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// Appendable.append turns null -> "null", which is not desired here
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Objects.requireNonNull(str);
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appendable.append(str, off, off + len);
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}
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@Override
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public Writer append(CharSequence csq) throws IOException {
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appendable.append(csq);
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return this;
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}
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@Override
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public Writer append(CharSequence csq, int start, int end) throws IOException {
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appendable.append(csq, start, end);
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return this;
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}
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/** A mutable char sequence pointing at a single char[]. */
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private static class CurrentWrite implements CharSequence {
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private char[] chars;
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private String cachedString;
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void setChars(char[] chars) {
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this.chars = chars;
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this.cachedString = null;
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}
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@Override
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public int length() {
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return chars.length;
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}
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@Override
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public char charAt(int i) {
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return chars[i];
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}
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@Override
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public CharSequence subSequence(int start, int end) {
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return new String(chars, start, end - start);
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}
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// Must return string representation to satisfy toString() contract
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@Override
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public String toString() {
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if (cachedString == null) {
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cachedString = new String(chars);
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}
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return cachedString;
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}
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}
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}
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}
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