com.ajjpj.afoundation.io.AJsonSerHelper Maven / Gradle / Ivy

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package com.ajjpj.afoundation.io;

import com.ajjpj.afoundation.collection.mutable.AStack;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.Charset;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.Locale;


/**
 * This class is a collection of helper methods for manually writing JSON to an OutputStream. 
 *
 * For details on the JSON spec, see http://json.org
 *
 * @author arno
 */
public class AJsonSerHelper {
    static final Charset UTF_8 = Charset.forName("UTF-8");

    private static final int[] TEN_POW = new int[] {1, 10, 100, 1000, 10*1000, 100*1000, 1000*1000, 10*1000*1000, 100*1000*1000, 1000*1000*1000};
    private static final String[] PATTERNS = new String[] {"0", "0.0", "0.00", "0.000", "0.0000", "0.00000", "0.000000", "0.0000000", "0.00000000", "0.000000000"};
    private static final DecimalFormatSymbols DECIMAL_FORMAT_SYMBOLS = new DecimalFormatSymbols(Locale.US);

    private final Writer out;
    private final AStack state = new AStack<>();

    public AJsonSerHelper(OutputStream out) {
        this.out = new OutputStreamWriter(out, UTF_8);
        state.push(JsonSerState.initial);
    }

    public void startObject() throws IOException {
        checkAcceptsValueAndPrefixComma();
        state.push(JsonSerState.startOfObject);
        out.write("{");
    }

    public void endObject() throws IOException {
        checkInObject();
        state.pop();
        out.write("}");
        afterValueWritten();
    }

    public void writeKey(String key) throws IOException {
        if(!state().acceptsKey) {
            throw new IllegalStateException("state " + state() + " does not accept a key");
        }
        if(state() == JsonSerState.inObject) {
            out.write(",");
        }
        _writeStringLiteral(key);
        out.write(":");
        state.push(JsonSerState.afterKey);
    }

    public void startArray() throws IOException {
        checkAcceptsValueAndPrefixComma();
        state.push(JsonSerState.startOfArray);
        out.write("[");
    }

    public void endArray() throws IOException {
        checkInArray();
        state.pop();
        out.write("]");
        afterValueWritten();
    }

    public void writeStringLiteral(String s) throws IOException {
        if (s == null) {
            writeNullLiteral ();
            return;
        }

        checkAcceptsValueAndPrefixComma();
        _writeStringLiteral(s);
        afterValueWritten();
    }

    private void _writeStringLiteral(String s) throws IOException {
        out.write('"');
        for(int i=0; i