java-topology/test/jdk/java/io/Reader/ReadCharBuffer.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * @test
 * @bug 4926314 8266014
 * @summary Test for Reader#read(CharBuffer).
 * @run junit ReadCharBuffer
 */

import java.io.BufferedReader;
import java.io.CharArrayReader;
import java.io.IOException;
import java.io.Reader;
import java.io.UncheckedIOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.util.Arrays;
import java.util.Objects;
import java.util.stream.Stream;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;

import static org.junit.jupiter.api.Assertions.assertEquals;

public class ReadCharBuffer {

    private static final int BUFFER_SIZE = 8 + 8192 + 2;

    public static Stream<CharBuffer> buffers() {
        // test both on-heap and off-heap buffers as they make use different code paths
        return Stream.of(CharBuffer.allocate(BUFFER_SIZE),
            ByteBuffer.allocateDirect(BUFFER_SIZE * 2).asCharBuffer());
    }

    @ParameterizedTest
    @MethodSource("buffers")
    public void read(CharBuffer buffer) throws IOException {
        fillBuffer(buffer);

        StringBuilder input = new StringBuilder(BUFFER_SIZE - 2 + 1);
        input.append("ABCDEF");
        for (int i = 0; i < 8192; i++) {
            input.append('y');
        }
        input.append("GH");

        try (Reader reader = new UnoptimizedStringReader(input.toString())) {
            // put only between position and limit in the target buffer
            int limit = 1 + 6;
            buffer.limit(limit);
            buffer.position(1);
            assertEquals(6, reader.read(buffer));
            assertEquals(limit, buffer.position());
            assertEquals(limit, buffer.limit());

            // read the full temporary buffer
            // and then accurately reduce the next #read call
            limit = 8 + 8192 + 1;
            buffer.limit(8 + 8192 + 1);
            buffer.position(8);
            assertEquals(8192 + 1, reader.read(buffer));
            assertEquals(limit, buffer.position());
            assertEquals(limit, buffer.limit());

            assertEquals('H', reader.read());
            assertEquals(-1, reader.read());
        }

        buffer.clear();
        StringBuilder expected = new StringBuilder(BUFFER_SIZE);
        expected.append("xABCDEFx");
        for (int i = 0; i < 8192; i++) {
            expected.append('y');
        }
        expected.append("Gx");
        assertEquals(expected.toString(), buffer.toString());
    }

    @Test
    public void readZeroLength() throws IOException {
        char[] buf = new char[] {1, 2, 3};
        BufferedReader r = new BufferedReader(new CharArrayReader(buf));
        int n = r.read(CharBuffer.allocate(0));
        assertEquals(0, n);
    }

    private void fillBuffer(CharBuffer buffer) {
        char[] filler = new char[buffer.remaining()];
        Arrays.fill(filler, 'x');
        buffer.put(filler);
        buffer.clear();
    }

    /**
     * Unoptimized version of StringReader in case StringReader overrides
     * #read(CharBuffer)
     */
    static final class UnoptimizedStringReader extends Reader {

        private String str;
        private int next = 0;

        UnoptimizedStringReader(String s) {
            this.str = s;
        }

        @Override
        public int read() throws IOException {
            synchronized (lock) {
                if (next >= str.length())
                    return -1;
                return str.charAt(next++);
            }
        }

        @Override
        public int read(char cbuf[], int off, int len) throws IOException {
            synchronized (lock) {
                Objects.checkFromIndexSize(off, len, cbuf.length);
                if (next >= str.length())
                    return -1;
                int n = Math.min(str.length() - next, len);
                str.getChars(next, next + n, cbuf, off);
                next += n;
                return n;
            }
        }

        @Override
        public void close() throws IOException {

        }
    }

}