common/io/CharStreamsTest.java

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * 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.google.common.io;

import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;

import java.io.EOFException;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.List;

/**
 * Unit test for {@link CharStreams}.
 *
 * @author Chris Nokleberg
 */
public class CharStreamsTest extends IoTestCase {

  private static final String TEXT
      = "The quick brown fox jumped over the lazy dog.";

  public void testToString() throws IOException {
    assertEquals(TEXT, CharStreams.toString(new StringReader(TEXT)));
  }

  public void testSkipFully_blockingRead() throws IOException {
    Reader reader = new NonSkippingReader("abcdef");
    CharStreams.skipFully(reader, 6);
    assertEquals(-1, reader.read());
  }

  private static class NonSkippingReader extends StringReader {
    NonSkippingReader(String s) {
      super(s);
    }

    @Override
    public long skip(long n) {
      return 0;
    }
  }

  public void testReadLines() throws IOException {
    List<String> lines = CharStreams.readLines(
        new StringReader("a\nb\nc"));
    assertEquals(ImmutableList.of("a", "b", "c"), lines);
  }

  public void testReadLines_withLineProcessor() throws IOException {
    String text = "a\nb\nc";

    // Test a LineProcessor that always returns false.
    Reader r = new StringReader(text);
    LineProcessor<Integer> alwaysFalse = new LineProcessor<Integer>() {
      int seen;
      @Override
      public boolean processLine(String line) {
        seen++;
        return false;
      }
      @Override
      public Integer getResult() {
        return seen;
      }
    };
    assertEquals("processLine was called more than once", 1,
        CharStreams.readLines(r, alwaysFalse).intValue());

    // Test a LineProcessor that always returns true.
    r = new StringReader(text);
    LineProcessor<Integer> alwaysTrue = new LineProcessor<Integer>() {
      int seen;
      @Override
      public boolean processLine(String line) {
        seen++;
        return true;
      }
      @Override
      public Integer getResult() {
        return seen;
      }
    };
    assertEquals("processLine was not called for all the lines", 3,
        CharStreams.readLines(r, alwaysTrue).intValue());

    // Test a LineProcessor that is conditional.
    r = new StringReader(text);
    final StringBuilder sb = new StringBuilder();
    LineProcessor<Integer> conditional = new LineProcessor<Integer>() {
      int seen;
      @Override
      public boolean processLine(String line) {
        seen++;
        sb.append(line);
        return seen < 2;
      }
      @Override
      public Integer getResult() {
        return seen;
      }
    };
    assertEquals(2, CharStreams.readLines(r, conditional).intValue());
    assertEquals("ab", sb.toString());
  }

  public void testSkipFully_EOF() throws IOException {
    Reader reader = new StringReader("abcde");
    try {
      CharStreams.skipFully(reader, 6);
      fail("expected EOFException");
    } catch (EOFException e) {
      // expected
    }
  }

  public void testSkipFully() throws IOException {
    String testString = "abcdef";
    Reader reader = new StringReader(testString);

    assertEquals(testString.charAt(0), reader.read());
    CharStreams.skipFully(reader, 1);
    assertEquals(testString.charAt(2), reader.read());
    CharStreams.skipFully(reader, 2);
    assertEquals(testString.charAt(5), reader.read());

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

  public void testAsWriter() {
    // Should wrap Appendable in a new object
    Appendable plainAppendable = new StringBuilder();
    Writer result = CharStreams.asWriter(plainAppendable);
    assertNotSame(plainAppendable, result);
    assertNotNull(result);

    // A Writer should not be wrapped
    Appendable secretlyAWriter = new StringWriter();
    result = CharStreams.asWriter(secretlyAWriter);
    assertSame(secretlyAWriter, result);
  }

  public void testCopy() throws IOException {
    StringBuilder builder = new StringBuilder();
    long copied = CharStreams.copy(new StringReader(ASCII), builder);
    assertEquals(ASCII, builder.toString());
    assertEquals(ASCII.length(), copied);

    StringBuilder builder2 = new StringBuilder();
    copied = CharStreams.copy(new StringReader(I18N), builder2);
    assertEquals(I18N, builder2.toString());
    assertEquals(I18N.length(), copied);
  }

  /**
   * Test for Guava issue 1061: http://code.google.com/p/guava-libraries/issues/detail?id=1061
   *
   * <p>CharStreams.copy was failing to clear its CharBuffer after each read call, which effectively
   * reduced the available size of the buffer each time a call to read didn't fill up the available
   * space in the buffer completely. In general this is a performance problem since the buffer size
   * is permanently reduced, but with certain Reader implementations it could also cause the buffer
   * size to reach 0, causing an infinite loop.
   */
  public void testCopyWithReaderThatDoesNotFillBuffer() throws IOException {
    // need a long enough string for the buffer to hit 0 remaining before the copy completes
    String string = Strings.repeat("0123456789", 100);
    StringBuilder b = new StringBuilder();
    // the main assertion of this test is here... the copy will fail if the buffer size goes down
    // each time it is not filled completely
    long copied = CharStreams.copy(newNonBufferFillingReader(new StringReader(string)), b);
    assertEquals(string, b.toString());
    assertEquals(string.length(), copied);
  }

  public void testNullWriter() throws Exception {
    // create a null writer
    Writer nullWriter = CharStreams.nullWriter();
    // write to the writer
    nullWriter.write('n');
    String test = "Test string for NullWriter";
    nullWriter.write(test);
    nullWriter.write(test, 2, 10);
    // nothing really to assert?
    assertSame(CharStreams.nullWriter(), CharStreams.nullWriter());
  }

  /**
   * Returns a reader wrapping the given reader that only reads half of the maximum number of
   * characters that it could read in read(char[], int, int).
   */
  private static Reader newNonBufferFillingReader(Reader reader) {
    return new FilterReader(reader) {
      @Override
      public int read(char[] cbuf, int off, int len) throws IOException {
        // if a buffer isn't being cleared correctly, this method will eventually start being called
        // with a len of 0 forever
        if (len <= 0) {
          fail("read called with a len of " + len);
        }
        // read fewer than the max number of chars to read
        // shouldn't be a problem unless the buffer is shrinking each call
        return in.read(cbuf, off, Math.max(len - 1024, 0));
      }
    };
  }
}