Merge pull request #1 from yegor256/master

Syncing fork.

src/main/java/org/cactoos/io/TailInput.java

@@ -0,0 +1,144 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.io;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import org.cactoos.Input;
+import org.cactoos.scalar.MinOf;
+import org.cactoos.text.FormattedText;
+
+/**
+ * Input showing only last N bytes of the stream.
+ *
+ * <p>There is no thread-safety guarantee.
+ *
+ * @author Krzysztof Krason (Krzysztof.Krason@gmail.com)
+ * @version $Id$
+ * @since 0.30
+ */
+public final class TailInput implements Input {
+
+    /**
+     * Input to decorate.
+     */
+    private final Input input;
+
+    /**
+     * Number of last bytes to show from the input.
+     */
+    private final int count;
+
+    /**
+     * Maximum number of bytes to read at once.
+     */
+    private final int max;
+
+    /**
+     * Constructor.
+     * @param inpt Input to decorate
+     * @param bytes Number of last bytes to show from input
+     */
+    public TailInput(final Input inpt, final int bytes) {
+        // @checkstyle MagicNumber (1 line)
+        this(inpt, bytes, 16384);
+    }
+
+    /**
+     * Constructor.
+     * @param inpt Input to decorate
+     * @param bytes Number of last bytes to show from input
+     * @param maximum Maximum number of bytes to read at once
+     */
+    public TailInput(final Input inpt, final int bytes, final int maximum) {
+        this.input = inpt;
+        this.count = bytes;
+        this.max = maximum;
+    }
+
+    @Override
+    public InputStream stream() throws IOException {
+        if (this.max < this.count) {
+            throw new IllegalArgumentException(
+                new FormattedText(
+                    "Can't tail %d bytes if buffer is set to %d",
+                    this.count, this.max
+                ).asString()
+            );
+        }
+        final byte[] buffer = new byte[this.max];
+        final byte[] response = new byte[this.count];
+        int num = 0;
+        final InputStream strm = this.input.stream();
+        for (int read = strm.read(buffer); read > 0; read = strm.read(buffer)) {
+            if (read < this.max && read < this.count) {
+                num = this.copyPartial(buffer, response, num, read);
+            } else {
+                num = this.copy(buffer, response, read);
+            }
+        }
+        return new ByteArrayInputStream(response, 0, num);
+    }
+
+    /**
+     * Copy full buffer to response.
+     * @param buffer The buffer array
+     * @param response The response array
+     * @param read Number of bytes read in buffer
+     * @return Number of bytes in the response buffer
+     */
+    private int copy(final byte[] buffer, final byte[] response,
+        final int read) {
+        System.arraycopy(
+            buffer, read - this.count, response, 0, this.count
+        );
+        return new MinOf(this.count, read).intValue();
+    }
+
+    /**
+     * Copy buffer to response for read count smaller then buffer size.
+     * @param buffer The buffer array
+     * @param response The response array
+     * @param num Number of bytes in response array from previous read
+     * @param read Number of bytes read in the buffer
+     * @return New count of bytes in the response array
+     * @checkstyle ParameterNumberCheck (3 lines)
+     */
+    private int copyPartial(final byte[] buffer, final byte[] response,
+        final int num, final int read) {
+        final int result;
+        if (num > 0) {
+            System.arraycopy(
+                response, read, response, 0, this.count - read
+            );
+            System.arraycopy(buffer, 0, response, this.count - read, read);
+            result = this.count;
+        } else {
+            System.arraycopy(buffer, 0, response, 0, read);
+            result = read;
+        }
+        return result;
+    }
+}

src/test/java/org/cactoos/io/TailInputTest.java

@@ -0,0 +1,126 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.io;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Random;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+/**
+ * Tests for {@link TailInput}.
+ * @author Krzysztof Krason (Krzysztof.Krason@gmail.com)
+ * @version $Id$
+ * @since 0.30
+ * @checkstyle JavadocMethodCheck (500 lines)
+ */
+public final class TailInputTest {
+
+    @Test
+    public void tailsOnLongStream() throws IOException {
+        final int size = 4;
+        final byte[] bytes = this.generate(size);
+        MatcherAssert.assertThat(
+            new BytesOf(
+                new TailInput(new InputOf(new BytesOf(bytes)), size - 1)
+            ).asBytes(),
+            Matchers.equalTo(Arrays.copyOfRange(bytes, 1, bytes.length))
+        );
+    }
+
+    @Test
+    public void tailsOnExactStream() throws IOException {
+        final int size = 4;
+        final byte[] bytes = this.generate(size);
+        MatcherAssert.assertThat(
+            new BytesOf(
+                new TailInput(new InputOf(new BytesOf(bytes)), size)
+            ).asBytes(),
+            Matchers.equalTo(bytes)
+        );
+    }
+
+    @Test
+    public void tailsOnExactStreamAndBuffer() throws IOException {
+        final int size = 4;
+        final byte[] bytes = this.generate(size);
+        MatcherAssert.assertThat(
+            new BytesOf(
+                new TailInput(new InputOf(new BytesOf(bytes)), size, size)
+            ).asBytes(),
+            Matchers.equalTo(bytes)
+        );
+    }
+
+    @Test
+    public void tailsOnShorterStream() throws IOException {
+        final int size = 4;
+        final byte[] bytes = this.generate(size);
+        MatcherAssert.assertThat(
+            new BytesOf(
+                new TailInput(new InputOf(new BytesOf(bytes)), size + 1)
+            ).asBytes(),
+            Matchers.equalTo(bytes)
+        );
+    }
+
+    @Test
+    public void tailsOnStreamLongerThanBufferAndBytes() throws IOException {
+        final int size = 4;
+        final byte[] bytes = this.generate(size);
+        MatcherAssert.assertThat(
+            new BytesOf(
+                new TailInput(
+                    new InputOf(new BytesOf(bytes)), size - 1, size - 1
+                )
+            ).asBytes(),
+            Matchers.equalTo(
+                Arrays.copyOfRange(bytes, 1, bytes.length)
+            )
+        );
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void failsIfBufferSizeSmallerThanTailSize() throws IOException {
+        final int size = 4;
+        new BytesOf(
+            new TailInput(
+                new InputOf(new BytesOf(this.generate(size))), size, size - 1
+            )
+        ).asBytes();
+    }
+
+    /**
+     * Generate random byte array.
+     * @param size Size of array
+     * @return Generated array
+     */
+    private byte[] generate(final int size) {
+        final byte[] bytes = new byte[size];
+        new Random().nextBytes(bytes);
+        return bytes;
+    }
+}