org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/SimilarityIndexTest.java

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package org.eclipse.jgit.diff;

import java.io.ByteArrayInputStream;
import java.io.IOException;

import junit.framework.TestCase;

import org.eclipse.jgit.lib.Constants;

public class SimilarityIndexTest extends TestCase {
	public void testIndexingSmallObject() {
		SimilarityIndex si = hash("" //
				+ "A\n" //
				+ "B\n" //
				+ "D\n" //
				+ "B\n" //
		);

		int key_A = keyFor("A\n");
		int key_B = keyFor("B\n");
		int key_D = keyFor("D\n");
		assertTrue(key_A != key_B && key_A != key_D && key_B != key_D);

		assertEquals(3, si.size());
		assertEquals(2, si.count(si.findIndex(key_A)));
		assertEquals(4, si.count(si.findIndex(key_B)));
		assertEquals(2, si.count(si.findIndex(key_D)));
	}

	public void testIndexingLargeObject() throws IOException {
		byte[] in = ("" //
				+ "A\n" //
				+ "B\n" //
				+ "B\n" //
				+ "B\n").getBytes("UTF-8");
		SimilarityIndex si = new SimilarityIndex();
		si.hash(new ByteArrayInputStream(in), in.length);
		assertEquals(2, si.size());
	}

	public void testCommonScore_SameFiles() {
		String text = "" //
				+ "A\n" //
				+ "B\n" //
				+ "D\n" //
				+ "B\n";
		SimilarityIndex src = hash(text);
		SimilarityIndex dst = hash(text);
		assertEquals(8, src.common(dst));
		assertEquals(8, dst.common(src));

		assertEquals(100, src.score(dst, 100));
		assertEquals(100, dst.score(src, 100));
	}

	public void testCommonScore_EmptyFiles() {
		SimilarityIndex src = hash("");
		SimilarityIndex dst = hash("");
		assertEquals(0, src.common(dst));
		assertEquals(0, dst.common(src));
	}

	public void testCommonScore_TotallyDifferentFiles() {
		SimilarityIndex src = hash("A\n");
		SimilarityIndex dst = hash("D\n");
		assertEquals(0, src.common(dst));
		assertEquals(0, dst.common(src));
	}

	public void testCommonScore_SimiliarBy75() {
		SimilarityIndex src = hash("A\nB\nC\nD\n");
		SimilarityIndex dst = hash("A\nB\nC\nQ\n");
		assertEquals(6, src.common(dst));
		assertEquals(6, dst.common(src));

		assertEquals(75, src.score(dst, 100));
		assertEquals(75, dst.score(src, 100));
	}

	private static SimilarityIndex hash(String text) {
		SimilarityIndex src = new SimilarityIndex() {
			@Override
			void hash(byte[] raw, int ptr, final int end) {
				while (ptr < end) {
					int hash = raw[ptr] & 0xff;
					int start = ptr;
					do {
						int c = raw[ptr++] & 0xff;
						if (c == '\n')
							break;
					} while (ptr < end && ptr - start < 64);
					add(hash, ptr - start);
				}
			}
		};
		byte[] raw = Constants.encode(text);
		src.setFileSize(raw.length);
		src.hash(raw, 0, raw.length);
		src.sort();
		return src;
	}

	private static int keyFor(String line) {
		SimilarityIndex si = hash(line);
		assertEquals("single line scored", 1, si.size());
		return si.key(0);
	}
}