Some algorithms like a diff or patch require efficient lookup of lines
within a source file, using a 1 based line number. lineMap produces a
list of offsets within the file where each line starts, providing O(1)
lookup time to locate those positions.
Signed-off-by: Shawn O. Pearce <spearce@xxxxxxxxxxx>
---
.../tst/org/spearce/jgit/util/IntListTest.java | 24 ++++++
.../jgit/util/RawParseUtils_LineMapTest.java | 88 ++++++++++++++++++++
.../src/org/spearce/jgit/util/IntList.java | 15 ++++
.../src/org/spearce/jgit/util/RawParseUtils.java | 31 +++++++
4 files changed, 158 insertions(+), 0 deletions(-)
create mode 100644 org.spearce.jgit.test/tst/org/spearce/jgit/util/RawParseUtils_LineMapTest.java
diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java
index f943075..c470d55 100644
--- a/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java
@@ -103,6 +103,30 @@ public void testAdd_LargeGroup() {
}
}
+ public void testFillTo0() {
+ final IntList i = new IntList();
+ i.fillTo(0, Integer.MIN_VALUE);
+ assertEquals(0, i.size());
+ }
+
+ public void testFillTo1() {
+ final IntList i = new IntList();
+ i.fillTo(1, Integer.MIN_VALUE);
+ assertEquals(1, i.size());
+ i.add(0);
+ assertEquals(Integer.MIN_VALUE, i.get(0));
+ assertEquals(0, i.get(1));
+ }
+
+ public void testFillTo100() {
+ final IntList i = new IntList();
+ i.fillTo(100, Integer.MIN_VALUE);
+ assertEquals(100, i.size());
+ i.add(3);
+ assertEquals(Integer.MIN_VALUE, i.get(99));
+ assertEquals(3, i.get(100));
+ }
+
public void testClear() {
final IntList i = new IntList();
final int n = 5;
diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/util/RawParseUtils_LineMapTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/util/RawParseUtils_LineMapTest.java
new file mode 100644
index 0000000..3f562a4
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/util/RawParseUtils_LineMapTest.java
@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2008, Google Inc.
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following
+ * disclaimer in the documentation and/or other materials provided
+ * with the distribution.
+ *
+ * - Neither the name of the Git Development Community nor the
+ * names of its contributors may be used to endorse or promote
+ * products derived from this software without specific prior
+ * written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.spearce.jgit.util;
+
+import java.io.UnsupportedEncodingException;
+
+import junit.framework.TestCase;
+
+public class RawParseUtils_LineMapTest extends TestCase {
+ public void testEmpty() {
+ final IntList map = RawParseUtils.lineMap(new byte[] {}, 0, 0);
+ assertNotNull(map);
+ assertEquals(1, map.size());
+ assertEquals(Integer.MIN_VALUE, map.get(0));
+ }
+
+ public void testOneBlankLine() {
+ final IntList map = RawParseUtils.lineMap(new byte[] { '\n' }, 0, 1);
+ assertEquals(2, map.size());
+ assertEquals(Integer.MIN_VALUE, map.get(0));
+ assertEquals(0, map.get(1));
+ }
+
+ public void testTwoLineFooBar() throws UnsupportedEncodingException {
+ final byte[] buf = "foo\nbar\n".getBytes("ISO-8859-1");
+ final IntList map = RawParseUtils.lineMap(buf, 0, buf.length);
+ assertEquals(3, map.size());
+ assertEquals(Integer.MIN_VALUE, map.get(0));
+ assertEquals(0, map.get(1));
+ assertEquals(4, map.get(2));
+ }
+
+ public void testTwoLineNoLF() throws UnsupportedEncodingException {
+ final byte[] buf = "foo\nbar".getBytes("ISO-8859-1");
+ final IntList map = RawParseUtils.lineMap(buf, 0, buf.length);
+ assertEquals(3, map.size());
+ assertEquals(Integer.MIN_VALUE, map.get(0));
+ assertEquals(0, map.get(1));
+ assertEquals(4, map.get(2));
+ }
+
+ public void testFourLineBlanks() throws UnsupportedEncodingException {
+ final byte[] buf = "foo\n\n\nbar\n".getBytes("ISO-8859-1");
+ final IntList map = RawParseUtils.lineMap(buf, 0, buf.length);
+ assertEquals(5, map.size());
+ assertEquals(Integer.MIN_VALUE, map.get(0));
+ assertEquals(0, map.get(1));
+ assertEquals(4, map.get(2));
+ assertEquals(5, map.get(3));
+ assertEquals(6, map.get(4));
+ }
+
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java b/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java
index 1445f88..2824074 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java
@@ -93,6 +93,21 @@ public void add(final int n) {
entries[count++] = n;
}
+ /**
+ * Pad the list with entries.
+ *
+ * @param toIndex
+ * index position to stop filling at. 0 inserts no filler. 1
+ * ensures the list has a size of 1, adding <code>val</code> if
+ * the list is currently empty.
+ * @param val
+ * value to insert into padded positions.
+ */
+ public void fillTo(int toIndex, final int val) {
+ while (count < toIndex)
+ add(val);
+ }
+
private void grow() {
final int[] n = new int[(entries.length + 16) * 3 / 2];
System.arraycopy(entries, 0, n, 0, count);
diff --git a/org.spearce.jgit/src/org/spearce/jgit/util/RawParseUtils.java b/org.spearce.jgit/src/org/spearce/jgit/util/RawParseUtils.java
index 8896d38..6143188 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/util/RawParseUtils.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/util/RawParseUtils.java
@@ -266,6 +266,37 @@ public static final int nextLF(final byte[] b, int ptr, final char chrA) {
}
/**
+ * Index the region between <code>[ptr, end)</code> to find line starts.
+ * <p>
+ * The returned list is 1 indexed. Index 0 contains
+ * {@link Integer#MIN_VALUE} to pad the list out.
+ * <p>
+ * Using a 1 indexed list means that line numbers can be directly accessed
+ * from the list, so <code>list.get(1)</code> (aka get line 1) returns
+ * <code>ptr</code>.
+ *
+ * @param buf
+ * buffer to scan.
+ * @param ptr
+ * position within the buffer corresponding to the first byte of
+ * line 1.
+ * @param end
+ * 1 past the end of the content within <code>buf</code>.
+ * @return a line map indexing the start position of each line.
+ */
+ public static final IntList lineMap(final byte[] buf, int ptr, int end) {
+ // Experimentally derived from multiple source repositories
+ // the average number of bytes/line is 36. Its a rough guess
+ // to initially size our map close to the target.
+ //
+ final IntList map = new IntList((end - ptr) / 36);
+ map.fillTo(1, Integer.MIN_VALUE);
+ for (; ptr < end; ptr = nextLF(buf, ptr))
+ map.add(ptr);
+ return map;
+ }
+
+ /**
* Locate the "author " header line data.
*
* @param b
--
1.6.1.rc2.306.ge5d5e
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