broke out from leaksoup.java so it can be used by tracesoup.

gc/boehm/leaksoup/FileTable.java

@@ -0,0 +1,92 @@
+/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ *
+ * The contents of this file are subject to the Netscape Public
+ * License Version 1.1 (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.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express oqr
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ *
+ * The Original Code is Mozilla Communicator client code, released
+ * March 31, 1998.
+ *
+ * The Initial Developer of the Original Code is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation. All
+ * Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Patrick C. Beard <beard@netscape.com>
+ *
+ * Alternatively, the contents of this file may be used under the
+ * terms of the GNU Public License (the "GPL"), in which case the
+ * provisions of the GPL are applicable instead of those above.
+ * If you wish to allow use of your version of this file only
+ * under the terms of the GPL and not to allow others to use your
+ * version of this file under the NPL, indicate your decision by
+ * deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL.  If you do not delete
+ * the provisions above, a recipient may use your version of this
+ * file under either the NPL or the GPL.
+ */
+
+import java.io.*;
+import java.util.*;
+
+/**
+ * Provides a way to map from byte offsets into a file to line numbers.
+ */
+public class FileTable {
+	private static class Line {
+		int mOffset;
+		int mLength;
+		
+		Line(int offset, int length) {
+			mOffset = offset;
+			mLength = length;
+		}
+	}
+	private Line[] mLines;
+
+	public FileTable(String path) throws IOException {
+		Vector lines = new Vector();
+		BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(path)));
+		int offset = 0;
+		for (String line = reader.readLine(); line != null; line = reader.readLine()) {
+			// always add 1 for the line feed.
+			int length = 1 + line.length();
+			lines.addElement(new Line(offset, length));
+			offset += length;
+		}
+		reader.close();
+		int size = lines.size();
+		mLines = new Line[size];
+		lines.copyInto(mLines);
+	}
+	
+	public int getLine(int offset) {
+		// use binary search to find the line which spans this offset.
+		int length = mLines.length;
+		int minIndex = 0, maxIndex = length - 1;
+		int index = maxIndex / 2;
+		while (minIndex <= maxIndex) {
+			Line line = mLines[index];
+			if (offset < line.mOffset) {
+				maxIndex = (index - 1);
+				index = (minIndex + maxIndex) / 2;
+			} else {
+				if (offset < (line.mOffset + line.mLength)) {
+					return index;
+				}
+				minIndex = (index + 1);
+				index = (minIndex + maxIndex) / 2;
+			}
+		}
+		// this case shouldn't happen, but provides a helpful value to detect errors.
+		return -1;
+	}
+}