From 71ae6cd4f933ed57d7a26457e8ab31a6fc16a025 Mon Sep 17 00:00:00 2001
From: Robert Greene <robgreene@users.sourceforge.net>
Date: Wed, 26 Feb 2003 01:29:12 +0000
Subject: [PATCH] Added getSaneNumber and getSignedWordValue.

---
 .../applecommander/storage/AppleUtil.java     | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/com/webcodepro/applecommander/storage/AppleUtil.java b/src/com/webcodepro/applecommander/storage/AppleUtil.java
index 9f164c7..4fa60cd 100644
--- a/src/com/webcodepro/applecommander/storage/AppleUtil.java
+++ b/src/com/webcodepro/applecommander/storage/AppleUtil.java
@@ -62,6 +62,14 @@ public class AppleUtil {
 		return getUnsignedByte(low) + getUnsignedByte(high)*256;
 	}
 	
+	/**
+	 * Compute the signed value of a word.
+	 */
+	public static int getSignedWordValue(byte[] buffer, int offset) {
+		int value = buffer[offset+1] * 256;
+		return value + getUnsignedByte(buffer[offset]);
+	}
+	
 	/**
 	 * Set a word value.
 	 */
@@ -404,4 +412,35 @@ public class AppleUtil {
 		}
 		return decompressedStream.toByteArray();
 	}
+	
+	/**
+	 * Pull a SANE formatted number from the buffer and return it
+	 * as a Java double datatype.  Fortunately, SANE is the IEEE 754
+	 * format which _is_ Java's double datatype.  The Double class
+	 * has an intrinsic longBitsToDouble method to do this.  The
+	 * SANE/IEEE 754 format is setup as such:
+	 * <pre>
+	 *   E SSSSSSSSSSS FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF...F<br>
+	 *   0 1........11 12....................................63<br>
+	 * </pre>
+	 * Where E is the sign bit, S is the exponent bits and F is the
+	 * fraction bits.  The format is discussed within the Double class
+	 * documentation as around the web.  Be aware that the fraction
+	 * bits are base 2.  Meaning that a fraction of .101 is, in reality,
+	 * a binary fraction.  In decimal, this is 1/2 + 0/4 + 1/8 = 5/8
+	 * or .625.
+	 * See http://www.psc.edu/general/software/packages/ieee/ieee.html
+	 * for an example.
+	 * <p>
+	 * Note: SANE numbers, as stored by AppleWorks are in typical
+	 * low/high format.
+	 */
+	public static double getSaneNumber(byte[] buffer, int offset) {
+		long doubleBits = 0;
+		for (int i=8; i>0; i--) {
+			doubleBits <<= 8;
+			doubleBits+= getUnsignedByte(buffer[offset+i-1]);
+		}
+		return Double.longBitsToDouble(doubleBits);
+	}
 }