Added and updated comments.

src/io/nayuki/fastqrcodegen/QrCode.java

@@ -197,9 +197,8 @@ public final class QrCode {
 	
 	
 	/**
-	 * Based on the specified number of border modules to add as padding, this returns a
-	 * string whose contents represents an SVG XML file that depicts this QR Code symbol.
-	 * Note that Unix newlines (\n) are always used, regardless of the platform.
+	 * Returns a string of SVG XML code representing an image of this QR Code symbol with the specified
+	 * number of border modules. Note that Unix newlines (\n) are always used, regardless of the platform.
 	 * @param border the number of border modules to add, which must be non-negative
 	 * @return a string representing this QR Code as an SVG document
 	 * @throws IllegalArgumentException if the border is negative
@@ -259,7 +258,7 @@ public final class QrCode {
 			setModule(size - 1 - i, 8, (bits >>> i) & 1);
 		for (int i = 8; i < 15; i++)
 			setModule(8, size - 15 + i, (bits >>> i) & 1);
-		setModule(8, size - 8, 1);
+		setModule(8, size - 8, 1);  // Always black
 	}
 	
 	

src/io/nayuki/fastqrcodegen/QrSegment.java

@@ -165,19 +165,20 @@ public final class QrSegment {
 	}
 	
 	
-	// Package-private helper function.
+	// Calculates the number of bits needed to encode the given segments at the given version.
+	// Returns a non-negative number if successful. Otherwise returns -1 if a segment has too
+	// many characters to fit its length field, or the total bits exceeds Integer.MAX_VALUE.
 	static int getTotalBits(List<QrSegment> segs, int version) {
 		Objects.requireNonNull(segs);
 		long result = 0;
 		for (QrSegment seg : segs) {
 			Objects.requireNonNull(seg);
 			int ccbits = seg.mode.numCharCountBits(version);
-			// Fail if segment length value doesn't fit in the length field's bit-width
 			if (seg.numChars >= (1 << ccbits))
-				return -1;
+				return -1;  // The segment's length doesn't fit the field's bit width
 			result += 4L + ccbits + seg.bitLength;
 			if (result > Integer.MAX_VALUE)
-				return -1;
+				return -1;  // The sum will overflow an int type
 		}
 		return (int)result;
 	}