[m-rev.] diff: bitmap in java

[Peter Wang]

Branches: main

library/bitmap.m:
        Add a constructor for the Java definition of MercuryBitmap which allows
        foreign code to construct a MercuryBitmap from an existing byte array.

        Add an `equals' method implementation.

        Fix bitmap_equal  in Java.  The old definition could return true two
        bitmaps had different number of bits but the same number of bytes in
        the underlying array.

diff --git a/library/bitmap.m b/library/bitmap.m
index 8c3d6f5..f17fa4d 100644
--- a/library/bitmap.m
+++ b/library/bitmap.m
@@ -1541,8 +1541,28 @@ public static class MercuryBitmap {
     public byte[] elements;
 
     public MercuryBitmap(int numBits) {
-        num_bits = numBits;
-        elements = new byte[numBits / 8 + (((numBits % 8) != 0) ? 1 : 0)];
+        this.num_bits = numBits;
+        this.elements = new byte[numBits / 8 + (((numBits % 8) != 0) ? 1 : 0)];
+    }
+
+    public MercuryBitmap(int numBits, byte[] elements) {
+        // This is provided so that foreign code can construct bitmaps from an
+        // existing byte array.
+        this.num_bits = numBits;
+        this.elements = elements;
+    }
+
+    @Override
+    public boolean equals(Object that) {
+        if (this == that) {
+            return true;
+        }
+        if (that instanceof MercuryBitmap) {
+            MercuryBitmap other = (MercuryBitmap)that;
+            return this.num_bits == other.num_bits
+                && java.util.Arrays.equals(this.elements, other.elements);
+        }
+        return false;
     }
 }
 ").
@@ -1585,7 +1605,7 @@ public class MercuryBitmap {
     bitmap_equal(BM1::in, BM2::in),
     [will_not_call_mercury, thread_safe, promise_pure, will_not_modify_trail],
 "
-    succeeded = java.util.Arrays.equals(BM1.elements, BM2.elements);
+    succeeded = BM1.equals(BM2);
 ").
 
 :- pragma foreign_proc("Erlang",

--------------------------------------------------------------------------
mercury-reviews mailing list
Post messages to:       mercury-reviews at csse.unimelb.edu.au
Administrative Queries: owner-mercury-reviews at csse.unimelb.edu.au
Subscriptions:          mercury-reviews-request at csse.unimelb.edu.au
--------------------------------------------------------------------------