NSNumber: Rewrite hashing method

Source/NSNumber.m

@@ -40,7 +40,6 @@
 #  endif
 #endif
 
-
 #import "common.h"
 #import "Foundation/NSCoder.h"
 #import "Foundation/NSDecimalNumber.h"
@@ -708,7 +707,68 @@ - (BOOL) isEqualToValue: (NSValue*)aValue
 
 - (NSUInteger) hash
 {
-  return (unsigned)[self doubleValue];
+  NSUInteger hash;
+  const char type = *[self objCType];
+
+  union DoubleComponents
+  {
+    double d;
+    uint64_t u; 
+  };
+  union FloatComponents
+  {
+    float f;
+    uint32_t u;
+  };
+
+  switch (type)
+  {
+    case 'd':
+      {
+        union DoubleComponents c;
+
+        c.d = [self doubleValue];
+
+        // Return the unsignedIntegerValue if the floating point's fractional
+        // component is zero.
+        if (c.d == floor(c.d))
+        {
+          return [self unsignedIntegerValue];
+        }
+
+        // Special cases. There is a positive and negative zero, make sure that
+        // the hashes are not different.
+        if (isnan(c.d) || c.d == 0.0)
+        {
+          return 0;
+        }
+
+        // Return the raw bit representation of the floating point.
+        return c.u;
+     }
+    case 'f':
+      {
+        union FloatComponents c;
+
+        c.f = [self floatValue];
+
+        if (c.f == floorf(c.f))
+        {
+          return [self unsignedIntegerValue];
+        }
+
+        if (isnanf(c.f) || c.f == 0.0)
+        {
+          return 0;
+        }
+
+        return c.u;
+     }
+    default:
+      hash = [self unsignedIntegerValue];
+  }
+
+  return hash;
 }
 
 - (NSString*) stringValue

Tests/base/NSNumber/test01.m

@@ -113,6 +113,60 @@ int main()
       PASS([zero compare: n] == NSOrderedDescending, "zero greater than -1.01")
 
     END_SET("zero checks")
+
+    START_SET("hashing")
+      // Consistency - a number's hash should be the same every time.
+      NSNumber *n = [NSNumber numberWithInt:42];
+      PASS([n hash] == [n hash], "hashing is consistent for int");
+      n = [NSNumber numberWithFloat:M_PI];
+      PASS([n hash] == [n hash], "hashing is consistent for float");
+      n = [NSNumber numberWithDouble:M_PI];
+      PASS([n hash] == [n hash], "hashing is consistent for double");
+
+      // Equality - equal numbers should have the same hash.
+      NSNumber *a = [NSNumber numberWithInt:42];
+      NSNumber *b = [NSNumber numberWithInt:42];
+      PASS([a hash] == [b hash], "equal int numbers have same hash");
+      a = [NSNumber numberWithFloat:42.0f];
+      b = [NSNumber numberWithDouble:42.0];
+      PASS([a hash] == [b hash], "42.0f and 42.0dd have the same hash");
+      a = [NSNumber numberWithLongLong:LLONG_MAX];
+      b = [NSNumber numberWithUnsignedLongLong:LLONG_MAX];
+      PASS([a hash] == [b hash], "LLONG_MAX and ULLONG_MAX-ish have same hash");
+
+      // Floating point numbers with zero fractional component.
+      a = [NSNumber numberWithDouble:42.0];
+      b = [NSNumber numberWithInt:42];
+      PASS([a hash] == [b hash], "double with zero fractional part hashes like int");
+      a = [NSNumber numberWithFloat:123.0f];
+      b = [NSNumber numberWithInt:123];
+      PASS([a hash] == [b hash], "float with zero fractional part hashes like int");
+
+      // Special Cases - Zero and NaN.
+      a = [NSNumber numberWithDouble:0.0];
+      PASS([a hash] == 0, "hash for 0.0 is 0");
+      a = [NSNumber numberWithDouble:-0.0];
+      PASS([a hash] == 0, "hash for -0.0 is 0");
+      a = [NSNumber numberWithFloat:0.0f];
+      PASS([a hash] == 0, "hash for 0.0f is 0");
+      a = [NSDecimalNumber notANumber];
+      PASS([a hash] == 0, "hash for NaN is 0");
+
+      // Verify different numbers have different hashes.
+      NSNumber *n1 = [NSNumber numberWithInt:1];
+      NSNumber *n2 = [NSNumber numberWithInt:2];
+      PASS([n1 hash] != [n2 hash], "different integers have different hashes");
+
+      NSNumber *f1 = [NSNumber numberWithFloat:1.0f];
+      NSNumber *f2 = [NSNumber numberWithFloat:1.1f];
+      PASS([f1 hash] != [f2 hash], "different floats have different hashes");
+
+      NSNumber *d1 = [NSNumber numberWithDouble:3.14159];
+      NSNumber *d2 = [NSNumber numberWithDouble:3.14158];
+      PASS([d1 hash] != [d2 hash], "different doubles have different hashes");
+
+    END_SET("hashing")
+
   END_SET("NSNumber")
 
   return 0;