Issue 85: Fix for min buffer sizes (#86)

* add test

* fix the bug

---------

Co-authored-by: Gorgi Kalamernikov <ggk@mca.dev>

Author: GKalamernikov

src/Hashids.net/Hashids.cs

@@ -567,7 +567,8 @@ private long[] GetNumbersFrom(string hash)
         {
             var result = NumbersFrom(hash);
 
-            Span<char> hashBuffer = hash.Length < MAX_STACKALLOC_SIZE ? stackalloc char[hash.Length] : new char[hash.Length];
+            int bufferSizeToAllocate = Math.Max(hash.Length, _minHashLength);
+            Span<char> hashBuffer = bufferSizeToAllocate < MAX_STACKALLOC_SIZE ? stackalloc char[bufferSizeToAllocate] : new char[bufferSizeToAllocate];
             var hashLength = GenerateHashFrom(result, ref hashBuffer);
             if (hashLength == -1)
                 return Array.Empty<long>();

test/Hashids.net.test/IssueSpecificTests.cs

@@ -86,5 +86,14 @@ void Issue75_TooShortHashWithLargerHashLengthShouldNotThrowException()
             var hashids = new Hashids("salt", 40);
             Assert.Throws<NoResultException>(() => hashids.DecodeSingle("ab"));
         }
+
+        [Fact]
+        void Issue85_hash_shorter_than_min_length_should_not_throw_exception()
+        {
+            Hashids hashids = new Hashids(salt: "Dqa2s3RJBYPHUzg&R5qkF3Z4HLaWp#A^kMc^DqKVmqag2tasQjhz-PSM23=4", minHashLength: 8);
+            int[] numbers = hashids.Decode("5111111"); // Length = 7
+
+            Assert.Empty(numbers);
+        }
     }
 }