aherbert commented on a change in pull request #160:
URL:
https://github.com/apache/commons-collections/pull/160#discussion_r426131444
##########
File path:
src/test/java/org/apache/commons/collections4/bloomfilter/hasher/HasherBuilderTest.java
##########
@@ -29,7 +32,8 @@
/**
* Tests the
- * {@link org.apache.commons.collections4.bloomfilter.hasher.Hasher.Builder
Hasher.Builder}.
+ * {@link org.apache.commons.collections4.bloomfilter.hasher.Hasher.Builder
+ * Hasher.Builder}.
Review comment:
I think I was not clear. The `byte[]` is just the part of the item T
that you want to hash. So you have two situations where you convert the item T
to either:
1. T -> List<byte[]>
2. T -> byte[]
These are then fed into the DynamicHasher. In case 1 you have a byte[] for
each property or part of T you want to add to the Bloom filter. In case 2 you
are adding the entire item T as a single entity.
You could group 1 and 2 into the same situation where I concatenate the
parts that would make up the List<byte[]> to a single longer array and create a
SimpleBuilder containing the result. The idea is the same: a single item T
should only add one set of indices to the Bloom filter.
I do not suggest by-passing the Hasher. I suggest making it easier to
specify case 2. Thus as a user I can convert my item to a binary form `byte[]`
then the SimpleBloomFilter would do the rest of the work to hash the binary
form and create a sequence of indexes for the filter shape.
This is why I suggested a `Function<T, byte[]>` version. The `byte[]` would
be used internally by the SimpleBloomFilter to create a Hasher and generate
indices for the Shape. Essentially this would be:
```java
byte[] b = ...;
Hasher h = new SimpleBuilder().with(b).build();
```
But this could be done using a specialised route that avoids all the object
creation, for example using a variant of DynamicHasher that has a single
`byte[]` to hash:
```java
byte[] b = ...; // The SimpleBloomFilter converts T to byte[]
HashFunction hf = ...; // From the SimpleBloomFilter
Hasher h = new DynamicHasher(hf, b);
```
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