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Readme for array

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Viktor Lofgren 2023-03-04 19:14:20 +01:00
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libraries/array/readme.md
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@ -31,10 +31,40 @@ array.forEach(0, 100, (pos, val) -> {
## Query Buffers ## Query Buffers
The library offers many operations for sorting and dealing with sorted data. The library offers many operations for sorting and dealing with sorted data.
Especially noteworthy are the operations `retain()` and `reject()` in The classes [IntQueryBuffer](src/main/java/nu/marginalia/array/buffer/IntQueryBuffer.java)
([IntArraySearch](src/main/java/nu/marginalia/array/algo/IntArraySearch.java) and [LongArraySearch](src/main/java/nu/marginalia/array/algo/LongArraySearch.java)) which act upon the and [LongQueryBuffer](src/main/java/nu/marginalia/array/buffer/LongQueryBuffer.java) are used
classes [IntQueryBuffer](src/main/java/nu/marginalia/array/buffer/IntQueryBuffer.java) heavily in the search engine's query processing.
and [LongQueryBuffer](src/main/java/nu/marginalia/array/buffer/LongQueryBuffer.java);
they keep or remove all items in the buffer that exist in the range. These are used
to offer an intersection operation for the B-Tree that has in practice sub-linear run time.
They are dual-pointer buffers that offer tools for filtering data.
```java
LongQueryBuffer buffer = new LongQueryBuffer(1000);
fillBuffer(buffer);
// A typical filtering operation may look like this:
while (buffer.hasMore()) { // read < end
if (someCondition(buffer.currentValue())) {
// copy the value pointed to by the read
// pointer to the read pointer, and
// advance both
buffer.retainAndAdvance();
}
else {
// advance the read pointer
buffer.rejectAndAdvance();
}
}
// set the read pointer to the read pointer
// after this we can filter again
buffer.finalizeFiltering();
```
Especially noteworthy are the operations `retain()` and `reject()` in
[IntArraySearch](src/main/java/nu/marginalia/array/algo/IntArraySearch.java) and [LongArraySearch](src/main/java/nu/marginalia/array/algo/LongArraySearch.java).
They keep or remove all items in the buffer that exist in the range. These are used
to offer an intersection operation for the B-Tree that has in practice sub-linear run time.