1.3 KiB
1.3 KiB
BTree
This package contains a small library for creating and reading a static b-tree.
The b-trees are specified through a BTreeContext which contains information about the data and index layout.
The b-trees are written through a BTreeWriter and read with a BTreeReader.
Demo
BTreeContext ctx = new BTreeContext(
4, // num layers max
1, // entry size
8); // block size bits, in practice this should be 8
// Allocate a memory area to work in, see the array library for how to do this with files
LongArray array = LongArray.allocate(8192);
// Write a btree at offset 123 in the area
long[] items = new long[400];
BTreeWriter writer = new BTreeWriter(array, ctx);
final int offsetInFile = 123;
long btreeSize = writer.write(offsetInFile, items.length, slice -> {
// here we *must* write items.length * entry.size words in slice
// these items must be sorted!!
for (int i = 0; i < items.length; i++) {
slice.set(i, items[i]);
}
});
// Read the BTree
BTreeReader reader = new BTreeReader(array, ctx, offsetInFile);
reader.findEntry(items[0]);