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