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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.slime;
/**
* Light-weight index structure describing the layout of a Slime value
* encoded in binary format.
**/
final class DecodeIndex {
private long[] data;
private int reserved;
private int used = 0;
private final int totalSize;
private final int rootOffset;
private int binarySize() { return totalSize - rootOffset; }
private int adjustSize(int minSize, int maxSize, int cnt, int byteOffset) {
double density = (double)cnt / (double)(byteOffset - rootOffset);
double estSize = 1.1 * density * binarySize();
double expSize = 1.25 * data.length;
double wantedSize = (estSize > expSize) ? estSize : expSize;
if (wantedSize < minSize) {
return minSize;
}
if (wantedSize > maxSize) {
return maxSize;
}
return (int)wantedSize;
}
DecodeIndex(int totalSize, int rootOffset) {
this.totalSize = totalSize;
this.rootOffset = rootOffset;
int initialCapacity = Math.max(16, binarySize() / 24);
data = new long[initialCapacity];
reserved = 1;
}
long[] getBacking() { return data; }
int tryReserveChildren(int n, int cnt, int byteOffset) {
int offset = reserved;
if (n > data.length - reserved) {
final int maxSize = (totalSize - byteOffset) + cnt;
if (n > maxSize - reserved) {
return -1; // error; too much space requested
}
long[] old = data;
data = new long[adjustSize(reserved + n, maxSize, cnt, byteOffset)];
System.arraycopy(old, 0, data, 0, reserved);
}
reserved += n;
return offset;
}
int size() { return reserved; }
int used() { return used; }
int capacity() { return data.length; }
void set(int idx, int byteOffset, int firstChild, int extBits) {
data[idx] = (long)(byteOffset & 0x7fff_ffff) << 33 |
(long)(firstChild & 0x7fff_ffff) << 2 |
extBits & 0x3;
++used;
}
}
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