Merge pull request #26518 from vespa-engine/havardpe/decode-index

added DecodeIndex utility class

1 files changed, 51 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/slime/DecodeIndex.java b/vespajlib/src/main/java/com/yahoo/slime/DecodeIndex.java
new file mode 100644
index 00000000000..17c7a86730e
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/slime/DecodeIndex.java
@@ -0,0 +1,51 @@
+// Copyright Yahoo. 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 {
+    static final int initial_capacity = 16;
+    private long[] data = new long[initial_capacity];
+    private int reserved = 0;
+
+    private int adjustSize(int minSize) {
+        int capacity = initial_capacity;
+        while (capacity < minSize) {
+            capacity = capacity << 1;
+        }
+        return capacity;
+    }
+
+    int reserve(int n) {
+        int offset = reserved;
+        if (reserved + n > data.length) {
+            long[] old = data;
+            data = new long[adjustSize(reserved + n)];
+            System.arraycopy(old, 0, data, 0, reserved);
+        }
+        reserved += n;
+        return offset;
+    }
+
+    int size() { return reserved; }
+
+    void set(int idx, int byteOffset, int firstChild, int extBits) {
+        data[idx] = (long)(byteOffset & 0x7fff_ffff) << 33 |
+            (long)(firstChild & 0x7fff_ffff) << 2 |
+            extBits & 0x3;
+    }
+
+    int getByteOffset(int idx) {
+        return (int)(data[idx] >> 33) & 0x7fff_ffff;
+    }
+
+    int getFirstChild(int idx) {
+        return (int)(data[idx] >> 2) & 0x7fff_ffff;
+    }
+
+    int getExtBits(int idx) {
+        return (int)data[idx] & 0x3;
+    }
+}