From 40bca93884b12c31a8abd9ab50b5e494a5e4d874 Mon Sep 17 00:00:00 2001
From: Viktor Lofgren <vlofgren@marginalia.nu>
Date: Mon, 24 Jun 2024 13:56:43 +0200
Subject: [PATCH] (gamma) Minor clean-up

---
 .../marginalia/sequence/GammaCodedSequence.java   | 15 ++++++++++++---
 .../java/nu/marginalia/sequence/io/BitWriter.java |  2 +-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/code/libraries/coded-sequence/java/nu/marginalia/sequence/GammaCodedSequence.java b/code/libraries/coded-sequence/java/nu/marginalia/sequence/GammaCodedSequence.java
index a2335fbf..25caa2dc 100644
--- a/code/libraries/coded-sequence/java/nu/marginalia/sequence/GammaCodedSequence.java
+++ b/code/libraries/coded-sequence/java/nu/marginalia/sequence/GammaCodedSequence.java
@@ -17,8 +17,8 @@ import java.util.StringJoiner;
 public class GammaCodedSequence implements BinarySerializable, Iterable<Integer> {
     private final ByteBuffer raw;
 
-    int startPos = 0;
-    int startLimit = 0;
+    private final int startPos;
+    private final int startLimit;
 
     /** Create a new GammaCodedSequence from a sequence of integers.
      *
@@ -116,6 +116,9 @@ public class GammaCodedSequence implements BinarySerializable, Iterable<Integer>
         return sj.toString();
     }
 
+    /** Return the backing ByteBuffer of the sequence, configured with a position and limit
+     * that is equal to the relevant data range
+     */
     public ByteBuffer buffer() {
         raw.position(startPos);
         raw.limit(startLimit);
@@ -123,11 +126,17 @@ public class GammaCodedSequence implements BinarySerializable, Iterable<Integer>
         return raw;
     }
 
+    /** Return the number of bytes used by the sequence in the buffer */
     public int bufferSize() {
-        return raw.capacity();
+        return startLimit - startPos;
     }
 
+    /** Return the number of items in the sequence */
     public int valueCount() {
+        // if the first byte is zero, the sequence is empty and we can skip decoding
+        if (0 == raw.get(startPos))
+            return 0;
+
         return EliasGammaCodec.readCount(buffer());
     }
 }
diff --git a/code/libraries/coded-sequence/java/nu/marginalia/sequence/io/BitWriter.java b/code/libraries/coded-sequence/java/nu/marginalia/sequence/io/BitWriter.java
index e5636064..f92876b1 100644
--- a/code/libraries/coded-sequence/java/nu/marginalia/sequence/io/BitWriter.java
+++ b/code/libraries/coded-sequence/java/nu/marginalia/sequence/io/BitWriter.java
@@ -88,7 +88,7 @@ public class BitWriter {
 
         var outBuffer = ByteBuffer.allocate(totalMeaningfulBytes);
 
-        outBuffer.put(underlying.array(), 0, totalMeaningfulBytes);
+        outBuffer.put(0, underlying, 0, totalMeaningfulBytes);
 
         outBuffer.position(0);
         outBuffer.limit(totalMeaningfulBytes);