From 48f6a10b59f00f85b4324ce5f420e374486e200b Mon Sep 17 00:00:00 2001
From: Jeroen Bos <jer123bos@gmail.com>
Date: Sat, 27 Apr 2024 17:14:11 +0200
Subject: [PATCH] wip

---
 .../Bits/IFloatingPointBitReaderExtensions.cs |  1 +
 .../Internals/BitReaderWithAlongTagger.cs     | 25 +++++++++++++++++--
 .../ULongLikeFloatingPointBitReader.cs        |  2 ++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/JBSnorro/Collections/Bits/IFloatingPointBitReaderExtensions.cs b/JBSnorro/Collections/Bits/IFloatingPointBitReaderExtensions.cs
index 3df32edb..60a6c5bd 100644
--- a/JBSnorro/Collections/Bits/IFloatingPointBitReaderExtensions.cs
+++ b/JBSnorro/Collections/Bits/IFloatingPointBitReaderExtensions.cs
@@ -22,6 +22,7 @@ public static double ReadDouble(this IBitReader reader, int bitCount, IFloatingP
     {
         if (reader == null) throw new ArgumentNullException(nameof(reader));
         if (bitCount < IFloatingPointBitReader.MIN_BIT_COUNT) throw new ArgumentOutOfRangeException(nameof(bitCount));
+        if ((ulong)bitCount > reader.RemainingLength) throw new ArgumentOutOfRangeException(nameof(bitCount));
         if (!Enum.IsDefined(floatingPointEncoding)) throw new ArgumentOutOfRangeException(nameof(floatingPointEncoding));
 
         switch (floatingPointEncoding)
diff --git a/JBSnorro/Collections/Bits/Internals/BitReaderWithAlongTagger.cs b/JBSnorro/Collections/Bits/Internals/BitReaderWithAlongTagger.cs
index b381a026..387ad858 100644
--- a/JBSnorro/Collections/Bits/Internals/BitReaderWithAlongTagger.cs
+++ b/JBSnorro/Collections/Bits/Internals/BitReaderWithAlongTagger.cs
@@ -1,4 +1,6 @@
-namespace JBSnorro.Collections.Bits.Internals;
+using JBSnorro.Diagnostics;
+
+namespace JBSnorro.Collections.Bits.Internals;
 
 /// <summary>
 /// A bit reader that reads floating point numbers assuming they're particularly encoded.
@@ -10,6 +12,19 @@ internal class BitReaderWithAlongTagger : BitReader
     public BitReaderWithAlongTagger(BitArray data, ulong position, ulong length, BitReader alongTagger)
         : base(data, position, length)
     {
+        Contract.Requires(alongTagger is not null);
+#if DEBUG
+        var set = new HashSet<BitReader>();
+        for (var a = alongTagger; a != null; a = (a as BitReaderWithAlongTagger)?.alongTagger)
+        {
+            if (set.Contains(a))
+            {
+                throw new ArgumentException("Infinite loop");
+            }
+            set.Add(a);
+        }
+#endif
+
         this.alongTagger = alongTagger;
     }
 
@@ -21,12 +36,18 @@ protected internal override ulong current
         }
         set
         {
+            if (this.alongTagger is null)
+            {
+                // we're called from the base constructor
+                base.current = value;
+                return;
+            }
             unchecked
             {
                 var delta = value - current;
                 if (delta != 0)
                 {
-                    this.current = value;
+                    base.current = value;
                     alongTagger.current += delta;
                 }
             }
diff --git a/JBSnorro/Collections/Bits/Internals/ULongLikeFloatingPointBitReader.cs b/JBSnorro/Collections/Bits/Internals/ULongLikeFloatingPointBitReader.cs
index d3e35f12..199b31f6 100644
--- a/JBSnorro/Collections/Bits/Internals/ULongLikeFloatingPointBitReader.cs
+++ b/JBSnorro/Collections/Bits/Internals/ULongLikeFloatingPointBitReader.cs
@@ -8,6 +8,8 @@ internal static double ReadDouble(IBitReader reader, int bitCount)
     {
         if (bitCount < IFloatingPointBitReader.MIN_BIT_COUNT || bitCount > 64)
             throw new ArgumentOutOfRangeException(nameof(bitCount));
+        if ((ulong)bitCount > reader.RemainingLength)
+            throw new ArgumentOutOfRangeException(nameof(bitCount));
 
         ulong value = reader.ReadUInt64(bitCount);
         if (value == 0)