From c33d71c5ffda4e7f887d93a2645a28ffc7dad55c Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 24 Nov 2020 16:37:55 +0100
Subject: [PATCH] AK: Add IntrusiveList::take_last()

---
 AK/IntrusiveList.h | 11 +++++++++++
 AK/MemoryStream.h  | 27 ++++++++++++++-------------
 2 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/AK/IntrusiveList.h b/AK/IntrusiveList.h
index 09f35737d7..46045f7f22 100644
--- a/AK/IntrusiveList.h
+++ b/AK/IntrusiveList.h
@@ -56,6 +56,7 @@ public:
     T* last() const;
 
     T* take_first();
+    T* take_last();
 
     class Iterator {
     public:
@@ -233,6 +234,16 @@ inline T* IntrusiveList<T, member>::take_first()
     return nullptr;
 }
 
+template<class T, IntrusiveListNode T::*member>
+inline T* IntrusiveList<T, member>::take_last()
+{
+    if (auto* ptr = last()) {
+        remove(*ptr);
+        return ptr;
+    }
+    return nullptr;
+}
+
 template<class T, IntrusiveListNode T::*member>
 inline T* IntrusiveList<T, member>::last() const
 {
diff --git a/AK/MemoryStream.h b/AK/MemoryStream.h
index 26618637eb..e1b8a12d5c 100644
--- a/AK/MemoryStream.h
+++ b/AK/MemoryStream.h
@@ -96,9 +96,9 @@ public:
     bool read_LEB128_unsigned(size_t& result)
     {
         const auto backup = m_offset;
-        result = 0;
 
-        size_t shift = 0;
+        result = 0;
+        size_t num_bytes = 0;
         while (true) {
             if (eof()) {
                 m_offset = backup;
@@ -106,11 +106,12 @@ public:
                 return false;
             }
 
-            const u8 byte = m_bytes[m_offset++];
-            result |= (byte & 0x7f) << shift;
-            if ((byte & 0x80) == 0)
+            const u8 byte = m_bytes[m_offset];
+            result = (result) | (static_cast<size_t>(byte & ~(1 << 7)) << (num_bytes * 7));
+            ++m_offset;
+            if (!(byte & (1 << 7)))
                 break;
-            shift += 7;
+            ++num_bytes;
         }
 
         return true;
@@ -121,11 +122,9 @@ public:
         const auto backup = m_offset;
 
         result = 0;
-        size_t shift = 0;
+        size_t num_bytes = 0;
         u8 byte = 0;
 
-        size_t size = sizeof(ssize_t) * 8;
-
         do {
             if (eof()) {
                 m_offset = backup;
@@ -133,13 +132,15 @@ public:
                 return false;
             }
 
-            byte = m_bytes[m_offset++];
-            result |= (byte & 0x7f) << shift;
+            byte = m_bytes[m_offset];
+            result = (result) | (static_cast<size_t>(byte & ~(1 << 7)) << (num_bytes * 7));
+            ++m_offset;
+            ++num_bytes;
         } while (byte & (1 << 7));
 
-        if (shift < size && (byte & 0x40)) {
+        if (num_bytes * 7 < sizeof(size_t) * 4 && (byte & 0x40)) {
             // sign extend
-            result |= (0xffffffffu << shift);
+            result |= ((size_t)(-1) << (num_bytes * 7));
         }
 
         return true;