From 132fc181cd3e6ee6c06172308a5ae3b0e58b3848 Mon Sep 17 00:00:00 2001
From: WerWolv <werwolv98@gmail.com>
Date: Sun, 12 Sep 2021 14:28:13 +0200
Subject: [PATCH] patterns: Fix bitfields with unaligned sizes

Correction for #292
---
 .../libimhex/include/hex/helpers/utils.hpp    | 18 +++++++++++++
 .../hex/pattern_language/pattern_data.hpp     | 27 +------------------
 2 files changed, 19 insertions(+), 26 deletions(-)

diff --git a/plugins/libimhex/include/hex/helpers/utils.hpp b/plugins/libimhex/include/hex/helpers/utils.hpp
index aa8383055..ba2ca8974 100644
--- a/plugins/libimhex/include/hex/helpers/utils.hpp
+++ b/plugins/libimhex/include/hex/helpers/utils.hpp
@@ -38,6 +38,24 @@ namespace hex {
         return (value & mask) >> to;
     }
 
+    [[nodiscard]] inline u64 extract(u32 from, u32 to, const std::vector<u8> &bytes) {
+        u8 index = 0;
+        while(from > 32 && to > 32) {
+            if (from - 8 < 0 || to - 8 < 0)
+                return 0;
+
+            from -= 8;
+            to -= 8;
+            index++;
+        }
+
+        u64 value = 0;
+        std::memcpy(&value, &bytes[index], std::min(sizeof(value), bytes.size() - index));
+        u64 mask = (std::numeric_limits<u64>::max() >> (64 - (from + 1)));
+
+        return (value & mask) >> to;
+    }
+
     template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
     template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 
diff --git a/plugins/libimhex/include/hex/pattern_language/pattern_data.hpp b/plugins/libimhex/include/hex/pattern_language/pattern_data.hpp
index f21629f0d..d1102b750 100644
--- a/plugins/libimhex/include/hex/pattern_language/pattern_data.hpp
+++ b/plugins/libimhex/include/hex/pattern_language/pattern_data.hpp
@@ -1244,14 +1244,6 @@ namespace hex::pl {
             return new PatternDataBitfieldField(*this);
         }
 
-        template<typename T>
-        T extractValue(const std::vector<u8> &value) {
-            T fieldValue = 0;
-            std::memcpy(&fieldValue, value.data(), value.size());
-
-            return hex::extract(this->m_bitOffset + (this->m_bitSize - 1), this->m_bitOffset, fieldValue);
-        }
-
         void createEntry(prv::Provider* &provider) override {
             std::vector<u8> value(this->getParent()->getSize(), 0);
             provider->read(this->getParent()->getOffset(), &value[0], value.size());
@@ -1281,24 +1273,7 @@ namespace hex::pl {
             {
                 u8 numBytes = (this->m_bitSize / 8) + 1;
 
-                u64 extractedValue;
-                switch (this->getSize()) {
-                    case 1:
-                        extractedValue = extractValue<u8>(value);
-                        break;
-                    case 2:
-                        extractedValue = extractValue<u16>(value);
-                        break;
-                    case 4:
-                        extractedValue = extractValue<u32>(value);
-                        break;
-                    case 8:
-                        extractedValue = extractValue<u64>(value);
-                        break;
-                    default:
-                        extractedValue = 0;
-                }
-
+                u64 extractedValue = hex::extract(this->m_bitOffset + (this->m_bitSize - 1), this->m_bitOffset, value);
                 ImGui::Text("%llu (0x%llX)", extractedValue, extractedValue);
             }