kstd: implement memcmp

2 files changed, 16 insertions, 0 deletions

diff --git a/libs/kstd/CMakeLists.txt b/libs/kstd/CMakeLists.txt
index 75c2315..e0c551c 100644
--- a/libs/kstd/CMakeLists.txt
+++ b/libs/kstd/CMakeLists.txt
@@ -4,6 +4,7 @@ add_library("libs::kstd" ALIAS "kstd")
 set(KSTD_LIBC_SYMBOLS
     "abort"
     "strlen"
+    "memcmp"
 )
 
 target_sources("kstd" PRIVATE
diff --git a/libs/kstd/src/libc/string.cpp b/libs/kstd/src/libc/string.cpp
index a42aedc..a9b85fc 100644
--- a/libs/kstd/src/libc/string.cpp
+++ b/libs/kstd/src/libc/string.cpp
@@ -1,5 +1,6 @@
 #include <algorithm>
 #include <cstddef>
+#include <span>
 
 namespace kstd::libc
 {
@@ -10,6 +11,20 @@ namespace kstd::libc
     {
       return std::distance(string, std::ranges::find(string, nullptr, '\0'));
     }
+
+    auto memcmp(void const * lhs, void const * rhs, std::size_t size) -> std::size_t
+    {
+      auto left_span = std::span{static_cast<std::byte const *>(lhs), size};
+      auto right_span = std::span{static_cast<std::byte const *>(rhs), size};
+      auto mismatched = std::ranges::mismatch(left_span, right_span);
+
+      if (mismatched.in1 == left_span.end())
+      {
+        return 0;
+      }
+
+      return std::bit_cast<char>(*mismatched.in1) - std::bit_cast<char>(*mismatched.in2);
+    }
   }
 
 }  // namespace kstd::libc
\ No newline at end of file