From 72fe8dd2d6d6a3a5592646950a4e43b9a79ed9b4 Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Mon, 2 Dec 2024 00:35:56 +0100
Subject: Start work on buffer

---
 asl/BUILD.bazel            |  2 ++
 asl/box.hpp                |  1 -
 asl/buffer.hpp             | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 asl/layout.hpp             |  2 ++
 asl/tests/buffer_tests.cpp |  8 ++++++++
 5 files changed, 58 insertions(+), 1 deletion(-)
 create mode 100644 asl/buffer.hpp
 create mode 100644 asl/tests/buffer_tests.cpp

(limited to 'asl')

diff --git a/asl/BUILD.bazel b/asl/BUILD.bazel
index 391ae9d..cbfe91e 100644
--- a/asl/BUILD.bazel
+++ b/asl/BUILD.bazel
@@ -5,6 +5,7 @@ cc_library(
         "annotations.hpp",
         "assert.hpp",
         "box.hpp",
+        "buffer.hpp",
         "config.hpp",
         "float.hpp",
         "format.hpp",
@@ -45,6 +46,7 @@ cc_library(
     ],
 ) for name in [
     "box",
+    "buffer",
     "float",
     "format",
     "functional",
diff --git a/asl/box.hpp b/asl/box.hpp
index eeb2b9c..7556d76 100644
--- a/asl/box.hpp
+++ b/asl/box.hpp
@@ -5,7 +5,6 @@
 #include "asl/annotations.hpp"
 #include "asl/memory.hpp"
 #include "asl/utility.hpp"
-#include "asl/box.hpp"
 
 namespace asl
 {
diff --git a/asl/buffer.hpp b/asl/buffer.hpp
new file mode 100644
index 0000000..abf29fe
--- /dev/null
+++ b/asl/buffer.hpp
@@ -0,0 +1,46 @@
+#pragma once
+
+#include "asl/meta.hpp"
+#include "asl/allocator.hpp"
+#include "asl/annotations.hpp"
+
+namespace asl
+{
+
+template<is_object T, allocator Allocator = DefaultAllocator>
+class buffer
+{
+    
+    T*         m_data{};
+    isize_t    m_capacity{};
+
+    // bit 63       : 0 = on heap, 1 = inline
+    // bits [62:56] : size when inline
+    // bits [52:0]  : size when on heap
+    size_t     m_size_encoded{};
+
+    ASL_NO_UNIQUE_ADDRESS Allocator m_allocator;
+    
+    static_assert(align_of<T> <= align_of<T*>);
+    static_assert(align_of<T*> == align_of<isize_t>);
+    static_assert(align_of<T*> == align_of<size_t>);
+    
+public:
+
+    static constexpr isize_t kInlineCapacity = []() {
+        // 1 byte is used for size inline in m_size_encoded.
+        // This is enough because we have at most 24 bytes available,
+        // so 23 chars of capacity.
+        const isize_t available_size = size_of<T*> + size_of<isize_t> + size_of<size_t> - 1;
+        return available_size / size_of<T>;
+    }();
+
+    constexpr buffer() requires default_constructible<Allocator> = default;
+
+    explicit constexpr buffer(Allocator allocator)
+        : m_allocator{ASL_MOVE(allocator)}
+    {}
+};
+
+} // namespace asl
+
diff --git a/asl/layout.hpp b/asl/layout.hpp
index 2295a1c..990af46 100644
--- a/asl/layout.hpp
+++ b/asl/layout.hpp
@@ -33,3 +33,5 @@ struct layout
 };
 
 } // namespace asl
+
+#define AslOffsetOf(S, M) (static_cast<isize_t>(__builtin_offsetof(S, M)))
diff --git a/asl/tests/buffer_tests.cpp b/asl/tests/buffer_tests.cpp
new file mode 100644
index 0000000..133a549
--- /dev/null
+++ b/asl/tests/buffer_tests.cpp
@@ -0,0 +1,8 @@
+#include <asl/buffer.hpp>
+
+#include <asl/testing/testing.hpp>
+
+static_assert(asl::buffer<int32_t>::kInlineCapacity == 5);
+static_assert(asl::buffer<int64_t>::kInlineCapacity == 2);
+static_assert(asl::buffer<char>::kInlineCapacity == 23);
+
-- 
cgit