Start work on span

MODULE.bazel.lock

@@ -64,20 +64,20 @@
     "@@apple_support~//crosstool:setup.bzl%apple_cc_configure_extension": {
       "general": {
         "bzlTransitiveDigest": "PjIds3feoYE8SGbbIq2SFTZy3zmxeO2tQevJZNDo7iY=",
-        "usagesDigest": "+hz7IHWN6A1oVJJWNDB6yZRG+RYhF76wAYItpAeIUIg=",
+        "usagesDigest": "aLmqbvowmHkkBPve05yyDNGN7oh7QE9kBADr3QIZTZs=",
         "recordedFileInputs": {},
         "recordedDirentsInputs": {},
         "envVariables": {},
         "generatedRepoSpecs": {
-          "local_config_apple_cc_toolchains": {
-            "bzlFile": "@@apple_support~//crosstool:setup.bzl",
-            "ruleClassName": "_apple_cc_autoconf_toolchains",
-            "attributes": {}
-          },
           "local_config_apple_cc": {
             "bzlFile": "@@apple_support~//crosstool:setup.bzl",
             "ruleClassName": "_apple_cc_autoconf",
             "attributes": {}
+          },
+          "local_config_apple_cc_toolchains": {
+            "bzlFile": "@@apple_support~//crosstool:setup.bzl",
+            "ruleClassName": "_apple_cc_autoconf_toolchains",
+            "attributes": {}
           }
         },
         "recordedRepoMappingEntries": [
@@ -92,7 +92,7 @@
     "@@platforms//host:extension.bzl%host_platform": {
       "general": {
         "bzlTransitiveDigest": "xelQcPZH8+tmuOHVjL9vDxMnnQNMlwj0SlvgoqBkm4U=",
-        "usagesDigest": "pCYpDQmqMbmiiPI1p2Kd3VLm5T48rRAht5WdW0X2GlA=",
+        "usagesDigest": "meSzxn3DUCcYEhq4HQwExWkWtU4EjriRBQLsZN+Q0SU=",
         "recordedFileInputs": {},
         "recordedDirentsInputs": {},
         "envVariables": {},

asl/BUILD.bazel

@@ -14,6 +14,7 @@ cc_library(
         "meta.hpp",
         "option.hpp",
         "print.hpp",
+        "span.hpp",
         "utility.hpp",
     ],
     srcs = [
@@ -40,5 +41,6 @@ cc_library(
     "maybe_uninit",
     "meta",
     "option",
+    "span",
     "utility",
 ]]

asl/span.hpp

@@ -0,0 +1,44 @@
+#pragma once
+
+#include "asl/meta.hpp"
+#include "asl/annotations.hpp"
+#include "asl/layout.hpp"
+
+namespace asl
+{
+
+static constexpr int64_t dynamic_size = -1;
+
+template<is_object T, int64_t kSize = dynamic_size>
+class span
+{
+    static constexpr bool kIsDynamic = kSize < 0;
+
+    using SizeType = select_t<kIsDynamic, int64_t, empty>;
+
+    T* m_data{};
+    ASL_NO_UNIQUE_ADDRESS SizeType m_size{};
+
+public:
+    constexpr span() = default;
+
+    constexpr span(const span&) = default;
+    constexpr span(span&&) = default;
+    
+    constexpr span& operator=(const span&) = default;
+    constexpr span& operator=(span&&) = default;
+
+    ~span() = default;
+
+    constexpr int64_t size() const
+    {
+        if constexpr (kIsDynamic) { return m_size; }
+        else { return kSize; }
+    }
+
+    constexpr int64_t size_bytes() const { return size() * size_of<T>; }
+
+    constexpr bool is_empty() const { return size() == 0; }
+};
+
+} // namespace asl

asl/tests/span_tests.cpp

@@ -0,0 +1,28 @@
+#include "asl/span.hpp"
+#include "asl/testing/testing.hpp"
+#include "asl/tests/test_types.hpp"
+
+static_assert(asl::trivially_destructible<asl::span<int>>);
+static_assert(asl::trivially_destructible<asl::span<HasDestructor>>);
+
+static_assert(asl::trivially_copyable<asl::span<int>>);
+static_assert(asl::trivially_copyable<asl::span<NonCopyConstructible>>);
+
+static_assert(asl::size_of<asl::span<int>> == asl::size_of<void*> * 2);
+static_assert(asl::size_of<asl::span<int, 2>> == asl::size_of<void*>);
+
+ASL_TEST(empty_dynamic)
+{
+    asl::span<int> s;
+    ASL_TEST_EXPECT(s.size() == 0);
+    ASL_TEST_EXPECT(s.size_bytes() == 0);
+    ASL_TEST_EXPECT(s.is_empty());
+}
+
+ASL_TEST(empty_static)
+{
+    asl::span<int, 0> s;
+    ASL_TEST_EXPECT(s.size() == 0);
+    ASL_TEST_EXPECT(s.size_bytes() == 0);
+    ASL_TEST_EXPECT(s.is_empty());
+}