From 66ba3d98e4c363e943912a867831e018f61ecac4 Mon Sep 17 00:00:00 2001
From: Ludovic 'Archivist' Lagouardette <ludovic@nekoit.xyz>
Date: Wed, 27 Oct 2021 11:52:38 +0200
Subject: [PATCH] Updating bottleneck with a semaphore

---
 extra_tests/001_test/Makefile    | 10 +++---
 extra_tests/001_test/main.cpp    |  2 +-
 extra_tests/001_test/syscall.hpp |  2 +-
 include/gp/ipc/bottleneck.hpp    | 54 ++++++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 7 deletions(-)

diff --git a/extra_tests/001_test/Makefile b/extra_tests/001_test/Makefile
index ac4f9ee..8df4f5b 100644
--- a/extra_tests/001_test/Makefile
+++ b/extra_tests/001_test/Makefile
@@ -1,17 +1,17 @@
 CXX= clang++
-CXXFLAGS= --std=c++20 -target x86_64-none-linux-elf -Os -ffreestanding -nostdlib -pedantic \
- -Wno-unknown-attributes -fno-omit-frame-pointer -MD -fno-use-cxa-atexit -fno-rtti -I../../include -I.
+CXXFLAGS= --std=c++20 -target x86_64-none-linux-elf -O2 -ffreestanding -nostdlib -pedantic \
+ -Wno-unknown-attributes -fno-omit-frame-pointer -MD -fno-use-cxa-atexit -fno-rtti -I.  -I../../include
  
 # -fsanitize=address  -fsanitize-blacklist=blacklist.txt
 
 all: tests
 
 tests: bin/tests
-	./bin/tests
+	./bin/tests potato
 
 bin/tests: main.cpp
 	@mkdir -p $(@D)
-	$(CXX) $(CXXFLAGS) main.cpp -o $@
+	$(CXX) $(CXXFLAGS) main.cpp -nostartfiles -s -static  -o $@
 
 clean: ./bin
-	@rm -rf $<
\ No newline at end of file
+	@rm -rf $<
diff --git a/extra_tests/001_test/main.cpp b/extra_tests/001_test/main.cpp
index 8c09aac..d0a8a06 100644
--- a/extra_tests/001_test/main.cpp
+++ b/extra_tests/001_test/main.cpp
@@ -1,4 +1,4 @@
-#include <gp/containers/array.hpp>
+#include <gp/containers/buffer.hpp>
 #include "syscall.hpp"
 
 gp::buffer<char> hello = "Hello world\n";
diff --git a/extra_tests/001_test/syscall.hpp b/extra_tests/001_test/syscall.hpp
index 62ed2a1..abe3f7a 100644
--- a/extra_tests/001_test/syscall.hpp
+++ b/extra_tests/001_test/syscall.hpp
@@ -133,7 +133,7 @@ inline int write(int fd, char* buffer, size_t sz) {
     return _write((int64_t)fd, (int64_t)buffer, (int64_t)sz);
 }
 
-inline void* mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset) {
+inline void* mmap(void *addr, size_t length, int prot, int flags, int fd, int64_t offset) {
     return (void*)_mmap((int64_t)addr, (int64_t)length, (int64_t)prot, (int64_t)flags, (int64_t)fd, (int64_t)offset);
 }
 
diff --git a/include/gp/ipc/bottleneck.hpp b/include/gp/ipc/bottleneck.hpp
index e57f2ce..d4e3764 100644
--- a/include/gp/ipc/bottleneck.hpp
+++ b/include/gp/ipc/bottleneck.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <atomic>
+#include <concepts>
 
 #include "gp_config.hpp"
 
@@ -55,4 +56,57 @@ namespace gp {
             return flag.compare_exchange_strong(t,f,std::memory_order::release);
         }
     };
+
+    /**
+     * @brief A fast semaphore exclusion handler WITHOUT deadlock detection
+     */
+    template<std::integral T, T default_increment, T maximum_increment>
+    class fast_semaphore {
+        std::atomic<T> flag;
+    public:
+        fast_semaphore() = default;
+        fast_semaphore(fast_semaphore&) = delete;
+        fast_semaphore(fast_semaphore&&) = delete;
+
+        enum class tristate {
+            success,
+            timing,
+            error
+        };
+
+        void lock_super() {
+            auto value = flag.fetch_add(maximum_increment, std::memory_order::relaxed);
+            while(value > maximum_increment) { value = flag.load(std::memory_order::release); }
+        }
+
+
+        template<T increment = default_increment>
+        void lock() {
+            while(not try_lock<increment>());
+        }
+
+        template<T increment = default_increment>
+        [[nodiscard]] bool try_lock() {
+            T expect = flag.load(std::memory_order::relaxed);
+            T target = expect + increment;
+            if(target > maximum_increment) return false;
+            return flag.compare_exchange_strong(expect,target,std::memory_order::acquire);
+        }
+
+        template<T increment = default_increment>
+        void unlock() {
+            tristate v;
+            do{ v = try_unlock<increment>(); }
+            while(v == tristate::timing);
+            gp_config::assertion(v == tristate::success, "Over unlocking may have happened");
+        }
+
+        template<T increment = default_increment>
+        [[nodiscard]] tristate try_unlock() {
+            T expect = flag.load(std::memory_order::relaxed);
+            T target = expect - increment;
+            if(target < 0) return tristate::error;
+            return flag.compare_exchange_strong(expect,target,std::memory_order::release) ? tristate::success : tristate::timing;
+        }
+    };
 }
\ No newline at end of file