From a5c69c5911d68dbece637830dfa52dc4d4250d03 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 12 Jan 2021 14:58:55 +1000
Subject: [PATCH] alloc/chunked: add untested initial implementation

---
 alloc/chunked.cpp | 75 +++++++++++++++++++++++++++++++++++++++++++++++
 alloc/chunked.hpp | 22 +++++++++-----
 2 files changed, 90 insertions(+), 7 deletions(-)

diff --git a/alloc/chunked.cpp b/alloc/chunked.cpp
index 22d14a95..ee6a1edb 100644
--- a/alloc/chunked.cpp
+++ b/alloc/chunked.cpp
@@ -8,7 +8,82 @@
 
 #include "chunked.hpp"
 
+#include "../log.hpp"
+#include "../maths.hpp"
+#include "../pointer.hpp"
+
+
 using cruft::alloc::chunked;
 
 
 ///////////////////////////////////////////////////////////////////////////////
+chunked::chunked (std::size_t initial_size)
+    : chunked (initial_size, DEFAULT_CHUNK_SIZE)
+{ ; }
+
+
+//-----------------------------------------------------------------------------
+chunked::chunked (std::size_t initial_size, std::size_t _chunk_size)
+    : m_chunk (_chunk_size)
+{
+    m_chunk = cruft::max (m_chunk, sizeof (node_t));
+
+    auto const initial_arenas = cruft::divup (initial_size, m_chunk);
+    m_data.resize (initial_arenas);
+
+    for (auto &i: m_data) {
+        i.data  = new std::byte[m_chunk];
+        *i.node = {
+            .size = m_chunk,
+            .next = nullptr
+        };
+    }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+void*
+chunked::do_allocate (std::size_t size, std::size_t alignment)
+{
+    // Find a chunk that can service this allocation.
+    for (auto &i: m_data) {
+        if (i.node->size < size + alignment)
+            continue;
+
+        auto base = cruft::align::up (i.data, alignment);
+        std::byte* newbase = base + size;
+        if (newbase > i.data + i.node->size)
+            continue;
+
+        std::size_t newsize = i.data + i.node->size - newbase;
+
+        i.data = newbase;
+        i.node->size = newsize;
+
+        return base;
+    }
+
+    // No chunk was found. We need to allocate a new chunk of at least enough size.
+    unimplemented ();
+}
+
+
+//-----------------------------------------------------------------------------
+void
+chunked::do_deallocate (void *p, std::size_t bytes, std::size_t alignment)
+{
+    (void)p;
+    (void)bytes;
+    (void)alignment;
+
+    LOG_WARNING ("chunked::do_deallocate is unimplemented");
+}
+
+
+//-----------------------------------------------------------------------------
+bool
+chunked::do_is_equal (memory_resource const &) const noexcept
+{
+    warn ("chunked::do_is_equal is unimplemented");
+    return false;
+}
\ No newline at end of file
diff --git a/alloc/chunked.hpp b/alloc/chunked.hpp
index c90342ea..299ebcaf 100644
--- a/alloc/chunked.hpp
+++ b/alloc/chunked.hpp
@@ -14,6 +14,7 @@
     #include <cstddef>
 #endif
 
+#include <memory>
 #include <vector>
 
 
@@ -28,15 +29,18 @@ namespace std::pmr {
         [[nodiscard]] void* allocate (
             std::size_t bytes,
             std::size_t alignment = alignof (std::max_align_t)
-        );
+        ) { return do_allocate (bytes, alignment); }
 
         void deallocate(
             void* p,
             std::size_t bytes,
             std::size_t alignment = alignof(std::max_align_t)
-        );
+        ) { return do_deallocate (p, bytes, alignment); }
 
-        bool is_equal (memory_resource const&) const noexcept;
+        bool is_equal (memory_resource const &rhs) const noexcept
+        {
+            return do_is_equal (rhs);
+        }
 
     private:
         virtual void *do_allocate (std::size_t bytes, std::size_t alignment) = 0;
@@ -77,13 +81,17 @@ namespace cruft::alloc {
         bool do_is_equal (memory_resource const&) const noexcept override;
 
         std::size_t m_chunk;
-        struct arena {
-            std::byte*  base;
+
+        struct node_t {
             std::size_t size;
-            std::byte*  next;
+            node_t*     next;
+        };
+
+        union arena {
+            std::byte *data;
+            node_t    *node;
         };
 
         std::vector<arena> m_data;
-        int m_next;
     };
 }
\ No newline at end of file