From a7330e880da883d5dec0b2ae277be081c66693d8 Mon Sep 17 00:00:00 2001
From: nocturn9x <hackhab@gmail.com>
Date: Sat, 21 Aug 2021 15:21:16 +0200
Subject: [PATCH] Added src/memory and related README section

---
 README.md                |  1 +
 src/memory/allocator.nim | 88 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 src/memory/allocator.nim

diff --git a/README.md b/README.md
index 8c0a446..a6e8e82 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,7 @@ The project is split into several directories and submodules:
     - `src/meta` -> Contains meta-structures used during compilation and parsing
   - `src/frontend` -> Contains the runtime environment of NimVM
     - `src/frontend/types` -> Contains the type system
+- `src/memory` -> Contains NimVM's allocator and memory manager
 
 
 
diff --git a/src/memory/allocator.nim b/src/memory/allocator.nim
new file mode 100644
index 0000000..7411210
--- /dev/null
+++ b/src/memory/allocator.nim
@@ -0,0 +1,88 @@
+# CONFIDENTIAL
+# ______________
+#
+#  2021 Mattia Giambirtone
+#  All Rights Reserved.
+#
+#
+# NOTICE: All information contained herein is, and remains
+# the property of Mattia Giambirtone. The intellectual and technical
+# concepts contained herein are proprietary to Mattia Giambirtone
+# and his suppliers and may be covered by Patents and are
+# protected by trade secret or copyright law.
+# Dissemination of this information or reproduction of this material
+# is strictly forbidden unless prior written permission is obtained
+# from Mattia Giambirtone
+
+## Memory allocator from JAPL
+
+
+const DEBUG_TRACE_ALLOCATION = false
+
+import segfaults
+import config
+when DEBUG_TRACE_ALLOCATION:
+    import strformat
+
+
+proc reallocate*(pointr: pointer, oldSize: int, newSize: int): pointer =
+    ## Wrapper around realloc/dealloc
+    try:
+        if newSize == 0 and pointr != nil:   # pointr is awful, but clashing with builtins is even more awful
+            when DEBUG_TRACE_ALLOCATION:
+                if oldSize > 1:
+                    echo &"DEBUG - Memory manager: Deallocating {oldSize} bytes"
+                else:
+                    echo "DEBUG - Memory manager: Deallocating 1 byte"
+            dealloc(pointr)
+            return nil
+        when DEBUG_TRACE_ALLOCATION:
+            if pointr == nil and newSize == 0:
+                echo &"DEBUG - Memory manager: Warning, asked to dealloc() nil pointer from {oldSize} to {newSize} bytes, ignoring request"
+        if oldSize > 0 and pointr != nil or oldSize == 0:
+            when DEBUG_TRACE_ALLOCATION:
+                if oldSize == 0:
+                    if newSize > 1:
+                        echo &"DEBUG - Memory manager: Allocating {newSize} bytes of memory"
+                    else:
+                        echo "DEBUG - Memory manager: Allocating 1 byte of memory"
+                else:
+                    echo &"DEBUG - Memory manager: Resizing {oldSize} bytes of memory to {newSize} bytes"
+            result = realloc(pointr, newSize)
+        when DEBUG_TRACE_ALLOCATION:
+            if oldSize > 0 and pointr == nil:
+                echo &"DEBUG - Memory manager: Warning, asked to realloc() nil pointer from {oldSize} to {newSize} bytes, ignoring request"
+    except NilAccessDefect:
+        stderr.write("A fatal error occurred -> could not manage memory, segmentation fault\n")
+        quit(71)   # For now, there's not much we can do if we can't get the memory we need
+
+
+template resizeArray*(kind: untyped, pointr: pointer, oldCount, newCount: int): untyped =
+    ## Handy macro (in the C sense of macro, not nim's) to resize a dynamic array
+    cast[ptr UncheckedArray[kind]](reallocate(pointr, sizeof(kind) * oldCount, sizeof(kind) * newCount))
+
+
+template freeArray*(kind: untyped, pointr: pointer, oldCount: int): untyped =
+    ## Frees a dynamic array
+    reallocate(pointr, sizeof(kind) * oldCount, 0)
+
+
+template free*(kind: untyped, pointr: pointer): untyped =
+    ## Frees a pointer by reallocating its
+    ## size to 0
+    reallocate(pointr, sizeof(kind), 0)
+
+
+template growCapacity*(capacity: int): untyped =
+    ## Handy macro used to calculate how much
+    ## more memory is needed when reallocating
+    ## dynamic arrays
+    if capacity < 8:
+        8
+    else:
+        capacity * ARRAY_GROW_FACTOR
+
+
+template allocate*(castTo: untyped, sizeTo: untyped, count: int): untyped =
+    ## Allocates an object and casts its pointer to the specified type
+    cast[ptr castTo](reallocate(nil, 0, sizeof(sizeTo) * count))