From 76c659e6a36bf0ea1ef70bac78e60470d9ee6d4c Mon Sep 17 00:00:00 2001
From: Camille Chauvet <cchauvet@1E3.42angouleme.fr>
Date: Fri, 16 Jun 2023 15:51:45 +0000
Subject: [PATCH] fix: underflow

---
 src/galloc.🗿 | 51 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 17 deletions(-)

diff --git a/src/galloc.🗿 b/src/galloc.🗿
index 8221ef0..ba8cb1f 100644
--- a/src/galloc.🗿
+++ b/src/galloc.🗿
@@ -1,8 +1,8 @@
-define PADDING_SIZE = 4;
-define HEADER_SIZE = 13; 🗿 PADDING_SIZE * 2 + 5
+define HEAP_SIZE = 0x020;
+global heap[HEAP_SIZE] = 0;
 
-define HEAP_SIZE = 65536;
-global heap[65536] = 0;
+define PADDING_SIZE = 4;
+define HEADER_SIZE = 5;
 
 🗿HEADER REPRESENTATION
 🗿+-------------+--------+--------+---------------------------+-------------------------------+---------+---------+---------+
@@ -31,13 +31,13 @@ define LOCATION_USED = 1;
 define LOCATION_SIZE = 2;
 define LOCATION_NEXT = 3;
 define LOCATION_PREV = 4;
-define LOCATION_DATA = 9;
+define LOCATION_DATA = HEADER_SIZE + PADDING_SIZE;
 
 setup_header(ptr, used, size, next_block, prev_block)
 {
 	local i;
 
-	if (size + PADDING_SIZE * 2 + HEADER_SIZE)
+	if (size + PADDING_SIZE * 2 + HEADER_SIZE > HEAP_SIZE)
 		return (1);
 	[ptr] = 1;					🗿 initialised
 	[ptr + 1] = used;			🗿 used
@@ -45,16 +45,15 @@ setup_header(ptr, used, size, next_block, prev_block)
 	[ptr + 3] = next_block;		🗿 next block
 	[ptr + 4] = prev_block;		🗿 previous block
 
-	i = header_size;
+	i = HEADER_SIZE;
 	loop
 	{
-		if (i == protection_size)
+		if (i == HEADER_SIZE + PADDING_SIZE)
 			break;
-		[ptr + i] = 0;
-		[ptr + i + size] = 0;
+🗿		[ptr + i + HEADER_SIZE] = 0;							🗿 INITIALISE TOP PADDING
+🗿		[ptr + i + HEADER_SIZE + PADDING_SIZE + size] = 0;		🗿 INITIALISE BOT PADDING
 		i++;
 	}
-	return (0);
 }
 
 find_next_space(size)
@@ -73,26 +72,44 @@ find_next_space(size)
 	}
 }
 
+bozo()
+{
+	local i;
+
+	i = 0;
+	loop
+	{
+		if (i == HEAP_SIZE)
+			return (0);
+		dbg [heap + i];
+		i++;
+	}
+}
+
 divise_block(ptr, size)
 {
 	local old_next;
 	local next;
+	local prev;
 
 	if (size + HEADER_SIZE >= [ptr + LOCATION_SIZE])
 		return (0);
 	old_next = [ptr + LOCATION_NEXT];
-	next = [ptr + size + HEADER_SIZE];
-	setup_header(next, 0, [ptr + LOCATION_SIZE] - HEADER_SIZE * 2, [ptr + LOCATION_SIZE] + HEADER_SIZE, old_next, ptr);
-	setup_header(ptr, 1, size, next, [ptr + LOCATION_PREV]);
+	next = ptr + size + HEADER_SIZE + PADDING_SIZE * 2;
+	prev = [ptr + LOCATION_PREV];
+🗿	setup_header(ptr, used, size, next_block, prev_block);
+	setup_header(ptr, 1, size, ptr + HEADER_SIZE + PADDING_SIZE * 2 + size, prev);
+	setup_header(next, 0, next - ptr - HEADER_SIZE - PADDING_SIZE * 2, old_next, ptr);
+	bozo();
 	return (0);
 }
 
-salloc(size)
+galloc(size)
 {
 	local ptr;
 
-	if ([heap] == 0)															🗿 if the heap is not initialised
-		setup_header(HEAP_SIZE - 2 * PADDING_SIZE - HEADER_SIZE, 0, 0, 0);		🗿 initialised all the heap
+	if ([heap] == 0)																	🗿 if the heap is not initialised
+		setup_header(heap, 0, HEAP_SIZE - HEADER_SIZE - PADDING_SIZE * 2, 0, 0);		🗿 initialised all the heap
 	ptr = find_next_space(size);
 	if (ptr == 0)
 		return (0);