From 3dc844c1dfea604bc43890794a5cbc4c5fdef89d Mon Sep 17 00:00:00 2001
From: Adam NAILI
Date: Mon, 2 Apr 2018 16:14:45 +0200
Subject: PageException created and LRU,Second Chance Handling

---
 secondchance.py | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 secondchance.py

(limited to 'secondchance.py')

diff --git a/secondchance.py b/secondchance.py
new file mode 100644
index 0000000..b0fb1f9
--- /dev/null
+++ b/secondchance.py
@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+
+# UPEM / Programmation système / Projet : Simulation de gestion de mémoire virtuelle
+# Pacien TRAN-GIRARD et Adam NAILI
+
+from mem import Memory
+from pageexception import *
+
+
+class SecondChancePaginator:
+  def __init__(self, mem):
+    self.mem = mem
+    self._check_table = [0 for _ in range(len(mem.main)+len(mem.virt))]
+    self._main_cursor = 0
+
+  def _put_main(self, page):
+    overwritten = self.mem.main[self._main_cursor]
+    while(overwritten is not None and self._check_table[overwritten] == 1):
+      self._main_cursor=(self._main_cursor + 1) % len(self.mem.main)
+      self._check_table[overwritten] = 0
+      overwritten = self.mem.main[self._main_cursor]
+    self.mem.main[self._main_cursor] = page
+    self._main_cursor = (self._main_cursor + 1) % len(self.mem.main)
+    return overwritten
+
+  def load(self, page):
+    if not self.mem.page_in_range(page): raise PageException
+    if page in self.mem.main: 
+      self._check_table[page] = 1
+      return
+    if page in self.mem.virt: self.mem.remove_virt(page)
+    overwritten = self._put_main(page)
+    if overwritten is not None: self.mem.put_virt(overwritten)
+
-- 
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