add python code for free space management.

.vscode/settings.json

@@ -2,5 +2,6 @@
     "files.associations": {
         "stdlib.h": "c",
         "stdio.h": "c"
-    }
+    },
+    "python.pythonPath": "/Users/toby/anaconda3/envs/py39/bin/python"
 }

freeSpaceManager/main.py

@@ -0,0 +1,113 @@
+"""
+Python prototype for the free space management
+"""
+import math
+
+
+class Ticket:
+    def __init__(self, size):
+        self.size = size
+
+
+class System:
+    def __init__(
+        self,
+        capacity: int,
+        logger: bool = True,
+        strategy: str = "BEST",
+        doCoalesce: bool = False,
+    ):
+        self.capacity = capacity
+        self.freeList = [(0, capacity)]  # list of tuple (address, space)
+        self.jobList = []
+        self.strategy = strategy
+        self.doCoalesce = doCoalesce
+        self.logger = logger
+        # by default we sort the free list by address
+
+    def malloc(self, Ticket: Ticket):
+        size = Ticket.size
+        if self.strategy == "BEST":
+            bestIndex, minDiff = -1, math.inf
+            for index, chunk in enumerate(self.freeList):
+                head, space = chunk
+                if space < size:
+                    continue
+                else:
+                    if space == size:
+                        del self.freeList[index]
+                        self.jobList.append((head, space))
+                        return (head, space)
+
+                    diff = space - size
+                    if diff < minDiff:
+                        minDiff = diff
+                        bestIndex = index
+            head, space = self.freeList[bestIndex]
+            del self.freeList[bestIndex]
+            # self.jobList.append((head, head + size))
+            self.jobList.append((head, size))
+            self.freeList.append((head + size, space - size))
+            # sort
+            self.freeList.sort()
+            self.jobList.sort()
+            print("Free list: ", self.freeList)
+            print("Job list: ", self.jobList)
+            print()
+
+    def coalese(self):
+        if not self.freeList:
+            return
+
+        tmp = [self.freeList.pop(0)]
+        while len(self.freeList) > 0:
+            head1, size1 = tmp[-1]
+            head2, size2 = self.freeList.pop(0)
+
+            # merge
+            if head1 + size1 == head2:
+                tmp[-1] = (head1, size1 + size2)
+            else:
+                tmp.append((head2, size2))
+        self.freeList = tmp
+        print("Free list: ", self.freeList)
+        print("Job list: ", self.jobList)
+        print()
+        return
+
+    def free(self, index):
+        if index < 0 or index >= len(self.jobList):
+            # raise error
+            print("Invalid free index.\n")
+            return
+        tmp = self.jobList.pop(index)
+        self.freeList.append(tmp)
+        # sort
+        self.freeList.sort()
+        print("Free list: ", self.freeList)
+        print("Job list: ", self.jobList)
+        print()
+
+
+def main():
+    freeSpaceManager = System(capacity=100)
+    job1 = Ticket(10)
+    job2 = Ticket(20)
+    job3 = Ticket(30)
+
+    freeSpaceManager.malloc(job1)
+    freeSpaceManager.malloc(job2)
+    freeSpaceManager.malloc(job3)
+
+    freeSpaceManager.free(1)
+
+    freeSpaceManager.malloc(job2)
+
+    # test coalesce
+    freeSpaceManager.free(1)
+
+    freeSpaceManager.coalese()
+
+
+if __name__ == "__main__":
+    main()