Simple C Dynamic Data Structure

Transcription

1 C Programming Simple C Dynamic Data Structure For this assignment, you will implement a program that manipulates a simple queue of integer values. Your program will include the following features: IntegerDT IntegerQueue Queue wrapper type to "duct-tape" an int32_t value to a queue node wrapper supplying a suitable queue interface for a queue of integers purely generic queue implementation, similar to generic doubly-linked list from notes To facilitate testing, your program will also make use of a supplied library for parsing files of commands. Your solution must conform exactly to the descriptions below, and your code must be organized exactly as described below. You will find header files for the elements described above on the course website. You must not make any changes to those files. For convenience, the header files are replicated at the end of this specification. You must implement the first three elements described above, placing the implementations in C source files IntegerDT.c, IntegerQueue.c, and Queue.c, respectively. Memory management requirements You must allocate the objects that make up the queue dynamically. As is the case with any non-garbage-collected language, it is your responsibility to deallocate all memory that you allocate dynamically as soon as you are done with it. The test code will not detect whether you have done this, but a TA will review your implementation to verify that you have done so. What to Submit You will create an uncompressed tar file containing your three implementation files: IntegerDT.c, IntegerQueue.c and Queue.c, and nothing else, and submit that tar file to the Curator. This assignment will be graded automatically. You will be allowed up to ten submissions for this assignment, so use them wisely. Test your functions thoroughly before submitting them. Make sure that your functions produce correct results for every logically valid test case you can think of. The Student Guide and other pertinent information, such as the link to the proper submit page, can be found at: 1

2 Pledge: Each of your program submissions must be pledged to conform to the Honor Code requirements for this course. Specifically, you must include the following pledge statement in the submitted file: On my honor: - I have not discussed the C language code in my program with anyone other than my instructor or the teaching assistants assigned to this course. - I have not used C language code obtained from another student, or any other unauthorized source, either modified or unmodified. - If any C language code or documentation used in my program was obtained from another source, such as a text book or course notes, that has been clearly noted with a proper citation in the comments of my program. <Student Name> Failure to include this pledge in a submission is a violation of the Honor Code. 2

3 Interfaces: Queue.h: /* Our queues have two header elements: the "front" just before the first element and the "rear" just after the last element. The 'prev' link of the front header is null, as is the 'next' link of the rear header. Their other two links point toward each other via the interior elements of the queue. An empty list looks like this: [- front <---> rear -] A queue with two elements in it looks like this: [- front <---> 1 <---> 2 <---> rear -] The symmetry of this arrangement eliminates lots of special cases in queue processing. (Because only one of the pointers in each header element is used, we could in fact combine them into a single header element without sacrificing this simplicity. But using two separate elements allows us to do a little bit of checking on some operations, which can be valuable.) This implementation of a queue does not require use of dynamically allocated memory. Instead, each structure that is a potential list element must embed a QNode member. All of the list functions operate on these QNode's. The QList_Entry macro allows conversion from a QNode back to a structure object that contains it. For example, suppose there is a need for a queue of 'struct Widget'. 'struct Widget' should contain a 'QNode' member, like so: struct Widget { QNode node; int bar;...other members... Then a list of 'struct Widget' can be be declared and initialized like so: Queue Widget_Q; QList_Init(&Widget_Q); Retrieval is a typical situation where it is necessary to convert from a QNode back to its enclosing structure. Here's an example using Widget_Q: QNode *e = Queue_Pop(Widget_Q); struct Widget *f = Queue_Entry (e, struct Widget, node); now, do something with f... The interface for this queue is inspired by the queue<> template in the 3

4 C++ STL. If you're familiar with queue<>, you should find this easy to use. However, it should be emphasized that these lists do *no* type checking and can't do much other correctness checking. If you screw up, it will bite you. Glossary of Queue terms: - "front": The first element in a queue. Undefined in an empty queue. Returned by Queue_Front(). - "back": The last element in a queue. Undefined in an empty list. Returned by Queue_Back(). - "tail": The element figuratively just after the last element of a queue. Well-defined even in an empty queue. Not returned by any Queue function. - "head": The element figuratively just before the first element of a queue. Well-defined even in an empty list. Not returned by any Queue function. */ - "interior element": An element that is not the head or tail, that is, a real queue element. An empty queue does not have any interior elements. Queue node: struct _QNode { struct _QNode *prev; struct _QNode *next; previous list element next list element typedef struct _QNode QNode; Queue object: struct _Queue { QNode front; QNode rear; sentinel node at the front of the queue sentinel node at the tail of the queue typedef struct _Queue Queue; Converts pointer to queue element NODE into a pointer to the structure that NODE is embedded inside. Supply the name of the outer structure STRUCT and the member name MEMBER of the NODE. See the big comment at the top of the file for an example. #define Queue_Entry(NODE, STRUCT, MEMBER) \ ((STRUCT *) ((uint8_t *) (NODE) - offsetof (STRUCT, MEMBER))) Initialize QNode pointers to NULL. Pre: pn points to a QNode object Post: pn->prev and pn->next are NULL void QNode_Init(QNode* pn); 4

5 Initialize Queue to empty state. Pre: pq points to a Queue object Post: *pq has been set to an empty state (see preceding comment void Queue_Init(Queue* pq); Return whether Queue is empty. Pre: pq points to a Queue object Returns true if *pq is empty, false otherwise bool Queue_Empty(const Queue* const pq); Insert *pnode as last interior element of Queue. Pre: pq points to a Queue object pnode points to a QNode object Post: *pnode has been inserted at the rear of *pq void Queue_Push(Queue* const pq, QNode* const pnode); Remove first interior element of Queue and return it. Pre: pq points to a Queue object Post: the interior QNode that was at the front of *pq has been removed Returns pointer to the QNode that was removed, NULL if *pq was empty QNode* const Queue_Pop(Queue* const pq); Return first interior element, if any. Pre: pq points to a Queue object Returns pointer first interior QNode in *pq, NULL if *pq is empty QNode* const Queue_Front(Queue* const pq); Return last interior element, if any. Pre: pq points to a Queue object Returns pointer last interior QNode in *pq, NULL if *pq is empty QNode* const Queue_Back(Queue* const pq); 5

6 IntegerQueue.h: /* IntegerQueue defines an interface suitable for a client who needs to create and manipulate a queue of integer values (int32_t). */ IntegerQueue uses the data wrapper IntegerDT, and the Queue type for the underlying physical structure. struct _IntegerQueue { Queue Q; generic Queue object typedef struct _IntegerQueue IntegerQueue; Initialize empty IntegerQueue. Pre: piq points to an IntegerQueue object Post: piq->q has been initialized to an empty state (see Queue.h for details) void IntegerQueue_Init(IntegerQueue* const piq); Return whether IntegerQueue is empty. Pre: piq points to aqn IntegerQueue object Returns true if piq->q is empty, false otherwise bool IntegerQueue_Empty(const IntegerQueue* const piq); Insert K at rear of IntegerQueue. Pre: piq points to an IntegerQueue object Post: An IntegerDT object containing the value K has been inserted at the rear of piq->q void IntegerQueue_Push(IntegerQueue* const piq, int32_t K); Remove and return data value from front of IntegerQueue. Pre: piq points to a nonempty IntegerQueue object Post: The IntegerDT object at the front of piq->q has been removed Returns the user data value that was in the IntegerDT object at the front of piq->q int32_t IntegerQueue_Pop(IntegerQueue* const piq); 6

7 IntegerDT.h: Wrapper type to "duct-tape" an int32_t payload to a QNode. struct _IntegerDT { int32_t payload; user data field QNode node; generic node typedef struct _IntegerDT IntegerDT; Insert K into payload field and set node pointers to NULL. Pre: pdt points to an IntegerDT object Post: pdt->payload == K pdt->node has its pointer fields set to NULL void IntegerDT_Init(IntegerDT* const pdt, int32_t K); 7