c - 将大型 C 程序分解为头文件和 C 文件

Question

我必须将以下代码分解为以下文件:main.c、student.c、students.h、mergesort.c、mergesort.h、aux.c 和 aux.h。然后我必须制作一个 makefile 来编译它们。 该程序是在链表上实现的归并排序。我已经分离了代码，但我不知道如何处理头文件和包含指令，更不知道如何创建 makefile。头文件中需要包含哪些内容，C 文件中需要包含哪些内容？例如，如果 mergesort.c 使用 Students.c 中的函数，我是否必须将 Students.h 包含在 mergesort.c 中？这是原始程序的代码:

#include <stdio.h>
#include <stdlib.h>

#define NAME_LEN 25

struct node {
  int number;
  char name[NAME_LEN+1];
  struct node* next;
};

/* The functions to manage the linked list.  The functions prompt the
   user and read the standard input if needed. */
struct node* insert        (struct node* student_list);
void         print_student (struct node* student);
void         print_list    (struct node* student_list);
void         search        (struct node* student_list);
struct node* delete        (struct node* student_list);
void         delete_list   (struct node* student_list);

/* Merge sort */
struct node* mergesort(struct node* student_list);
struct node* merge    (struct node* list1, struct node *list2);

                                     /* Auxiliary functions */
int read_line(char line[], int len); /* Read at most len characters
                    from the standard input and
                    ignore the rest of the line. */
int line_skip(); /* Read the standard input to the end of the line. */
int line_copy(); /* Read the standard input to the end of the line
            and copy to the standard output. */
int pause();     /* Ask user to press Enter to continue. */

int main() {
  int option;
  struct node* student_list = NULL;

  for (;;) {
    printf("\n-- OPTIONS MENU -----------------\n");
    printf("1: Add a student\n");
    printf("2: Search for a student by number\n");
    printf("3: Delete a student by number\n");
    printf("4: Display all students\n");
    printf("5: Sort students by number\n");
    printf("0: Exit\n");
    printf("\n");

    printf("Enter an option: ");
    if ( scanf("%d", &option) != 1 ) {
      if ( feof(stdin) ) break;
      printf("Invalid option: "); line_copy(); pause();
      continue;
    }

    /* Read the rest of the line after option number.  Usually, it is
       just one new-line character */
    line_skip(); 

    if (option == 0) break;

    switch(option) {
    case 1: student_list = insert(student_list);    break;
    case 2: search(student_list);                   break;
    case 3: student_list = delete(student_list);    break;
    case 4: print_list(student_list);               break;
    case 5: student_list = mergesort(student_list); break;
    default:
      printf("Incorrect option: %d\n", option); pause();
    }
  }

  delete_list(student_list); /* Not necessary in this example */
  printf("Bye!\n");
  return 0;
}

struct node* mergesort(struct node* student_list) {
  struct node* list1 = student_list;
  struct node* list2 = student_list;

  if (student_list == NULL || student_list->next == NULL)
    return student_list;

  while ((list2 = list2->next) != NULL && 
         (list2 = list2->next) != NULL)
    list1 = list1->next;

  list2 = list1->next;

  list1->next = NULL ;
  list1 = student_list;

  list1 = mergesort(list1);
  list2 = mergesort(list2);

  return merge(list1, list2);
}

struct node* merge(struct node* list1, struct node* list2) {
  struct node *list, *prev;

  if (list1 == NULL) return list2;
  if (list2 == NULL) return list1;

  if (list1->number <= list2->number) {
    list = list1; list1 = list1->next;
  } else {
    list = list2; list2 = list2->next;
  }

  prev = list;

  while (list1 != NULL && list2 != NULL) {
    if (list1->number <= list2->number) {
      prev->next = list1;
      list1 = list1->next;
    } else {
      prev->next = list2;
      list2 = list2->next;
    }
    prev = prev->next ;
  }

  if (list1 != NULL)
    prev->next = list1;
  else
    prev->next = list2;

  return list;
}

struct node* insert(struct node* student_list) {
  struct node* student = malloc(sizeof(struct node));
  /* Why would it be incorrect to use "struct node student;" ? */

  if (student == NULL ) {
    printf("Out of memory for a new student!\n"); pause();
    return student_list;
  }

  printf("\nAdding a new student\n");
  printf("Enter student's number: ");
  if (scanf("%d", &student->number) != 1) {
    printf("Incorrect student number: ");
    line_copy(); pause();
    free(student); /**/
    return student_list;
  }
  line_skip();          /* to skip the newline character */

  printf("Enter student's name: ");
  read_line(student->name, NAME_LEN);

  student->next = student_list;
  printf("Student %d added.\n", student->number); pause();

  return student;
}

void print_student(struct node* student) {
  printf("Number:%3d  Name: %s\n", student->number, student->name);
}

void print_list(struct node* student_list) {
  printf("\nStudent List:\n");
  while (student_list != NULL) {
    print_student(student_list);
    student_list = student_list->next;
  }
  pause();
}

void search(struct node* student_list) {
  int number;

  printf("Enter student number: ");
  if (scanf("%d", &number) != 1) {
    printf("Incorrect student number: ");
    line_copy(); pause();
    return;
  }
  line_skip();

  while (student_list != NULL && number != student_list->number) 
    student_list = student_list->next;

  if (student_list == NULL)
    printf("Not found.\n");
  else
    print_student(student_list);
  pause();
}

struct node* delete(struct node* student_list) {
  int number;
  struct node *prev, *cur;

  printf("Enter student number: ");
  if (scanf("%d", &number) != 1) {
    printf("Incorrect student number: "); line_copy(); pause();
    return student_list;
  }
  line_skip();

  for (cur = student_list, prev = NULL;
       cur != NULL && cur -> number != number;
       prev = cur, cur = cur->next)
    ;

  if (cur == NULL) {
    printf("Student not found!\n"); pause();
    return student_list;
  }

  if (prev == NULL)
    student_list = student_list->next;
  else
    prev->next = cur->next;

  free(cur);
  return student_list;
}

void delete_list(struct node* student_list) {
  struct node* temp;

  while (student_list != NULL) {
    temp = student_list;
    student_list = student_list->next;
    free(temp);
  }
}

/*Auxiliary Function
int read_line(char line[], int len) {
  int ch, i = 0;

  while ((ch = getchar()) != '\n' && ch != EOF) 
    if (i < len) 
      line[i++] = ch;

  line[i] = '\0';

  return i;
}

int line_skip() {
  int ch;
  while ( (ch=getchar()) != '\n' && ch != EOF )
    ;
  return ch != EOF;
}

int line_copy() {
  int ch;
  while ( (ch=getchar()) != '\n' && ch != EOF )
    putchar(ch);
  putchar('\n');
  return ch != EOF;
}

int pause() {
  printf("Press Enter to continue...");
  return line_skip();
}

Answer 1

您的 header 将包含相关代码部分的类型定义和函数声明。请注意，如果用户代码(主要是 main.c )仅调用 mergesort()而不是merge() ，然后 mergesort.h header 应该只声明 mergesort()和merge()应该是 mergesort.c 中的静态函数，对代码的其余部分隐藏。 header 应该只定义“客户”需要知道的内容；应隐藏实现细节。请记住确保 header 是独立的(例如，如果 mergesort.h 需要了解 struct node ，则它包括声明 struct node 的 header )。还要确保它们是幂等的(因此写入 #include "header.h" 两次不会导致编译错误)。这是通过 header 防护完成的，例如:

#ifndef HEADER_H_INCLUDED
#define HEADER_H_INCLUDED

…body of header file…

#endif /* HEADER_H_INCLUDED */

源文件将包含 header 中声明的函数的实现。源文件将包含相关的 header 。不需要了解给定结构类型的代码部分不需要包含声明该结构类型的 header 。

makefile 的大纲可以很简单:

FILES.c = main.c student.c mergesort.c aux.c
FILES.o = ${FILES.c:.c=.o}

all: students

students: ${FILES.o}
    ${CC} ${CFLAGS} -o $@ ${FILES.o} ${LDFLAGS} ${LDLIBS}

students.o:  students.h
mergesort.o: mergesort.h
aux.o:       aux.h

自 make知道如何构建xyz.o来自xyz.c ，您不需要指定这些依赖项。您应该声明 main.c 使用的 header (因此您需要诸如 main.o: students.h mergesort.h aux.h 之类的行，但您没有指出正确的内容)。