使用列表进行 Shell 模拟

Question

现在我正在学习 C，但我在内存分配方面遇到了问题，至少我从我的代码错误中了解到这一点。

代码

    #ifndef __FILE_H__
#define __FILE_H__

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

typedef struct Files Files;
typedef struct DirList DirList;
typedef struct NodeFile NodeFile;
typedef struct NodeDir NodeDir;

typedef struct Directory {
    // The name of the directory
    char *name;

    // TODO: The list of files of the current directory
    Files *files;

    // TODO: The list of dirs of the current directory
    DirList *dirs;

    // The parent directory of the current directory (NULL for the root
    // directory)
    struct Directory *parentDir;
} Directory;

// DO NOT MODIFY THIS STRUCTURE
typedef struct File {
    // The name of the file
    char *name;

    // The size of the file
    int size;

    // The content of the file
    char *data;

    // The directory in which the file is located
    Directory *dir;
} File;

typedef struct Files {
    NodeFile *first;
    NodeFile *last;
} Files;

typedef struct DirList {
    NodeDir *first;
    NodeDir *last;
} DirList;

typedef struct NodeFile {
    struct NodeFile *next;
    struct NodeFile *prev;
    File *newfile;
} NodeFile;

typedef struct NodeDir {
    struct NodeDir *next;
    struct NodeDir *prev;
    Directory *newdir;
} NodeDir;

// create root of file system
void makeroot(Directory **root)
{
    *root = (Directory *) malloc(sizeof(Directory));

    (*root)->parentDir = NULL;
    (*root)->name = strdup("/");
    (*root)->files = NULL;
    (*root)->dirs = NULL;
}

// remove root of file system
void deleteroot(Directory *root)
{
    root = NULL;
    free(root);
}

//add new file to current directory
File *touch(Directory *root, char *nume, char *content)
{
    NodeFile *new = (NodeFile *) malloc(sizeof(NodeFile));

    new->newfile = (File *) malloc(sizeof(File));

    new->newfile->name = (char *) malloc(strlen(nume) + 1);
    new->newfile->data = (char *) malloc(strlen(content) + 1);

    strcpy(new->newfile->name, nume);
    strcpy(new->newfile->data, content);

    if (root->files == NULL) {
        root->files = (Files *) malloc(sizeof(Files));
        root->files->first = (NodeFile *) malloc(sizeof(NodeFile));
        root->files->last = (NodeFile *) malloc(sizeof(NodeFile));
        //if no file in folder root has first and last position
        root->files->first = new;
        root->files->last = new;
    } else if (strcmp(root->files->first->newfile->name,
                        new->newfile->name) > 0) {
        new->next = root->files->first;
        root->files->first = new;
    } else if (strcmp(root->files->last->newfile->name,
                        new->newfile->name) < 0) {
        root->files->last->next = new;
        root->files->last = new;
    } else {
        NodeFile *i = root->files->first;

        while (i != root->files->last) {
            if (strcmp(i->next->newfile->name,
                    new->newfile->name) > 0) {
                if (i == root->files->first->next)
                    i = root->files->first;
                i->next->prev = new;
                new->next = i->next;
                new->prev = i;
                i->next = new;
                break;
            }
            i = i->next;
        }
    }
    return new->newfile;
}

// Create directory
Directory *mkdir(Directory *parent, char *name)
{
    NodeDir *new = (NodeDir *) malloc(sizeof(NodeDir));

    //new->newdir = (Directory *) malloc(sizeof(Directory));
    new->newdir = (Directory *) malloc(strlen(Directory) + 1);

    new->newdir->name = (char *) malloc(strlen(name) + 1);

    strcpy(new->newdir->name, name);
    new->newdir->parentDir = parent;

    if (parent->dirs == NULL) {
        parent->dirs = (DirList *)malloc(sizeof(DirList));
        parent->dirs->first = (NodeDir *) malloc(sizeof(NodeDir));
        parent->dirs->last = (NodeDir *) malloc(sizeof(NodeDir));
        parent->dirs->first = new;
        parent->dirs->last = new;
    } else if (strcmp(parent->dirs->first->newdir->name,
                        new->newdir->name) > 0) {
        new->next = parent->dirs->first;
        parent->dirs->first = new;
    } else if (strcmp(parent->dirs->last->newdir->name,
                        new->newdir->name) < 0) {
        parent->dirs->last->next = new;
        parent->dirs->last = new;
    } else {
        NodeDir *i = parent->dirs->first->next;

        while (i != NULL) {
            if (strcmp(i->newdir->name, new->newdir->name) > 0) {
                if (i == parent->dirs->first->next)
                    i = parent->dirs->first;
                i->next->prev = new;
                new->next = i->next;
                new->prev = i;
                i->next = new;
                break;
            }
            i = i->next;
        }
    }
    return new->newdir;
}

// traverse list and print files and folders names
void ls(Directory *parent)
{
    if (parent->files != NULL) {
        NodeFile *i;

        for (i = parent->files->first; i != NULL; i = i->next)
            printf("%s ", i->newfile->name);
    }

    if (parent->dirs != NULL) {
        NodeDir *j;

        for (j = parent->dirs->first; j != NULL; j = j->next)
            printf("%s ", j->newdir->name);
    }

    printf("\n");
}

// working directory
void pwd(Directory *dir)
{
    if (dir->parentDir == NULL)
        return;
    if (dir->parentDir != NULL) {
        pwd(dir->parentDir);
        printf("/%s", dir->name);
    }
}


Directory *cd(Directory *dir, char *where)
{
    if (strcmp(where, "..") == 0 && dir->parentDir != NULL) {
        return dir->parentDir;
    } else if (dir->dirs == NULL)
        printf("Cannot move to ‘%s’: No such directory!\n", where);
    else {
        NodeDir *it = dir->dirs->first;

        while (it != NULL) {
            if (strcmp(it->newdir->name, where) == 0) {
                dir = it->newdir;
                break;
            }
            it = it->next;
        }
        if (it == NULL)
            printf("Cannot move to ‘%s’: No such directory!\n",
                    where);
        free(it);
    }
    return dir;
}

void tree(Directory *parent, int i)
{

    if (i == 1)
        printf("\n%s\n", parent->name);
    if (parent->files != NULL) {
        NodeFile *it;

        for (it = parent->files->first; it != NULL; it = it->next) {
            if (i != 1) {
                int j;

                for (j = 0; j < i; j++)
                    printf("   ");
            }
            printf("   %s\n", it->newfile->name);
        }
        free(it);
    }
    if (parent->dirs != NULL) {
        NodeDir *it = parent->dirs->first;

        while (it != NULL) {

            int j;

            for (j = 0; j < i; j++)
                printf("   ");
            printf("%s\n", it->newdir->name);
            i = i + 1;
            tree(it->newdir, i);
            it = it->next;
            i = i - 1;
        }
        free(it);
    }
}


void rm(Directory *parent, char *dirname)
{ //it -- item
    NodeFile *it;

    for (it = parent->files->first; it != NULL; it = it->next) {
        if (strcmp(it->newfile->name, dirname) == 0) {
            if (it == parent->files->first) {
                parent->files->first =
                parent->files->first->next;
            } else if (it == parent->files->last) {
                parent->files->last = it->prev;
            } else {
                it->prev->next = it->next;
                it->next->prev = it->prev;
            }
            it = NULL;
            free(it);
            return;
        }
    }
    if (it == NULL) {
        printf("Cannot remove ‘%s’: No such file!\n", dirname);
        free(it);
    }
}


void rmdir(Directory *parent, char *dirname)
{

    NodeDir *it;

    for (it = parent->dirs->first; it != NULL; it = it->next) {
        if (strcmp(it->newdir->name, dirname) == 0) {
            if (it == parent->dirs->first) {
                parent->dirs->first =
                parent->dirs->first->next;
            } else if (it == parent->dirs->last) {
                parent->dirs->last =
                parent->dirs->last->prev;
            } else {
                it->prev->next = it->next;
                it->next->prev = it->prev;
            }
            it = NULL;
            free(it);
            return;
        }
    }
    if (it == NULL) {
        printf("Cannot remove ‘%s’: No such directory!\n", dirname);
        free(it);
    }
}

#endif
/* __FILE_H__ */

Valgrind 输出：

> create fs ls
> 
> ls
> 
> mkdir test ls
> ==11466== Conditional jump or move depends on uninitialised value(s)
> ==11466==    at 0x109025: ls (file.h:189)
> ==11466==    by 0x1097D4: main (main.c:86)
> ==11466==  Uninitialised value was created by a heap allocation
> ==11466==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==11466==    by 0x108D44: mkdir (file.h:134)
> ==11466==    by 0x109766: main (main.c:81)

Answer 1

在 touch 中，您错过了将字段 next 和 rev

设置为 NULL

在 mkdir 中，您错过了将字段 files 和 dirs 设置为 NULL，有时还有 next

为了简化您的代码并使其健壮，我鼓励您为每个 struct 添加一个构造函数，该构造函数执行 malloc 并在值为 NULL 时初始化所有字段，包括 NULL还不知道，并且还为每个添加一个析构函数以释放所有分配的元素。当然，在您的情况下，您也可以使用 calloc 而不是 malloc 将所有内容置于 0

deleteroot 不会释放内存，因为您在调用 free 之前将 root 设置为 NULL，并且因为您没有按照链接进行释放链接资源。

在 rmdir 中，在 for 中调用 free 之前，您有相同的意外分配给 NULL。最后 if 没用检查 it 是否为 NULL，因为 for 的延续测试是 it != NULL，而 free最后一个block没用了

由于您从不释放资源而导致内存泄漏，您还会在 mkdir 中引入内存泄漏

    parent->dirs->first = (NodeDir *) malloc(sizeof(NodeDir));
    parent->dirs->last = (NodeDir *) malloc(sizeof(NodeDir));
    parent->dirs->first = new;
    parent->dirs->last = new;

前两行必须删除

在

new->newdir = (Directory *) malloc(strlen(Directory) + 1);

strlen(Directory) 无效，必须是

new->newdir = (Directory *) malloc(sizeof(Directory));

---

在 pwd 中你会这样做

if (dir->parentDir == NULL)
    return;
if (dir->parentDir != NULL) {

因为前两行没有用

此外，在 root 的情况下你什么也不打印，可以是：

void pwd(Directory *dir)
{
  if (dir->parentDir != NULL) {
    pwd(dir->parentDir);
    printf("%s/", dir->name);
  }
  else
    putchar('/');
}

---

在 cd 中，必须删除对 free 的调用

如果是 .. 如果有父目录，您将始终指出错误，因为您考虑了子目录。请注意，在根级别 cd .. 什么都不做，所以替换

if (strcmp(where, "..") == 0 && dir->parentDir != NULL) {
    return dir->parentDir;
} else if (dir->dirs == NULL)

通过

if (strcmp(where, "..") == 0) {
    return (dir->parentDir != NULL) ? dir->parentDir : dir;
} else if (dir->dirs == NULL)

---

---

我鼓励您将字段 newfile 重命名为 file 并将 newdir 重命名为 dir，因为 新的没有理由

---

在 tree 中，必须删除对 free 的调用

---

可见所有都在头文件中，我鼓励您只将 struct 定义和函数声明放在头文件中，并将函数定义移动到源文件中，否则如果您 #include 几次你的头文件，你将拥有多重定义的函数