对结构数组使用realloc [英] Using realloc for array of structs

问题描述

我正在使用realloc增加结构数组的内存量，而且似乎根本没有增加.我已经阅读了所有与此相关的帖子，但无法弄清楚自己在做什么错.这是我的代码:

I'm using realloc to increase the amount of memory for an array of structs and it doesn't seem to be increasing at all. I've read all of the posts relating to this and I can't figure out what I'm doing wrong. Here is my code:

struct fileInfo {
char name[MAXNAMLEN];
struct stat stbuf;
};

...

 struct fileInfo * newFileInfoPtr;
 struct fileInfo * fileInfoPtr = (struct fileInfo *) realloc (NULL, sizeof (struct fileInfo));
    // loop through directory to find all filenames
    while ((direntPtr = readdir (dirFilePtr)) != NULL) {
        (void) strcpy (direntName, filename);
        (void) strcat (direntName, "/");
        (void) strcat (direntName, direntPtr->d_name);
        (void) strcat (direntName, "\0");
        // check for vaild file
        if (lstat (direntName, &st)) {
            if (errno) {
                (void) snprintf (buffer, BUFSIZ, STR_LSTAT_ERR);
                perror (buffer);
            }
            exit (EXIT_FAILURE);
        }

        // reallocate memory for new fileInfo struct
        newFileInfoPtr = (struct fileInfo *) realloc (fileInfoPtr, 
                                    (count+1) * sizeof (struct fileInfo));

        // check for allocation success and increase count
        if (newFileInfoPtr != NULL) {
            (void) memset (newFileInfoPtr->name, NULL, MAXNAMLEN);
            (void) strcpy (newFileInfoPtr->name, direntPtr->d_name);
            newFileInfoPtr->stbuf = st; 
            fileInfoPtr = newFileInfoPtr;
            count++;
        } else {
            if (errno) {
                (void) snprintf (buffer, BUFSIZ, STR_ALLOC_ERR);
                perror (buffer);
            }
            exit (EXIT_FAILURE);
        }
        ...

direntPtr是指向打开的目录的指针，我正在读取其中所有文件的名称.该部分正在工作，因为我可以打印出每个条目的名称.我的问题是最终得到的最终结构数组.我了解使用realloc可以基于旧数组分配内存，将返回值分配给新指针，用信息填充新指针，并将旧指针设置为新指针.但是，完成循环后，fileInfoPtr只是一个结构.我可以访问索引为0的字段，但之后它们都是空的.我打印出每个索引的内存地址，它们都是相同的... 感谢您的帮助

direntPtr is a pointer to an opened directory and I am reading all the names of the files within. That part is working because I can print out the names of each entry. My problem is the final struct array I end up with. I understand with realloc you allocate memory based on the old array, assign the return value to a new pointer, fill the new pointer with information, and set the old pointer to the new pointer. However, after finishing the loop, fileInfoPtr is just one struct. I can access the fields at index 0, but after that they are all empty. I printed out the memory addresses of each index and they are all the same... Thanks for any help

推荐答案

您的newFileInfoPtr指向新分配的数组的第一个条目.通过memset和strcpy调用，您可以在newFileInfoPtr->name上进行操作，这将覆盖第一个条目的名称.你想要

Your newFileInfoPtr points to the first entry of the newly allocated array. With your memset and strcpy calls, you operate on newFileInfoPtr->name, which overwrites the name of the first entry. You want

(void) memset (newFileInfoPtr[count].name, NULL, MAXNAMLEN);
(void) strcpy (newFileInfoPtr[count].name, direntPtr->d_name);

(在递增之前)访问索引为count的最后一个条目.

to access the last entry at index count (before incrementing).

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