复制多维数组(指针) [英] copying multidimensional array (pointers)

问题描述

我有两个指向指针的结构指针

I have two structs pointers to pointers

typedef struct Square {
...
...
}Square;

Square **s1; //Representing 2D array of say, 100*100
Square **s2; //Representing 2D array of say, 200*200

两者都使用malloc()在堆上分配. 我已经将s1初始化为某些值，并且将s2完全初始化为默认值. 基本上，我需要将s1的大小调整为<​​c2>的大小，同时保持其(s1)值，并且添加的"值将与它们在s2中的默认值一样.

Both are allocated on the heap using malloc(). I have s1 initialized with certain values and s2 initialized completely with the default values. Basically I need to resize s1 to the size of s2 while maintaining its (s1) values, and the 'added' values would be just as they were in s2 - the default value.

我写了这个问题 memcpy()从较小的数组到较大的数组但显然我在数组和指针之间感到困惑/

I wrote this question memcpy() from smaller array to larger one but apparently I'm confusing between arrays and pointers/

我的问题是，如何实现将s1的大小调整为<​​c2>的大小.我不必保留原始指针.我可以将s1复制到s2并返回s2(如果这样更好) 我希望我能正确解释我的要求. 谢谢！

My question is, how to implement this resizing of s1 to the size of s2. I don't have to keep the original pointer. I can copy s1 to s2 and return s2 if that's a better way I hope I explained what I'm after properly. Thanks!

推荐答案

二维数组按顺序排列在内存中:row1 row2 row3等.

Two dimensional arrays are laid out in memory sequentially: row1 row2 row3 etc.

memcpy从一个内存位置到另一个内存位置进行线性复制.

memcpy does a linear copy from one memory location to another.

因此，实现您所需要的:

So to achieve what you need:

a)创建一个新数组

Square **s3 = malloc(sizeof(s2));

b)将s2复制到其中

b) Copy s2 into it

c)将s1中的内容逐行复制到新内容中

c) Copy stuff from s1, row by row into new

for(r = 0; r < NROWS_S1; r++)
    memcpy(s3[r], s1[r], sizeof(Square) * NCOLS_S1);

http://www.fredosaurus. com/notes-cpp/arrayptr/23two-dim-array-memory-layout.html

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