将返回的指针重写为输出参数 [英] Rewriting a returned pointer to an output parameter

问题描述

我正在玩OpenSSL库，它需要我刷新指针，并且遇到了困难。

我有一个objective-c （unsigned char *）encryptTake1：（unsigned char *）输入inputLength：（int）inLen outputLength：（int（））方法：

  *）outLen; 
  

它需要一些数据，对它进行加密并返回一个指向数据的指针和数据长度一个输出参数。

我想改变它，以便加密数据也作为输出参数处理，返回值用于指示成功或失败。这是我的：
$ b $ pre $ - （int）encryptTake2 :(无符号字符*）输入inputLength：（int）inLen输出： （unsigned char *）output outputLength：（int *）outLen;


这不起作用。我究竟做错了什么？我认为问题在于（unsigned char *）是错误的。如果（unsigned char *）不对，那么我认为我还需要改变方法中引用 output 的方式。如何？

解决方案

这取决于您如何处理内存分配。

-encryptTake1：是否返回？如果它返回一个新分配的缓冲区，调用者必须释放这个缓冲区，那么你可以在encryptTake2中使用 unsigned char ** ：

<$ （unsigned char *）输入inputLength：（int）inLen输出：（unsigned char **）outputPtr outputLength：（int *）outLen
{$（$） b $ b * outputPtr = malloc（1024）;
unsigned char * output = * outputPtr;
strcpy（输出，hello）;
...
}

I'm playing around with the openSSL library and it requires me to brush up on pointers, and I'm having difficulty.

I have a objective-c method:

-(unsigned char *)encryptTake1:(unsigned char *)input inputLength:(int)inLen outputLength:(int*)outLen;

It takes some data, encrypts it and returns a pointer to the data and the length of the data as an output parameter.

I want to change this so that the encrypted data is also handled as an output parameter and the return value is used to indicate success or failure. This is what I have:

-(int)encryptTake2:(unsigned char *)input inputLength:(int)inLen output:(unsigned char *)output outputLength:(int*)outLen;

This doesn't work. What am I doing wrong? I think the problem is that (unsigned char *) is the wrong. If (unsigned char *) is wrong then I presume I will also need to change how output is referenced within the method. How?

解决方案

It depends on how you are handling memory allocation.

What does -encryptTake1: return? If it returns a newly allocated buffer that the caller must free then you would use unsigned char** in encryptTake2:

-(int)encryptTake2:(unsigned char *)input inputLength:(int)inLen output:(unsigned char **)outputPtr outputLength:(int*)outLen
{
    *outputPtr = malloc(1024);
    unsigned char* output = *outputPtr;
    strcpy(output, "hello");
    ...
}

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