在Swift中获取一个指向C char数组的指针 [英] Obtain a pointer to a C char array in Swift

问题描述

A具有这样的结构(在mongodb c驱动程序的bson.h中定义):

A have a structure like this (defined in bson.h of mongodb c driver):

typedef struct
{
  uint32_t domain;
  uint32_t code;
  char message[504];
} bson_error_t;

在Swift中，我有一个指向这种结构的指针，如下所示:

In Swift I have a pointer to this structure like this:

err: UnsafePointer<bson_error_t> = ...

现在无论如何我都无法将message[504](Swift视为(Int8，Int8，Int8，... 504次)的元组)转换为char*以便在String.fromCString()中使用它. 甚至有可能在Swift中做到这一点吗?作为一个临时解决方案，我在一个单独的.c文件中创建了一个辅助C函数，该文件使用err *bson_error_t并返回char*，但是如果这很奇怪 Swift无法独自做到这一点.

Now whatever I do I cannot convert message[504] (which Swift sees as a tuple of (Int8, Int8, Int8, ...504 times)) to char* to use it in String.fromCString(). Is it even possible to do that in Swift? As a temporary solution I created a helper C function in a separate .c file which takes err *bson_error_t and returns char*, but this is weird if Swift cannot do it by itself.

推荐答案

这是我的建议(类似于林太郎的方法，也许稍微简单些):

Here my suggestion (similar to rintaro's approach, perhaps slightly simpler):

var err: UnsafeMutablePointer<bson_error_t> = ...

var msg = err.memory.message
let msgString = withUnsafePointer(&msg) { String.fromCString(UnsafePointer($0)) }
println(msgString)

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