在C++;和目标C 我有一个示例项目,在这里我为一个外部的C++库创建了一个C++包装类,我想在Objtovi.C.
我不明白为什么我返回的指针有时是正确的,有时是错误的。以下是示例输出:在C++;和目标C 我有一个示例项目,在这里我为一个外部的C++库创建了一个C++包装类,我想在Objtovi.C.,c++,objective-c,ios,C++,Objective C,Ios,我不明白为什么我返回的指针有时是正确的,有时是错误的。以下是示例输出: Test Data = 43343008 In Compress 43343008 Returned Value = 43343008 Casted Value = 43343008 Test Data = 2239023 In Compress 2239023 Returned Value = 2239023 Casted Value = 2239023 Test Data = 29459973 In Compress
Test Data = 43343008
In Compress 43343008
Returned Value = 43343008
Casted Value = 43343008
Test Data = 2239023
In Compress 2239023
Returned Value = 2239023
Casted Value = 2239023
Test Data = 29459973
In Compress 29459973
Returned Value = 29459973
Casted Value = l.remote
Test Data = 64019670
In Compress 64019670
Returned Value =
Casted Value = stem.syslog.master
在上面的输出中,您可以看到第一次和第二次单击按钮会输出我期望的结果。在其他每次单击中,返回值或转换值无效。我假设这是因为我的指针指向了一个我没有预料到的地址。在多次运行应用程序时,任何按钮的点击都可能是对的或错的
我也尝试了一个单一的线程,但经历了类似的结果
完整的代码已打开,但以下是重要的部分
ViewController.m
#import "ViewController.h"
extern const char * CompressCodeData(const char * strToCompress);
@implementation ViewController
...
// IBAction on the button
- (IBAction)testNow:(id)sender
{
[self performSelectorInBackground:@selector(analyze) withObject:nil];
}
- (void)analyze
{
@synchronized(self) {
const char *testData = [[NSString stringWithFormat:@"%d",
(int)(arc4random() % 100000000)] UTF8String];
NSLog(@"Test Data = %s", testData);
const char *compressed = CompressCodeData(testData);
NSLog(@"Returned Value = %s", compressed);
NSString *casted = [NSString stringWithCString:compressed
encoding:NSASCIIStringEncoding];
NSLog(@"Casted Value = %@\n\n", casted);
}
}
@end
SampleWrapper.cpp
#include <iostream>
#include <string.h>
#include <CoreFoundation/CoreFoundation.h>
using namespace std;
extern "C"
{
extern void NSLog(CFStringRef format, ...);
/**
* This function simply wraps a library function so that
* it can be used in objective-c.
*/
const char * CompressCodeData(const char * strToCompress)
{
const string s(strToCompress);
// Omitted call to static method in c++ library
// to simplify this test case.
//const char *result = SomeStaticLibraryFunction(s);
const char *result = s.c_str();
NSLog(CFSTR("In Compress %s"), result);
return result;
}
}
#包括
#包括
#包括
使用名称空间std;
外部“C”
{
外部无效NSLog(CFStringRef格式,…);
/**
*此函数仅包装库函数,以便
*它可用于objective-c。
*/
const char*CompressCodeData(const char*strotcompress)
{
常量字符串s(strToCompress);
//在C++库中调用静态方法
//简化这个测试用例。
//const char*result=SomeStaticLibraryFunction;
const char*result=s.c_str();
NSLog(CFSTR(“压缩%s”),结果);
返回结果;
}
}
您正在返回指向已解除分配的at对象的指针
const string s(strToCompress);
…
const char *result = s.c_str();
NSLog(CFSTR("In Compress %s"), result);
return result;
s
在CompressCodeData()
函数结束后不存在,因此指向其内部内存的指针无效
您可以分配一块内存来保存响应,但释放响应将取决于调用方
char *compressed = CompressCodeData(testData);
NSLog(@"Returned Value = %s", compressed);
NSString *casted = [NSString stringWithCString:compressed
encoding:NSASCIIStringEncoding];
free(compressed);
NSLog(@"Casted Value = %@\n\n", casted);
…
const char * CompressCodeData(const char * strToCompress)
…
char *result = strdup(s.c_str());
另一个解决方案是传入内存以将数据存储到中
char compressed[2048]; // Or whatever!
CompressCodeData(testData, compressed, sizeof(compressed));
NSLog(@"Returned Value = %s", compressed);
NSString *casted = [NSString stringWithCString:compressed
encoding:NSASCIIStringEncoding];
NSLog(@"Casted Value = %@\n\n", casted);
…
void CompressCodeData(const char * strToCompress, char *result, size_t size)
…
s.copy(result, size - 1);
result[s.length() < size ? s.length() : size-1] = '\0';
char压缩[2048];//或者别的什么!
CompressCodeData(testData,压缩,sizeof(压缩));
NSLog(@“返回值=%s”,已压缩);
NSString*casted=[NSString stringWithCString:压缩
编码:NSASCIIStringEncoding];
NSLog(@“铸造值=%@\n\n”,铸造);
…
void CompressCodeData(常量字符*strotcompress,字符*结果,大小)
…
s、 副本(结果,大小-1);
结果[s.length()
您正在返回指向已解除分配的at对象的指针
const string s(strToCompress);
…
const char *result = s.c_str();
NSLog(CFSTR("In Compress %s"), result);
return result;
s
在CompressCodeData()
函数结束后不存在,因此指向其内部内存的指针无效
您可以分配一块内存来保存响应,但释放响应将取决于调用方
char *compressed = CompressCodeData(testData);
NSLog(@"Returned Value = %s", compressed);
NSString *casted = [NSString stringWithCString:compressed
encoding:NSASCIIStringEncoding];
free(compressed);
NSLog(@"Casted Value = %@\n\n", casted);
…
const char * CompressCodeData(const char * strToCompress)
…
char *result = strdup(s.c_str());
另一个解决方案是传入内存以将数据存储到中
char compressed[2048]; // Or whatever!
CompressCodeData(testData, compressed, sizeof(compressed));
NSLog(@"Returned Value = %s", compressed);
NSString *casted = [NSString stringWithCString:compressed
encoding:NSASCIIStringEncoding];
NSLog(@"Casted Value = %@\n\n", casted);
…
void CompressCodeData(const char * strToCompress, char *result, size_t size)
…
s.copy(result, size - 1);
result[s.length() < size ? s.length() : size-1] = '\0';
char压缩[2048];//或者别的什么!
CompressCodeData(testData,压缩,sizeof(压缩));
NSLog(@“返回值=%s”,已压缩);
NSString*casted=[NSString stringWithCString:压缩
编码:NSASCIIStringEncoding];
NSLog(@“铸造值=%@\n\n”,铸造);
…
void CompressCodeData(常量字符*strotcompress,字符*结果,大小)
…
s、 副本(结果,大小-1);
结果[s.length()