iOS 7.1 CommonCrypto 库抱怨:隐式转换失去整数精度:'NSUInteger' (unsigned long) to CC_LONG (unsigned int) [英] iOS 7.1 CommonCrypto library complains: Implicit conversion loses integer precision: 'NSUInteger' (unsigned long) to CC_LONG (unsigned int)
问题描述
我在从文件中执行 MD5 时收到上述错误(在标题中).. 我通常可以处理这些类型的 32->64 位转换问题..但在这种情况下,我不知道我应该做什么CC_MD5 是 CommonCrypto->CommonDigest
的一部分,后者是 iOS7.1 附带的库.我假设 [inputData length]
正在返回 NSUInteger,这就是问题所在,但是我可以简单地从 UL 转换为 UI 吗?如果文件很大,我可能会失去精度.为什么 Apple 附带的库需要 int
支持 64 位语言(例如 iOS)?是有人忽略了什么,还是我真的很愚蠢并误诊了问题?
I get the above error (in title) whilst doing a MD5 from file.. I can usually cope with these type of 32->64bit conversion issues..but in this case, I do not know what I should do as CC_MD5 is part of CommonCrypto->CommonDigest
, a library that ships with iOS7.1. I am assuming [inputData length]
is returning NSUInteger and therein lies the issue, however can I simply cast down from UL to UI? I will possibly lose precision if the file is large. Why would a library that Apple ships with require int
in a 64 bit capable language such as iOS? Did someone overlook something or am I being really stupid and mis-diagnosing the problem?
- (NSString*) getMD5FromFile:(NSString *)pathToFile {
unsigned char outputData[CC_MD5_DIGEST_LENGTH];
NSData *inputData = [[NSData alloc] initWithContentsOfFile:pathToFile];
CC_MD5([inputData bytes], [inputData length], outputData);
[inputData release];
NSMutableString *hash = [[NSMutableString alloc] init];
for (NSUInteger i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
[hash appendFormat:@"%02x", outputData[i]];
}
return [hash autorelease];
}
来自 CommonCrypto->CommonDigest.h:
From CommonCrypto->CommonDigest.h:
extern unsigned char *CC_MD5(const void *data, CC_LONG len, unsigned char *md)
我向 Apple (#17256918) 提交了错误报告,但没有办法在没有错误的情况下做到这一点吗?
I filed bug report with apple (#17256918) but isn't there a way to do this without the error?
推荐答案
您只需要将 [inputData length]
转换为 int
或 uint32_t代码>正如你所怀疑的那样.
You simply need to cast [inputData length]
to either int
or uint32_t
as you suspect.
如果你想断言这个数字对于类型来说不是太大,你可以使用 UINT32_MAX
来检查.这是您可以使用的 NSAssert 示例.
If you want to assert that number is not too large for type you can use the UINT32_MAX
to check. Here is an example on an NSAssert you could use.
NSAssert([inputData length] < UINT32_MAX, @"too big!");
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