iOS Obj-C convert byte array to plist to string - ios

Question

Argh, I'm going nuts.
I've got the following function which I am trying to log with a custom logger
CFWriteStreamWrite(CFWriteStreamRef stream, const UInt8 *buffer,
CFIndex bufferLength) {
NSData *data = [[NSData alloc] initWithBytes:buffer length: bufferLength];
NSString *errorDesc = nil;
NSPropertyListFormat format;
NSString * str = (NSString*)[NSPropertyListSerialization
propertyListFromData:data
mutabilityOption:NSPropertyListMutableContainersAndLeaves
format:&format
errorDescription:&errorDesc];
custom_log(CF, "CFURLCreateWithString: %s", str);
}
When I use my custom logger I get rubbish output
CFURLCreateWithString: < °3€
But when using NSLog, everything works fine,
Feb 10 00:36:39: {
bundleID = "com.test.testapp";
pid = 2852;
}
Custom Logger
EXPORT void custom_log(unsigned int facility, const char *msg, ...) {
if (minLogLevel <= INFO) {
char *msgBuffer;
va_list args;
va_start(args, msg);
vasprintf(&msgBuffer, msg, args);
va_end(args);
dispatch_async(logQueue, ^{
write(facility, INFO, msgBuffer);
});
}
}
Please tell me where I'm going wrong, I have spent the past 3 hours trying to convert to different data types. No luck.
Also, is it possible to get the output from NSLog into a string and then I'll just pass it to my logger instead?

Answer 1

One of the problems that you might be experiencing here is that NSString is not the same as the c_str that your vasprintf method is likely expecting to substitute for %s.
To compound this issue, I'm pretty sure you can't directly convert NSPropertyListSerialization to NSString, though I didn't test it myself. You might be looking for such an alternative instead:
NSString * str = [NSString stringWithFormat:#"%#", [NSPropertyListSerialization
propertyListFromData:data
mutabilityOption:NSPropertyListMutableContainersAndLeaves
format:&format
errorDescription:&errorDesc]];
custom_log(CF, "CFURLCreateWithString: %s", [str UTF8String]);
Of course, since you're already compositing a string, why not just do it all in the same place?
NSString * str = [NSString stringWithFormat:#"CFURLCreateWithString: %#", [NSPropertyListSerialization
propertyListFromData:data
mutabilityOption:NSPropertyListMutableContainersAndLeaves
format:&format
errorDescription:&errorDesc]];
custom_log(CF, [str UTF8String]);
As a fun side project, you might consider doing something like this in your main.mm. Replace stderr with stdout if you want more than just error stuff:
#if COPY_NSLOG_TO_CUSTOM
typedef int (*MyStdWriter)(void *, const char *, int);
static MyStdWriter _oldStdWrite;
int __customStderrWrite(void *inFD, const char *buffer, int size) {
if (minLogLevel <= INFO) {
// write to your custom stream here.
}
return _oldStdWrite(inFD, buffer, size);
}
void __copyNSLogToCustom(void) {
_oldStdWrite = stderr->_write;
stderr->_write = __customStderrWrite;
}
#endif
int main(int argc, char *argv[]) {
#if COPY_NSLOG_TO_CUSTOM
__copyNSLogToCustom();
#endif
// ...
}