str2OSType in utils.cpp in ConvertFile example

• Subject: str2OSType in utils.cpp in ConvertFile example
• From: "William DeShazer" <email@hidden>
• Date: Wed, 28 Mar 2007 23:27:33 -0400
• Delivered-to: email@hidden
• Delivered-to: email@hidden
• Dkim-signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=gTX9bgSRDX6DE3e0tyii5wBGTXic1JaC3ixeA++zY2d1sOBJ0zQo/toh165wcVVanH2FBb4RmKeDwOi59lv1/M0HJIiUeB2k72O1JMXwNDm0Hf5tFoSvNUQWiZWaoupKzFRyKg81fd9wWH1+h2bnsvjVGqbjsb1tIEqLFqzZn8U=
• Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=R+GZgNgB2CviuCSO2nPpTyI49l3XkIZHzIT8SytFEZm8mBjzm6HhowbRLplqUau4YsqjnQeVvDIfOKMh8JYpjclD5a1SWnn7ydLh5i5sr7Xe+iShSuyMruCYXB5PS1ZC6usfGRkaWOAZqyphu71QBFCSe+K8Q82gB98kYtpOZlw=

I am trying to understand one of the CoreAudio examples and I am
really having a hard time. In the utils.cpp file, there is a method
called str2OSType.

void str2OSType (const char * inString, OSType &outType)
{
	if (inString == NULL) {
		outType = 0;
		return;
	}
	
	size_t len = strlen(inString);
	if (len <= 4) {
		char workingString[5];
		
		workingString[4] = 0;
		workingString[0] = workingString[1] = workingString[2] =
workingString[3] = ' ';
		memcpy (workingString, inString, strlen(inString));
		outType = 	*(workingString + 0) <<	24	|
					*(workingString + 1) <<	16	|
					*(workingString + 2) <<	8	|
					*(workingString + 3);
		return;
	}

	if (len <= 8) {
		if (sscanf (inString, "%lx", &outType) == 0) {
			printf ("* * Bad conversion for OSType\n");
			UsageString(1);
		}
		return;
	}
	printf ("* * Bad conversion for OSType\n");
	UsageString(1);
}

First, I don't understand the need to convert a 4 byte string into a 4
byte OSType. That being said, where is there any documentation on
OSTypes. I found a definition in wikipedia that says that it is a 4
byte sequence used as a File/Directory identifier. However, I can't
find anything beyond that. For instance, what are the accepted values
for the identifiers? Furthermore, is the type definition in
CoreFoundation or does it reside deeper than that? I can't find
anything to give me any guidance on this.

Beyond my inability to locate documentation on OSType, I am having a
hard time with the assignment of "outType". I generally don't have an
appreciation for bit mathematics. If inString is a 4 character string
and workingString is a 4 character array, what is the function of the
bit shift and the bit Or? I don't understand what this section of code
is trying to do.

Any guidance would be greatly appreciated.

Thanks,
Will DeShazer
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/coreaudio-api/email@hidden

• Prev by Date: Re: setting Input property for USB headsets
• Next by Date: 192000 Hz won't render
• Previous by thread: Re: setting Input property for USB headsets
• Next by thread: 192000 Hz won't render
• Index(es):
  • Date
  • Thread