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SoClose · Nov 9, 2001, 08:58 AM

Does anyone have some sample code for making a string value (or char) such as "sysz" into the appropriate FourCharCode Mac OS type? I want to loop through a series of FourCharCodes, but I want to define them in an external file (and let others add new ones). What would be great is if I could create a function like:

<BLOCKQUOTE>code:<HR><pre>OSType myType = MakeFourCharCode(CFStringRef aString) [/code]

I'm pretty new to C programming, so any guidance would be appreciated. I'm assuming that all I have to do is pack the CFStringRef bytes into a 32-bit word, but I'm not sure how to do that.

Many thanks!

int69h · Nov 9, 2001, 10:49 AM

The following code could be tighter and much more terse; however, I wanted it to be as clear as possible.

<BLOCKQUOTE>code:<HR><pre>
char *s = "WIND";
unsigned int mac_type = 0;
unsigned int temp = 0;

temp = (unsigned int)s[0] << 24;
mac_type = mac_type | temp;

temp = (unsigned int)s[1] << 16;
mac_type = mac_type | temp;

temp = (unsigned int)s[2] << 8;
mac_type = mac_type | temp;

temp = s[3];
mac_type = mac_type | temp;
[/code]

[ 11-09-2001: Message edited by: int69h ]

SoClose · Nov 9, 2001, 12:18 PM

Originally posted by int69h:
The following code could be tighter and much more terse; however, I wanted it to be as clear as possible.]

Thanks for the code! I'll give it a whirl!

Angus_D · Nov 9, 2001, 01:02 PM

I'm sure there are much nicer ways of doing it, like for example just doing a memcpy on 4 bytes from a char * into a FourCharCode.

SoClose · Nov 9, 2001, 01:56 PM

Originally posted by Angus_D:
I'm sure there are much nicer ways of doing it, like for example just doing a memcpy on 4 bytes from a char * into a FourCharCode.

Is BlockMove() an analogous call to memcopy()?

int69h · Nov 9, 2001, 02:25 PM

Originally posted by Angus_D:
I'm sure there are much nicer ways of doing it, like for example just doing a memcpy on 4 bytes from a char * into a FourCharCode.

Angus is right. memcpy(3) or bcopy(3) would be a much nicer (and faster) way to do it. Silly me, bitwise operators were the first thing that came to mind.

SoClose · Nov 12, 2001, 08:05 AM

OK, thanks for the suggestions but I'm still slightly lost. I'm getting the string I want as a CFStringRef. I would assume that I'd first get the C string from the CFStringRef using something like CFStringGetCString() which copies the string bytes in a char *buf. Would I then just do:

OSType myType;
char *buffer;

memcpy(&buffer, &myType, sizeof(buffer));

Do I need to explicitly cast myType when calling memcpy?

Many thanks...

Angus_D · Nov 12, 2001, 12:44 PM

Well actually, I think that this should work:
<BLOCKQUOTE>code:<HR><pre>FourCharCode myCode;
char *buffer;

memcpy(&myCode, buffer, sizeof(FourCharCode));[/code]

Where did OSType come from? you shouldn't coy the sizeof(buffer) bytes because that is wrong (you don't want to copy a pointer, you want to copy a FourCharCode), and the function prototype of memcpy is:
void *
memcpy(void *dst, const void *src, size_t len)
So you got the argument order mixed up. For going the other way, you would probably want something like this:
<BLOCKQUOTE>code:<HR><pre>FourCharCode myCode;
char buffer[4];
memcpy(&buffer[0], &myCode, sizeof(FourCharCode));
buffer[4] = 0;[/code]

That was jus toff the top of my head so I haven't tested it

smeger · Dec 8, 2001, 03:26 AM

How about the super-turbo version?

<BLOCKQUOTE>code:<HR><pre>
char *original = 'WIND';
OSType fourCharValue;

// fourCharValue uses four bytes of storage
// original is a c-string, so it's stored as
// 'W','I','N','D','\0'
// so just coerce it to the right type and copy it over

fourCharValue = *(OSType *)original;
[/code]

But this is also off the top of my head, so definitely check it first

wadesworld · Dec 8, 2001, 01:56 PM

[blockquote]char *buffer;

memcpy(&myCode, buffer, sizeof(FourCharCode));[/blockquote]

You can't do that. buffer doesn't point to anything. You'll be trashing random memory.

Wade

Diggory Laycock · Dec 9, 2001, 05:04 AM

You can't do that. buffer doesn't point to anything. You'll be trashing random memory.

True, I think that the original poster and subsequent repliers (is that a word?) took it as read that you would have to allocate the memory first.

I happened to need that code recently and this is the full code I used:

char *buffer;
OSType theCreatorCode;
.
.
.
.
buffer=malloc(sizeof(FourCharCode));
bundleSignature=[[someAppBundle infoDictionary] objectForKey:@"CFBundleSignature"];
[bundleSignature getCString: buffer];
memcpy(&theCreatorCode, buffer, sizeof(FourCharCode));
free(buffer);