Thanks for your responses.
Looks like stringWithContentsOfFile:encoding:error: does what I need.
Jens, at least I know not to pursue the NSScanner thing any further in
this case.
Thanks,
Ian.
On 23/07/2008, at 3:39 AM, Jens Alfke wrote:
On 22 Jul '08, at 2:09 AM, Ian Jackson wrote:
NSString *path = ...;
NSData *data = [NSData dataWithContentsOfFile:path];
// assuming data is in UTF8
NSString *string = [NSString stringWithUTF8String:[data bytes]];
The reason this doesn't work is that -stringWithUTF8String: expects
a NUL-terminated C string, but [data bytes] just returns the raw
contents of the data block. So the string factory method will keep
reading past the end of the data until it finds a zero byte in
whatever happens to be randomly out there. That means it'll read
garbage past the end of the string, and if that garbage doesn't look
like valid UTF-8, it'll fail.
The correct call to make would be
[[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding]
although as Patrick already replied, the best way to read a string
from a file is +stringWithContentsOfFile:usedEncoding:error:, which
will attempt to determine the encoding.
However, the files also include identifiers such as "usemtl", which
could appear at any time. So any ideas how you go about searching
for a set of characters, and a set of strings simultaneously? i.e.
how do I search for the characters without momentarily ignoring the
strings or vice versa? This seems to be quite straightforward with
fscanf, but it seems a bit odd going to C, when I'm trying to do
this in Objective-C.
This is beyond what NSScanner can do. You have a number of options,
like scanning the string character by character using a 'for' loop,
using a parser generator like ANTLR, or simply calling fscanf.
(There's nothing wrong with using C APIs, when appropriate.)
—Jens
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