how i can convert PWSTR variable to uppercase in vc++. I googled but didn't get the code sample.
EDITED
What i want to do with PWSTR variable is, a method's return type is PWSTR. I have to check whether the returned value is equal to string "Y". so whatever comes from return I am trying to UPPER its case then checking.
One more thing I want to know, how to use PWSTR var in if() condition checking.
thanks
There is _tcsupr_s and friends which should get you in the right direction.
EDIT:
Following on from your edit, you don't need to worry about converting to upper case for you to then do the comparison -- you can instead call the case insensitive string comparison function, _tcsicmp (or its friends if you're not compiling for Unicode) - there is example code if you follow the link, which also explains the importance of having set the correct locale to give the results you're expecting.
There you are - http://msdn.microsoft.com/en-us/library/sch3dy08%28v=VS.80%29.aspx
Related
I was working on a simple task yesterday, just needed to sum the values in a handful of dropdown menus to display in a textbox via Javascript. Unexpectedly, it was just building a string so instead of giving me the value 4 it gave me "1111". I understand what was happening; but I don't understand how.
With a loosely typed language like Javascript or PHP, how does the computer "know" what type to treat something as? If I just type everything as a var, how does it differentiate a string from an int from an object?
What the + operator will do in Javascript is determined at runtime, when both actual arguments (and their types) are known.
If the runtime sees that one of the arguments is a string, it will do string concatenation. Otherwise it will do numeric addition (if necessary coercing the arguments into numbers).
This logic is coded into the implementation of the + operator (or any other function like it). If you looked at it, you would see if typeof(a) === 'string' statements (or something very similar) in there.
If I just type everything as a var
Well, you don't type it at all. The variable has no type, but any actual value that ends up in that variable has a type, and code can inspect that.
I have a question, if I'm comparing ints, is there a performance difference in calling thenComparingInt(My::intMethod) vs thenComparing(My::intMethod), in other words, if I'm comparing differemt types, both reference and primitive, e.g. String, int, etc. Part of me just wants to say comparing().thenComparing().thenComparing() etc, but should I do comparing.thenComparing().thenComparingInt() if the 3rd call was comparing an int or Integer value?
I am assuming that comparing() and thenComparing() use the compareTo method to compare any given type behind the scenes or possibly for ints, the Integer.compare? I'm also assuming the answer to my original question may involve performance in that thenComparingInt would know an int is being passed in, whereas, thenComparing would have to autobox int to Integer then maybe cast to Object?
Also, another question whilst I think of it - is there a way of chaining method references, e.g. Song::getArtist::length where getArtist returns a string? Reason is I wanted to do something like this:
songlist.sort(
Comparator.comparing((Song s) -> s.getArtist().length()));
songlist.sort(
Comparator.comparing(Song::getArtist,
Comparator.comparingInt(String::length)));
songlist.sort(
Comparator.comparing(Song::getArtist, String::length));
Of the 3 examples, the top two compile but the bottom seems to throw a compilation error in Eclipse, I would have thought the 2nd argument of String::length was valid? But maybe not as it's expecting a Comparator not a function?
Question 1
I would think thenComparingInt(My::intMethod) might be better since it should avoid boxing, but you would have to try out both versions to see if it really makes a difference.
Question 2
songlist.sort(
Comparator.comparing(Song::getArtist, String::length));
Is invalid because the 2nd parameter should be a Comparator not a method that returns int.
Looking at the Windows SDK, I found this #define directive for MAKEINTRESOURCEW:
#define MAKEINTRESOURCEW(i) ((LPWSTR)((ULONG_PTR)((WORD)(i))))
Can someone explain to me what the heck that means? For example, what would be the value of MAKEINTRESOURCEW(0)? (1)? (-1)?
The result of this macro will be pointer to long string with value equal to given parameter. You can see it by reading precompiler output (see /P C++ compiler options). All casting is required to compile this macro result, when LP[w]WSTR pointer is required, both in Win32 and x64 configurations.
Some Windows API, like LoadIcon, expect string pointer as their parameter. Possibly, these functions test the pointer value, and if it is less than some maximum, they interpret it as resource index, and not as string (problems of ugly C-style interface). So, this macro allows to pass WORD as string, without changing its value, with appropriate casting.
For the most part, it leaves the value unchanged, but converts it from an int to a pointer so it's acceptable to functions that expect to see a pointer. The intermediate casts widen the input int to the same size as a pointer, while ensuring against it's being sign extended. In case you care, ULONG_PTR is not a "ULONG POINTER" like you might guess -- rather, it's an unsigned long the same size as a pointer. Back before 64-bit programming became a concern, the definition was something like:
#define MAKEINTRESOURCE(i) (LPTSTR) ((DWORD) ((WORD) (i)))
Nowadays, they use ULONG_PTR, which is a 32-bit unsigned long for a 32-bit target, and a 64-bit unsigned long for a 64-bit target.
That's a macro that casts an argument i to a word, then casts that result to a pointer to an unsigned long, then again to a long pointer to a wide-character string.
Like other users said - it just casts an integer into a "pointer to a string".
The reason for this is the following: At the ancient times of Windows 3.0 people tried to be minimalistic as much as possible.
It was assumed that resources in the executable can have either string identifier or integer. Hence when you try to access such a resource - you specify one of the above, and the function distinguish what you meant automatically (by checking if the provided "pointer" looks like a valid pointer).
Since the function could not receive a "variable argument type" - they decided to make it receive LPCTSTR (or similar), whereas the actual parameter passed may be integer.
Another example from Windows API: A pointer to the window procedure. Every window has a window procedure (accessed via GetWindowLong with GWL_WNDPROC flag.
However sometimes it's just an integer which specifies what "kind" of a window is that.
Then there's a CallWindowProc which knows to distinguish those cases.
Something like this (yes, this doesn't deal with some edge cases - that's not the point):
int CountDigits(int num) {
int count = 1;
while (num >= 10) {
count++;
num /= 10;
}
return count;
}
What's your opinion about this? That is, using function arguments as local variables.
Both are placed on the stack, and pretty much identical performance wise, I'm wondering about the best-practices aspects of this.
I feel like an idiot when I add an additional and quite redundant line to that function consisting of int numCopy = num, however it does bug me.
What do you think? Should this be avoided?
As a general rule, I wouldn't use a function parameter as a local processing variable, i.e. I treat function parameters as read-only.
In my mind, intuitively understandabie code is paramount for maintainability, and modifying a function parameter to use as a local processing variable tends to run counter to that goal. I have come to expect that a parameter will have the same value in the middle and bottom of a method as it does at the top. Plus, an aptly-named local processing variable may improve understandability.
Still, as #Stewart says, this rule is more or less important depending on the length and complexity of the function. For short simple functions like the one you show, simply using the parameter itself may be easier to understand than introducing a new local variable (very subjective).
Nevertheless, if I were to write something as simple as countDigits(), I'd tend to use a remainingBalance local processing variable in lieu of modifying the num parameter as part of local processing - just seems clearer to me.
Sometimes, I will modify a local parameter at the beginning of a method to normalize the parameter:
void saveName(String name) {
name = (name != null ? name.trim() : "");
...
}
I rationalize that this is okay because:
a. it is easy to see at the top of the method,
b. the parameter maintains its the original conceptual intent, and
c. the parameter is stable for the rest of the method
Then again, half the time, I'm just as apt to use a local variable anyway, just to get a couple of extra finals in there (okay, that's a bad reason, but I like final):
void saveName(final String name) {
final String normalizedName = (name != null ? name.trim() : "");
...
}
If, 99% of the time, the code leaves function parameters unmodified (i.e. mutating parameters are unintuitive or unexpected for this code base) , then, during that other 1% of the time, dropping a quick comment about a mutating parameter at the top of a long/complex function could be a big boon to understandability:
int CountDigits(int num) {
// num is consumed
int count = 1;
while (num >= 10) {
count++;
num /= 10;
}
return count;
}
P.S. :-)
parameters vs arguments
http://en.wikipedia.org/wiki/Parameter_(computer_science)#Parameters_and_arguments
These two terms are sometimes loosely used interchangeably; in particular, "argument" is sometimes used in place of "parameter". Nevertheless, there is a difference. Properly, parameters appear in procedure definitions; arguments appear in procedure calls.
So,
int foo(int bar)
bar is a parameter.
int x = 5
int y = foo(x)
The value of x is the argument for the bar parameter.
It always feels a little funny to me when I do this, but that's not really a good reason to avoid it.
One reason you might potentially want to avoid it is for debugging purposes. Being able to tell the difference between "scratchpad" variables and the input to the function can be very useful when you're halfway through debugging.
I can't say it's something that comes up very often in my experience - and often you can find that it's worth introducing another variable just for the sake of having a different name, but if the code which is otherwise cleanest ends up changing the value of the variable, then so be it.
One situation where this can come up and be entirely reasonable is where you've got some value meaning "use the default" (typically a null reference in a language like Java or C#). In that case I think it's entirely reasonable to modify the value of the parameter to the "real" default value. This is particularly useful in C# 4 where you can have optional parameters, but the default value has to be a constant:
For example:
public static void WriteText(string file, string text, Encoding encoding = null)
{
// Null means "use the default" which we would document to be UTF-8
encoding = encoding ?? Encoding.UTF8;
// Rest of code here
}
About C and C++:
My opinion is that using the parameter as a local variable of the function is fine because it is a local variable already. Why then not use it as such?
I feel silly too when copying the parameter into a new local variable just to have a modifiable variable to work with.
But I think this is pretty much a personal opinion. Do it as you like. If you feel sill copying the parameter just because of this, it indicates your personality doesn't like it and then you shouldn't do it.
If I don't need a copy of the original value, I don't declare a new variable.
IMO I don't think mutating the parameter values is a bad practice in general,
it depends on how you're going to use it in your code.
My team coding standard recommends against this because it can get out of hand. To my mind for a function like the one you show, it doesn't hurt because everyone can see what is going on. The problem is that with time functions get longer, and they get bug fixes in them. As soon as a function is more than one screen full of code, this starts to get confusing which is why our coding standard bans it.
The compiler ought to be able to get rid of the redundant variable quite easily, so it has no efficiency impact. It is probably just between you and your code reviewer whether this is OK or not.
I would generally not change the parameter value within the function. If at some point later in the function you need to refer to the original value, you still have it. in your simple case, there is no problem, but if you add more code later, you may refer to 'num' without realizing it has been changed.
The code needs to be as self sufficient as possible. What I mean by that is you now have a dependency on what is being passed in as part of your algorithm. If another member of your team decides to change this to a pass by reference then you might have big problems.
The best practice is definitely to copy the inbound parameters if you expect them to be immutable.
I typically don't modify function parameters, unless they're pointers, in which case I might alter the value that's pointed to.
I think the best-practices of this varies by language. For example, in Perl you can localize any variable or even part of a variable to a local scope, so that changing it in that scope will not have any affect outside of it:
sub my_function
{
my ($arg1, $arg2) = #_; # get the local variables off the stack
local $arg1; # changing $arg1 here will not be visible outside this scope
$arg1++;
local $arg2->{key1}; # only the key1 portion of the hashref referenced by $arg2 is localized
$arg2->{key1}->{key2} = 'foo'; # this change is not visible outside the function
}
Occasionally I have been bitten by forgetting to localize a data structure that was passed by reference to a function, that I changed inside the function. Conversely, I have also returned a data structure as a function result that was shared among multiple systems and the caller then proceeded to change the data by mistake, affecting these other systems in a difficult-to-trace problem usually called action at a distance. The best thing to do here would be to make a clone of the data before returning it*, or make it read-only**.
* In Perl, see the function dclone() in the built-in Storable module.
** In Perl, see lock_hash() or lock_hash_ref() in the built-in Hash::Util module).
This is general programming, but if it makes a difference, I'm using objective-c. Suppose there's a method that returns a value, and also performs some actions, but you don't care about the value it returns, only the stuff that it does. Would you just call the method as if it was void? Or place the result in a variable and then delete it or forget about it? State your opinion, what you would do if you had this situation.
A common example of this is printf, which returns an int... but you rarely see this:
int val = printf("Hello World");
Yeah just call the method as if it was void. You probably do it all the time without noticing it. The assignment operator '=' actually returns a value, but it's very rarely used.
It depends on the environment (the language, the tools, the coding standard, ...).
For example in C, it is perfectly possible to call a function without using its value. With some functions like printf, which returns an int, it is done all the time.
Sometimes not using a value will cause a warning, which is undesirable. Assigning the value to a variable and then not using it will just cause another warning about an unused variable. For this case the solution is to cast the result to void by prefixing the call with (void), e.g.
(void) my_function_returning_a_value_i_want_to_ignore().
There are two separate issues here, actually:
Should you care about returned value?
Should you assign it to a variable you're not going to use?
The answer to #2 is a resounding "NO" - unless, of course, you're working with a language where that would be illegal (early Turbo Pascal comes to mind). There's absolutely no point in defining a variable only to throw it away.
First part is not so easy. Generally, there is a reason value is returned - for idempotent functions the result is function's sole purpose; for non-idempotent it usually represents some sort of return code signifying whether operation was completed normally. There are exceptions, of course - like method chaining.
If this is common in .Net (for example), there's probably an issue with the code breaking CQS.
When I call a function that returns a value that I ignore, it's usually because I'm doing it in a test to verify behavior. Here's an example in C#:
[Fact]
public void StatService_should_call_StatValueRepository_for_GetPercentageValues()
{
var statValueRepository = new Mock<IStatValueRepository>();
new StatService(null, statValueRepository.Object).GetValuesOf<PercentageStatValue>();
statValueRepository.Verify(x => x.GetStatValues());
}
I don't really care about the return type, I just want to verify that a method was called on a fake object.
In C it is very common, but there are places where it is ok to do so and other places where it really isn't. Later versions of GCC have a function attribute so that you can get a warning when a function is used without checking the return value:
The warn_unused_result attribute causes a warning to be emitted if a caller of the function with this attribute does not use its return value. This is useful for functions where not checking the result is either a security problem or always a bug, such as realloc.
int fn () __attribute__ ((warn_unused_result));
int foo ()
{
if (fn () < 0) return -1;
fn ();
return 0;
}
results in warning on line 5.
Last time I used this there was no way of turning off the generated warning, which causes problems when you're compiling 3rd-party code you don't want to modify. Also, there is of course no way to check if the user actually does something sensible with the returned value.