int firstInt =10;
int *pointerFirstInt = &firstInt;
printf("The address of firstInt is: %u", &firstInt);
printf("\n");
printf("The address of firstInt is: %p", pointerFirstInt);
printf("\n");
The above code returns the following:
The address of firstInt is: 1606416332
The address of firstInt is: 0x7fff5fbff7cc
I know that 0x7fff5fbff7cc is in hexadecimal, but when i attempt to convert that number to decimal it does not equal 1606416332. Why is this? Shouldn't both return the same memory address?
The reason for this is lies here:
C11: 7.21.6:
If a conversion specification is invalid, the behavior is undefined.288) If any argument is
not the correct type for the corresponding conversion specification, the behavior is
undefined.
From your hexadecimal address-
The address of firstInt is: 0x7fff5fbff7cc
The size of the address is 6 bytes long. But Size of unsignedint is 4 bytes. When you trying to print the address using %u, It will cause undefined behaviour.
So always print the address using %p.
it seems that you are working on an 64bit machine. so your pointer is 64bit long
both (&firstInt and pointerFirstInt) are exactly same. but are displayed differently.
"%p" knows that pointers are 64bit and displays them in hexadecimal. "%u" shows decimal number and assumes 32bit. so only a part is shown.
if you convert 1606416332 to hexadecimal it looks like: 0x5FBFF7CC. you see that this is the lower half of the 64bit address.
edit:
further explanations:
since printf is a var-arg function all the parametes you give to it were put on the stack. since you put 8 byte on it in both cases. since Pcs using little endian the lower bytes are put on it first.
the printf function parses the string and comes to an %[DatatypeSpecifier] point and reads as many bytes from stack as the datatype that is refered by DatatypeSpecifier requires. so in case of "%u" it only reads 4 bytes and ignores the other bytes. Since you wrote "%u" and not "%x" it displays the value in decimal and not in hexadecimal form.
Related
Does
if(strncmp(buf, buf2, 7) == 0)
do the same thing as
if(memcmp(buf, buf2, 7) == 0)
buf and buf2 are char* arrays or similar.
I was going to append this to another question but then decided perhaps it was better to post it separately. Presumably the answer is either a trivial "yes" or if not then what is the difference?
(I found these functions from online documentation, but wasn't sure about strncmp because the documentation was slightly unclear.)
Like strcmp(), strncmp() is for comparing strings, therefore it stops comparing when it finds a string terminator in at least one argument. Any differences past that point have no effect on the result. strncmp() differs in that it will also stop comparing after the specified number of bytes if it does not encounter a terminator before then.
memcmp(), on the other hand, is for comparing blocks of random memory. It compares up to the specified number of bytes from each block until it finds a difference, regardless of the values of the bytes. That is, it does not stop at string terminators.
In C and C++ the end of a string is indicated by a byte with value 0.
The function memcmp does not care about the end of a strig but will in any case compare exactly the number of bytes specified.
In contrast to that, the function strncmp will stop at a byte with value 0 even though the passed number of bytes to compare is not yet reached.
The main difference between strncmp() and memcmp() is that the first is sensible to (stops at) '\0' where the latest is not. If the first 7 bytes of memory from buf and buf2 do not contain a '\0' in it, then the behaviour is the same.
Consider the following example:
#include <stdio.h>
#include <string.h>
int main(void) {
char buf[] = "123\0 12";
char buf2[] = "123\0 34";
printf("strncmp(): %d\n", strncmp(buf, buf2, 7));
printf("memcmp(): %d\n", memcmp(buf, buf2, 7));
return 0;
}
It will output:
strncmp(): 0
memcmp(): -2
Because strncmp() will stop at buf[3], where it'll find a '\0', where memcmp() will continue until all 7 bytes are compared.
I know how to return a Unicode character from a code point. That's not what I'm after. What I want to know is how to return the name associated with a particular code point. For example, The code point for 🍀 is 1F340. And its name is FOUR LEAF CLOVER. Is it possible for us to return this name with its code point? I've read about 100 topics involving Unicode. But I haven't see one discussing my question. I hope that's possible.
Thank you for your help.
Have you considered the ICU library? It offers the following C API: http://icu-project.org/apiref/icu4c/uchar_8h.html#aa488f2a373998c7decb0ecd3e3552079
int32_t u_charName(
UChar32 code,
UCharNameChoice nameChoice,
char* buffer,
int32_t bufferLength,
UErrorCode* pErrorCode)
Retrieve the name of a Unicode character.
Depending on nameChoice, the character name written into the buffer is the "modern" name or the name that was defined in Unicode version 1.0. The name contains only "invariant" characters like A-Z, 0-9, space, and '-'. Unicode 1.0 names are only retrieved if they are different from the modern names and if the data file contains the data for them. gennames may or may not be called with a command line option to include 1.0 names in unames.dat.
Parameters
code The character (code point) for which to get the name. It must be 0<=code<=0x10ffff.
nameChoice Selector for which name to get.
buffer Destination address for copying the name. The name will always be zero-terminated. If there is no name, then the buffer will be set to the empty string.
bufferLength ==sizeof(buffer)
pErrorCode Pointer to a UErrorCode variable; check for U_SUCCESS() after u_charName() returns.
Returns
The length of the name, or 0 if there is no name for this character. If the bufferLength is less than or equal to the length, then the buffer contains the truncated name and the returned length indicates the full length of the name. The length does not include the zero-termination.
ICU is the right approach, but it's even simpler than Chris said. Foundation includes ICU already, for various text processing functions, including CFStringTransform(). Its transform parameter accepts "any valid ICU transform ID defined in the ICU User Guide for Transforms".
One of ICU's transforms is Any-Name:
Converts between characters and their Unicode names in curly braces. For example:
., ⇆ {FULL STOP}{COMMA}
(The syntax isn't exactly as documented, but it's close enough you can figure it out.)
There's also an Any-Hex transform which can be used for translating to/from the codepoint hex value.
what is the method by which I can read the input of the user, say the input is "500"
then store this number in a variable?
The only method I know would be to store them character by character with possibly the need of register offsets.
Is there any other way, preferably storing the number directly?
i.e. something like:
mov var1, inbuffer
Details on environment:
32 bit Assembly w/ DGJPP
Thank you.
Ahhh... DJGPP, that'd be dos I guess. Look into int 21h/0Ah (0Ah in ah). Or you might be better off with the readfile subfunction (3Fh ???) on stdin. Look it up in Ralf Brown's Interrupt list.
In any case, what you're going to get is the characters '5', '0', and '0' - 35h, 30h, 30h. It will take some processing to get the number 500 out of this. If you're reading numbers from left to right, zero up a register to use as "result so far". Read a character from your input buffer. If it's a valid decimal digit, subtract '0' to convert character to number, multiply "result so far" by ten, and add in your new number. Repeat until you run out of characters.
I am trying to configure a GPS device to my systems. The GPS device send the data packet to my IP in the following format :
$$�W��¬ÿÿÿÿ™U042903.000,A,2839.6408,N,07717.0905,E,0.00,,230111,,,A*7C|1.2|203|0000÷
I am able to extract the latitude, longitude and other information but I am not able to extract the Tracker ID out of the string.
According to the manual the ID is in hex format.And the format of the packet is
$$<L(2 bytes)><ID(7 bytes)><command (2 bytes)><data><checksum (2 bytes)>\r\n
I don't know what to do with it, I have tried converting this to hex..but it didn't work.
Any help will be greatly appreciated.
How about more information? What GPS? What interface (USB, serial)? What language are you working in?
Your data certainly looks odd. In my experience with GPS data, it's generally alphanumeric and separators, but it looks like you have either a corrupt string or non-alphanumeric values.
Update based upon additional information you provided:
The GPRS manual you supplied explains the format:
$$ - 2 bytes - in ASCII code (Hex code: 0x24)
L - 2 bytes - in hex code
ID 7 bytes - in the format of hex code.
For example, if ID is 13612345678, then it will be shown as follows:
0x13, 0x61, 0x23, 0x45, 0x67, 0x8f, 0xff.
command - 2 bytes - hex code
If I understand correctly, the gibberish characters after $$ and before the data field are not printable ASCII characters. They're actual numeric values, provided one byte at a time. If you convert each byte to a hexadecimal-formatted string and display it, you should see what I mean.
I don't remember my PHP well, but I think the ID could be formed into a hexadecimal-formatted string by something like this:
$s = GetYourGPRSStringFromWherever()
$sID = sprintf("0x%02x%02x%02x%02x%02x%02x%02x", $s[4], $s[5], $s[6],
$s[7], $s[8], $s[9], $s[10]);
(also, strip out or ignore any 0xFF values, as per the documentation's example)
I need to use something like NSLog but without the timestamp and newline character, so I'm using printf. How can I use this with NSString?
You can convert an NSString into a UTF8 string by calling the UTF8String method:
printf("%s", [string UTF8String]);
//public method that accepts a string argument
- (void) sayThis : ( NSString* ) this
{
printf("%s",[this cString]);
}
According to the NSString.h ( html version ) the UTF8String method is only available on Mac OSX.
(see below )
All the other methods I looked at are marked as 'availability:Openstep'
There are further methods that will return regular char* strings but they might throw character conversion exceptions.
NOTE The string pointers point to memory that might go away so you have to copy the strings if you want to keep a copy of the string contents, but immediate printing should be fine ?
There are also methods that will return an encoded string, and a method to test if the encoding you want will work ( I think ) so you can check if your required encoding will work and then request a string that has been encoded as required.
From reading through the .h file itself there are many encodings and translations between encodings.
These are managed using enumerations so you can pass the type of encoding you want as an argument.
On linux etc. do :
locate NSString.h
** Note this found the html doc file also
otherwise do a :
find /usr -name NSString.h
NOTE Your mileage may vary :)
Thanks.
From the NSString.h html doc file :
cString
- (const char*) cString;
Availability: OpenStep
Returns a pointer to a null terminated string of 8-bit characters in the default encoding. The memory pointed to is not owned by the caller, so the caller must copy its contents to keep it. Raises an NSCharacterConversionException if loss of information would occur during conversion. (See -canBeConvertedToEncoding: .)
cStringLength
- (NSUInteger) cStringLength;
Availability: OpenStep
Returns length of a version of this unicode string converted to bytes using the default C string encoding. If the conversion would result in information loss, the results are unpredictable. Check -canBeConvertedToEncoding: first.
cStringUsingEncoding:
- (const char*) cStringUsingEncoding: (NSStringEncoding)encoding;
Availability: MacOS-X 10.4.0, Base 1.2.0
Returns a pointer to a null terminated string of characters in the specified encoding.
NB. under GNUstep you can used this to obtain a nul terminated utf-16 string (sixteen bit characters) as well as eight bit strings.
The memory pointed to is not owned by the caller, so the caller must copy its contents to keep it.
Raises an NSCharacterConversionException if loss of information would occur during conversion.
canBeConvertedToEncoding:
- (BOOL) canBeConvertedToEncoding: (NSStringEncoding)encoding;
Availability: OpenStep
Returns whether this string can be converted to the given string encoding without information loss.