The interface is simpler: one parameter in, the answer returned. You just check whether the pointer is null to verify success. The first form has some kind of other return value to check, which could be boolean, but I cannot tell, so I would have to look up the definitions of OK and NOK. And it is unclear from the interface whether I also need to check the pointer value, or indeed whether the pointer is NULL on failure. Looking into you implementation I can see that OK is returned if and only if the pointer is valid and the pointer is NULL on failure, but then I can write
so the return value is redundant -- it gives me no extra information.
However, if you want the function to indicate more than just a simple fail/succeed (e.g. different failure modes) then the first way is the only way to do it.
It mimics the standard malloc(3) function -- or it would do if the parameter was of type size_t rather than int -- and therefore has the benefit of familiarity, and makes it easier to port code written with malloc to use my_malloc.
void main()
{
int a={1,2,3,4,5,6,7,8,9,10};
int *p=a;
int *q=&a;
cout<<q-p+1<<endl;
}
The output is 10, how?
if we give cout<<q it will print the address, value won't print....
if we give cout<<p it will print the address, value won't print....
p has the base addr; q... (1 Reply)
Hi,
char *s="yamaha";
cout<<s<<endl;
int *p;
int i=10;
p=&i;
cout<<p<<endl;
1) For the 1st "cout" we will get "yamaha" as output. That is we are getting "content of the address" for cout<<s.
2) But for integer "cout<<p" we are getting the "address only".
Please clarify how we are... (2 Replies)
Hello all
im trying to build function that will return void function pointer
what is mean is ( not working )
the main function
void * myClass::getFunction(int type){
if(type==1)
return &myClass::Test1;
if(type==2)
return &myClass::Test2;
}
void myClass::Test1(){... (1 Reply)
I have a fundamental question on C pointer arithmetry..
Suppose i have a c string pointer already pointing to a valid location, Can I just do a
charptr = charptr +1;
to get to the next location, irregardless if my program is 32 or 64 bits?
or should i do it this way:
charptr =... (1 Reply)
Hi guys, I'm trying to understand pointers in C and made a simple example and I've problems with It.
Can someone help?
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
int f1(char **str_);
int main(int argc, char **argv)
{
char *str = NULL;
f1(&str);
... (3 Replies)
I am struggling with the pointer to 2D-array (cf: 2D array of pointers). Can anybody help me elaborate how the pointer x moves in the memory to access the individual of y, especially the high lighted lines?
I have talked to one of the curators of the forum, but I am still not quite clear.
Here... (1 Reply)
I am passing a char* to the function "reverse" and when I execute it with gdb I get:
Program received signal SIGSEGV, Segmentation fault.
0x000000000040083b in reverse (s=0x400b2b "hello") at pointersExample.c:72
72 *q = *p;
Attached is the source code.
I do not understand why... (9 Replies)
Discussion started by: jose_spain
9 Replies
LEARN ABOUT DEBIAN
judyhsins
JudyHS_funcs(3) Library Functions Manual JudyHS_funcs(3)NAME
JudyHS functions - C library for creating and accessing a dynamic array, using an array-of-bytes of a length: Length as an Index and a word
as a Value.
SYNOPSIS
PPvoid_t JudyHSIns(PPvoid_t PPJHS, void *Index, Word_t Length, PJError_t PJError);
int JudyHSDel(PPvoid_t PPJHS, void *Index, Word_t Length, PJError_t PJError);
PPvoid_t JudyHSGet(Pcvoid_t PJHS, void *Index, Word_t Length, PJError_t PJError);
Word_t JudyHSFreeArray(PPvoid_t PPJHS, PJError_t PJError);
DESCRIPTION
A macro equivalent exists for each function call. Because the macro forms are sometimes faster and have a simpler error handling interface
than the equivalent functions, they are the preferred way of calling the JudyHS functions. See JudyHS(3) for more information. The func-
tion call definitions are included here for completeness.
One of the difficulties in using the JudyHS function calls lies in determining whether to pass a pointer or the address of a pointer.
Since the functions that modify the JudyHS array must also modify the pointer to the JudyHS array, you must pass the address of the pointer
rather than the pointer itself. This often leads to hard-to-debug programmatic errors. In practice, the macros allow the compiler to
catch programming errors when pointers instead of addresses of pointers are passed.
The JudyHS function calls have an additional parameter beyond those specified in the macro calls. This parameter is either a pointer to an
error structure, or NULL (in which case the error information is not returned -- only PJERR in the return parameter).
In the following descriptions, the functions are described in terms of how the macros use them. This is the suggested use of the macros
after your program has been fully debugged. When the JUDYERROR_NOTEST macro is not specified, an error structure is declared to store
error information returned from the JudyHS functions when an error occurs.
Notice the placement of the & in the different functions.
JudyHSIns(&PJHS, Index, Length, &JError)
#define JHSI(PValue, PJHS, Index)
PValue = JudyLIns(&PJHS, Index, PJE0)
JudyHSDel(&PJHS, Index, Length, &JError)
#define JHSD(Rc_int, PJHS, Index, Length)
Rc_int = JudyHSDel(&PJHS, Index, Length, PJE0)
JudyHSGet(PJHS, Index, Length)
#define JHSG(PValue, PJHS, Index, Length)
PValue = JudyHSIns(PJHS, Index, Length)
JudyHSFreeArray(&PJHS, &JError)
#define JHSFA(Rc_word, PJHS)
Rc_word = JudyHSFreeArray(&PJHS, PJE0)
Definitions for all the Judy functions, the types Pvoid_t, Pcvoid_t, PPvoid_t, Word_t , JError_t, and PJError_t, the constants NULL,
JU_ERRNO_*, JERR, PPJERR, and PJE0 are provided in the Judy.h header file (/usr/include/Judy.h). Note: Callers should define JudyHS
arrays as type Pvoid_t, which can be passed by value to functions that take Pcvoid_t (constant Pvoid_t), and also by address to functions
that take PPvoid_t.
The return type from most JudyHS functions is PPvoid_t so that the values stored in the array can be pointers to other objects, which is a
typical usage, or cast to a Word_t * when a pointer to a value is required instead of a pointer to a pointer.
AUTHOR
JudyHS was invented and implemented by Doug Baskins after retiring from Hewlett-Packard.
SEE ALSO Judy(3), Judy1(3), JudyL(3), JudySL(3), JudyHS(3),
malloc(),
the Judy website, http://judy.sourceforge.net, for more information and Application Notes.
JudyHS_funcs(3)