Unclear pointer and array Post: 302884482

9 More Discussions You Might Find Interesting

1. Programming

pointer

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...

2. UNIX for Dummies Questions & Answers

Storing pointer array in C

All .. I am having a pointer array . And trying to store the addess into that pointer array . please see below the problem i faced code: int cnt1; char *t_array; char *f_array; for(cnt1=0; cnt1<1000; cnt1++) { t_array =...

3. Programming

pass a pointer-to-pointer, or return a pointer?

If one wants to get a start address of a array or a string or a block of memory via a function, there are at least two methods to achieve it: (1) one is to pass a pointer-to-pointer parameter, like: int my_malloc(int size, char **pmem) { *pmem=(char *)malloc(size); if(*pmem==NULL)...

4. Programming

C pointer/array duality confusion

Hi all, Can anyone provide help with getting the right syntax regarding array/pointers in C in the following code? Can't locate a specific example which clarifies this... Say I declare a typedef to an array of pointers to some type... /** * An array of ptrs to sections */ typedef...

5. Programming

help with char pointer array in C

i have an array like #define NUM 8 .... new_socket_fd = accept(socket_fd, (struct sockaddr *) &cli_addr, &client_length); char *items = {"one", "two", "three", "four", "five", "six", "seven", "eight"}; char *item_name_length = {"3", "3", "5", "4", "4", "3", "5", "5"}; ...

6. Programming

structure pointer array as function parameters

if i create an array of pointers to a structure "struct node" as: struct node *r; and create "n" number of "linked lists" and assign it to the various struct pointers r using some function with a return type as structure pointer as: r=multiplty(.......) /*some parameters*/ is...

7. Shell Programming and Scripting

best practises for scripting + a few unclear points

Hi guys, Besides the points bellow, what would best practices for scripting be ? 1) set the PATH 2) unset the current environment (set -u ?) 3) (re)set the IFS to default value - space (IFS="" <- is this correct ?) 4) check the return code for each action inside the script (cd, rsync,...

8. Programming

Character pointer to Character array

how to copy content of character pointer to character array in c programming.. char *num; char name=num;

9. Programming

Pointer for 2D array seems to be 3D in C

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...

LEARN ABOUT SUNOS

id32_lookup

id32_alloc(9F)						   Kernel Functions for Drivers 					    id32_alloc(9F)

NAME

       id32_alloc, id32_free, id32_lookup - 32-bit driver ID management routines

SYNOPSIS

       #include <sys/ddi.h>
       #include <sys/id32.h>

       uint32_t id32_alloc(void *ptr, int flag);

       void id32_free(uint32_t token);

       void *id32_lookup(uint32_t token);

INTERFACE LEVEL

       Solaris architecture specific (Solaris DDI).

PARAMETERS

       ptr	       any valid 32- or 64-bit pointer

       flag	       determines whether caller can sleep for memory (see kmem_alloc(9F) for a description)

DESCRIPTION

       These  routines	were  originally  developed so that device drivers could manage 64-bit pointers on devices that save space only for 32-bit
       pointers.

       Many device drivers need to pass a 32-bit value to the hardware when attempting I/O.  Later, when that I/O  completes,  the  only  way  the
       driver has to identify the request that generated that I/O is via a "token". When the I/O is initiated, the driver passes this token to the
       hardware. When the I/O completes the hardware passes back this 32-bit token.

       Before Solaris supported 64-bit pointers, device drivers just passed a raw 32-bit pointer to the hardware. When pointers grew to be 64 bits
       this was no longer possible. The id32_*() routines were created to help drivers translate between 64-bit pointers and a 32-bit token.

       Given  a 32- or 64-bit pointer, the routine id32_alloc() allocates a 32-bit token, returning 0 if KM_NOSLEEP was specified and memory could
       not be allocated. The allocated token is passed back to id32_lookup() to obtain the original 32- or 64-bit pointer.

       The routine id32_free() is used to free an allocated token. Once id32_free() is called, the supplied token is no longer valid.

       Note that these routines have some degree of error checking. This is done so that an invalid token passed  to  id32_lookup()  will  not	be
       accepted as valid. When id32_lookup() detects an invalid token it returns NULL. Calling routines should check for this return value so that
       they do not try to dereference a NULL pointer.

CONTEXT

       These functions can be called from user or interrupt context. The routine id32_alloc() should not be called from interrupt context when the
       KM_SLEEP flag is passed in. All other routines can be called from interrupt or kernel context.

SEE ALSO

       kmem_alloc(9F)

       Writing Device Drivers

SunOS 5.10							    12 Dec 2001 						    id32_alloc(9F)