Here i am attaching my code that handle single hashtable operation.I need to modify this program that should handle nested hashtable.The hashtable whose KEYs are strings and Values are again hashtables.
Now i am trying to implement h(sports)=>hashtable,ie it should contain hash table that should contain records of cricket,football,tennis etc.....
Thanks in advance
Last edited by Franklin52; 01-13-2011 at 02:53 PM..
Reason: Code tags
Dear Reader,
Is is necessary to attach / dettach the shared memory segments for write operations , if more than one program is accessing same shared memory segments..
I have used semaphore mutex and still I'm getting segmentation fault when I write to the segment when other program is already... (1 Reply)
I am running HP-UX B.11.11.
I'm increasing a parameter for a database engine so that it uses more memory to buffer the disk drive (to speed up performance). I have over 5GB of memory not being used.
But when I try to start the DB with the increased buffer parameter I get told.
"Not... (1 Reply)
Hi all :confused: ,
I am new to unix.I have been asked to implement shared memory in user's mode.What does this mean?What is the difference it makes in kernel mode and in users mode?What are the advantages of this impemenation(user's mode)?
And also i would like to know why exactly shared... (0 Replies)
what i want to do is have an int that can been written into by 2 processes but my code doesn't seem to work.
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include<stdio.h>
#define KEY1 (1492)
int main()
{
int shmid;
volatile int * addr;... (6 Replies)
hi,
this is the problem: i want to swap a linked list between 4 processes (unrelated), is there any way i can do that just by sending a pointer to a structure?
//example
typedef struct node
{
int x;
char c;
struct node *next;
} node;
or i should send the items ( x,c ) by... (9 Replies)
I need to create a shared library to access an in memory DB. The DB is not huge, but big enough to make it cumbersome to carry around in every single process using the shared library. Luckily, it is pretty static information, so I don't need to worry much about synchronizing the data between... (12 Replies)
I am writing a shared library in Linux (but compatible with other UNIXes) and I want to allow multiple instances to share a piece of memory -- 1 byte is enough. What's the "best" way to do this? I want to optimize for speed and portability.
Obviously, I'll have to worry about mutual exclusion. (0 Replies)
Hello.
I am new to this forum and I would like to ask for advice about low level POSIX programming.
I have to implement a POSIX compliant C shared library.
A file will have some variables and the shared library will have some functions which need those variables.
There is one special... (5 Replies)
Discussion started by: iamjag
5 Replies
LEARN ABOUT DEBIAN
hash
HASH(9) BSD Kernel Developer's Manual HASH(9)NAME
hash, hash32, hash32_buf, hash32_str, hash32_strn, hash32_stre, hash32_strne -- general kernel hashing functions
SYNOPSIS
#include <sys/hash.h>
uint32_t
hash32_buf(const void *buf, size_t len, uint32_t hash);
uint32_t
hash32_str(const void *buf, uint32_t hash);
uint32_t
hash32_strn(const void *buf, size_t len, uint32_t hash);
uint32_t
hash32_stre(const void *buf, int end, const char **ep, uint32_t hash);
uint32_t
hash32_strne(const void *buf, size_t len, int end, const char **ep, uint32_t hash);
DESCRIPTION
The hash32() functions are used to give a consistent and general interface to a decent hashing algorithm within the kernel. These functions
can be used to hash ASCII NUL terminated strings, as well as blocks of memory.
The hash32_buf() function is used as a general buffer hashing function. The argument buf is used to pass in the location, and len is the
length of the buffer. The argument hash is used to extend an existing hash, or is passed the initial value HASHINIT to start a new hash.
The hash32_str() function is used to hash a NUL terminated string passed in buf with initial hash value given in hash.
The hash32_strn() function is like the hash32_str() function, except it also takes a len argument, which is the maximal length of the
expected string.
The hash32_stre() and hash32_strne() functions are helper functions used by the kernel to hash pathname components. These functions have the
additional termination condition of terminating when they find a character given by end in the string to be hashed. If the argument ep is
not NULL, it is set to the point in the buffer at which the hash function terminated hashing.
RETURN VALUES
The hash32() functions return a 32 bit hash value of the buffer or string.
EXAMPLES
LIST_HEAD(head, cache) *hashtbl = NULL;
u_long mask = 0;
void
sample_init(void)
{
hashtbl = hashinit(numwanted, type, flags, &mask);
}
void
sample_use(char *str, int len)
{
uint32_t hash;
hash = hash32_str(str, HASHINIT);
hash = hash32_buf(&len, sizeof(len), hash);
hashtbl[hash & mask] = len;
}
SEE ALSO free(9), hashinit(9), malloc(9)LIMITATIONS
The hash32() functions are only 32 bit functions. They will prove to give poor 64 bit performance, especially for the top 32 bits. At the
current time, this is not seen as a great limitation, as these hash values are usually used to index into an array. Should these hash values
be used for other means, this limitation should be revisited.
HISTORY
The hash functions were first committed to NetBSD 1.6. The OpenBSD versions were written and massaged for OpenBSD 2.3 by Tobias Weingartner,
and finally committed for OpenBSD 3.2.
BSD April 3, 2007 BSD