Efective way to avoid integer overflow when multiplying?

Posted by Jonathan on Stack Overflow See other posts from Stack Overflow or by Jonathan
Published on 2010-05-04T19:02:25Z Indexed on 2010/05/04 19:08 UTC
Read the original article Hit count: 345

Filed under:

c

|

hash

|

homework

Hi, I'm working on a hash function which gets a string as input.

Right now I'm doing a loop and inside the hash (an int variable) is being multiplied by a value and then the ASCII code for the current character is added to the mix.

hash = hash * seed + string[i]

But sometimes, if the string is big enough there is an integer overflow there, what can I do to avoid it while maintaining the same hash structure? Maybe a bit operation included inside the loop?

Related posts about hash

Problem with hash function: hash(1) == hash(1.0)

as seen on Stack Overflow - Search for 'Stack Overflow'
I have an instance of dict with ints, floats, strings as keys, but the problem is when there are a as int and b as float, and float(a) == b, then their hash values are the same, and thats what I do NOT want to get because I need unique hash vales for this cases in order to get corresponding values… >>> More
Hash table vs Hash list vs Hash tree?

as seen on Stack Overflow - Search for 'Stack Overflow'
What property makes Hash table, Hash list and Hash tree different from each other? Which one is used when? When is table superior than tree. >>> More
Constructing a hash table/hash function.

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I would like to construct a hash table that looks up keys in sequences (strings) of bytes ranging from 1 to 15 bytes. I would like to store an integer value, so I imagine an array for hashing would suffice. I'm having difficulty conceptualizing how to construct a hash function such that given… >>> More
Hash of unique value = unique hash?

as seen on Stack Overflow - Search for 'Stack Overflow'
Theoretically does hashing a unique value yield a unique value? Let's say I have a DB table with 2 columns: id and code. id is an auto-incrementing int and code is a varchar. If I do ... $code = sha1($id); ... and then store $code into the same row as $id. Will my code column be unique as well… >>> More
EMERGENCY - Major Problems After Perl Module Installed via WHM

as seen on Stack Overflow - Search for 'Stack Overflow'
I attempted to install the perl module Net::Twitter::Role::API::Lists using WHM and after doing so my whole site came down. It seems that something that was updated with the install isn't functioning correctly and since our website it written in Perl none of our site scripts will run. In almost 8… >>> More

Developer IT

Efective way to avoid integer overflow when multiplying? - Developer IT

Efective way to avoid integer overflow when multiplying?

c

hash

homework

Related posts about c

Related posts about hash

Problem with hash function: hash(1) == hash(1.0)

Hash table vs Hash list vs Hash tree?

Constructing a hash table/hash function.

Hash of unique value = unique hash?

EMERGENCY - Major Problems After Perl Module Installed via WHM

Categories cloud