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Explanation of a macro

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# 1  
Old 07-26-2016
Explanation of a macro
Can some body explain this part in a header file for me?
Code:
#include <limits.h> 
 
#define BIGNUM unsigned long long
typedef BIGNUM (*hash_t) (char *str); 
 ......

I have hard time for the second part:
Code:
typedef BIGNUM (*hash_t) (char *str);

First, I could not find the definition of hash_t, which may be from standard library. Is it? If so, where is the header file for hash_t?
The second is the whole typedef.
Thanks a lot!
Last edited by yifangt; 07-26-2016 at 05:55 PM..
# 2  
Old 07-26-2016
This is a function typedef -
Code:
typedef BIGNUM (*hash_t) (char *str);

The function returns unsigned long long, a pointer to signed char is the argument.

hash_t is now a function declaration rather than a pure datatype declaration.

The Function Pointer Tutorials - Syntax

As to what header file, I do not know. If you have a hash library (example pcre) check there. I am guessing you want to use this and expect it to be on your system already.
Try
Code:
grep 'hash_t' $(find /usr/include -type f -name '*.h')

Last edited by jim mcnamara; 07-26-2016 at 06:07 PM..
These 2 Users Gave Thanks to jim mcnamara For This Post:
frank_rizzo yifangt
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