hashpjw.h

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#ifndef __HASHPJW_H__
#define __HASHPJW_H__

// HashPjw -- swiped from Dragon book
//
// 97/01/29 -- J.W.Welch        -- swiped code

// the following code fragments assume:
//  s -- contains the input C-string to be hashed
//  h -- is defined to contain the hash value

#define HashPjwCode                                     \
    unsigned h = 0;                                     \
{                                                       \
    unsigned g;                                         \
    for( ; ; ) {                                        \
        char ch = *s;                                   \
        if( 0 == ch ) break;                            \
        ++s;                                            \
        /* ( h & ~0x0fff ) == 0 is always true here */  \
        h = (h << 4) + ch;                              \
        g = h & ~0x0fff;                                \
        h ^= g;                                         \
        h ^= g >> 12;                                   \
    }                                                   \
}

#define HashPjwCodeIns                                  \
    unsigned h = 0;                                     \
{                                                       \
    unsigned g;                                         \
    for( ; ; ) {                                        \
        char ch = *s;                                   \
        if( 0 == ch ) break;                            \
        ++s;                                            \
        /* ( h & ~0x0fff ) == 0 is always true here */  \
        h = (h << 4) + (ch | ' ');                      \
        g = h & ~0x0fff;                                \
        h ^= g;                                         \
        h ^= g >> 12;                                   \
    }                                                   \
}

#ifdef __cplusplus
inline
unsigned HashPjw                // CASE-SENSITIVE HASH
    ( char const * s )
{
    HashPjwCode
    return h;
}


inline
unsigned HashPjwInsensitive     // CASE-INSENSITIVE HASH
    ( char const * s )
{
    HashPjwCodeIns
    return h;
}
#endif // __cplusplus

#endif // __HASHPJW_H__