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libhashstrings.c
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libhashstrings.c
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//
// Created by paul on 1/23/21.
//
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <stdbool.h>
#include "libhashstrings.h"
const uint64_t kFieldMask = 0x01FFL; // mask for the 9 lsb
static const int kHashFactor = 43;
void setCharMap( tCharMap * charMap,
const unsigned char c,
const tMappedChar mappedC )
{
unsigned short shft = (c % 7) * 9;
charMap[ c/7 ] = (charMap[ c/7 ] & ~(kFieldMask << shft)) |
((mappedC & kFieldMask) << shft);
}
tMappedChar remapChar( tCharMap * charMap, const unsigned char c )
{
return ((charMap[ c/7 ] >> (( c % 7 ) * 9)) & kFieldMask);
}
tHash hashChar( tHash hash, tMappedChar mappedC )
{
return (hash ^ ((hash * kHashFactor) + mappedC));
}
tHash hashString(const char * string, tCharMap * charMap )
{
tHash hash = 0;
const unsigned char * p = (const unsigned char *)string;
tMappedChar c;
do {
c = remapChar( charMap, *p++ );
if ( c != '\0' && c < 256 )
{
hash = hashChar( hash, c );
}
} while ( c != '\0' );
return hash;
}
tIndex findHash( tRecord skipTable[], tHash hash )
{
tIndex i = 0;
do {
// fprintf(stderr, "%02d-0x%016lx ", i, skipTable[i].hash);
if ( skipTable[i].hash == hash )
{ // we found it, return the corresponding tIndex (1-based)
// fprintf( stderr, "match (%s)\n", skipTable[i].hashedString );
return skipTable[i].index;
}
else if ( skipTable[i].hash > hash )
{ /* hash is lower than this record */
i = skipTable[i].lower;
// fprintf( stderr, "lower (%u)\n", i );
}
else
{ /* hash is higher than this record */
i = skipTable[i].higher;
// fprintf( stderr, "higher (%u)\n", i );
}
} while ( i != kLeaf );
// fprintf( stderr, "no match\n" );
return 0;
}
void dumpHashMap( FILE * out, tRecord skipTable[] )
{
unsigned int max = 1;
for ( unsigned int i = 0; i < max; i++)
{
if (max < skipTable[i].higher)
{
max = skipTable[i].higher;
}
fprintf( out, "%d: 0x%016lx,\"%s\",%d,%d,%d\n",
i, skipTable[i].hash, skipTable[i].hashedString,
skipTable[i].index, skipTable[i].higher, skipTable[i].lower);
}
}