ml1_hash.c

#include <stdint.h>
#include "lowl.h"

/*
 * ML/I Hash.
 *
 * This is used by both the runtime and the emitter.
 */

/* A little fun in hashing.
 * A Pearson hash table that maps the static entries in the ML/I
 * hash table in the order defined in the source, from 1 to N. */
static uint8_t t[256] = {
	173, 192, 110,  25,  97, 174, 132, 119, 
	138, 170, 125, 118,  27, 233, 140,  51, 
	 87,  16, 177, 107, 234, 169,  56,  68, 
	 30,  60,   1,  73, 188,  40,  36,  65, 
	 49, 213, 104, 190,  57, 211, 148, 223, 
	 48, 115,  64, 175, 196, 186, 210,  28, 
	121,   9, 103,  70,  22,  58,  75,  78, 
	183,  59, 238, 157, 124, 147, 172, 144, 
	176, 161, 141,   8,   7,   6,   5, 253, 
	156, 241,  79,  46, 168, 198,  41, 254, 
	178,  85,  83, 237, 250, 154, 133,  88, 
	 35, 206,  95, 116, 252,  14,  54, 221, 
	102, 218, 255, 240,  82, 106, 158, 201, 
	 61, 194,  89, 181,  42, 155, 159,  93, 
	 13,  80,  50,  34,   2, 195, 100,  99, 
	 26, 150, 197, 145, 243,  33,  86, 189, 
	 12,  15,  77,  72, 208, 245, 130, 122, 
	143,  55, 105, 134,  29, 164, 185,   3, 
	193, 239, 101, 242, 128, 171, 126,  11, 
	 74, 203, 137, 228, 108, 191, 232, 139, 
	 66,  24,  81,  20, 127,  17,  91,  92, 
	251, 151, 225, 207,  21,  98, 113, 112, 
	 84, 226,  18, 214, 199, 187, 166,  32, 
	 94, 220, 224, 212, 247, 204,  67,  43, 
	249, 236,  45, 244, 111, 182, 153, 136, 
	129,  90, 217, 202, 231, 165,  19,  71, 
	230, 142,  96, 227,  62, 179, 246, 114, 
	162,  53, 160, 215, 205, 180,  47, 109, 
	  4,  38,  31, 149, 135,   0, 216,  52, 
	 63,  23,  37,  69,  39, 117, 146, 184, 
	163, 200, 222, 235, 248,  44, 219,  10, 
	152, 131, 123, 229, 167,  76, 120, 209, 
};

uint8_t
ml1_hash(char *s, lowlint_t len)
{
	uint8_t hprev, h = 0;
	char *e = s + len;
	while ( s != e ) {
		hprev = h;
		h = t[ hprev ^ *s++ ];	
	}
	return h;
}