mirrors
/
nnn
mirror of https://github.com/jarun/nnn.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
nnn/src/icons-hash.c

269 lines
7.9 KiB
C
Raw Blame History

/*
* simple program which outputs a hash-table of `icons_ext` with low collusion.
* the hash function is case-insensitive, it also doesn't hash beyond the
* length of the longest extension.
*/
#include <stddef.h>
#include <stdint.h>
#include <inttypes.h>
#define GOLDEN_RATIO_32 UINT32_C(2654442313) /* golden ratio for 32bits: (2^32) / 1.61803 */
#define ICONS_TABLE_SIZE 8 /* size in bits. 8 = 256 */
#ifndef TOUPPER
#define TOUPPER(ch) (((ch) >= 'a' && (ch) <= 'z') ? ((ch) - 'a' + 'A') : (ch))
#endif
/* all of this is just for the static hash-table generation. only the hash
* function gets included in `nnn` binary.
*/
#ifdef ICONS_GENERATE
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include "icons.h"
#ifdef NDEBUG
#error "The hash-table generator relies on assert() to verify correctness."
#endif
#define ASSERT(X) assert(X)
#define ARRLEN(X) (sizeof(X) / sizeof((X)[0]))
#define MAX(A, B) ((A) > (B) ? (A) : (B))
#define HGEN_ITERARATION (1ul << 14)
#define ICONS_PROBE_MAX_ALLOWED 6
#define ICONS_MATCH_MAX ((size_t)-1)
#if 0 /* for logging some interesting info to stderr */
#define log(...) fprintf(stderr, "[INFO]: " __VA_ARGS__)
#else
#define log(...) ((void)0)
#endif
static uint32_t icon_ext_hash(const char *s);
/* change ICONS_TABLE_SIZE to increase the size of the table */
static struct icon_pair table[1u << ICONS_TABLE_SIZE];
static uint8_t seen[ARRLEN(table)];
/* arbitrarily picked starting position. change if needed.
* but ensure they're above 1 and prefer prime numbers.
*/
static uint32_t hash_start = 7;
static uint32_t hash_mul = 251;
/*
* use robin-hood insertion to reduce the max probe length
*/
static void
rh_insert(const struct icon_pair item, uint32_t idx, uint32_t n)
{
assert(n != 0);
for (uint32_t tries = 0; tries < ARRLEN(table); ++tries, ++n) {
if (seen[idx] < n) {
struct icon_pair tmp_item = table[idx];
uint32_t tmp_n = seen[idx];
assert(n < (uint8_t)-1);
table[idx] = item;
seen[idx] = n;
if (tmp_n != 0) /* the slot we inserted to wasn't empty */
rh_insert(tmp_item, idx, tmp_n);
return;
}
idx = (idx + 1) % ARRLEN(table);
}
assert(0); /* unreachable */
}
static unsigned int
table_populate(void)
{
memset(seen, 0x0, sizeof seen);
memset(table, 0x0, sizeof table);
for (size_t i = 0; i < ARRLEN(icons_ext); ++i) {
if (icons_ext[i].icon[0] == '\0') /* skip empty entries */
continue;
uint32_t h = icon_ext_hash(icons_ext[i].match);
rh_insert(icons_ext[i], h, 1);
}
unsigned int max_probe = 0;
for (size_t i = 0; i < ARRLEN(seen); ++i)
max_probe = MAX(max_probe, seen[i]);
return max_probe;
}
int
main(void)
{
assert(ARRLEN(icons_ext) <= ARRLEN(table));
assert(ICONS_TABLE_SIZE < 16);
assert(1u << ICONS_TABLE_SIZE == ARRLEN(table));
assert((GOLDEN_RATIO_32 & 1) == 1); /* must be odd */
assert(hash_start > 1);
assert(hash_mul > 1);
/* ensure power of 2 hashtable size which allows compiler to optimize
* away mod (`%`) operations
*/
assert((ARRLEN(table) & (ARRLEN(table) - 1)) == 0);
unsigned int max_probe = (unsigned)-1;
uint32_t best_hash_start, best_hash_mul;
for (size_t i = 0; i < HGEN_ITERARATION; ++i) {
unsigned z = table_populate();
if (z < max_probe) {
max_probe = z;
best_hash_start = hash_start;
best_hash_mul = hash_mul;
}
hash_start *= GOLDEN_RATIO_32;
hash_mul *= GOLDEN_RATIO_32;
}
assert(max_probe < ICONS_PROBE_MAX_ALLOWED);
hash_start = best_hash_start;
hash_mul = best_hash_mul;
{
unsigned tmp = table_populate();
assert(tmp == max_probe);
}
/* sanity check */
double nitems = 0;
for (size_t i = 0; i < ARRLEN(icons_ext); ++i) {
if (icons_ext[i].icon[0] == 0)
continue;
uint32_t found = 0, h = icon_ext_hash(icons_ext[i].match);
for (uint32_t k = 0; k < max_probe; ++k) {
uint32_t z = (h + k) % ARRLEN(table);
if (table[z].match && strcasecmp(icons_ext[i].match, table[z].match) == 0) {
found = 1;
}
}
assert(found);
++nitems;
}
size_t match_max = 0, icon_max = 0;
for (size_t i = 0; i < ARRLEN(icons_name); ++i) {
match_max = MAX(match_max, strlen(icons_name[i].match) + 1);
icon_max = MAX(icon_max, strlen(icons_name[i].icon) + 1);
}
for (size_t i = 0; i < ARRLEN(icons_ext); ++i) {
match_max = MAX(match_max, strlen(icons_ext[i].match) + 1);
icon_max = MAX(icon_max, strlen(icons_ext[i].icon) + 1);
}
icon_max = MAX(icon_max, strlen(dir_icon.icon) + 1);
icon_max = MAX(icon_max, strlen(exec_icon.icon) + 1);
icon_max = MAX(icon_max, strlen(file_icon.icon) + 1);
const char *uniq[ARRLEN(icons_ext)] = {0};
size_t uniq_head = 0;
for (size_t i = 0; i < ARRLEN(icons_ext); ++i) {
if (icons_ext[i].icon[0] == 0)
continue;
int isuniq = 1;
for (size_t k = 0; k < uniq_head; ++k) {
if (strcasecmp(uniq[k], icons_ext[i].icon) == 0) {
isuniq = 0;
break;
}
}
if (isuniq) {
assert(uniq_head < ARRLEN(uniq));
uniq[uniq_head++] = icons_ext[i].icon;
}
}
assert(uniq_head < (unsigned char)-1);
log("load-factor: %.2f (%u/%zu)\n", (nitems * 100.0) / (double)ARRLEN(table),
(unsigned int)nitems, ARRLEN(table));
log("max_probe : %6u\n", max_probe);
log("uniq icons : %6zu\n", uniq_head);
log("no-compact : %6zu bytes\n", ARRLEN(table) * icon_max);
log("compaction : %6zu bytes\n", uniq_head * icon_max + ARRLEN(table));
log("hash_start : %6" PRIu32 "\n", hash_start);
log("hash_mul : %6" PRIu32 "\n", hash_mul);
printf("#ifndef INCLUDE_ICONS_GENERATED\n");
printf("#define INCLUDE_ICONS_GENERATED\n\n");
printf("/*\n * NOTE: This file is automatically generated.\n");
printf(" * DO NOT EDIT THIS FILE DIRECTLY.\n");
printf(" * Use `icons.h` to customize icons\n */\n\n");
printf("#define hash_start UINT32_C(%" PRIu32 ")\n", hash_start);
printf("#define hash_mul UINT32_C(%" PRIu32 ")\n\n", hash_mul);
printf("#define ICONS_PROBE_MAX %uu\n", max_probe);
printf("#define ICONS_MATCH_MAX %zuu\n\n", match_max);
printf("#define ICONS_STR_MAX %zuu\n\n", icon_max);
printf("struct icon_pair { const char match[ICONS_MATCH_MAX]; "
"const char icon[ICONS_STR_MAX]; unsigned char color; };\n\n");
printf("static const char icons_ext_uniq[%zu][ICONS_STR_MAX] = {\n", uniq_head);
for (size_t i = 0; i < uniq_head; ++i)
printf("\t\"%s\",\n", uniq[i]);
printf("};\n\n");
printf("static const struct {\n\tconst char match[ICONS_MATCH_MAX];\n"
"\tunsigned char idx;\n\tunsigned char color;\n} icons_ext[%zu] = {\n",
ARRLEN(table));
for (size_t i = 0; i < ARRLEN(table); ++i) {
if (table[i].icon == NULL || table[i].icon[0] == '\0') /* skip empty entries */
continue;
int k;
for (k = 0; k < uniq_head; ++k) {
if (strcasecmp(table[i].icon, uniq[k]) == 0)
break;
}
assert(k < uniq_head);
printf("\t[%3zu] = {\"%s\", %d, %hhu },\n",
i, table[i].match, k, table[i].color);
}
printf("};\n\n");
printf("#endif /* INCLUDE_ICONS_GENERATED */\n");
}
#else
#define ASSERT(X) ((void)0)
#endif /* ICONS_GENERATE */
#if defined(ICONS_GENERATE) || defined(ICONS_ENABLED)
static uint32_t
icon_ext_hash(const char *str)
{
uint32_t i, hash = hash_start;
const unsigned int z = (sizeof hash * CHAR_BIT) - ICONS_TABLE_SIZE;
/* FNV style xor-mul hashing. Some other hashing which gives good results:
* Jenkin's one-at-a-time: https://en.wikipedia.org/wiki/Jenkins_hash_function#one_at_a_time
* xor-rotate: ((hash >> (32 - 5)) | (hash << 5)) ^ TOUPPER((unsigned char)str[i]);
*/
for (i = 0; i < ICONS_MATCH_MAX && str[i] != '\0'; ++i) {
hash ^= TOUPPER((unsigned char)str[i]);
hash *= hash_mul;
}
/* due to the multiply, the entropy of our hash is hidden in the high
* bits. so we take the high bits as our map into the table.
*/
#if 0
/* enable this part if the hash function is to be changed to a non-multiplying one.
* gives better distribution than modulo: https://probablydance.com/2018/06/16/
*/
hash ^= (hash >> z);
hash *= GOLDEN_RATIO_32;
#endif
hash >>= z;
ASSERT(hash < ARRLEN(table));
return hash;
}
#endif
Reference in New Issue View Git Blame Copy Permalink