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https://github.com/jarun/nnn.git
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icons-hash: comments and cleanups
adds some comments, references and cleanups. no change in functionality.
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parent
f415924c7e
commit
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116
src/icons-hash.c
116
src/icons-hash.c
@ -6,10 +6,18 @@
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#include <stddef.h>
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#include <stdint.h>
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#include <inttypes.h>
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#define GOLDEN_RATIO_16 40503u /* golden ratio for 16bits: (2^16) / 1.61803 */
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#define GOLDEN_RATIO_32 UINT32_C(2654442313) /* golden ratio for 32bits: (2^32) / 1.61803 */
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#define ICONS_TABLE_SIZE 8 /* size in bits. 8 = 256 */
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#ifndef TOUPPER
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#define TOUPPER(ch) (((ch) >= 'a' && (ch) <= 'z') ? ((ch) - 'a' + 'A') : (ch))
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#endif
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/* all of this is just for the static hash-table generation. only the hash
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* function gets included in `nnn` binary.
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*/
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#ifdef ICONS_GENERATE
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#include <assert.h>
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@ -19,7 +27,7 @@
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#include "icons.h"
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#ifdef NDEBUG
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#error "NDEBUG"
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#error "The hash-table generator relies on assert() to verify correctness."
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#endif
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#define ASSERT(X) assert(X)
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@ -29,22 +37,22 @@
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#define ICONS_PROBE_MAX_ALLOWED 6
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#define ICONS_MATCH_MAX ((size_t)-1)
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#if 0 /* enable for debugging */
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#if 0 /* for logging some interesting info to stderr */
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#define log(...) fprintf(stderr, "[INFO]: " __VA_ARGS__)
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#else
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#define log(...) ((void)0)
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#endif
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static uint16_t icon_ext_hash(const char *s);
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static uint32_t icon_ext_hash(const char *s);
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/* change ICONS_TABLE_SIZE to increase the size of the table */
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static struct icon_pair table[1u << ICONS_TABLE_SIZE];
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static uint16_t seen[ARRLEN(table)];
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static uint8_t seen[ARRLEN(table)];
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/* arbitrarily picked starting position. change if needed.
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* but ensure they're above 1 and prefer prime numbers.
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*/
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static uint16_t hash_start = 7;
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static uint16_t hash_mul = 251;
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static uint32_t hash_start = 7;
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static uint32_t hash_mul = 251;
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/*
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* use robin-hood insertion to reduce the max probe length
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@ -58,6 +66,7 @@ rh_insert(const struct icon_pair item, uint32_t idx, uint32_t n)
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struct icon_pair tmp_item = table[idx];
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uint32_t tmp_n = seen[idx];
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assert(n < (uint8_t)-1);
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table[idx] = item;
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seen[idx] = n;
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@ -92,17 +101,18 @@ int
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main(void)
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{
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assert(ARRLEN(icons_ext) <= ARRLEN(table));
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assert(ICONS_TABLE_SIZE < 16); /* the hash function only supports upto 16 bits */
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assert(ICONS_TABLE_SIZE < 16);
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assert(1u << ICONS_TABLE_SIZE == ARRLEN(table));
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assert((GOLDEN_RATIO_16 & 1) == 1); /* must be odd */
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assert(hash_start > 1); assert(hash_mul > 1);
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assert((GOLDEN_RATIO_32 & 1) == 1); /* must be odd */
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assert(hash_start > 1);
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assert(hash_mul > 1);
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/* ensure power of 2 hashtable size which allows compiler to optimize
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* away mod (`%`) operations
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*/
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assert((ARRLEN(table) & (ARRLEN(table) - 1)) == 0);
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unsigned int max_probe = (unsigned)-1;
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uint16_t best_hash_start, best_hash_mul;
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uint32_t best_hash_start, best_hash_mul;
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for (size_t i = 0; i < HGEN_ITERARATION; ++i) {
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unsigned z = table_populate();
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@ -111,8 +121,8 @@ main(void)
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best_hash_start = hash_start;
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best_hash_mul = hash_mul;
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}
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hash_start *= GOLDEN_RATIO_16;
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hash_mul *= GOLDEN_RATIO_16;
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hash_start *= GOLDEN_RATIO_32;
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hash_mul *= GOLDEN_RATIO_32;
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}
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assert(max_probe < ICONS_PROBE_MAX_ALLOWED);
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hash_start = best_hash_start;
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@ -123,22 +133,21 @@ main(void)
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}
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/* sanity check */
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double nitems = 0;
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for (size_t i = 0; i < ARRLEN(icons_ext); ++i) {
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if (icons_ext[i].icon[0] == 0) continue;
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uint16_t found = 0, h = icon_ext_hash(icons_ext[i].match);
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for (uint16_t k = 0; k < max_probe; ++k) {
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uint16_t z = (h + k) % ARRLEN(table);
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if (table[z].match && strcmp(icons_ext[i].match, table[z].match) == 0) {
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if (icons_ext[i].icon[0] == 0)
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continue;
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uint32_t found = 0, h = icon_ext_hash(icons_ext[i].match);
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for (uint32_t k = 0; k < max_probe; ++k) {
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uint32_t z = (h + k) % ARRLEN(table);
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if (table[z].match && strcasecmp(icons_ext[i].match, table[z].match) == 0) {
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found = 1;
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}
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}
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assert(found);
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++nitems;
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}
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log("hash_start: %6u\n", (unsigned)hash_start);
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log("hash_mul : %6u\n", (unsigned)hash_mul);
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log("max_probe : %6u\n", max_probe);
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size_t match_max = 0, icon_max = 0;
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for (size_t i = 0; i < ARRLEN(icons_name); ++i) {
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match_max = MAX(match_max, strlen(icons_name[i].match) + 1);
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@ -155,10 +164,11 @@ main(void)
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const char *uniq[ARRLEN(icons_ext)] = {0};
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size_t uniq_head = 0;
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for (size_t i = 0; i < ARRLEN(icons_ext); ++i) {
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if (icons_ext[i].icon[0] == 0) continue;
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if (icons_ext[i].icon[0] == 0)
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continue;
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int isuniq = 1;
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for (size_t k = 0; k < uniq_head; ++k) {
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if (strcmp(uniq[k], icons_ext[i].icon) == 0) {
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if (strcasecmp(uniq[k], icons_ext[i].icon) == 0) {
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isuniq = 0;
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break;
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}
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@ -170,9 +180,14 @@ main(void)
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}
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assert(uniq_head < (unsigned char)-1);
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log("uniq icons: %6zu\n", uniq_head);
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log("no-compact: %6zu bytes\n", ARRLEN(table) * icon_max);
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log("compaction: %6zu bytes\n", uniq_head * icon_max + ARRLEN(table));
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log("load-factor: %.2f (%u/%zu)\n", (nitems * 100.0) / (double)ARRLEN(table),
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(unsigned int)nitems, ARRLEN(table));
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log("max_probe : %6u\n", max_probe);
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log("uniq icons : %6zu\n", uniq_head);
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log("no-compact : %6zu bytes\n", ARRLEN(table) * icon_max);
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log("compaction : %6zu bytes\n", uniq_head * icon_max + ARRLEN(table));
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log("hash_start : %6" PRIu32 "\n", hash_start);
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log("hash_mul : %6" PRIu32 "\n", hash_mul);
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printf("#ifndef INCLUDE_ICONS_GENERATED\n");
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printf("#define INCLUDE_ICONS_GENERATED\n\n");
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@ -181,27 +196,31 @@ main(void)
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printf(" * DO NOT EDIT THIS FILE DIRECTLY.\n");
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printf(" * Use `icons.h` to customize icons\n */\n\n");
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printf("#define hash_start %uu\n", hash_start);
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printf("#define hash_mul %uu\n\n", hash_mul);
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printf("#define ICONS_PROBE_MAX %u\n", max_probe);
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printf("#define hash_start UINT32_C(%" PRIu32 ")\n", hash_start);
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printf("#define hash_mul UINT32_C(%" PRIu32 ")\n\n", hash_mul);
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printf("#define ICONS_PROBE_MAX %uu\n", max_probe);
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printf("#define ICONS_MATCH_MAX %zuu\n\n", match_max);
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printf("#define ICONS_STR_MAX %zuu\n\n", icon_max);
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printf("struct icon_pair { const char match[%zu]; const char icon[%zu]; unsigned char color; };\n\n",
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match_max, icon_max);
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printf("struct icon_pair { const char match[ICONS_MATCH_MAX]; "
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"const char icon[ICONS_STR_MAX]; unsigned char color; };\n\n");
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printf("static const char icons_ext_uniq[%zu][%zu] = {\n", uniq_head, icon_max);
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printf("static const char icons_ext_uniq[%zu][ICONS_STR_MAX] = {\n", uniq_head);
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for (size_t i = 0; i < uniq_head; ++i)
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printf("\t\"%s\",\n", uniq[i]);
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printf("};\n\n");
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printf("static const struct {\n\tconst char match[%zu];"
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"\n\tunsigned char idx;\n\tunsigned char color;\n} icons_ext[%zu] = {\n",
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match_max, ARRLEN(table));
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printf("static const struct {\n\tconst char match[ICONS_MATCH_MAX];\n"
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"\tunsigned char idx;\n\tunsigned char color;\n} icons_ext[%zu] = {\n",
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ARRLEN(table));
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for (size_t i = 0; i < ARRLEN(table); ++i) {
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if (table[i].icon == NULL || table[i].icon[0] == '\0') /* skip empty entries */
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continue;
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int k;
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for (k = 0; k < uniq_head; ++k) if (strcmp(table[i].icon, uniq[k]) == 0) break;
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for (k = 0; k < uniq_head; ++k) {
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if (strcasecmp(table[i].icon, uniq[k]) == 0)
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break;
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}
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assert(k < uniq_head);
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printf("\t[%3zu] = {\"%s\", %d, %hhu },\n",
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i, table[i].match, k, table[i].color);
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@ -215,23 +234,34 @@ main(void)
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#define ASSERT(X) ((void)0)
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#endif /* ICONS_GENERATE */
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#ifndef TOUPPER
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#define TOUPPER(ch) (((ch) >= 'a' && (ch) <= 'z') ? ((ch) - 'a' + 'A') : (ch))
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#endif
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#if defined(ICONS_GENERATE) || defined(ICONS_ENABLED)
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static uint16_t
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static uint32_t
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icon_ext_hash(const char *str)
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{
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uint32_t i, hash = hash_start;
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const unsigned int z = (sizeof hash * CHAR_BIT) - ICONS_TABLE_SIZE;
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/* FNV style xor-mul hashing. Some other hashing which gives good results:
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* Jenkin's one-at-a-time: https://en.wikipedia.org/wiki/Jenkins_hash_function#one_at_a_time
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* xor-rotate: ((hash >> (32 - 5)) | (hash << 5)) ^ TOUPPER((unsigned char)str[i]);
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*/
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for (i = 0; i < ICONS_MATCH_MAX && str[i] != '\0'; ++i) {
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hash ^= TOUPPER((unsigned char)str[i]);
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hash *= hash_mul;
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}
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/* due to the multiply, the entropy of our hash is hidden in the high
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* bits. so we take the high bits as our map into the table.
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*/
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#if 0
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/* enable this part if the hash function is to be changed to a non-multiplying one.
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* gives better distribution than modulo: https://probablydance.com/2018/06/16/
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*/
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hash ^= (hash >> z);
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hash *= GOLDEN_RATIO_16;
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hash *= GOLDEN_RATIO_32;
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#endif
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hash >>= z;
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ASSERT(hash < ARRLEN(table));
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return hash;
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}
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