diff --git a/compile_flags.txt b/compile_flags.txt new file mode 100644 index 0000000..0b721d8 --- /dev/null +++ b/compile_flags.txt @@ -0,0 +1,2 @@ +-std=c99 +-Iinclude diff --git a/include/atom.h b/include/atom.h new file mode 100644 index 0000000..9732e60 --- /dev/null +++ b/include/atom.h @@ -0,0 +1,9 @@ +#ifndef ATOM_INDCLUDED +#define ATOM_INDCLUDED + +extern int Atom_length(const char *str); +extern const char *Atom_new (const char *str, int len); +extern const char *Atom_string(const char *str); +extern const char *Atom_int (long n); + +#endif diff --git a/src/atom.c b/src/atom.c new file mode 100644 index 0000000..d3be57b --- /dev/null +++ b/src/atom.c @@ -0,0 +1,156 @@ +// Includes +#include "atom.h" + +#include +#include +#include +#include "assert.h" + +// TODO: Include "mem.h" when that's available. + +// Macros +# define NELEMS(x) ((sizeof (x))/(sizeof ((x)[0]))) + +// Data +static struct atom { + struct atom *link; + int len; + char *str; +} *buckets[2048]; + +// scatter is used for hashing byte sequences, each number was randomly generated. +static unsigned long scatter[] = { +2078917053, 143302914, 1027100827, 1953210302, 755253631, 2002600785, +1405390230, 45248011, 1099951567, 433832350, 2018585307, 438263339, +813528929, 1703199216, 618906479, 573714703, 766270699, 275680090, +1510320440, 1583583926, 1723401032, 1965443329, 1098183682, 1636505764, +980071615, 1011597961, 643279273, 1315461275, 157584038, 1069844923, +471560540, 89017443, 1213147837, 1498661368, 2042227746, 1968401469, +1353778505, 1300134328, 2013649480, 306246424, 1733966678, 1884751139, +744509763, 400011959, 1440466707, 1363416242, 973726663, 59253759, +1639096332, 336563455, 1642837685, 1215013716, 154523136, 593537720, +704035832, 1134594751, 1605135681, 1347315106, 302572379, 1762719719, +269676381, 774132919, 1851737163, 1482824219, 125310639, 1746481261, +1303742040, 1479089144, 899131941, 1169907872, 1785335569, 485614972, +907175364, 382361684, 885626931, 200158423, 1745777927, 1859353594, +259412182, 1237390611, 48433401, 1902249868, 304920680, 202956538, +348303940, 1008956512, 1337551289, 1953439621, 208787970, 1640123668, +1568675693, 478464352, 266772940, 1272929208, 1961288571, 392083579, +871926821, 1117546963, 1871172724, 1771058762, 139971187, 1509024645, +109190086, 1047146551, 1891386329, 994817018, 1247304975, 1489680608, +706686964, 1506717157, 579587572, 755120366, 1261483377, 884508252, +958076904, 1609787317, 1893464764, 148144545, 1415743291, 2102252735, +1788268214, 836935336, 433233439, 2055041154, 2109864544, 247038362, +299641085, 834307717, 1364585325, 23330161, 457882831, 1504556512, +1532354806, 567072918, 404219416, 1276257488, 1561889936, 1651524391, +618454448, 121093252, 1010757900, 1198042020, 876213618, 124757630, +2082550272, 1834290522, 1734544947, 1828531389, 1982435068, 1002804590, +1783300476, 1623219634, 1839739926, 69050267, 1530777140, 1802120822, +316088629, 1830418225, 488944891, 1680673954, 1853748387, 946827723, +1037746818, 1238619545, 1513900641, 1441966234, 367393385, 928306929, +946006977, 985847834, 1049400181, 1956764878, 36406206, 1925613800, +2081522508, 2118956479, 1612420674, 1668583807, 1800004220, 1447372094, +523904750, 1435821048, 923108080, 216161028, 1504871315, 306401572, +2018281851, 1820959944, 2136819798, 359743094, 1354150250, 1843084537, +1306570817, 244413420, 934220434, 672987810, 1686379655, 1301613820, +1601294739, 484902984, 139978006, 503211273, 294184214, 176384212, +281341425, 228223074, 147857043, 1893762099, 1896806882, 1947861263, +1193650546, 273227984, 1236198663, 2116758626, 489389012, 593586330, +275676551, 360187215, 267062626, 265012701, 719930310, 1621212876, +2108097238, 2026501127, 1865626297, 894834024, 552005290, 1404522304, +48964196, 5816381, 1889425288, 188942202, 509027654, 36125855, +365326415, 790369079, 264348929, 513183458, 536647531, 13672163, +313561074, 1730298077, 286900147, 1549759737, 1699573055, 776289160, +2143346068, 1975249606, 1136476375, 262925046, 92778659, 1856406685, +1884137923, 53392249, 1735424165, 1602280572 +}; + +// Functions + +const char *Atom_string(const char *str) { + assert(str); + return Atom_new(str, strlen(str)); +} + +const char *Atom_int(long n) { + char str[43]; + char *s = str + sizeof str; + unsigned long m; + + // Both limits are in 2's compliment. + // LONG_MIN's magnitude is one more than LONG_MAX because the range is asymetric. + // `m` just contains the magnitude. We must do this becuse there's no way to negate + // n and keep its full magnitude. + if (n == LONG_MIN) + m = LONG_MAX + 1UL; + else if (n < 0) + // If n is not min, we can safely negate it to get the magnitude. + m = -n; + else + m = n; + + // The pointer starts at one past the buffer. + // We pre-decrement on each write, and use a + // `do` to easily account for 0. + do + *--s = m%10 + '0'; + while ((m /= 10) > 0); + if (n < 0) + *--s = '-'; + + return Atom_new(s, (str + sizeof str) - s); +} + +const char *Atom_new(const char *str, int len) { + unsigned long h; + int i; + struct atom *p; + + assert(str); + assert(len >= 0); + + // Hash the string. + for (h = 0, i = 0; i < len; i++) + h = (h<<1) + scatter[(unsigned char)str[i]]; + h %= NELEMS(buckets); + + for (p = buckets[h]; p; p = p -> link) + if (len == p->len) { + for (i = 0; i < len && p->str[i] == str[i]; ) + i++; + if (i == len) + return p->str; + } + // Allocate a new entry. + // Struct size, plus the string lenght, plus null terminator. + // TODO: Replace malloc with ALLOC from "mem.h" when that's implemented. + p = malloc(sizeof (*p) + len + 1); + p->len = len; + p->str = (char *)(p + 1); + if (len > 0) + memcpy(p->str, str, len); + p->str[len] = '\0'; + + // This works only if buckets are initialized to null pointers. + // Which in this case is true because buckets has a static lifetime. + p->link = buckets[h]; + buckets[h] = p; + + return p->str; +} + +int Atom_length(const char *str) { + struct atom *p; + int i; + + assert(str); + // TODO: Could hash to find the bucket instead. + for (i = 0; i < NELEMS(buckets); i++) + for (p = buckets[i]; p; p = p->link) + if (p->str == str) + return p->len; + + // Should not call Atom_length witn a non-atom string. + assert(0); + return 0; +}