struct atom_t

atom.c

#include "atom.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#include <assert.h>
#include <string.h>
#include <limits.h>

#define NELEMS(x) ((sizeof(x) / sizeof((x)[0])))

static struct atom_t {
        struct atom_t *link;
        int len;
        char *str;
} *buckets[2039];

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
};

int
atom_length(const char *str)
{
        assert(str);

        struct atom_t *p;
        int i;
        for (i = 0; i < NELEMS(buckets); i++) {
                for (p = buckets[i]; p; p = p->link) {
                        if (p->str == str) {
                                return p->len;
                        }
                }
        }
        assert(0);
        return 0;
}

const char *
atom_new(const char *str, int len)
{
        assert(str);
        assert(len >= 0);

        unsigned long h = 0;
        int i;
        for (i = 0; i < len; i++) {
                h = (h << 1) + scatter[(unsigned char)str[i]];
        }
        h %= NELEMS(buckets);

        struct atom_t *p;
        for (p = buckets[h]; p; p = p->link) {
                if (p->len == len) {
                        for (i = 0; i < len && p->str[i] == str[i];) {
                                i++;
                        }
                        if (i == len) {
                                return p->str;
                        }
                }
        }
        p = malloc(sizeof(*p) + len + 1);
        p->len = len;
        p->str = (char *)(p + 1);
        if (len > 0) {
                strncpy(p->str, str, len);
        }
        p->str[len] = '\0';
        p->link = buckets[h];
        buckets[h] = p;
        return p->str;
}

const char *
atom_string(const char *str)
{
          assert(str);
        return atom_new(str, strlen(str));
}

void
atom_vload(const char *str, ...)
{
        assert(str);

        int len;
        char *buf;

        va_list ap;
        va_start(ap, str);

        if ((len = vsnprintf(NULL, 0, str, ap)) < 0) {
                printf("Oops!\n");
                exit(1);
        }
        buf = malloc(len);
        vsnprintf(buf, len, str, ap);
        va_end(ap);

        atom_new(buf, len);
        free(buf);
}

void
atom_aload(const char *strs[])
{
        int i;
        for (i = 0; strs[i]; i++) {
                atom_string(strs[i]);
        }
}

const char *
atom_int(long n)
{
        char str[43];
        char *s = str + sizeof(str);
        unsigned long m;

        if (n == LONG_MIN) {
                m = LONG_MAX + 1UL;
        } else if (n < 0) {
                m = -n;
        } else {
                m = n;
        }

        do {
                *--s = m%10 + '0';
        } while ((m = m/10) > 0);

        if (n < 0) {
                *--s = '-';
        }

        return atom_new(s, (str + sizeof(str)) - s);
}

void
atom_free(const char *str)
{
        assert(str);

        int i;
        struct atom_t **pp, *p;
        for (i = 0; i < NELEMS(buckets); i++) {
                pp = &buckets[i];
                while (*pp) {
                        p = *pp;
                        if (p->str == str) {
                                *pp = p->link;
                                free(p);
                                return;
                        }
                        pp = &p->link;
                }
        }
        assert(0);
}

void
atom_reset(void)
{
        int i;
        for (i = 0; i < NELEMS(buckets); i++) {
                struct atom_t *p, *temp;
                for (p = buckets[i]; p;) {
                        temp = p;
                        p = p->link;
                        free(temp);
                }
        }
}

atom.h

#ifndef ATOM_INCLUDED
#define ATOM_INCLUDED

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 void atom_vstring(const char *str, ...);
extern void atom_astring(const char *strs[]);

extern const char *atom_int(long n);

extern void atom_free(const char *str);
extern void atom_reset(void);

#endif /* ATOM_INCLUDED */