ref: ea413b4a62be9993e4b63bf237f0b1d482f4aafa
dir: /sys/src/cmd/upas/bayes/hash.c/
#include <u.h> #include <libc.h> #include <bio.h> #include "hash.h" /*** * String hash tables. */ Stringtab *tfree; Stringtab* taballoc(void) { static Stringtab *t; static uint nt; if(tfree){ Stringtab *tt = tfree; tfree = tt->link; return tt; } if(nt == 0){ t = malloc(64000*sizeof(Stringtab)); if(t == 0) sysfatal("out of memory"); nt = 64000; } nt--; return t++; } void tabfree(Stringtab *tt) { tt->link = tfree; tfree = tt; } char* xstrdup(char *s, int len) { char *r; static char *t; static int nt; if(nt < len){ t = malloc(512*1024+len); if(t == 0) sysfatal("out of memory"); nt = 512*1024; } r = t; t += len; nt -= len; memmove(r, s, len); return r; } static uint hash(char *s, int n) { uint h; uchar *p, *ep; h = 0; for(p=(uchar*)s, ep=p+n; p<ep; p++) h = h*37 + *p; return h; } static void rehash(Hash *hh) { int h; Stringtab *s; if(hh->nstab == 0) hh->nstab = 1024; else hh->nstab = hh->ntab*2; free(hh->stab); hh->stab = mallocz(hh->nstab*sizeof(Stringtab*), 1); if(hh->stab == nil) sysfatal("out of memory"); for(s=hh->all; s; s=s->link){ h = hash(s->str, s->n) % hh->nstab; s->hash = hh->stab[h]; hh->stab[h] = s; } } Stringtab* findstab(Hash *hh, char *str, int n, int create) { uint h; Stringtab *tab, **l; if(hh->nstab == 0) rehash(hh); h = hash(str, n) % hh->nstab; for(tab=hh->stab[h], l=&hh->stab[h]; tab; l=&tab->hash, tab=tab->hash) if(n==tab->n && memcmp(str, tab->str, n) == 0){ *l = tab->hash; tab->hash = hh->stab[h]; hh->stab[h] = tab; return tab; } if(!create) return nil; hh->sorted = 0; tab = taballoc(); tab->str = xstrdup(str, n); tab->hash = hh->stab[h]; tab->link = hh->all; hh->all = tab; tab->n = n; tab->count = 0; tab->date = 0; hh->stab[h] = tab; hh->ntab++; if(hh->ntab > 2*hh->nstab && !(hh->ntab&(hh->ntab-1))) rehash(hh); return tab; } int scmp(Stringtab *a, Stringtab *b) { int n, x; if(a == 0) return 1; if(b == 0) return -1; n = a->n; if(n > b->n) n = b->n; x = memcmp(a->str, b->str, n); if(x != 0) return x; if(a->n < b->n) return -1; if(a->n > b->n) return 1; return 0; /* shouldn't happen */ } Stringtab* merge(Stringtab *a, Stringtab *b) { Stringtab *s, **l; l = &s; while(a || b){ if(scmp(a, b) < 0){ *l = a; l = &a->link; a = a->link; }else{ *l = b; l = &b->link; b = b->link; } } *l = 0; return s; } Stringtab* mergesort(Stringtab *s) { Stringtab *a, *b; int delay; if(s == nil) return nil; if(s->link == nil) return s; a = b = s; delay = 1; while(a && b){ if(delay) /* easy way to handle 2-element list */ delay = 0; else a = a->link; if(b = b->link) b = b->link; } b = a->link; a->link = nil; a = mergesort(s); b = mergesort(b); return merge(a, b); } Stringtab* sortstab(Hash *hh) { if(!hh->sorted){ hh->all = mergesort(hh->all); hh->sorted = 1; } return hh->all; } int Bwritehash(Biobuf *b, Hash *hh) { Stringtab *s; int now; now = time(0); s = sortstab(hh); Bprint(b, "# hash table\n"); for(; s; s=s->link){ if(s->count <= 0) continue; /* * Entries that haven't been updated in thirty days get tossed. */ if(s->date+30*86400 < now) continue; Bwrite(b, s->str, s->n); Bprint(b, "\t%d %d\n", s->count, s->date); } if(Bflush(b) == Beof) return -1; return 0; } void Breadhash(Biobuf *b, Hash *hh, int scale) { char *s; char *t; int n; int date; Stringtab *st; s = Brdstr(b, '\n', 1); if(s == nil) return; if(strcmp(s, "# hash table") != 0) sysfatal("bad hash table format"); while(s = Brdline(b, '\n')){ s[Blinelen(b)-1] = 0; t = strrchr(s, '\t'); if(t == nil) sysfatal("bad hash table format"); *t++ = '\0'; if(*t < '0' || *t > '9') sysfatal("bad hash table format"); n = strtol(t, &t, 10); date = time(0); if(*t != 0){ if(*t == ' '){ t++; date = strtol(t, &t, 10); } if(*t != 0) sysfatal("bad hash table format"); } st = findstab(hh, s, strlen(s), 1); if(date > st->date) st->date = date; st->count += n*scale; } } void freehash(Hash *h) { Stringtab *s, *next; for(s=h->all; s; s=next){ next = s->link; tabfree(s); } free(h->stab); free(h); } Biobuf* Bopenlock(char *file, int mode) { int i; Biobuf *b; char err[ERRMAX]; b = nil; for(i=0; i<120; i++){ if((b = Bopen(file, mode)) != nil) break; rerrstr(err, sizeof err); if(strstr(err, "file is locked")==nil && strstr(err, "exclusive lock")==nil) break; sleep(1000); } return b; }