ref: 963cfc9a6f6e721f52aa949e6d1af0c3e8dc2ecc
dir: /sys/src/cmd/sam/disk.c/
#include "sam.h" static Block *blist; static int tempdisk(void) { char buf[128]; int i, fd; snprint(buf, sizeof buf, "/tmp/X%d.%.4ssam", getpid(), getuser()); for(i='A'; i<='Z'; i++){ buf[5] = i; if(access(buf, AEXIST) == 0) continue; fd = create(buf, ORDWR|ORCLOSE|OCEXEC, 0600); if(fd >= 0) return fd; } return -1; } Disk* diskinit() { Disk *d; d = emalloc(sizeof(Disk)); d->fd = tempdisk(); if(d->fd < 0){ fprint(2, "sam: can't create temp file: %r\n"); exits("diskinit"); } return d; } static uint ntosize(uint n, uint *ip) { uint size; if(n > Maxblock) panic("internal error: ntosize"); size = n; if(size & (Blockincr-1)) size += Blockincr - (size & (Blockincr-1)); /* last bucket holds blocks of exactly Maxblock */ if(ip) *ip = size/Blockincr; return size * sizeof(Rune); } Block* disknewblock(Disk *d, uint n) { uint i, j, size; Block *b; size = ntosize(n, &i); b = d->free[i]; if(b) d->free[i] = b->next; else{ /* allocate in chunks to reduce malloc overhead */ if(blist == nil){ blist = emalloc(100*sizeof(Block)); for(j=0; j<100-1; j++) blist[j].next = &blist[j+1]; } b = blist; blist = b->next; b->addr = d->addr; d->addr += size; } b->n = n; return b; } void diskrelease(Disk *d, Block *b) { uint i; ntosize(b->n, &i); b->next = d->free[i]; d->free[i] = b; } void diskwrite(Disk *d, Block **bp, Rune *r, uint n) { int size, nsize; Block *b; b = *bp; size = ntosize(b->n, nil); nsize = ntosize(n, nil); if(size != nsize){ diskrelease(d, b); b = disknewblock(d, n); *bp = b; } if(pwrite(d->fd, r, n*sizeof(Rune), b->addr) != n*sizeof(Rune)) panic("write error to temp file"); b->n = n; } void diskread(Disk *d, Block *b, Rune *r, uint n) { if(n > b->n) panic("internal error: diskread"); ntosize(b->n, nil); /* called only for sanity check on Maxblock */ if(pread(d->fd, r, n*sizeof(Rune), b->addr) != n*sizeof(Rune)) panic("read error from temp file"); }