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	disk.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	---
	disk.c (2058B)
	---
	1 #include "sam.h"
	2
	3 static Block *blist;
	4
	5 #if 0
	6 static int
	7 tempdisk(void)
	8 {
	9 char buf[128];
	10 int i, fd;
	11
	12 snprint(buf, sizeof buf, "/tmp/X%d.%.4ssam", getpid(), getuser()…
	13 for(i='A'; i<='Z'; i++){
	14 buf[5] = i;
	15 if(access(buf, AEXIST) == 0)
	16 continue;
	17 fd = create(buf, ORDWR\|ORCLOSE\|OCEXEC, 0600);
	18 if(fd >= 0)
	19 return fd;
	20 }
	21 return -1;
	22 }
	23 #else
	24 extern int tempdisk(void);
	25 #endif
	26
	27 Disk*
	28 diskinit(void)
	29 {
	30 Disk *d;
	31
	32 d = emalloc(sizeof(Disk));
	33 d->fd = tempdisk();
	34 if(d->fd < 0){
	35 fprint(2, "sam: can't create temp file: %r\n");
	36 exits("diskinit");
	37 }
	38 return d;
	39 }
	40
	41 static
	42 uint
	43 ntosize(uint n, uint *ip)
	44 {
	45 uint size;
	46
	47 if(n > Maxblock)
	48 panic("internal error: ntosize");
	49 size = n;
	50 if(size & (Blockincr-1))
	51 size += Blockincr - (size & (Blockincr-1));
	52 /* last bucket holds blocks of exactly Maxblock */
	53 if(ip)
	54 *ip = size/Blockincr;
	55 return size * sizeof(Rune);
	56 }
	57
	58 Block*
	59 disknewblock(Disk *d, uint n)
	60 {
	61 uint i, j, size;
	62 Block *b;
	63
	64 size = ntosize(n, &i);
	65 b = d->free[i];
	66 if(b)
	67 d->free[i] = b->u.next;
	68 else{
	69 /* allocate in chunks to reduce malloc overhead */
	70 if(blist == nil){
	71 blist = emalloc(100*sizeof(Block));
	72 for(j=0; j<100-1; j++)
	73 blist[j].u.next = &blist[j+1];
	74 }
	75 b = blist;
	76 blist = b->u.next;
	77 b->addr = d->addr;
	78 d->addr += size;
	79 }
	80 b->u.n = n;
	81 return b;
	82 }
	83
	84 void
	85 diskrelease(Disk d, Block b)
	86 {
	87 uint i;
	88
	89 ntosize(b->u.n, &i);
	90 b->u.next = d->free[i];
	91 d->free[i] = b;
	92 }
	93
	94 void
	95 diskwrite(Disk d, Block bp, Rune r, uint n)
	96 {
	97 int size, nsize;
	98 Block *b;
	99
	100 b = *bp;
	101 size = ntosize(b->u.n, nil);
	102 nsize = ntosize(n, nil);
	103 if(size != nsize){
	104 diskrelease(d, b);
	105 b = disknewblock(d, n);
	106 *bp = b;
	107 }
	108 if(pwrite(d->fd, r, nsizeof(Rune), b->addr) != nsizeof(Rune))
	109 panic("write error to temp file");
	110 b->u.n = n;
	111 }
	112
	113 void
	114 diskread(Disk d, Block b, Rune *r, uint n)
	115 {
	116 if(n > b->u.n)
	117 panic("internal error: diskread");
	118
	119 ntosize(b->u.n, nil); /* called only for sanity check on …
	120 if(pread(d->fd, r, nsizeof(Rune), b->addr) != nsizeof(Rune))
	121 panic("read error from temp file");
	122 }