ref: a8083462e62459b2ae8a243dc4ba88416eba03b1
dir: /os/boot/pc/kfsboot.c/
#include "u.h"
#include "lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "fs.h"
typedef struct Tag Tag;
/*
* tags on block
*/
enum
{
Tnone = 0,
Tsuper, /* the super block */
Tdir, /* directory contents */
Tind1, /* points to blocks */
Tind2, /* points to Tind1 */
Tfile, /* file contents */
Tfree, /* in free list */
Tbuck, /* cache fs bucket */
Tvirgo, /* fake worm virgin bits */
Tcache, /* cw cache things */
MAXTAG
};
#define QPDIR 0x80000000L
#define QPNONE 0
#define QPROOT 1
#define QPSUPER 2
/* DONT TOUCH, this is the disk structure */
struct Tag
{
short pad;
short tag;
long path;
};
static int thisblock = -1;
static Fs *thisfs;
static uchar *block;
/*
* we end up reading 2x or 3x the number of blocks we need to read.
* this is okay because we need to read so few. if it wasn't okay, we could
* have getblock return a pointer to a block, and keep a cache of the last
* three read blocks. that would get us down to the minimum.
* but this is fine.
*/
static int
getblock(Fs *fs, ulong n)
{
if(!block)
block = malloc(16384);
if(thisblock == n && thisfs == fs)
return 0;
thisblock = -1;
if(fs->diskseek(fs, (vlong)n*fs->kfs.RBUFSIZE) < 0)
return -1;
if(fs->diskread(fs, block, fs->kfs.RBUFSIZE) != fs->kfs.RBUFSIZE)
return -1;
thisblock = n;
thisfs = fs;
return 1;
}
static int
checktag(Fs *fs, uchar *block, int tag, long qpath)
{
Tag *t;
t = (Tag*)(block+fs->kfs.BUFSIZE);
if(t->tag != tag)
return -1;
if(qpath != QPNONE && (qpath&~QPDIR) != t->path)
return -1;
return 1;
}
static int
getblocktag(Fs *fs, ulong n, int tag, long qpath)
{
if(getblock(fs, n) < 0 || checktag(fs, block, tag, qpath) < 0)
return -1;
return 1;
}
static int
readinfo(Fs *fs)
{
fs->kfs.RBUFSIZE = 512;
if(getblock(fs, 0) < 0)
return -1;
if(memcmp(block+256, "kfs wren device\n", 16) != 0)
return -1;
fs->kfs.RBUFSIZE = atoi((char*)block+256+16);
if(!fs->kfs.RBUFSIZE || (fs->kfs.RBUFSIZE&(fs->kfs.RBUFSIZE-1)))
return -1;
fs->kfs.BUFSIZE = fs->kfs.RBUFSIZE - sizeof(Tag);
fs->kfs.DIRPERBUF = fs->kfs.BUFSIZE / sizeof(Dentry);
fs->kfs.INDPERBUF = fs->kfs.BUFSIZE / sizeof(long);
fs->kfs.INDPERBUF2 = fs->kfs.INDPERBUF * fs->kfs.INDPERBUF;
return 1;
}
static int
readroot(Fs *fs, Dentry *d)
{
Dentry *d2;
if(getblocktag(fs, 2, Tdir, QPROOT) < 0)
return -1;
d2 = (Dentry*)block;
if(strcmp(d2->name, "/") != 0)
return -1;
*d = *(Dentry*)block;
return 1;
}
static long
indfetch(Fs *fs, long addr, long off, int tag, long path)
{
if(getblocktag(fs, addr, tag, path) < 0)
return -1;
return ((long*)block)[off];
}
static long
rel2abs(Fs *fs, Dentry *d, long a)
{
long addr;
if(a < NDBLOCK)
return d->dblock[a];
a -= NDBLOCK;
if(a < fs->kfs.INDPERBUF){
if(d->iblock == 0)
return 0;
addr = indfetch(fs, d->iblock, a, Tind1, d->qid.path);
if(addr == 0)
print("rel2abs indfetch 0 %s %ld\n", d->name, a);
return addr;
}
a -= fs->kfs.INDPERBUF;
if(a < fs->kfs.INDPERBUF2){
if(d->diblock == 0)
return 0;
addr = indfetch(fs, d->diblock, a/fs->kfs.INDPERBUF, Tind2, d->qid.path);
if(addr == 0){
print("rel2abs indfetch 0 %s %ld\n", d->name, a/fs->kfs.INDPERBUF);
return 0;
}
addr = indfetch(fs, addr, a%fs->kfs.INDPERBUF, Tind1, d->qid.path);
return addr;
}
print("rel2abs trip ind %s %ld\n", d->name, a);
return -1;
}
static int
readdentry(Fs *fs, Dentry *d, int n, Dentry *e)
{
long addr, m;
m = n/fs->kfs.DIRPERBUF;
if((addr = rel2abs(fs, d, m)) <= 0)
return addr;
if(getblocktag(fs, addr, Tdir, d->qid.path) < 0)
return -1;
*e = *(Dentry*)(block+(n%fs->kfs.DIRPERBUF)*sizeof(Dentry));
return 1;
}
static int
getdatablock(Fs *fs, Dentry *d, long a)
{
long addr;
if((addr = rel2abs(fs, d, a)) == 0)
return -1;
return getblocktag(fs, addr, Tfile, QPNONE);
}
static int
walk(Fs *fs, Dentry *d, char *name, Dentry *e)
{
int i, n;
Dentry x;
for(i=0;; i++){
if((n=readdentry(fs, d, i, &x)) <= 0)
return n;
if(strcmp(x.name, name) == 0){
*e = x;
return 1;
}
}
}
static long
kfsread(File *f, void *va, long len)
{
uchar *a;
long tot, off, o, n;
Fs *fs;
a = va;
fs = f->fs;
off = f->kfs.off;
tot = 0;
while(tot < len){
if(getdatablock(fs, &f->kfs, off/fs->kfs.BUFSIZE) < 0)
return -1;
o = off%fs->kfs.BUFSIZE;
n = fs->kfs.BUFSIZE - o;
if(n > len-tot)
n = len-tot;
memmove(a+tot, block+o, n);
off += n;
tot += n;
}
f->kfs.off = off;
return tot;
}
static int
kfswalk(File *f, char *name)
{
int n;
n = walk(f->fs, &f->kfs, name, &f->kfs);
if(n < 0)
return -1;
f->kfs.off = 0;
return 1;
}
int
kfsinit(Fs *fs)
{
if(readinfo(fs) < 0 || readroot(fs, &fs->root.kfs) < 0)
return -1;
fs->root.fs = fs;
fs->read = kfsread;
fs->walk = kfswalk;
return 0;
}