shithub: riscv

ref: 52b773d635aa7ffefac5f1e64ed97c3d67d34e5f
dir: /sys/src/cmd/disk/9660/path.c/

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <libsec.h>

#include "iso9660.h"

/*
 * Add the requisite path tables to the CD image.
 * They get put on the end once everything else is done.
 * We use the path table itself as a queue in the breadth-first
 * traversal of the tree.  
 *
 * The only problem with this is that the path table does not
 * store the lengths of the directories.  So we keep an explicit
 * map in an array in memory.
 */

enum {
	Big,
	Little
};

static void
Crdpath(Cdimg *cd, Cpath *p)
{
	p->namelen = Cgetc(cd);
	if(p->namelen == 0) {
		Crseek(cd, (Croffset(cd)+Blocksize-1)/Blocksize * Blocksize);
		p->namelen = Cgetc(cd);
		assert(p->namelen != 0);
	}

	p->xlen = Cgetc(cd);
	assert(p->xlen == 0);	/* sanity, might not be true if we start using the extended fields */

	Cread(cd, p->dloc, 4);
	Cread(cd, p->parent, 2);
	p->name[0] = '\0';
	Crseek(cd, Croffset(cd)+p->namelen+p->xlen+(p->namelen&1));	/* skip name, ext data */
}

static void
writepath(Cdimg *cd, Cdir *c, int parent, int size)
{
/*
	DO NOT UNCOMMENT THIS CODE.
	This commented-out code is here only so that no one comes
	along and adds it later.

	The ISO 9660 spec is silent about whether path table entries
	need to be padded so that they never cross block boundaries.
	It would be reasonable to assume that they are like every other
	data structure in the bloody spec; this code pads them out.

	Empirically, though, they're NOT padded.  Windows NT and
	derivatives are the only known current operating systems
	that actually read these things.

	int l;

	l = 1+1+4+2+c->namelen;
	if(Cwoffset(cd)/Blocksize != (Cwoffset(cd)+l)/Blocksize)
		Cpadblock(cd);
*/
	Cputc(cd, c->namelen);
	Cputc(cd, 0);
	Cwrite(cd, c->dloc + (size==Little ? 0 : 4), 4);
	(size==Little ? Cputnl : Cputnm)(cd, parent, 2);
	Cwrite(cd, c->name, c->namelen);
	if(c->namelen & 1)
		Cputc(cd, 0);
}

static ulong*
addlength(ulong *a, ulong x, int n)
{
	if(n%128==0)
		a = erealloc(a, (n+128)*sizeof a[0]);
	a[n] = x;
	return a;
}

static ulong
writepathtable(Cdimg *cd, ulong vdblock, int size)
{
	int rp, wp;
	uchar buf[Blocksize];
	ulong bk, i, *len, n;
	uvlong start, end, rdoff;
	Cdir *c;
	Cpath p;

	Creadblock(cd, buf, vdblock, Blocksize);
	c = (Cdir*)(buf + offsetof(Cvoldesc, rootdir[0]));

	rp = 0;
	wp = 0;
	len = nil;
	start = (vlong)cd->nextblock * Blocksize;
	Cwseek(cd, start);
	Crseek(cd, start);
	writepath(cd, c, 1, size);
	len = addlength(len, little(c->dlen, 4), wp);
	wp++;

	while(rp < wp) {
		Crdpath(cd, &p);
		n = (len[rp]+Blocksize-1)/Blocksize;
		rp++;
		bk = (size==Big ? big : little)(p.dloc, 4);
		rdoff = Croffset(cd);
		for(i=0; i<n; i++) {
			Creadblock(cd, buf, bk+i, Blocksize);
			c = (Cdir*)buf;
			if(i != 0 && c->namelen == 1 && c->name[0] == '\0')
				break;	/* hit another directory; stop */
			while(c->len && c->namelen &&
			    (uchar*)c + c->len < buf + Blocksize) {
				if(c->flags & 0x02 &&
				    (c->namelen > 1 || c->name[0] > '\001')) {
					/* directory */
					writepath(cd, c, rp, size);
					len = addlength(len, little(c->dlen, 4), wp);
					wp++;
				}
				c = (Cdir*)((uchar*)c+c->len);
			}
		}
		Crseek(cd, rdoff);
	}
	end = Cwoffset(cd);
	Cpadblock(cd);
	return end-start;
}


static void
writepathtablepair(Cdimg *cd, ulong vdblock)
{
	ulong bloc, lloc, sz, sz2;

	lloc = cd->nextblock;
	sz = writepathtable(cd, vdblock, Little);
	bloc = cd->nextblock;
	sz2 = writepathtable(cd, vdblock, Big);
	assert(sz == sz2);
	setpathtable(cd, vdblock, sz, lloc, bloc);
}

void
writepathtables(Cdimg *cd)
{
	cd->pathblock = cd->nextblock;

	writepathtablepair(cd, cd->iso9660pvd);
	if(cd->flags & CDjoliet)
		writepathtablepair(cd, cd->jolietsvd);
}