#include <u.h>
#include <libc.h>
#include <bio.h>
#include "cram.h"

uint
getle(uchar *buf, int n)
{
	uint x;

	x = 0;
	while(--n >= 0)
		x = x<<8 | buf[n];
	return x;
}

u8int
get8(uchar *buf)
{
	return getle(buf, 1);
}

u16int
get16(uchar *buf)
{
	return getle(buf, 2);
}

u32int
get24(uchar *buf)
{
	return getle(buf, 3);
}

u32int
get32(uchar *buf)
{
	return getle(buf, 4);
}

long
Bpread(Biobuf *b, void *buf, long n, vlong o)
{
	if(Bseek(b, o, 0) < 0)
		return -1;
	return Bread(b, buf, n);
}

int
readdentry(Biobuf *disk, Dentry *dentry, vlong offset)
{
	uchar buf[12];
	int n, mode;
	
	if((n = Bpread(disk, buf, sizeof buf, offset)) < 0)
		return -1;
	if(n < sizeof buf) {
		werrstr("short read: %d/%d", n, sizeof buf);
		return -1;
	}
	dentry->offset = offset;

	dentry->mode = (mode = get16(buf+0)) & 0777;
	if(mode & 040000)
		dentry->mode |= DMDIR;

	dentry->uid = get16(buf+2);
	dentry->length = get24(buf+4);
	dentry->gid = get8(buf+7);

	dentry->index = (get24(buf+9)<<2 | *(buf+8)>>6) << 2;
	if(~dentry->mode & DMDIR)
		dentry->data = dentry->index + (dentry->length + Blocksz-1)/Blocksz * 4;
	else
		dentry->data = dentry->index;

	dentry->namelen = (get8(buf+8) & 0x3F) << 2;
	if((n = Bpread(disk, dentry->name, dentry->namelen, offset+12)) < 0) {
		werrstr("name: %r");
		return -1;
	}
	dentry->name[n] = '\0';
	while(dentry->namelen > 0 && dentry->name[dentry->namelen-1] == '\0')
		dentry->namelen--;

	return 12+n;
}

void
printdentry(char *pfx, Dentry *d)
{
	print("%s%#llx	%#.4uo	%d %d	%d	%#llx	%#llx	%d	%s\n",
		pfx, d->offset, d->mode, d->uid, d->gid, d->length,
		d->index, d->data, d->namelen, d->name );
}

void
readsuper(Biobuf *disk, Super *super)
{
	uchar buf[64];
	int n;

	if((n = Bread(disk, buf, sizeof buf)) < 0)
		sysfatal("read header: %r");
	if(n < sizeof buf)
		sysfatal("short header: %d/%d", n, sizeof buf);

	if(get32(buf+0) != 0x28cd3d45)
		sysfatal("bad magic: %#.8ux", get32(buf+0));
	super->size = get32(buf+4);
	super->flags = get32(buf+8);

	if(strncmp((char *)buf+16, "Compressed ROMFS", 16) != 0)
		sysfatal("bad signature: %.16s", (char *)buf+16);

	super->crc = get32(buf+32);
	super->edition = get32(buf+36);
	super->nblocks = get32(buf+40);
	super->nfiles = get32(buf+44);

	if(readdentry(disk, &super->root, 64) < 0)
		sysfatal("read root dentry: %r");
}