From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58900) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y8v2Y-0006oO-Ql for qemu-devel@nongnu.org; Wed, 07 Jan 2015 13:09:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y8v2U-0006is-Cg for qemu-devel@nongnu.org; Wed, 07 Jan 2015 13:09:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34063) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y8v2U-0006ii-67 for qemu-devel@nongnu.org; Wed, 07 Jan 2015 13:09:02 -0500 Message-ID: <54AD7638.8020204@redhat.com> Date: Wed, 07 Jan 2015 13:08:56 -0500 From: John Snow MIME-Version: 1.0 References: <1420566495-13284-1-git-send-email-peter@lekensteyn.nl> <1420566495-13284-10-git-send-email-peter@lekensteyn.nl> In-Reply-To: <1420566495-13284-10-git-send-email-peter@lekensteyn.nl> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 09/12] block/dmg: use SectorNumber from BLKX header List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Wu , qemu-devel@nongnu.org Cc: Kevin Wolf , Stefan Hajnoczi On 01/06/2015 12:48 PM, Peter Wu wrote: > Previously the sector table parsing relied on the previous offset of > the DMG file. Now it uses the sector number from the BLKX header > (see http://newosxbook.com/DMG.html). > > The implementation of dmg2img (from vu1tur) does not base the output > sector on the location of the terminator (0xffffffff) either so it > should be safe to drop this dependency on the previous state. > > (It makes somehow makes sense, a terminator should halt further > processing of a block and is perhaps used to preallocate some space.) > > Signed-off-by: Peter Wu > --- > v2: initial patch after suggestions from John Snow to read and use > these fields. > --- > block/dmg.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/block/dmg.c b/block/dmg.c > index 130efac..57922c5 100644 > --- a/block/dmg.c > +++ b/block/dmg.c > @@ -189,7 +189,6 @@ typedef struct DmgHeaderState { > /* used internally by dmg_read_mish_block to remember offsets of blocks > * across calls */ > uint64_t data_fork_offset; > - uint64_t last_out_offset; > /* exported for dmg_open */ > uint32_t max_compressed_size; > uint32_t max_sectors_per_chunk; > @@ -205,6 +204,7 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, > int64_t offset = 0; > uint64_t data_offset; > uint64_t in_offset = ds->data_fork_offset; > + uint64_t out_offset; > > type = buff_read_uint32(buffer, offset); > /* skip data that is not a valid MISH block (invalid magic or too small) */ > @@ -213,6 +213,9 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, > return 0; > } > > + /* chunk offsets are relative to this sector number */ > + out_offset = buff_read_uint64(buffer, offset + 8); > + > /* location in data fork for (compressed) blob (in bytes) */ > data_offset = buff_read_uint64(buffer, offset + 0x18); > in_offset += data_offset; > @@ -233,10 +236,6 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, > offset += 4; > if (s->types[i] != 0x80000005 && s->types[i] != 1 && > s->types[i] != 2) { > - if (s->types[i] == 0xffffffff && i > 0) { > - ds->last_out_offset = s->sectors[i - 1] + > - s->sectorcounts[i - 1]; > - } This is exactly what I was hoping to see could be eliminated by reading the mish headers. Thanks for this. > chunk_count--; > i--; > offset += 36; > @@ -245,7 +244,7 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, > offset += 4; > > s->sectors[i] = buff_read_uint64(buffer, offset); > - s->sectors[i] += ds->last_out_offset; > + s->sectors[i] += out_offset; > offset += 8; > > s->sectorcounts[i] = buff_read_uint64(buffer, offset); > @@ -419,7 +418,6 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, > s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL; > /* used by dmg_read_mish_block to keep track of the current I/O position */ > ds.data_fork_offset = 0; > - ds.last_out_offset = 0; > ds.max_compressed_size = 1; > ds.max_sectors_per_chunk = 1; > > Much nicer. Reviewed-by: John Snow