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* Added some hopefully helpful comments.

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* Replaced my bogus comment that Ingo pointed out with a description that
  mentions LogicalPartitions also being used to describe so called "inner
  extended" partitions, which are only needed to point to the next PTS.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@27624 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Stephan Aßmus 2008-09-18 14:56:49 +00:00
parent e73923b0c2
commit aecd884e05
2 changed files with 31 additions and 17 deletions
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18
src/add-ons/kernel/partitioning_systems/intel/PartitionMap.cpp
View File

@ -576,14 +576,16 @@ LogicalPartition::SetTo(const partition_descriptor *descriptor,
{
Unset();
if (descriptor && primary) {
// TODO: I am wondering if this is wrong, since it always uses the
// offset of the primary partition as base offset, even for
// logical partitions that come much later in the chain. For each,
// PTS in the chain of logical partitions, there should be one
// extended and one non-extended in the four possible table entries.
// So baseOffset would be wrong for all but the first three? The
// forth logical partition, assuming it's the extended one, would
// get a wrong baseOffset.
// There are two types of LogicalPartitions. There are so called
// "inner extended" partitions and the "real" logical partitions
// which contain data. The "inner extended" partitions don't contain
// data and are only used to point to the next PTS in the linked
// list of logical partitions. For "inner extended" partitions,
// the baseOffset is in relation to the (first sector of the)
// "primary extended" partition, in another words, all inner extended
// partitions use the same base offset for reference.
// The data containing, real logical partitions use the offset of the
// PTS that contains their partition descriptor as their baseOffset.
off_t baseOffset = (descriptor->is_extended() ? primary->Offset()
: ptsOffset);
Partition::SetTo(descriptor, ptsOffset, baseOffset);

30
src/add-ons/kernel/partitioning_systems/intel/PartitionMap.h
View File

@ -10,6 +10,8 @@
for related classes.
*/
// NOTE: <http://www.win.tue.nl/~aeb/partitions/partition_tables-2.html>
#ifndef _INTEL_PARTITION_MAP_H
#define _INTEL_PARTITION_MAP_H
@ -55,6 +57,8 @@ fill_buffer(char *buffer, uint32 length, char ch)
void get_partition_type_string(uint8 type, char *buffer);
// chs
// NOTE: The CHS cannot express locations within larger disks and is therefor
// mostly obsolete.
struct chs {
uint8 cylinder;
uint16 head_sector; // head[15:10], sector[9:0]
@ -64,11 +68,11 @@ struct chs {
// partition_descriptor
struct partition_descriptor {
uint8 active;
chs begin;
uint8 type;
chs end;
uint32 start;
uint32 size;
chs begin; // mostly ignored
uint8 type; // empty, filesystem or extended
chs end; // mostly ignored
uint32 start; // in sectors
uint32 size; // in sectors
bool is_empty() const { return is_empty_type(type); }
bool is_extended() const { return is_extended_type(type); }
@ -92,9 +96,9 @@ class LogicalPartition;
/*!
\brief Class for validating partition types.
To this class we can set partition type and then we can check whether
this type is valid, empty or if it represents extended partition.
We can also retrieve the name of that partition type or find next
To this class we can set a partition type and then we can check whether
this type is valid, empty or if it represents an extended partition.
We can also retrieve the name of that partition type or find the next
supported type.
*/
class PartitionType {
@ -134,15 +138,23 @@ public:
bool IsEmpty() const { return is_empty_type(fType); }
bool IsExtended() const { return is_extended_type(fType); }
// NOTE: Both PTSOffset() and Offset() are absolute with regards to the
// session (usually the disk). Ie, for all primary partitions, including
// the primary extended partition, the PTSOffset() points to the MBR (0).
// For logical partitions, the PTSOffset() is located within the primary
// extended partition, but again, the returned values are absolute with
// regards to the session. All values are expressed in bytes.
off_t PTSOffset() const { return fPTSOffset; }
// offset of the sector containing the descriptor for this partition
off_t Offset() const { return fOffset; }
// start offset of the partition contents
off_t Size() const { return fSize; }
uint8 Type() const { return fType; }
bool Active() const { return fActive; }
void GetTypeString(char *buffer) const
{ get_partition_type_string(fType, buffer); }
void GetPartitionDescriptor(partition_descriptor *descriptor,
off_t baseOffset) const;
off_t baseOffset) const;
void SetPTSOffset(off_t offset) { fPTSOffset = offset; }
void SetOffset(off_t offset) { fOffset = offset; }