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authorMiles Bader <miles@gnu.org>1996-05-06 19:23:41 +0000
committerMiles Bader <miles@gnu.org>1996-05-06 19:23:41 +0000
commit9d89509e5c3c6c3511bf7af9caaed429c3f1c842 (patch)
tree01bdc2defcce980b7430106eb2aa7b5cf9325153
parent6d0ba0d731122abda049b6f67fef837b13fdca80 (diff)
Frob comments on enum file_storage_class.
-rw-r--r--hurd/hurd_types.h117
1 files changed, 65 insertions, 52 deletions
diff --git a/hurd/hurd_types.h b/hurd/hurd_types.h
index c03611c7..4ecd26e1 100644
--- a/hurd/hurd_types.h
+++ b/hurd/hurd_types.h
@@ -149,11 +149,69 @@ enum term_bottom_type
TERM_ON_HURDIO,
TERM_ON_MASTERPTY,
};
-
-/* Flags for file_get_storage_info. */
-#define STORAGE_MUTATED 0x00000001 /* data as stored is munged from file */
-
-/* Classes for file_get_storage_info. */
+
+/* Types of storage, as returned by file_get_storage_info.
+
+ STORAGE_DEVICE is a mach device_t (for random access devices)
+ STORAGE_HURD_FILE is a hurd file_t (as if a file were mapped)
+ STORAGE_TASK is a task_t (the storage is in the vm of the task)
+ STORAGE_MEMORY is a memory object port
+ STORAGE_NULL is a fixed-size constant source of zeros
+ STORAGE_INTERLEAVE is a set of other storage types interleaved at a fixed
+ interval
+ STORAGE_CONCAT is a set of other storage types concatenated end-to-end
+ STORAGE_LAYER is a set of storage types, representing the same address
+ range; all will be written too, and will be read in turn until one
+ succeeds
+ STORAGE_NETWORK means that the file is stored elsewhere on the
+ network; all the remaining fields contan type-specific information.
+ STORAGE_OTHER means none of these apply; and should be used when no
+ meaningful answer can be given
+
+ The vectors returned by file_get_storage_info encode each of the above
+ (note that the first int is always the storage type). There are four:
+ ports, ints, offsets (off_t), and data (char); each type of store uses the
+ following entries in each vector:
+
+ -type- -ports- -ints- -offsets- -data- -kids-
+ device DEVICE TY, FL, BS, NR, NL, ML NR * (OFFS, LEN) NL + ML -
+ file FILE TY, FL, BS, NR, NL, ML NR * (OFFS, LEN) NL + ML -
+ memory MEMOBJ TY, FL, BS, NR, NL, ML NR * (OFFS, LEN) NL + ML -
+ task TASK TY, FL, BS, NR, NL, ML NR * (OFFS, LEN) NL + ML -
+ (the data for the above is a name (incl '\0') and a misc data block)
+ null - TY, FL SIZE - -
+ (BS is 1)
+ ileave - TY, FL, IL, NC - - NC
+ (BS is the LCM of its children; SIZE is the minimum of theirs * IL)
+ concat - TY, FL, NC - - NC
+ (BS is the LCM of its children; SIZE is the sum of theirs)
+ layer - TY, FL, NC - - NC
+ (BS is the LCM of its children; SIZE is the minimum of theirs)
+
+ For ileave, concat, and layer, the children are encoded following the parent.
+ The first int must always be TY.
+
+ key: TY = type code, FL = flags, BS = block size, NR = num runs,
+ NL = name len, ML = misc len, NC = num children,
+ IL = interleave (bytes), SIZE = Size of storage (blocks),
+ LEN = run length (blocks), OFFS = run offset (blocks),
+
+ The NR * (OFFS, LEN) offsets for some of the types is the set of block
+ ranges in the underlying address space that, concatenated, make up the
+ contents of the storage -- for instance, doing file_get_storage_info on a
+ file may return storage of type STORAGE_DEVICE, and the accompanying block
+ ranges are the set of blocks on the given device that correspond to that
+ file. Any OFFS == -1 designates a hole in the address range. Note that
+ the total size (SIZE) for these types is the sum of their LEN's.
+
+ The optional NAME returned by some types (if NL != 0) is a type specific
+ name for the same object referenced by the port also returned. E.g.:
+ device -- The mach device name
+ file -- The file name (unreliable, as the root may not be the same)
+ task -- The pid
+ Unless it is MACH_PORT_NULL, the port should generally be used instead of
+ trying to regenerate it from the associated name, which is intended more for
+ printing messages, etc. */
enum file_storage_class
{
STORAGE_OTHER,
@@ -168,53 +226,8 @@ enum file_storage_class
STORAGE_LAYER,
};
-/* STORAGE_DEVICE implies that:
-
- STORAGE_PORT, if non-null, is a device_t holding the data.
-
- STORAGE_NAME, if non-null, is the name (as for device_open) of the
- device holding the data. (Caveat: use storage_port in preference
- to storage_name for actual I/O)
-
- The even members of ADDRESSES specify the physical addresses of the
- data of the file, in order (in units appropriate as a RECNUM to
- device_read/write) . The odd members specify the lengths (in
- bytes) of the storage at the preceding address. An address of -1
- identifies a hole, a length of zero should be ignored along with
- the preceding address.
-
- STORAGE_MISC may contain additional type specific information.
- */
-
-/* STORAGE_HURD_FILE implies that:
-
- STORAGE_PORT, if non-null, is a file_t holding the data.
-
- STORAGE_NAME, if non-null, is the filename of the file referenced
- by STORAGE_PORT. (Caveat: use storage_port in preference to
- storage_name if both are provided.)
-
- ADDRESSES are pairs of address pairs; the even numbers are off_t
- offsets from the start of the file and the odd numbers are the
- length of the segment. -1 addresses are holes; zero lengths
- should be ignored.
-
- STORAGE_MISC may contain additional type-specific information.
-*/
-
-/* STORAGE_TASK is like STORAGE_HURD_FILE, except that the data is found
- in the virtual address space of the task identified by STORAGE_PORT. */
-
-/* STORAGE_MEMORY is similar, except the data is found in the memory
- object identified by STORAGE_PORT. */
-
-/* STORAGE_NETWORK means that the file is stored elsewhere on the
- network; all the remaining fields contan type-specific information. */
-
-/* STORAGE_OTHER means none of these apply; and should be used when no
- meaningful answer can be given. */
-
-
+/* Flags for the flags word returned by some types . */
+#define STORAGE_MUTATED 0x00000001 /* data as stored is munged from file */
/* Data types */