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NAME
smlist - shared memory list management library
SYNOPSIS
#include "smlist.h"
typedef int (*SmListCompareFn)
(PsmPartition partition, PsmAddress eltData, void *argData);
typedef void (*SmListDeleteFn)
(PsmPartition partition, PsmAddress eltData, void *argument);
[see description for available functions]
DESCRIPTION
The smlist library provides functions to create, manipulate and destroy doubly-linked
lists in shared memory. As with lyst(3), smlist uses two types of objects, list objects
and element objects. However, as these objects are stored in shared memory which is
managed by psm(3), pointers to these objects are carried as PsmAddress values. A list
knows how many elements it contains and what its first and last elements are. An element
knows what list it belongs to and the elements before and after it in its list. An
element also knows its content, which is normally the PsmAddress of some object in shared
memory.
PsmAddress sm_list_create(PsmPartition partition)
Create a new list object without any elements in it, within the memory segment
identified by partition. Returns the PsmAddress of the list, or 0 on any error.
void sm_list_unwedge(PsmPartition partition, PsmAddress list, int interval)
Unwedge, as necessary, the mutex semaphore protecting shared access to the indicated
list. For details, see the explanation of the sm_SemUnwedge() function in
platform(3).
int sm_list_clear(PsmPartition partition, PsmAddress list, SmListDeleteFn delete, void
*argument);
Empty a list. Frees each element of the list. If the delete function is non-NULL,
that function is called once for each freed element; when called, that function is
passed the PsmAddress that is the element's data and the argument pointer passed to
sm_list_clear(). Returns 0 on success, -1 on any error.
int sm_list_destroy(PsmPartition partition, PsmAddress list, SmListDeleteFn delete, void
*argument);
Destroy a list. Same as sm_list_clear(), but additionally frees the list structure
itself. Returns 0 on success, -1 on any error.
int sm_list_user_data_set(PsmPartition partition, PsmAddress list, PsmAddress userData);
Set the value of a user data variable associated with the list as a whole. This value
may be used for any purpose; it is typically used to store the PsmAddress of a shared
memory block containing data (e.g., state data) which the user wishes to associate
with the list. Returns 0 on success, -1 on any error.
PsmAddress sm_list_user_data(PsmPartition partition, PsmAddress list);
Return the value of the user data variable associated with the list as a whole, or 0
on any error.
int sm_list_length(PsmPartition partition, PsmAddress list);
Return the number of elements in the list.
PsmAddress sm_list_insert(PsmPartition partition, PsmAddress list, PsmAddress data,
SmListCompareFn compare, void *dataBuffer);
Create a new list element whose data value is data and insert it into the given list.
If the compare function is NULL, the new list element is simply appended to the list;
otherwise, the new list element is inserted after the last element in the list whose
data value is "less than or equal to" the data value of the new element (in
dataBuffer) according to the collating sequence established by compare. Returns the
PsmAddress of the new element, or 0 on any error.
PsmAddress sm_list_insert_first(PsmPartition partition, PsmAddress list, PsmAddress data);
PsmAddress sm_list_insert_last(PsmPartition partition, PsmAddress list, PsmAddress data);
Create a new list element and insert it at the start/end of a list. Returns the
PsmAddress of the new element on success, or 0 on any error. Disregards any
established sort order in the list.
PsmAddress sm_list_insert_before(PsmPartition partition, PsmAddress elt, PsmAddress data);
PsmAddress sm_list_insert_after(PsmPartition partition, PsmAddress elt, PsmAddress data);
Create a new list element and insert it before/after a given element. Returns the
PsmAddress of the new element on success, or 0 on any error. Disregards any
established sort order in the list.
int sm_list_delete(PsmPartition partition, PsmAddress elt, SmListDeleteFn delete, void
*argument);
Delete an element from a list. If the delete function is non-NULL, that function is
called upon deletion of elt; when called, that function is passed the PsmAddress that
is the element's data value and the argument pointer passed to sm_list_delete().
Returns 0 on success, -1 on any error.
PsmAddress sm_list_first(PsmPartition partition, PsmAddress list);
PsmAddress sm_list_last(PsmPartition partition, PsmAddress list);
Return the PsmAddress of the first/last element in list, or 0 on any error.
PsmAddress sm_list_next(PsmPartition partition, PsmAddress elt);
PsmAddress sm_list_prev(PsmPartition partition, PsmAddress elt);
Return the PsmAddress of the element following/preceding elt in that element's list,
or 0 on any error.
PsmAddress sm_list_search(PsmPartition partition, PsmAddress elt, SmListCompareFn compare,
void *dataBuffer);
Search a list for an element whose data matches the data in dataBuffer. If the
compare function is non-NULL, the list is assumed to be sorted in the order implied by
that function and the function is automatically called once for each element of the
list until it returns a value that is greater than or equal to zero (where zero
indicates an exact match and a value greater than zero indicates that the list
contains no matching element); each time compare is called it is passed the PsmAddress
that is the element's data value and the dataBuffer value passed to sm_list_search().
If compare is NULL, then the entire list is searched until an element is located whose
data value is equal to ((PsmAddress) dataBuffer). Returns the PsmAddress of the
matching element if one is found, 0 otherwise.
PsmAddress sm_list_list(PsmPartition partition, PsmAddress elt);
Return the PsmAddress of the list to which elt belongs, or 0 on any error.
PsmAddress sm_list_data(PsmPartition partition, PsmAddress elt);
Return the PsmAddress that is the data value for elt, or 0 on any error.
PsmAddress sm_list_data_set(PsmPartition partition, PsmAddress elt, PsmAddress data);
Set the data value for elt to data, replacing the original value. Returns the
original data value for elt, or 0 on any error. The original data value for elt may
or may not have been the address of an object in memory; even if it was, that object
was NOT deleted.
Warning: changing the data value of an element of an ordered list may ruin the
ordering of the list.
USAGE
A user normally creates an element and adds it to a list by doing the following:
1 obtaining a shared memory block to contain the element's data;
2 converting the shared memory block's PsmAddress to a character pointer;
3 using that pointer to write the data into the shared memory block;
4 calling one of the sm_list_insert functions to create the element structure (which
will include the shared memory block's PsmAddress) and insert it into the list.
When inserting elements or searching a list, the user may optionally provide a compare
function of the form:
int user_comp_name(PsmPartition partition, PsmAddress eltData,
void *dataBuffer);
When provided, this function is automatically called by the smlist function being invoked;
when the function is called it is passed the content of a list element (eltData, nominally
the PsmAddress of an item in shared memory) and an argument, dataBuffer, which is
nominally the address in local memory of some other item in the same format. The user-
supplied function normally compares some key values of the two data items and returns 0 if
they are equal, an integer less than 0 if eltData's key value is less than that of
dataBuffer, and an integer greater than 0 if eltData's key value is greater than that of
dataBuffer. These return values will produce a list in ascending order. If the user
desires the list to be in descending order, the function must reverse the signs of these
return values.
When deleting an element or destroying a list, the user may optionally provide a delete
function of the form:
void user_delete_name(PsmPartition partition, PsmAddress eltData,
void *argData)
When provided, this function is automatically called by the smlist function being invoked;
when the function is called it is passed the content of a list element (eltData, nominally
the PsmAddress of an item in shared memory) and an argument, argData, which if non-NULL is
normally the address in local memory of a data item providing context for the list element
deletion. The user-supplied function performs any application-specific cleanup associated
with deleting the element, such as freeing the element's content data item and/or other
memory associated with the element.
EXAMPLE
For an example of the use of smlist, see the file smlistsh.c in the utils directory of
ICI.
SEE ALSO
lyst(3), platform(3), psm(3)