From 78e51a8c6678b6e3dff3d619aa786669f531f4bc Mon Sep 17 00:00:00 2001 From: rsc Date: Fri, 14 Jan 2005 03:45:44 +0000 Subject: checkpoint --- man/man3/9p-intmap.html | 110 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 man/man3/9p-intmap.html (limited to 'man/man3/9p-intmap.html') diff --git a/man/man3/9p-intmap.html b/man/man3/9p-intmap.html new file mode 100644 index 00000000..f6d1822f --- /dev/null +++ b/man/man3/9p-intmap.html @@ -0,0 +1,110 @@ + +9p-intmap(3) - Plan 9 from User Space + + + + +
+
+
9P-INTMAP(3)9P-INTMAP(3) +
+
+

NAME
+ +
+ + Intmap, allocmap, freemap, insertkey, caninsertkey, lookupkey, + deletekey – integer to data structure maps
+ +
+

SYNOPSIS
+ +
+ + #include <u.h>
+ #include <libc.h>
+ #include <fcall.h>
+ #include <thread.h>
+ #include <9p.h>
+ +
+ + Intmap* allocmap(void (*inc)(void*))
+ void      freemap(Intmap *map, void (*dec)(void*))
+ void*     lookupkey(Intmap *map, ulong key)
+ void*     insertkey(Intmap *map, ulong key, void *val)
+ int       caninsertkey(Intmap *map, ulong key, void *val)
+ void*     lookupkey(Intmap *map, ulong key)
+ void*     deletekey(Intmap *map, ulong key)
+ +
+

DESCRIPTION
+ +
+ + An Intmap is an arbitrary mapping from integers to pointers. Allocmap + creates a new map, and freemap destroys it. The inc function is + called each time a new pointer is added to the map; similarly, + dec is called on each pointer left in the map when it is being + freed. Typically these functions maintain reference counts. + New entries are added to the map by calling insertkey, which will + return the previous value associated with the given key, or zero + if there was no previous value. Caninsertkey is like insertkey + but only inserts val if there is no current mapping. It returns + 1 if val was inserted, 0 otherwise. Lookupkey returns the pointer + associated with key, or zero if there is no such pointer. Deletekey + removes the entry for id from the map, returning the associated + pointer, if any. +
+ + Concurrent access to Intmaps is safe, moderated via a QLock stored + in the Intmap structure. +
+ + In anticipation of the storage of reference-counted structures, + an increment function inc may be specified at map creation time. + Lookupkey calls inc (if non-zero) on pointers before returning + them. If the reference count adjustments were left to the caller + (and thus not protected by the lock), it would be possible to + accidentally reclaim a structure if, for example, it was deleted + from the map and its reference count decremented between the return + of insertkey and the external increment. Insertkey and caninsertkey + do not call inc when inserting val into the map, nor do insertkey + or deletekey call inc when returning old map entries. + The rationale is that calling an insertion function transfers + responsibility for the reference to the map, and responsibility + is given back via the return value of deletekey or the next insertkey. + +
+ + Intmaps are used by the 9P library to implement Fidpools and Reqpools.
+ +
+

SOURCE
+ +
+ + /usr/local/plan9/src/lib9p/intmap.c
+ +
+

SEE ALSO
+ +
+ + 9p(3), 9p-fid(3)
+ +
+ +

 +
+
+ + +
+
+
+Space Glenda +
+
+ + -- cgit v1.2.3