include/linux/idr.h

   1 /*
   2  * include/linux/idr.h
   3  *
   4  * 2002-10-18  written by Jim Houston jim.houston@ccur.com
   5  *      Copyright (C) 2002 by Concurrent Computer Corporation
   6  *      Distributed under the GNU GPL license version 2.
   7  *
   8  * Small id to pointer translation service avoiding fixed sized
   9  * tables.
  10  */
  11
  12 #ifndef __IDR_H__
  13 #define __IDR_H__
  14
  15 #include <linux/types.h>
  16 #include <linux/bitops.h>
  17
  18 #if BITS_PER_LONG == 32
  19 # define IDR_BITS 5
  20 # define IDR_FULL 0xfffffffful
  21 /* We can only use two of the bits in the top level because there is
  22    only one possible bit in the top level (5 bits * 7 levels = 35
  23    bits, but you only use 31 bits in the id). */
  24 # define TOP_LEVEL_FULL (IDR_FULL >> 30)
  25 #elif BITS_PER_LONG == 64
  26 # define IDR_BITS 6
  27 # define IDR_FULL 0xfffffffffffffffful
  28 /* We can only use two of the bits in the top level because there is
  29    only one possible bit in the top level (6 bits * 6 levels = 36
  30    bits, but you only use 31 bits in the id). */
  31 # define TOP_LEVEL_FULL (IDR_FULL >> 62)
  32 #else
  33 # error "BITS_PER_LONG is not 32 or 64"
  34 #endif
  35
  36 #define IDR_SIZE (1 << IDR_BITS)
  37 #define IDR_MASK ((1 << IDR_BITS)-1)
  38
  39 #define MAX_ID_SHIFT (sizeof(int)*8 - 1)
  40 #define MAX_ID_BIT (1U << MAX_ID_SHIFT)
  41 #define MAX_ID_MASK (MAX_ID_BIT - 1)
  42
  43 /* Leave the possibility of an incomplete final layer */
  44 #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
  45
  46 /* Number of id_layer structs to leave in free list */
  47 #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
  48
  49 struct idr_layer {
  50         unsigned long            bitmap; /* A zero bit means "space here" */
  51         struct idr_layer        *ary[1<<IDR_BITS];
  52         int                      count;  /* When zero, we can release it */
  53 };
  54
  55 struct idr {
  56         struct idr_layer *top;
  57         struct idr_layer *id_free;
  58         int               layers;
  59         int               id_free_cnt;
  60         spinlock_t        lock;
  61 };
  62
  63 #define IDR_INIT(name)                                          \
  64 {                                                               \
  65         .top            = NULL,                                 \
  66         .id_free        = NULL,                                 \
  67         .layers         = 0,                                    \
  68         .id_free_cnt    = 0,                                    \
  69         .lock           = SPIN_LOCK_UNLOCKED,                   \
  70 }
  71 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
  72
  73 /*
  74  * This is what we export.
  75  */
  76
  77 void *idr_find(struct idr *idp, int id);
  78 int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
  79 int idr_get_new(struct idr *idp, void *ptr, int *id);
  80 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
  81 void idr_remove(struct idr *idp, int id);
  82 void idr_destroy(struct idr *idp);
  83 void idr_init(struct idr *idp);
  84
  85 #endif /* __IDR_H__ */