minix/fs/ptyfs/node.c

   1 /* PTYFS slave node management */
   2 /*
   3  * While the interface of this module should be flexible enough to implement
   4  * various memory management approaches, the current code simply relies on
   5  * NR_PTYS being small enough to preallocate all data structures.  In the
   6  * future, NR_PTYS will no longer be a system-global definition, and future
   7  * implementations of this module should not rely on NR_PTYS at all.
   8  */
   9
  10 #include <minix/drivers.h>
  11
  12 #include "node.h"
  13
  14 static bitchunk_t node_map[BITMAP_CHUNKS(NR_PTYS)];
  15 static struct node_data node_data[NR_PTYS];
  16
  17 /*
  18  * Initialize the node module.
  19  */
  20 void
  21 init_nodes(void)
  22 {
  23
  24         memset(&node_map, 0, sizeof(node_map));
  25 }
  26
  27 /*
  28  * Allocate a node with a given node index number, and save node data for it.
  29  * It is possible that the node is in use already; in that case, only update
  30  * its associated data.  Return OK on success, or an error code on failure.
  31  */
  32 int
  33 set_node(node_t index, struct node_data * data)
  34 {
  35
  36         if (index >= NR_PTYS)
  37                 return ENOMEM;
  38
  39         SET_BIT(node_map, index);
  40
  41         node_data[index] = *data;
  42
  43         return OK;
  44 }
  45
  46 /*
  47  * Deallocate a node using its node index number.  This function always
  48  * succeeds, intentionally ignoring the case that the node was not allocated.
  49  */
  50 void
  51 clear_node(node_t index)
  52 {
  53
  54         UNSET_BIT(node_map, index);
  55 }
  56
  57 /*
  58  * Return a pointer to the node data associated with the given node index
  59  * number.  If the node is not allocated, return NULL.
  60  */
  61 struct node_data *
  62 get_node(node_t index)
  63 {
  64
  65         if (index >= NR_PTYS || !GET_BIT(node_map, index))
  66                 return NULL;
  67
  68         return &node_data[index];
  69 }
  70
  71 /*
  72  * Return the highest allocated node index number, plus one.  This value is
  73  * used to check given node indices and limit linear iterations.
  74  */
  75 node_t
  76 get_max_node(void)
  77 {
  78
  79         /*
  80          * NR_PTYS is low enough that we can always return it instead of
  81          * tracking the actual value.
  82          */
  83         return NR_PTYS;
  84 }