stdlib/FreeBSD/tsearch.3

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   2 .\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
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  27 .\"     OpenBSD: tsearch.3,v 1.2 1998/06/21 22:13:49 millert Exp
  28 .\" $FreeBSD: src/lib/libc/stdlib/tsearch.3,v 1.15 2006/06/23 13:36:33 keramida Exp $
  29 .\"
  30 .Dd June 15, 1997
  31 .Dt TSEARCH 3
  32 .Os
  33 .Sh NAME
  34 .Nm tdelete ,
  35 .Nm tfind ,
  36 .Nm tsearch ,
  37 .Nm twalk
  38 .Nd manipulate binary search trees
  39 .Sh SYNOPSIS
  40 .In search.h
  41 .Ft void *
  42 .Fo tdelete
  43 .Fa "const void *restrict key"
  44 .Fa "void **restrict rootp"
  45 .Fa "int (*compar) (const void *key1, const void *key2)"
  46 .Fc
  47 .Ft void *
  48 .Fo tfind
  49 .Fa "const void *key"
  50 .Fa "void *const *rootp"
  51 .Fa "int (*compar) (const void *key1, const void *key2)"
  52 .Fc
  53 .Ft void *
  54 .Fo tsearch
  55 .Fa "const void *key"
  56 .Fa "void **rootp"
  57 .Fa "int (*compar) (const void *key1, const void *key2)"
  58 .Fc
  59 .Ft void
  60 .Fo twalk
  61 .Fa "const void *root"
  62 .Fa "void (*action) (const void *node, VISIT order, int level)"
  63 .Fc
  64 .Sh DESCRIPTION
  65 The
  66 .Fn tdelete ,
  67 .Fn tfind ,
  68 .Fn tsearch ,
  69 and
  70 .Fn twalk
  71 functions manage binary search trees, based on algorithms T and D
  72 from Knuth (6.2.2).
  73 The comparison function passed in by
  74 the user takes two arguments, each of which is a key
  75 pointer.
  76 This function has the same style of return values as
  77 .Xr strcmp 3 .
  78 .Pp
  79 The
  80 .Fn tfind
  81 function
  82 searches for a node whose key matches the argument
  83 .Fa key
  84 in the binary tree rooted at
  85 .Fa rootp ,
  86 returning a pointer to the node if it is found and NULL
  87 if it is not.
  88 .Pp
  89 Note that a node is itself a pointer to the key of the node.
  90 Thus, you should generally cast this result to a
  91 double pointer to the data type stored in the tree, for example
  92 (struct myType **), and use double indirection to retrieve the
  93 original key value.
  94 .Pp
  95 The
  96 .Fn tsearch
  97 function is identical to
  98 .Fn tfind
  99 except that, if no match is found,
 100 it inserts a new node for the
 101 .Fa key
 102 into the tree and returns a pointer to the node.
 103 If
 104 .Fa rootp
 105 points to a NULL value, a new binary search tree is created.
 106 .Pp
 107 The
 108 .Fn tdelete
 109 function deletes a node from the specified binary search tree
 110 and returns a pointer to the parent of the node that was deleted.
 111 It takes the same arguments as
 112 .Fn tfind
 113 and
 114 .Fn tsearch .
 115 If the node to be deleted is the root of the binary search tree,
 116 .Fa rootp
 117 will be adjusted.
 118 .Pp
 119 The
 120 .Fn twalk
 121 function walks the binary search tree rooted in
 122 .Fa root
 123 and calls the function
 124 .Fa action
 125 on each node.
 126 The
 127 .Fa action
 128 function is called with three arguments: a pointer to the current node,
 129 a value from the enum
 130 .Sy "typedef enum { preorder, postorder, endorder, leaf } VISIT;"
 131 specifying the traversal type, and a node level (where level
 132 zero is the root of the tree).
 133 .Pp
 134 As
 135 .Fn twalk
 136 traverses the tree, it calls the
 137 .Fa action
 138 function with the traversal type "preorder"
 139 before visiting the left subtree of the
 140 .Fa node ,
 141 with the
 142 traversal type "postorder" before visiting the right subtree
 143 of the
 144 .Fa node ,
 145 and with the traversal type "endorder" after
 146 visiting the right subtree of the
 147 .Fa node .
 148 .Pp.
 149 The
 150 .Fa action
 151 function is called only once for a leaf-node, with the
 152 traversal type "leaf."
 153 .Pp
 154 Note: the names for the traversal types differ somewhat from
 155 common parlance.  The traversal type "postorder" corresponds
 156 to what would typically be referred to as in-order, and the
 157 traversal type "endorder" corresponds to what would typically
 158 be referred to as post-order.
 159 .Sh RETURN VALUES
 160 The
 161 .Fn tsearch
 162 function returns NULL if allocation of a new node fails (usually
 163 due to a lack of free memory).
 164 .Pp
 165 The
 166 .Fn tfind ,
 167 .Fn tsearch ,
 168 and
 169 .Fn tdelete
 170 functions
 171 return NULL if
 172 .Fa rootp
 173 is NULL or the node cannot be found.
 174 .Pp
 175 The
 176 .Fn twalk
 177 function returns no value.
 178 .Sh SEE ALSO
 179 .Xr bsearch 3 ,
 180 .Xr hsearch 3 ,
 181 .Xr lsearch 3