diff options
Diffstat (limited to 'manual')
| -rw-r--r-- | manual/examples/twalk.c | 56 | ||||
| -rw-r--r-- | manual/search.texi | 25 |
2 files changed, 80 insertions, 1 deletions
diff --git a/manual/examples/twalk.c b/manual/examples/twalk.c new file mode 100644 index 0000000000..04e32731d6 --- /dev/null +++ b/manual/examples/twalk.c @@ -0,0 +1,56 @@ +/* Implement twalk using twalk_r. + Copyright (C) 2019 Free Software Foundation, Inc. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, see <http://www.gnu.org/licenses/>. +*/ + +#include <search.h> + +struct twalk_with_twalk_r_closure +{ + void (*action) (const void *, VISIT, int); + int depth; +}; + +static void +twalk_with_twalk_r_action (const void *nodep, VISIT which, void *closure0) +{ + struct twalk_with_twalk_r_closure *closure = closure0; + + switch (which) + { + case leaf: + closure->action (nodep, which, closure->depth); + break; + case preorder: + closure->action (nodep, which, closure->depth); + ++closure->depth; + break; + case postorder: + /* The preorder action incremented the depth. */ + closure->action (nodep, which, closure->depth - 1); + break; + case endorder: + --closure->depth; + closure->action (nodep, which, closure->depth); + break; + } +} + +void +twalk (const void *root, void (*action) (const void *, VISIT, int)) +{ + struct twalk_with_twalk_r_closure closure = { action, 0 }; + twalk_r (root, twalk_with_twalk_r_action, &closure); +} diff --git a/manual/search.texi b/manual/search.texi index 1574c96562..979732f027 100644 --- a/manual/search.texi +++ b/manual/search.texi @@ -618,5 +618,28 @@ Since the functions used for the @var{action} parameter to @code{twalk} must not modify the tree data, it is safe to run @code{twalk} in more than one thread at the same time, working on the same tree. It is also safe to call @code{tfind} in parallel. Functions which modify the tree -must not be used, otherwise the behavior is undefined. +must not be used, otherwise the behavior is undefined. However, it is +difficult to pass data external to the tree to the callback function +without resorting to global variables (and thread safety issues), so +see the @code{twalk_r} function below. +@end deftypefun + +@deftypefun void twalk_r (const void *@var{root}, void (*@var{action}) (const void *@var{key}, VISIT @var{which}, void *@var{closure}), void *@var{closure}) +@standards{GNU, search.h} +@safety{@prelim{}@mtsafe{@mtsrace{:root}}@assafe{}@acsafe{}} +For each node in the tree with a node pointed to by @var{root}, the +@code{twalk_r} function calls the function provided by the parameter +@var{action}. For leaf nodes the function is called exactly once with +@var{value} set to @code{leaf}. For internal nodes the function is +called three times, setting the @var{value} parameter or @var{action} to +the appropriate value. The @var{closure} parameter is passed down to +each call of the @var{action} function, unmodified. + +It is possible to implement the @code{twalk} function on top of the +@code{twalk_r} function, which is why there is no separate level +parameter. + +@smallexample +@include twalk.c.texi +@end smallexample @end deftypefun |