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Diffstat (limited to 'cmake/TopologicalSort.cmake')
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diff --git a/cmake/TopologicalSort.cmake b/cmake/TopologicalSort.cmake new file mode 100644 index 00000000..b85e7749 --- /dev/null +++ b/cmake/TopologicalSort.cmake @@ -0,0 +1,148 @@ +############################################################################## +# @file TopologicalSort.cmake +# @brief CMake implementation of topological sorting algorithm. +# +# Perform a reverse topological sort on the given LIST. +# +# topological_sort(my_list "MY_" "_EDGES") +# +# LIST is the name of a variable containing a list of elements to be +# sorted in reverse topological order. Each element in the list has a +# set of outgoing edges (for example, those other list elements that +# it depends on). In the resulting reverse topological ordering +# (written back into the variable named LIST), an element will come +# later in the list than any of the elements that can be reached by +# following its outgoing edges and the outgoing edges of any vertices +# they target, recursively. Thus, if the edges represent dependencies +# on build targets, for example, the reverse topological ordering is +# the order in which one would build those targets. +# +# For each element E in this list, the edges for E are contained in +# the variable named ${PREFIX}${E}${SUFFIX}. If no such variable +# exists, then it is assumed that there are no edges. For example, if +# my_list contains a, b, and c, one could provide a dependency graph +# using the following variables: +# +# MY_A_EDGES b +# MY_B_EDGES +# MY_C_EDGES a b +# +# With the involcation of topological_sort shown above and these +# variables, the resulting reverse topological ordering will be b, a, c. +# +# @verbatim +############################################################################## +# Modified from Boost Utilities +# +# Copyright 2010 Kitware, Inc. +############################################################################## +# Copyright 2007 Douglas Gregor <doug.gregor@gmail.com> +# Copyright 2007 Troy Straszheim +# +# Distributed under the Boost Software License, Version 1.0. +############################################################################## +# Boost Software License - Version 1.0 - August 17th, 2003 +# +# Permission is hereby granted, free of charge, to any person or organization +# obtaining a copy of the software and accompanying documentation covered by +# this license (the "Software") to use, reproduce, display, distribute, +# execute, and transmit the Software, and to prepare derivative works of the +# Software, and to permit third-parties to whom the Software is furnished to +# do so, all subject to the following: +# +# The copyright notices in the Software and this entire statement, including +# the above license grant, this restriction and the following disclaimer, +# must be included in all copies of the Software, in whole or in part, and +# all derivative works of the Software, unless such copies or derivative +# works are solely in the form of machine-executable object code generated by +# a source language processor. +# +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +# FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT +# SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE +# FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, +# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +# DEALINGS IN THE SOFTWARE. +############################################################################## +# @endverbatim +# +# @ingroup CMakeUtilities +############################################################################## + +function(topological_sort LIST PREFIX SUFFIX) + # Clear the stack and output variable + set(VERTICES "${${LIST}}") + set(STACK) + set(${LIST}) + + # Loop over all of the vertices, starting the topological sort from + # each one. + foreach(VERTEX ${VERTICES}) + + # If we haven't already processed this vertex, start a depth-first + # search from where. + if (NOT FOUND_${VERTEX}) + # Push this vertex onto the stack with all of its outgoing edges + string(REPLACE ";" " " NEW_ELEMENT + "${VERTEX};${${PREFIX}${VERTEX}${SUFFIX}}") + list(APPEND STACK ${NEW_ELEMENT}) + + # We've now seen this vertex + set(FOUND_${VERTEX} TRUE) + + # While the depth-first search stack is not empty + list(LENGTH STACK STACK_LENGTH) + while(STACK_LENGTH GREATER 0) + # Remove the vertex and its remaining out-edges from the top + # of the stack + list(GET STACK -1 OUT_EDGES) + list(REMOVE_AT STACK -1) + + # Get the source vertex and the list of out-edges + separate_arguments(OUT_EDGES) + list(GET OUT_EDGES 0 SOURCE) + list(REMOVE_AT OUT_EDGES 0) + + # While there are still out-edges remaining + list(LENGTH OUT_EDGES OUT_DEGREE) + while (OUT_DEGREE GREATER 0) + # Pull off the first outgoing edge + list(GET OUT_EDGES 0 TARGET) + list(REMOVE_AT OUT_EDGES 0) + + if (NOT FOUND_${TARGET}) + # We have not seen the target before, so we will traverse + # its outgoing edges before coming back to our + # source. This is the key to the depth-first traversal. + + # We've now seen this vertex + set(FOUND_${TARGET} TRUE) + + # Push the remaining edges for the current vertex onto the + # stack + string(REPLACE ";" " " NEW_ELEMENT + "${SOURCE};${OUT_EDGES}") + list(APPEND STACK ${NEW_ELEMENT}) + + # Setup the new source and outgoing edges + set(SOURCE ${TARGET}) + set(OUT_EDGES + ${${PREFIX}${SOURCE}${SUFFIX}}) + endif(NOT FOUND_${TARGET}) + + list(LENGTH OUT_EDGES OUT_DEGREE) + endwhile (OUT_DEGREE GREATER 0) + + # We have finished all of the outgoing edges for + # SOURCE; add it to the resulting list. + list(APPEND ${LIST} ${SOURCE}) + + # Check the length of the stack + list(LENGTH STACK STACK_LENGTH) + endwhile(STACK_LENGTH GREATER 0) + endif (NOT FOUND_${VERTEX}) + endforeach(VERTEX) + + set(${LIST} ${${LIST}} PARENT_SCOPE) +endfunction(topological_sort) |