1 files changed, 144 insertions, 0 deletions
diff --git a/modules/order.c b/modules/order.c
new file mode 100644
index 0000000..d77943a
--- /dev/null
+++ b/modules/order.c
@@ -0,0 +1,144 @@
+/* Copyright Vladimir Prus 2004. Distributed under the Boost */
+/* Software License, Version 1.0. (See accompanying */
+/* file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) */
+
+#include "../native.h"
+#include "../lists.h"
+#include "../strings.h"
+#include "../newstr.h"
+#include "../variable.h"
+
+
+/* Use quite klugy approach: when we add order dependency from 'a' to 'b',
+   just append 'b' to of value of variable 'a'.
+*/
+LIST *add_pair( PARSE *parse, FRAME *frame )
+{
+    LIST* arg = lol_get( frame->args, 0 );    
+
+    var_set(arg->string, list_copy(0, arg->next), VAR_APPEND);
+
+    return L0;
+}
+
+/** Given a list and a value, returns position of that value in
+    the list, or -1 if not found.
+*/
+int list_index(LIST* list, const char* value)
+{
+    int result = 0;
+    for(; list; list = list->next, ++result) {
+        if (strcmp(list->string, value) == 0)
+            return result;
+    }
+    return -1;
+}
+
+enum colors { white, gray, black };
+
+/* Main routite of topological sort. Calls itself recursively on all
+   adjacent vertices which were not yet visited. After that, 'current_vertex'
+   is added to '*result_ptr'.
+*/
+void do_ts(int** graph, int current_vertex, int* colors, int** result_ptr)
+{
+    int i;
+
+    colors[current_vertex] = gray;
+    for(i = 0; graph[current_vertex][i] != -1; ++i) {
+        int adjacent_vertex = graph[current_vertex][i];
+
+        if (colors[adjacent_vertex] == white)
+            do_ts(graph, adjacent_vertex, colors, result_ptr);
+        /* The vertex is either black, in which case we don't have to do
+           anything, a gray, in which case we have a loop. If we have a loop,
+           it's not clear what useful diagnostic we can emit, so we emit
+           nothing.  */
+    }
+    colors[current_vertex] = black;
+    **result_ptr = current_vertex;    
+    (*result_ptr)++;
+}
+
+void topological_sort(int** graph, int num_vertices, int* result)
+{
+    int i;
+    int* colors = (int*)BJAM_CALLOC(num_vertices, sizeof(int));
+    for (i = 0; i < num_vertices; ++i)
+        colors[i] = white;
+
+    for(i = 0; i < num_vertices; ++i)
+        if (colors[i] == white)
+            do_ts(graph, i, colors, &result);
+
+    BJAM_FREE(colors);
+}
+
+LIST *order( PARSE *parse, FRAME *frame )
+{
+    LIST* arg = lol_get( frame->args, 0 );  
+    LIST* tmp;
+    LIST* result = 0;
+    int src;
+
+    /* We need to create a graph of order dependencies between
+       the passed objects. We assume that there are no duplicates
+       passed to 'add_pair'.
+    */
+    int length = list_length(arg);
+    int** graph = (int**)BJAM_CALLOC(length, sizeof(int*));
+    int* order = (int*)BJAM_MALLOC((length+1)*sizeof(int));
+   
+    for(tmp = arg, src = 0; tmp; tmp = tmp->next, ++src) {
+        /* For all object this one depend upon, add elements
+           to 'graph' */
+        LIST* dependencies = var_get(tmp->string);
+        int index = 0;
+
+        graph[src] = (int*)BJAM_CALLOC(list_length(dependencies)+1, sizeof(int));
+        for(; dependencies; dependencies = dependencies->next) {          
+            int dst = list_index(arg, dependencies->string);
+            if (dst != -1)
+                graph[src][index++] = dst;
+        }
+        graph[src][index] = -1;               
+    }
+
+    topological_sort(graph, length, order);
+
+    {
+        int index = length-1;
+        for(; index >= 0; --index) {
+            int i;
+            tmp = arg;
+            for (i = 0; i < order[index]; ++i, tmp = tmp->next);
+            result = list_new(result, tmp->string);
+        }
+    }
+
+    /* Clean up */
+    {
+        int i;
+        for(i = 0; i < length; ++i)
+            BJAM_FREE(graph[i]);
+        BJAM_FREE(graph);
+        BJAM_FREE(order);
+    }
+
+    return result;
+}
+
+void init_order()
+{
+    {
+        char* args[] = { "first", "second", 0 };
+        declare_native_rule("class@order", "add-pair", args, add_pair, 1);
+    }
+
+    {
+        char* args[] = { "objects", "*", 0 };
+        declare_native_rule("class@order", "order", args, order, 1);
+    }
+
+
+}