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1 office 1 /**
2 * @file backtrack.c
3 * @author Ambroz Bizjak <ambrop7@gmail.com>
4 *
5 * @section LICENSE
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the author nor the
15 * names of its contributors may be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * @section DESCRIPTION
30 *
31 * Synopsis:
32 * backtrack_point()
33 * backtrack_point::go()
34 * backtrack_point::rgo()
35 *
36 * Description:
37 * The backtrack_point() statement creates a backtrack point, going up immedietely.
38 * The go() method triggers backtracking to the backtrack point, i.e. makes the
39 * backtrack_point() statement go down and back up at atomically. The go() method
40 * itself goes up immedietely, but side effects of triggering backtracking have
41 * priority.
42 * The rgo() method triggers backtracking when it deinitializes. In this case,
43 * the immediate effects of triggering backtracking in the backtrack_point() have
44 * priority over the immediate effects of rgo() deinitialization completion.
45 */
46  
47 #include <ncd/module_common.h>
48  
49 #include <generated/blog_channel_ncd_backtrack.h>
50  
51 struct rgo_instance {
52 NCDModuleInst *i;
53 NCDModuleRef bp_ref;
54 };
55  
56 static void func_new (void *unused, NCDModuleInst *i, const struct NCDModuleInst_new_params *params)
57 {
58 // check arguments
59 if (!NCDVal_ListRead(params->args, 0)) {
60 ModuleLog(i, BLOG_ERROR, "wrong arity");
61 goto fail0;
62 }
63  
64 // go up
65 NCDModuleInst_Backend_Up(i);
66 return;
67  
68 fail0:
69 NCDModuleInst_Backend_DeadError(i);
70 }
71  
72 static void go_func_new (void *unused, NCDModuleInst *i, const struct NCDModuleInst_new_params *params)
73 {
74 // check arguments
75 if (!NCDVal_ListRead(params->args, 0)) {
76 ModuleLog(i, BLOG_ERROR, "wrong arity");
77 goto fail0;
78 }
79  
80 // get backtrack point
81 NCDModuleInst *backtrack_point_inst = params->method_user;
82  
83 // go up (after toggling)
84 NCDModuleInst_Backend_Up(i);
85  
86 // toggle backtrack point
87 NCDModuleInst_Backend_DownUp(backtrack_point_inst);
88 return;
89  
90 fail0:
91 NCDModuleInst_Backend_DeadError(i);
92 }
93  
94 static void rgo_func_new (void *vo, NCDModuleInst *i, const struct NCDModuleInst_new_params *params)
95 {
96 struct rgo_instance *o = vo;
97 o->i = i;
98  
99 // check arguments
100 if (!NCDVal_ListRead(params->args, 0)) {
101 ModuleLog(i, BLOG_ERROR, "wrong arity");
102 goto fail0;
103 }
104  
105 // get backtrack point
106 NCDModuleInst *backtrack_point_inst = params->method_user;
107  
108 // init object reference to the backtrack_point
109 NCDModuleRef_Init(&o->bp_ref, backtrack_point_inst);
110  
111 // go up
112 NCDModuleInst_Backend_Up(i);
113 return;
114  
115 fail0:
116 NCDModuleInst_Backend_DeadError(i);
117 }
118  
119 static void rgo_func_die (void *vo)
120 {
121 struct rgo_instance *o = vo;
122  
123 // deref backtrack_point
124 NCDModuleInst *backtrack_point_inst = NCDModuleRef_Deref(&o->bp_ref);
125  
126 // free object reference
127 NCDModuleRef_Free(&o->bp_ref);
128  
129 // die
130 NCDModuleInst_Backend_Dead(o->i);
131  
132 // toggle backtrack_point
133 if (backtrack_point_inst) {
134 NCDModuleInst_Backend_DownUp(backtrack_point_inst);
135 }
136 }
137  
138 static struct NCDModule modules[] = {
139 {
140 .type = "backtrack_point",
141 .func_new2 = func_new
142 }, {
143 .type = "backtrack_point::go",
144 .func_new2 = go_func_new
145 }, {
146 .type = "backtrack_point::rgo",
147 .func_new2 = rgo_func_new,
148 .func_die = rgo_func_die,
149 .alloc_size = sizeof(struct rgo_instance)
150 }, {
151 .type = NULL
152 }
153 };
154  
155 const struct NCDModuleGroup ncdmodule_backtrack = {
156 .modules = modules
157 };