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graph.c
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graph.c
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#include <assert.h>
#include <stdio.h>
#include "graph.h"
#include "list.h"
#include "string.h"
#include "xmalloc.h"
struct graph {
/* List of all of the nodes in the graph */
struct list *nodes;
/*
* List of nodes that need to be updated and
* all of their dependencies have been resolved.
*/
struct list *ready_nodes;
};
struct graph_node {
struct string *name;
struct list *commands;
struct list *dependencies;
struct list *dependents;
/*
* If the dependency occurs multiple time in the makefile, it will be
* multiple times in this list. This is used exclusively for the
* $^ automatic variable.
*/
struct list *repeated_dependencies;
/* File modification time */
struct my_timespec time;
/* Non-zero if the user specified this node as the target to be built */
int target;
/* For internal usage only by the DFS algorithm */
int visit;
int needs_update;
int exists;
int resolved;
size_t unresolved_dependencies;
};
struct graph *graph_init() {
struct graph *graph = xmalloc(sizeof (*graph));
graph->nodes = list_init();
graph->ready_nodes = list_init();
return (graph);
}
void graph_destroy(struct graph *graph) {
struct list_item *item = list_head(graph->nodes);
while (item != NULL) {
struct graph_node *node = list_get_data(item);
graph_node_destroy(node);
item = list_next(item);
}
list_destroy(graph->nodes);
list_destroy(graph->ready_nodes);
free(graph);
}
void graph_add_node(struct graph *graph, struct graph_node *node) {
list_push_back(graph->nodes, node);
list_push_back(graph->ready_nodes, node);
}
struct list *graph_get_nodes(struct graph *graph) {
return (graph->nodes);
}
struct graph_node *graph_get_node_by_name(
struct graph *graph,
const struct string *name) {
struct list_item *item = list_head(graph->nodes);
while (item) {
struct graph_node *node = list_get_data(item);
if (string_equal(name, node->name)) {
return (node);
}
item = list_next(item);
}
return (NULL);
}
int graph_node_is_newer(
const struct graph_node *n1,
const struct graph_node *n2) {
if (n1->needs_update || !n2->exists) {
return (1);
}
if (n1->time.sec != n2->time.sec) {
return (n1->time.sec > n2->time.sec);
}
return (n1->time.nsec > n2->time.nsec);
}
void graph_add_dependency(
struct graph *graph,
struct graph_node *dependent,
struct graph_node *dependency) {
list_push_back(dependent->repeated_dependencies, dependency);
if (list_find(dependent->dependencies, dependency) != NULL) {
return;
}
if (!dependency->resolved) {
if (dependent->unresolved_dependencies == 0 &&
!dependent->resolved) {
struct list_item *item;
item = list_find(graph->ready_nodes, dependent);
assert(item != NULL);
list_remove(graph->ready_nodes, item);
}
++dependent->unresolved_dependencies;
}
list_push_back(dependent->dependencies, dependency);
list_push_back(dependency->dependents, dependent);
}
static void propagate_needs_update(struct graph_node *node) {
struct list_item *item;
if (!node->exists) {
node->needs_update = 1;
return;
}
item = list_head(node->dependencies);
while (item != NULL) {
struct graph_node *dependency = list_get_data(item);
if (graph_node_is_newer(dependency, node)) {
node->needs_update = 1;
break;
}
item = list_next(item);
}
}
static int dfs(struct list *stack) {
while (!list_empty(stack)) {
struct graph_node *node;
struct list_item *item;
node = list_front(stack);
if (node->visit == 0) {
/* entering node */
node->visit = 1;
item = list_head(node->dependencies);
while (item) {
struct graph_node *dependency;
dependency = list_get_data(item);
if (dependency->visit == 0) {
list_push_front(stack, dependency);
} else if (dependency->visit == 1) {
const char *name;
name = string_get_cstr(node->name);
fprintf(stderr, "Dependency graph "
"contains a cycle "
"containing node "
"\"%s\"\n", name);
return (-1);
} else {
assert(dependency->visit == 2);
}
item = list_next(item);
}
} else if (node->visit == 1) {
/* leaving node */
node->visit = 2;
list_pop_front(stack);
propagate_needs_update(node);
} else {
/* node already processed */
assert(node->visit == 2);
list_pop_front(stack);
}
}
return (0);
}
int graph_process(struct graph *graph) {
struct list_item *item;
struct list *stack;
item = list_head(graph->nodes);
while (item) {
struct graph_node *node = list_get_data(item);
node->visit = 0;
item = list_next(item);
}
stack = list_init();
item = list_head(graph->nodes);
while (item) {
struct graph_node *node = list_get_data(item);
assert(node->visit == 0 || node->visit == 2);
if (node->target && !node->visit) {
/* Find all nodes this target depends on */
list_push_front(stack, node);
if (dfs(stack)) {
/* If you find a dependency cycle, abort */
list_destroy(stack);
return (-1);
}
}
assert(list_empty(stack));
item = list_next(item);
}
list_destroy(stack);
item = list_head(graph->nodes);
while (item) {
struct graph_node *node = list_get_data(item);
item = list_next(item);
if (node->visit) {
/*
* Check that we know how to built
* all the nodes we need
*/
if (node->needs_update && list_empty(node->commands) &&
list_empty(node->dependencies)) {
fprintf(stderr, "No rule to make \"%s\"\n",
string_get_cstr(node->name));
return (-1);
}
} else {
/* Mark nodes that we don't need as resolved. */
graph_node_mark_resolved(graph, node);
}
}
return (0);
}
struct graph_node *graph_get_ready_node(struct graph *graph) {
struct list_item *item;
struct graph_node *node;
item = list_head(graph->ready_nodes);
if (item == NULL) {
return (NULL);
}
node = list_get_data(item);
list_remove(graph->ready_nodes, item);
return (node);
}
struct graph_node *graph_node_init(const struct string *name) {
struct graph_node *node = xmalloc(sizeof (*node));
node->name = string_init_copy(name);
node->commands = list_init();
node->dependencies = list_init();
node->dependents = list_init();
node->repeated_dependencies = list_init();
node->time.sec = 0;
node->time.nsec = 0;
node->target = 0;
node->visit = 0;
node->needs_update = 0;
node->exists = 0;
node->resolved = 0;
node->unresolved_dependencies = 0;
return (node);
}
void graph_node_destroy(struct graph_node *node) {
struct list_item *item = list_head(node->commands);
while (item != NULL) {
struct string *command = list_get_data(item);
string_destroy(command);
item = list_next(item);
}
string_destroy(node->name);
list_destroy(node->commands);
list_destroy(node->dependencies);
list_destroy(node->dependents);
list_destroy(node->repeated_dependencies);
free(node);
}
const struct string *graph_node_get_name(const struct graph_node *node) {
return (node->name);
}
void graph_node_set_time(
struct graph_node *node,
const struct my_timespec *time) {
node->time.sec = time->sec;
node->time.nsec = time->nsec;
node->exists = 1;
}
void graph_node_mark_target(struct graph_node *node) {
node->target = 1;
}
void graph_node_mark_resolved(struct graph *graph, struct graph_node *node) {
struct list_item *item;
if (node->resolved) {
return;
}
node->resolved = 1;
item = list_find(graph->ready_nodes, node);
if (item != NULL) {
list_remove(graph->ready_nodes, item);
}
item = list_head(node->dependents);
while (item != NULL) {
struct graph_node *dependent = list_get_data(item);
assert(dependent->unresolved_dependencies > 0);
--dependent->unresolved_dependencies;
if (dependent->unresolved_dependencies == 0 &&
!dependent->resolved) {
list_push_back(graph->ready_nodes, dependent);
}
item = list_next(item);
}
}
void graph_node_add_command(
struct graph_node *node,
const struct string *command) {
struct string *command_copy = string_init_copy(command);
list_push_back(node->commands, command_copy);
}
int graph_node_needs_update(const struct graph_node *node) {
return (node->needs_update);
}
int graph_node_exists(const struct graph_node *node) {
return (node->exists);
}
struct list *graph_node_get_commands(const struct graph_node *node) {
return (node->commands);
}
struct list *graph_node_get_dependencies(const struct graph_node *node) {
return (node->dependencies);
}
struct list *graph_node_get_repeated_dependencies(
const struct graph_node *node) {
return (node->repeated_dependencies);
}