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#include <stdint.h>
#include <assert.h>
#include <memory.h>
#include <stdio.h>
#include "runtime.h"
struct node_base* alloc_node() {
struct node_base* new_node = malloc(sizeof(struct node_app));
new_node->gc_next = NULL;
new_node->gc_reachable = 0;
assert(new_node != NULL);
return new_node;
}
struct node_app* alloc_app(struct node_base* l, struct node_base* r) {
struct node_app* node = (struct node_app*) alloc_node();
node->base.tag = NODE_APP;
node->left = l;
node->right = r;
return node;
}
struct node_num* alloc_num(int32_t n) {
struct node_num* node = (struct node_num*) alloc_node();
node->base.tag = NODE_NUM;
node->value = n;
return node;
}
struct node_global* alloc_global(void (*f)(struct gmachine*), int32_t a) {
struct node_global* node = (struct node_global*) alloc_node();
node->base.tag = NODE_GLOBAL;
node->arity = a;
node->function = f;
return node;
}
struct node_ind* alloc_ind(struct node_base* n) {
struct node_ind* node = (struct node_ind*) alloc_node();
node->base.tag = NODE_IND;
node->next = n;
return node;
}
void free_node_direct(struct node_base* n) {
if(n->tag == NODE_DATA) {
free(((struct node_data*) n)->array);
}
}
void gc_visit_node(struct node_base* n) {
if(n->gc_reachable) return;
n->gc_reachable = 1;
if(n->tag == NODE_APP) {
struct node_app* app = (struct node_app*) n;
gc_visit_node(app->left);
gc_visit_node(app->right);
} if(n->tag == NODE_IND) {
struct node_ind* ind = (struct node_ind*) n;
gc_visit_node(ind->next);
} if(n->tag == NODE_DATA) {
struct node_data* data = (struct node_data*) n;
struct node_base** to_visit = data->array;
while(*to_visit) {
gc_visit_node(*to_visit);
to_visit++;
}
}
}
void stack_init(struct stack* s) {
s->size = 4;
s->count = 0;
s->data = malloc(sizeof(*s->data) * s->size);
assert(s->data != NULL);
}
void stack_free(struct stack* s) {
free(s->data);
}
void stack_push(struct stack* s, struct node_base* n) {
while(s->count >= s->size) {
s->data = realloc(s->data, sizeof(*s->data) * (s->size *= 2));
assert(s->data != NULL);
}
s->data[s->count++] = n;
}
struct node_base* stack_pop(struct stack* s) {
assert(s->count > 0);
return s->data[--s->count];
}
struct node_base* stack_peek(struct stack* s, size_t o) {
assert(s->count > o);
return s->data[s->count - o - 1];
}
void stack_popn(struct stack* s, size_t n) {
assert(s->count >= n);
s->count -= n;
}
void gmachine_init(struct gmachine* g) {
stack_init(&g->stack);
g->gc_nodes = NULL;
g->gc_node_count = 0;
g->gc_node_threshold = 128;
}
void gmachine_free(struct gmachine* g) {
stack_free(&g->stack);
struct node_base* to_free = g->gc_nodes;
struct node_base* next;
while(to_free) {
next = to_free->gc_next;
free_node_direct(to_free);
free(to_free);
to_free = next;
}
}
void gmachine_slide(struct gmachine* g, size_t n) {
assert(g->stack.count > n);
g->stack.data[g->stack.count - n - 1] = g->stack.data[g->stack.count - 1];
g->stack.count -= n;
}
void gmachine_update(struct gmachine* g, size_t o) {
assert(g->stack.count > o + 1);
struct node_ind* ind =
(struct node_ind*) g->stack.data[g->stack.count - o - 2];
ind->base.tag = NODE_IND;
ind->next = g->stack.data[g->stack.count -= 1];
}
void gmachine_alloc(struct gmachine* g, size_t o) {
while(o--) {
stack_push(&g->stack,
gmachine_track(g, (struct node_base*) alloc_ind(NULL)));
}
}
void gmachine_pack(struct gmachine* g, size_t n, int8_t t) {
assert(g->stack.count >= n);
struct node_base** data = malloc(sizeof(*data) * (n + 1));
assert(data != NULL);
memcpy(data, &g->stack.data[g->stack.count - n], n * sizeof(*data));
data[n] = NULL;
struct node_data* new_node = (struct node_data*) alloc_node();
new_node->array = data;
new_node->base.tag = NODE_DATA;
new_node->tag = t;
stack_popn(&g->stack, n);
stack_push(&g->stack, gmachine_track(g, (struct node_base*) new_node));
}
void gmachine_split(struct gmachine* g, size_t n) {
struct node_data* node = (struct node_data*) stack_pop(&g->stack);
for(size_t i = 0; i < n; i++) {
stack_push(&g->stack, node->array[i]);
}
}
struct node_base* gmachine_track(struct gmachine* g, struct node_base* b) {
g->gc_node_count++;
b->gc_next = g->gc_nodes;
g->gc_nodes = b;
if(g->gc_node_count >= g->gc_node_threshold) {
uint64_t nodes_before = g->gc_node_count;
gc_visit_node(b);
gmachine_gc(g);
g->gc_node_threshold = g->gc_node_count * 2;
}
return b;
}
void gmachine_gc(struct gmachine* g) {
for(size_t i = 0; i < g->stack.count; i++) {
gc_visit_node(g->stack.data[i]);
}
struct node_base** head_ptr = &g->gc_nodes;
while(*head_ptr) {
if((*head_ptr)->gc_reachable) {
(*head_ptr)->gc_reachable = 0;
head_ptr = &(*head_ptr)->gc_next;
} else {
struct node_base* to_free = *head_ptr;
*head_ptr = to_free->gc_next;
free_node_direct(to_free);
free(to_free);
g->gc_node_count--;
}
}
}
void unwind(struct gmachine* g) {
struct stack* s = &g->stack;
while(1) {
struct node_base* peek = stack_peek(s, 0);
if(peek->tag == NODE_APP) {
struct node_app* n = (struct node_app*) peek;
stack_push(s, n->left);
} else if(peek->tag == NODE_GLOBAL) {
struct node_global* n = (struct node_global*) peek;
assert(s->count > n->arity);
for(size_t i = 1; i <= n->arity; i++) {
s->data[s->count - i]
= ((struct node_app*) s->data[s->count - i - 1])->right;
}
n->function(g);
} else if(peek->tag == NODE_IND) {
struct node_ind* n = (struct node_ind*) peek;
stack_pop(s);
stack_push(s, n->next);
} else {
break;
}
}
}
extern void f_main(struct gmachine* s);
void print_node(struct node_base* n) {
if(n->tag == NODE_APP) {
struct node_app* app = (struct node_app*) n;
print_node(app->left);
putchar(' ');
print_node(app->right);
} else if(n->tag == NODE_DATA) {
printf("(Packed)");
} else if(n->tag == NODE_GLOBAL) {
struct node_global* global = (struct node_global*) n;
printf("(Global: %p)", global->function);
} else if(n->tag == NODE_IND) {
print_node(((struct node_ind*) n)->next);
} else if(n->tag == NODE_NUM) {
struct node_num* num = (struct node_num*) n;
printf("%d", num->value);
}
}
int main(int argc, char** argv) {
struct gmachine gmachine;
struct node_global* first_node = alloc_global(f_main, 0);
struct node_base* result;
gmachine_init(&gmachine);
gmachine_track(&gmachine, (struct node_base*) first_node);
stack_push(&gmachine.stack, (struct node_base*) first_node);
unwind(&gmachine);
result = stack_pop(&gmachine.stack);
printf("Result: ");
print_node(result);
putchar('\n');
gmachine_free(&gmachine);
}