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#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
typedef void (*toes_func)(void);
void even_toes(void) {
printf("with even-toed hoofs");
}
void odd_toes(void) {
printf("with odd-toed hoofs");
}
/* Assume this function has the address 0x4012ce */
void shellcode(void) {
printf("Uh-oh, this looks like some sort of attack\n");
exit(42);
}
struct herbivore {
struct herbivore *next;
toes_func func;
};
struct herbivore *herbivore_list = 0;
struct carnivore {
struct carnivore *next;
long num_teeth;
};
struct carnivore *carnivore_list = 0;
#define NUM_ANIMALS 256
/* Initialized to all null pointers */
void *animals_by_num[NUM_ANIMALS];
void new_herbivore(long x) {
int loc = x & (NUM_ANIMALS - 1);
struct herbivore *hp = malloc(sizeof(struct herbivore));
printf("Allocating herbivore at %p\n", hp);
if (!hp)
exit(1);
if (x & 1)
hp->func = odd_toes;
else
hp->func = even_toes;
hp->next = herbivore_list;
herbivore_list = hp;
animals_by_num[loc] = hp;
}
void new_carnivore(long x) {
int loc = x & (NUM_ANIMALS - 1);
struct carnivore *cp = malloc(sizeof(struct carnivore));
printf("Allocating carnivore at %p\n", cp);
if (!cp)
exit(1);
cp->num_teeth = x;
cp->next = carnivore_list;
carnivore_list = cp;
animals_by_num[loc] = cp;
}
void release_animal(long x) {
int loc = x & (NUM_ANIMALS - 1);
if (!animals_by_num[loc]) {
fprintf(stderr, "Attempt to release non-existant animal\n");
exit(1);
}
free(animals_by_num[loc]);
animals_by_num[loc] = 0;
}
void list_animals(void) {
struct herbivore *hp;
struct carnivore *cp;
for (hp = herbivore_list; hp; hp = hp->next) {
printf("A herbivore ");
(hp->func)();
printf("\n");
}
for (cp = carnivore_list; cp; cp = cp->next) {
printf("A carnivore with %ld teeth\n", cp->num_teeth);
}
}
void syntax_error(void) {
fprintf(stderr, "Unrecognized syntax\n");
exit(1);
}
int main(int argc, char **argv) {
for (;;) {
int c = getchar();
long x;
while (isspace(c))
c = getchar();
if (c == EOF)
return 0;
switch (c) {
case 'h':
if (scanf(" %li", &x) != 1)
syntax_error();
new_herbivore(x);
break;
case 'c':
if (scanf(" %li", &x) != 1)
syntax_error();
new_carnivore(x);
break;
case 'r':
if (scanf(" %li", &x) != 1)
syntax_error();
release_animal(x);
break;
case 'l':
list_animals();
break;
case 'q':
return 0;
break;
default:
fprintf(stderr, "Unrecognized command %c\n", c);
exit(1);
}
}
}
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