#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>

// begin C++ pain
#include <queue>

using namespace std;

#define A(inst) ((inst >> 0x6) & 0x7)
#define B(inst) ((inst >> 0x3) & 0x7)
#define C(inst) (inst & 0x7)
#define A13(inst) ((inst >> 25) & 0x7)
#define DATA(inst) (inst & 0x1ffffff)
#define OP(inst) (inst >> 28)
#define REG(num) (registers[num])
#define REGA(inst) (REG(A(inst)))
#define REGB(inst) (REG(B(inst)))
#define REGC(inst) (REG(C(inst)))
#define REGA13(inst) (REG(A13(inst)))

#define MEMSIZ (1024 * 1024 * 32)

typedef unsigned int platter;

platter registers[8] = {0,0,0,0,0,0,0,0};
platter * arrays[MEMSIZ];
size_t siz_arrays[MEMSIZ];
size_t num_array = 1;
platter finger = 0;
int last_free = 0;

int main(int argc, char *argv[]) {
    int lastloc = 0, i;
    platter cur;
    platter * temp;
    struct stat x;
    queue<int> free_list;

    stat(argv[1], &x);
    
    temp = (platter *) mmap(NULL, x.st_size,
                                PROT_READ | PROT_WRITE, MAP_PRIVATE,
                                open(argv[1], O_RDONLY, 0600), (off_t) 0);
    arrays[0] = (platter *) malloc(x.st_size);
    memcpy(arrays[0], temp, x.st_size);
    munmap(temp, x.st_size);

    siz_arrays[0] = x.st_size;
    
    while(1) {
        cur = htonl(arrays[0][finger++]);

        switch(OP(cur)) {
            // condmove
            case 0:
                if (REGC(cur) != 0) {
                    REGA(cur) = REGB(cur);
                }
                break;
            //  index
            case 1:
                REGA(cur) = arrays[REGB(cur)][REGC(cur)];
                break;
            //  amend
            case 2:
        assert(arrays[REGA(cur)] != 0);
                arrays[REGA(cur)][REGB(cur)] = REGC(cur);
                break;
            //  add
            case 3:
                REGA(cur) = REGB(cur) + REGC(cur);
                break;
            //  mult
            case 4:
                REGA(cur) = REGB(cur) * REGC(cur);
                break;
            //  div
            case 5:
                REGA(cur) = REGB(cur) / REGC(cur);
                break;
            //  not_and
            case 6:
                REGA(cur) = ~ (REGB(cur) & REGC(cur));
                break;

            //  halt
            case 7:
                exit(0);
                break;

            //  alloc
            case 8:
                // try and pop a location off the stack, otherwise start counting up
                if (!free_list.empty()) {
                    i = free_list.front();
                    free_list.pop();
                }   else { 
                    for (i = lastloc+1; 
                            arrays[i] != NULL && i != lastloc; 
                            i = (i + 1) % MEMSIZ) ;
                }
              // this tracks the last insertion instead
              /* for (i = last_free; 
                        arrays[i] != NULL && i != last_free-1; 
                        i = (i + 1) % MEMSIZ) ; */
                        
              // this version walks forward in the array                        
                /* for (i = lastloc+1; 
                        arrays[i] != NULL && i != lastloc; 
                        i = (i + 1) % MEMSIZ) ; */
                //assert(i != lastloc);
        //assert(i != last_free-1);
        
        // move last_free somewhere random, for fun
        //last_free = rand() % MEMSIZ;

                lastloc = i;
                arrays[i] = (platter *) calloc(REGC(cur), sizeof(platter));
                siz_arrays[i] = REGC(cur);
                REGB(cur) = i;
                break;
            //  abandon
            case 9:
                free(arrays[REGC(cur)]);
                arrays[REGC(cur)] = 0;
                //last_free = REGC(cur);
                free_list.push(REGC(cur));
                break;
            //  out
            case 10:
                if (REGC(cur) < 256) {
                    putchar(REGC(cur));
                    fflush(stdout);
                }
                break;
            //  in
            case 11:
                REGC(cur) = getchar();
                break;
            //  load
            case 12:
                if (REGB(cur) != 0) {
                    free(arrays[0]);
                    arrays[0] = (platter *) calloc(siz_arrays[REGB(cur)], sizeof(platter));
                    assert(arrays[0] != 0);
                    assert(arrays[REGB(cur)] != 0);
                    memcpy(arrays[0], arrays[REGB(cur)], 
                            siz_arrays[REGB(cur)] * sizeof(platter));
                    siz_arrays[0] = siz_arrays[REGB(cur)];
                }
                finger = REGC(cur);
                break;
            //  data
            case 13:
                REGA13(cur) = DATA(cur);
                break;
            default:
                fprintf(stderr, "Died!\n");
                exit(1);
        }
    }
}