#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFS 256
#define NAMS 200

void rstr(char* str, int len) {
  int i;
  static char alf[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  for (i=0; i<len; i++) str[i] = alf[rand() % 26];
  str[len] = '\0';
}

int startswith(char* x, char* y) {
  int i, n = strlen(y);
  for (i=0; i<n; i++) {
    if (x[i] != y[i]) return 0;
  }
  return 1;
}

void strcpyn(char* dest, char* src, int n) {
  int i;
  for (i=0; i<n; i++) dest[i] = src[i];
  dest[n] = '\0';
}

int main(int argc, char** argv) {
  FILE *f, *xf;
  int i, n;
  char sname[BUFS], city[BUFS], line[BUFS], buf[BUFS];
  if (argc == 1) {
    printf("options: create NREC | all | idx [ seek ]\n");
    return 0;
  }
  if (argc > 2 && !strcmp(argv[1], "create")) {
    n = atoi(argv[2]);
    f = fopen("tmp.dbd", "w");
    xf = fopen("tmp.dbi", "wb");
    for (i=0; i<n; i++) {
      rstr(sname, NAMS);
      rstr(city, 3);
      fprintf(f, "%s%8d%s\n", sname, i, city);
      fwrite(sname, 1, 4, xf);
      fwrite(&i, 4, 1, xf);
    }
    fclose(f);
    fclose(xf);
  } else if (argc > 1 && !strcmp(argv[1], "all")) {
    f = fopen("tmp.dbd", "r");
    while (fgets(line, BUFS, f) != NULL) {
      if (startswith(line, "ABCD")) printf("%s", line);
    }
  } else if (argc > 1 && !strcmp(argv[1], "idx")) {
    f = fopen("tmp.dbd", "r");
    xf = fopen("tmp.dbi", "rb");
    while (fread(buf, 1, 4, xf) > 0) {
      fread(&i, 4, 1, xf);
      buf[4] = '\0';
      if (startswith(buf, "ABCD")) {
        printf("%s %d\n", buf, i); 
        if (argc > 2 && !strcmp(argv[2], "seek")) {
          fseek(f, (long)i*(NAMS+8+3+1), SEEK_SET);
          fgets(buf, BUFS, f);
          printf("%s", buf);
        }
      }
    }
  }
}