c-program-strings-Program a-la strings

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>

int free_data(char **data, int size) {
  for (int i = 0; i < size; ++i) {
    free(data[i]);
  }
  free(data);
  return 0;
}

int isquote(int c) {
  return ((c < 32 && c != '\t') || c > 126);
}

int IsBadData(char *pointer) {
  if (pointer == NULL) {
    perror("Bad alloc");
    free(pointer);
    return 1;
  }
  return 0;
}

int AddMemory(char *data, int *cap, int size) {
  if (*cap == size) {
    *cap *= 2;
    data = (char*)realloc(data, *cap);
    return IsBadData(data);
  }
  return 0;
}

int strings(FILE * input) {
  size_t capasity = 1 << 17;
  char **data = (char**)calloc(capasity, sizeof(char*));
  if (data == NULL) {
    perror("Allocation error");
    free_data(data, 0);
    return 1;
  }

  int data_size = 0;
  int size = 4; // size of current word
  int cap;  // capasity of memory, that alloc for current word
  int c;    // current char
  int prev_c = 1; // previous char
  while ((c = fgetc(input)) != EOF) {
    if (isquote(prev_c) && !isquote(c)) {
      if (size < 4) {
        free(data[data_size - 1]);
      }
      else {
        if (data_size > 0) {
          if (AddMemory(data[data_size - 1], &cap, size)) {
            free_data(data, data_size);
            return 0;
          }
          data[data_size - 1][size++] = '\0';
        }
        ++data_size;
      }
      data[data_size - 1] = (char*)malloc(sizeof(char) * 4);
      if (IsBadData(data[data_size - 1])) {
        free_data(data, data_size);
        return 0;
      }
      cap = 4;
      size = 0;
      data[data_size - 1][size++] = c;
    }
    else if (!isquote(prev_c) && !isquote(c)) {
      if (AddMemory(data[data_size - 1], &cap, size)) {
        free_data(data, data_size);
        return 0;
      }
      data[data_size - 1][size++] = c;
    }
    prev_c = c;
  }
  if (size < 4) {
    free(data[data_size - 1]);
    --data_size;
  }
  else if (data_size > 0) {
    if (AddMemory(data[data_size - 1], &cap, size)) {
      free_data(data, data_size);
      return 0;
    }
    data[data_size - 1][size++] = '\0';
  }

  for (int i = 0; i < data_size; ++i) {
    printf("%s\n", data[i]);
  }

  free_data(data, data_size);
  return 0;
}

int main(int argc, char **argv) {
  if (argc == 1) {
    strings(stdin);
  }
  else {
    for (int i = 1; i < argc; ++i) {
      FILE *fin = fopen(argv[i], "r");
      if (fin != NULL) {
        strings(fin);
        fclose(fin);
      }
      else {
        perror("Invalid file");
      }
    }
  }
}