house/phase2/tome_utils.c

#include "tome_utils.h"

#define strlen invalid // make sure that the built-in strlen is not used

#ifndef BUFFER_SIZE    // If the GCC compiler does not define any value
#define BUFFER_SIZE 40 // Give it a default one (lines)
#endif                 // This should make clangd shut up about it

#ifndef DEBUG
#define DEBUG FALSE
#endif

// INFO: THINGS TO KEEP IN MIND:
// printf is not used in this challenge, by default it's not being used unless
// it's for debugging for simplicity sake.

/*
 * @info This is a simple implementation of the strlen function
 *
 * @brief Returns the length of a string
 * @param str The string to measure
 * @return The length of the string
 * @error Returns 0 if str is NULL
 */
int strlen(const char *str) {
  if (str == NULL) {
    return 0;
  }
  int i = 0;
  while (str[i] != '\0') {
    i++;
  }
  return i;
}

/*
 * @info crude and basic implementation of "print"
 *
 * @brief Writes a string to STDOUT
 * @param str The string to write
 * @error does nothing if str is NULL
 */
void printer(char *str) {
  if (str == NULL) {
    return;
  }
  write(1, str, strlen(str));
}

/*
 * @info Convenience function to get the file descriptor
 *
 * @brief Returns the file descriptor of a file
 * @param filename The name of the file
 * @param mode The mode to open the file in
 * @return The file descriptor of the file
 * @error Returns -1 if the file cannot be opened
 */
int get_fd(char *filename, int mode) {
  if (filename == NULL)
    return ERR;
  int fd = open(filename, mode);
  if (fd == ERR)
    return ERR;
  return fd;
}

/*
 * @info This function checks if a string contains a newline character
 *
 * @brief Returns TRUE (1) if the string contains a newline character, FALSE (0)
 * otherwise
 * @param str The string to check
 * @error Returns ERR (-1) if str is NULL
 */
int newlineexists(const char *str) {
  if (str == NULL)
    return ERR;
  for (int i = 0; str[i] != '\0'; i++) {
    if (str[i] == '\n') {
      return TRUE;
    }
  }
  return FALSE;
}

/*
 * @info This function concatenates two strings
 *
 * @brief Returns a new string that is the concatenation of str1 and str2
 * @param str1 The first string
 * @param str2 The second string
 * @return The concatenated string
 * @error Returns NULL if str1 or str2 is NULL, or if memory allocation fails
 */
char *concat(char const *str1, char const *str2) {
  char *result;
  int i, j;
  // Sanity check
  if (!str1 || !str2)
    return NULL;
  result = malloc(strlen(str1) + strlen(str2) + 1); // +1 for eof

  if (result == NULL)
    return NULL;
  for (i = 0; str1[i] != '\0'; i++) {
    result[i] = str1[i];
  }
  if (DEBUG)
    printf("[DEBUG]: Concatenating: [%s] + [%s]\n", str1, str2);
  for (j = 0; str2[j] != '\0'; j++, i++) {
    result[i] = str2[j];
  }
  result[i] = '\0';
  return result;
}

/*
 * @info This function reads from a file descriptor and stores the content in a
 * string
 *
 * @brief Reads from a file descriptor and stores the content in a string
 * @param fd The file descriptor to read from
 * @param buf The buffer to store the content
 * @param str The string to store the content
 * @return The string containing the content read from the file descriptor
 * @error Returns NULL if there is an error reading from the file descriptor or
 * if memory allocation fails
 */
char *read_content(int fd, char *buf, char *temp, char *str) {
  int bytes;
  while (TRUE) {
    bytes = read(fd, buf, BUFFER_SIZE);
    if (bytes == ERR) {
      return NULL;
    }
    if (DEBUG)
      printf("[DEBUG]: Bytes gives : [%d]\n", bytes);
    buf[bytes] = '\0';
    if (DEBUG)
      printf("[DEBUG]: Buffer is: [%s]\n", buf);

    if (DEBUG)
      printf("[DEBUG]: read %d bytes: \"%s\"\n", bytes, buf);
    temp = str; // move the temporary data to str
    if (temp == NULL) {
      temp = malloc(sizeof(char));
      if (temp == NULL) {
        return NULL;
      }
      temp[0] = '\0';
    }
    if (DEBUG)
      printf("[DEBUG]:We got a [%s] and [%s]\n", temp, buf);
    str = concat(temp, buf); // concatenate the temporary data with the buffer
    if (DEBUG)
      printf("[DEBUG]:Variable temp: (%s), buf: (%s)\n", temp, buf);
    if (DEBUG)
      printf("[DEBUG]: Concatenated str is: [%s]\n", str);
    free(temp);

    if (newlineexists(str) == TRUE || bytes == 0) {
      break;
    }
  }
  free(buf);
  return str;
}

/*
 * @info This function returns a string up to the first newline character
 *
 * @brief Returns a string up to the first newline character
 * @param str The string to search
 * @return A string up to the first newline character
 * @error Returns NULL if str is NULL or if there is no newline character in the
 * string
 * @details
 * This function allocates memory for the new string, so it is the
 * responsibility of the caller to free it when it is no longer needed.
 */
char *before_nl(const char *str) {
  int i;
  char *ptr = NULL;
  // Sanity check
  if (str == NULL || str[0] == '\0')
    return NULL; // We got nothing or it's already EOF, we don't need this.
  for (i = 0; str[i] != '\n' && str[i] != '\0';
       i++) { // Count up until we reach a newline or EOF
    continue;
  }
  ptr = malloc(
      (i + 1 + 1) *  // The str count plus the newline plus the null terminator
      sizeof(char)); // Dynamically allocate *just enough* space for the str
  if (ptr == NULL) {
    return NULL;
  }
  for (i = 0; str[i] != '\n' && str[i] != '\0'; i++) { // Same thing here.
    ptr[i] = str[i];
  }
  if (str[i] == '\n') {
    ptr[i] = '\n';
    i++;
  }
  ptr[i] = '\0';
  return ptr;
}

/*
 * @info This function returns what's after the first newline character
 *
 * @brief I'm not repeating this ^
 * @param str The string to search
 * @return What's after the first newline character
 * @error Returns NULL if str is NULL, or malloc is going funky
 */
char *after_nl(char *str) {
  int i, j;
  char *ptr;
  if (str == NULL)
    return NULL;
  for (i = 0; str[i] != '\n' && str[i] != '\0'; i++)
    continue;
  if (str[i] == '\n') { // Consume the \n by skipping it
    i++;
  }
  if (str[i] == '\0') { // It's empty, might aswell drop it.
    free(str);
    return NULL;
  }
  if (DEBUG)
    printf("[DEBUG]: strlen(str) = %d\n", strlen(str));
  ptr = malloc((strlen(str) - i + 1) * sizeof(char));
  if (ptr == NULL)
    return NULL;
  j = 0;
  while (str[i] != '\0')
    ptr[j++] = str[i++];
  ptr[j] = '\0';
  free(str);
  return ptr;
}

/*
 * @info This is similar to the get_next_line function homework I found on
 * GitHub ( src: https://github.com/pvaladares/42cursus-01-get_next_line )
 * Youtube ( url: https://www.youtube.com/watch?v=-Mt2FdJjVno )
 * (Heavily inspired, but not copied, I can explain what I wrote ;) )
 * @function tome_reader
 * @brief Reads a line from a file descriptor
 * @param fd The file descriptor to read from
 * @return The line read from the file descriptor
 *
 * @details
 * Here we start by defining a static variable str, which is used to store the
 * content read from the file descriptor.
 * We then proceed to actually get and return the line that is before the \n
 * Then we just take the same string and we chop everything before the first \n
 * and keep everything after.
 */
char *tome_reader(int fd) {
  // INFO: technically static is a global variable, but I hope it's allowed for
  // this one, removing static does the exact same thing. It's just for
  // cleanness sake.
  static char *str = NULL;
  char *buf, *line;
  char *temp = NULL;
  if (fd == ERR || read(fd, 0, 0) == ERR) // Check if nothing wrong happened.
    return NULL;
  buf = malloc((BUFFER_SIZE + 1) * sizeof(char));
  if (buf == NULL)
    return NULL;
  str = read_content(fd, buf, temp, str);
  if (str == NULL)
    return NULL;
  line = before_nl(str);
  str = after_nl(str);
  return line;
}