Utility functions

Generally useful utility functions are located in the file utilities.C, with an associated header file utilities.h. These functions include:

• char *stringdup(char *)
  Creates a duplicate of the given string.

• char *stringtoupper(char *)
  Converts the given string to upper case; returns pointer to the same string.

• int strupcmp(char *a, char *b)
  Compares string a to string b in a case-insensitive manner. Otherwise acts like a call to strcmp.

• int strupncmp(char *a, char *b, int n)
  Like strupcmp, but only considers the first n characters.

• void breakup_filename(char *s, char **p, char **n
  Takes the filename in string s and breaks it into the file name n and directory d. Space is allocated for both the name and path strings.

• char *command_tokenize(char *s, int *argc, char **argv)
  Breaks the command string s into tokens, provides as pointers to the different token strings in argv (argv should be an array of pointers to char with enough items to hold a pointer for each token in the given string). argc is set to the total number of tokens found. Tokens are only searched for in the string until a # character is reached; the rest of the string s is then skipped if this comment character is found. If the first non-whitespace character is a # symbol, the routine returns NULL. A command string is a string of the form

  <keyword> = <string>

  If the equal sign is not present as the second token in the string, this routine returns NULL.

• char *str_tokenize(char *s, int *argc, char **argv)
  Similar to command_tokenize, without the restriction of having the string in the format of a command string, instead s may be any string.

• double time_of_day(void)
  Returns the elapsed time, in seconds, from some reference time (which may vary between different versions of Unix). Best used for calculating time differences, not for finding the ``current'' time.

• char *username(void)
  Returns a pointer to a string with the username of the person running the program.

• int str2bool(char *s)
  Returns 1 if the string s is any type of string indicating ``yes'' in some form, or 0 if the string indicates ``no'' in some form. If the routine cannot determine if yes or no was indicates, this returns -1.

• float *cross_prod(float *x1, float *x2, float *x3)
  Calculates $\vec{x1} = \vec{x2} \times \vec{x3}$, and returns a pointer to x1. The array x1 must be different than the storage used for x2 and x3.

• float dot_prod(float *x1, float *x2)
  Returns the value of $\vec{x1} \cdot \vec{x2}$.

• float *normalize(float *x)
  Normalizes the vector $\vec{x}$; returns a pointer to x.

• float norm(float *x)
  Returns the norm (length) $n$ of a vector $\vec{x}$: $n = \sqrt{\vec{x}\cdot\vec{x}}$.

• void add(float *x1, float *x2, float *x3)
  Computes quickly $\vec{x1} = \vec{x2} + \vec{x3}$.

• void subtract(float *x1, float *x2, float *x3)
  Computes quickly $\vec{x1} = \vec{x2} - \vec{x3}$.