trader/src/utils.c

/************************************************************************
*                                                                       *
*             Star Traders: A Game of Interstellar Trading              *
*                Copyright (C) 1990-2011, John Zaitseff                 *
*                                                                       *
************************************************************************/

/*
  Author: John Zaitseff <J.Zaitseff@zap.org.au>
  $Id$

  This file, utils.c, contains the implementation of various utility
  functions used in Star Traders.


  This program is free software: you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see http://www.gnu.org/licenses/.
*/


#include "trader.h"


/************************************************************************
*                      Global variable definitions                      *
************************************************************************/

// Global copy, suitably modified, of localeconv() information
struct lconv lconvinfo;


/************************************************************************
*          Module-specific constants and variable definitions           *
************************************************************************/

#define GAME_FILENAME_PROTO	"game%d"
#define GAME_FILENAME_BUFSIZE	16

// Default values used to override POSIX locale
#define MOD_POSIX_CURRENCY_SYMBOL	"$"
#define MOD_POSIX_FRAC_DIGITS		2
#define MOD_POSIX_P_CS_PRECEDES		1
#define MOD_POSIX_P_SEP_BY_SPACE	0


/************************************************************************
*                       Module-specific variables                       *
************************************************************************/

static char *program_name_str   = NULL;		// Canonical program name
static char *home_directory_str = NULL;		// Full pathname to home
static char *data_directory_str = NULL;		// Writable data dir pathname

static char *current_mon_locale;		// As returned by setlocale()
static bool add_currency_symbol = false;	// Do we need to add "$"?


/************************************************************************
*          Initialisation and environment function definitions          *
************************************************************************/

// These functions are documented in the file "utils.h"


/***********************************************************************/
// init_program_name: Make the program name "canonical"

void init_program_name (char *argv[])
{
    if (argv == NULL || argv[0] == NULL || *argv[0] == '\0') {
	program_name_str = PACKAGE;
    } else {
	char *p = strrchr(argv[0], '/');

	if (p != NULL && *++p != '\0') {
	    argv[0] = p;
	}

	program_name_str = argv[0];
    }
}


/***********************************************************************/
// program_name: Return the canonical program name

const char *program_name (void)
{
    if (program_name_str == NULL) {
	init_program_name(NULL);
    }

    return program_name_str;
}


/***********************************************************************/
// home_directory: Return home directory pathname

const char *home_directory (void)
{
    if (home_directory_str == NULL) {
	// Use the HOME environment variable where possible
	char *home = getenv("HOME");

	if (home != NULL && *home != '\0') {
	    home_directory_str = xstrdup(home);
	}
    }

    return home_directory_str;
}


/***********************************************************************/
// data_directory: Return writable data directory pathname

const char *data_directory (void)
{
    /* This implementation assumes a POSIX environment by using "/" as
       the directory separator.  It also assumes a dot-starting directory
       name is permissible (again, true on POSIX systems) */

    if (data_directory_str == NULL) {
	const char *name = program_name();
	const char *home = home_directory();

	if (name != NULL && home != NULL) {
	    char *p = xmalloc(strlen(home) + strlen(name) + 3);

	    strcpy(p, home);
	    strcat(p, "/.");
	    strcat(p, name);
	    data_directory_str = p;
	}
    }

    return data_directory_str;
}


/***********************************************************************/
// game_filename: Convert an integer to a game filename

char *game_filename (int gamenum)
{
    /* This implementation assumes a POSIX environment by using "/" as
       the directory separator */

    char buf[GAME_FILENAME_BUFSIZE];	// Buffer for part of filename
    const char *dd;			// Data directory


    if (gamenum < 1 || gamenum > 9) {
	return NULL;
    }

    dd = data_directory();
    snprintf(buf, GAME_FILENAME_BUFSIZE, GAME_FILENAME_PROTO, gamenum);

    if (dd == NULL) {
	return xstrdup(buf);
    } else {
	char *p = xmalloc(strlen(dd) + strlen(buf) + 2);

	strcpy(p, dd);
	strcat(p, "/");
	strcat(p, buf);
	return p;
    }
}


/************************************************************************
*                 Error-reporting function definitions                  *
************************************************************************/

// These functions are documented in the file "utils.h"


/***********************************************************************/
// err_exit: Print an error and exit

void err_exit (const char *restrict format, ...)
{
    va_list args;


    end_screen();

    fprintf(stderr, _("%s: "), program_name());
    va_start(args, format);
    vfprintf(stderr, format, args);
    va_end(args);
    fputs("\n", stderr);

    exit(EXIT_FAILURE);
}


/***********************************************************************/
// errno_exit: Print an error message (using errno) and exit

void errno_exit (const char *restrict format, ...)
{
    va_list args;
    int saved_errno = errno;


    end_screen();

    fprintf(stderr, _("%s: "), program_name());
    if (format != NULL) {
	va_start(args, format);
	vfprintf(stderr, format, args);
	va_end(args);
	fputs(_(": "), stderr);
    }
    fprintf(stderr, "%s\n", strerror(saved_errno));

    exit(EXIT_FAILURE);
}


/***********************************************************************/
// err_exit_nomem: Print an "out of memory" error and exit

void err_exit_nomem (void)
{
    err_exit(_("out of memory"));
}


/************************************************************************
*                  Random-number function definitions                   *
************************************************************************/

// These functions are documented in the file "utils.h"


/***********************************************************************/
// init_rand: Initialise the random number generator

void init_rand (void)
{
    /* Ideally, initialisation of the random number generator should be
       made using seed48() and lcong48().  However, since this is "only a
       game", 32 bits of "randomness" as returned by gettimeofday() is
       probably more than enough... */

    struct timeval tv;
    unsigned long int seed;

    gettimeofday(&tv, NULL);		// If this fails, tv is random enough!
    seed = tv.tv_sec + tv.tv_usec;

    srand48(seed);
}


/***********************************************************************/
// randf: Return a random number between 0.0 and 1.0

extern double randf (void)
{
    return drand48();
}


/***********************************************************************/
// randi: Return a random number between 0 and limit

extern int randi (int limit)
{
    return drand48() * (double) limit;
}


/************************************************************************
*                   Locale-aware function definitions                   *
************************************************************************/

// These functions are documented in the file "utils.h"


/***********************************************************************/
// init_locale: Initialise locale-specific variables

void init_locale (void)
{
    struct lconv *lc;


    current_mon_locale = setlocale(LC_MONETARY, NULL);
    lc = localeconv();

    assert(current_mon_locale != NULL);
    assert(lc != NULL);

    lconvinfo = *lc;

    /* Are we in the POSIX locale?  This test may not be portable as the
       string returned by setlocale() is supposed to be opaque. */
    add_currency_symbol = false;
    if (   strcmp(current_mon_locale, "POSIX")   == 0
	|| strcmp(current_mon_locale, "C")       == 0
	|| strcmp(current_mon_locale, "C.UTF-8") == 0
	|| strcmp(current_mon_locale, "C.utf8")  == 0) {

	add_currency_symbol = true;
	lconvinfo.currency_symbol = MOD_POSIX_CURRENCY_SYMBOL;
	lconvinfo.frac_digits     = MOD_POSIX_FRAC_DIGITS;
	lconvinfo.p_cs_precedes   = MOD_POSIX_P_CS_PRECEDES;
	lconvinfo.p_sep_by_space  = MOD_POSIX_P_SEP_BY_SPACE;
    }
}


/***********************************************************************/
// l_strfmon: Convert monetary value to a string

ssize_t l_strfmon (char *restrict s, size_t maxsize,
		   const char *restrict format, double val)
{
    /* The current implementation assumes MOD_POSIX_P_CS_PRECEDES is 1
       (currency symbol precedes value) and that MOD_POSIX_P_SEP_BY_SPACE
       is 0 (no space separates currency symbol and value).  It does,
       however, handle currency symbols of length > 1 */
    assert(MOD_POSIX_P_CS_PRECEDES  == 1);
    assert(MOD_POSIX_P_SEP_BY_SPACE == 0);

    ssize_t ret = strfmon(s, maxsize, format, val);

    if (ret > 0 && add_currency_symbol) {
	if (strstr(format, "!") == NULL) {
	    /* Insert lconvinfo.currency_symbol to s.

	       NB: add_currecy_symbol == true assumes a POSIX locale and
	       that MOD_POSIX_CURRENCY_SYMBOL contains only ASCII-safe
	       characters that work with strlen(), etc. */
	    const char *sym = lconvinfo.currency_symbol;
	    int symlen = strlen(sym);
	    char *p;
	    int spc;

	    assert(maxsize > (unsigned int) symlen);

	    // Count number of leading spaces
	    for (p = s, spc = 0; *p == ' '; p++, spc++)
		;

	    if (symlen <= spc) {
		/* Enough space for currency symbol: copy it WITHOUT
		   copying terminating NUL character */
		for (p -= symlen; *sym != '\0'; p++, sym++) {
		    *p = *sym;
		}
	    } else {
		// Make space for currency symbol, then copy it

		memmove(s + symlen - spc, s, maxsize - (symlen - spc));
		s[maxsize - 1] = '\0';

		for ( ; *sym != '\0'; sym++, s++) {
		    // Make sure terminating NUL character is NOT copied!
		    *s = *sym;
		}

		ret = MIN((unsigned int) ret + symlen - spc, maxsize - 1);
	    }
	}
    }

    return ret;
}


/************************************************************************
*                    Encryption function definitions                    *
************************************************************************/

// These functions are documented in the file "utils.h"


/***********************************************************************/
// scramble: Scramble (encrypt) the buffer

char *scramble (int key, char *restrict buf, int bufsize)
{
    /* The algorithm used here is reversable: scramble(scramble(...))
       will (or, at least, should!) return the same as the original
       buffer.  Problematic characters are ignored; however, this
       function assumes all other characters are permitted in files.
       This is true on all POSIX systems. */

    if (buf != NULL && key != 0) {
	char *p = buf;
	unsigned char k = ~key;

	for (int i = 0; i < bufsize && *p != '\0'; i++, k++, p++) {
	    char c = *p;
	    char r = c ^ k;	// Simple encryption: XOR on a moving key

	    if (c != '\r' && c != '\n'
		&& r != '\r' && r != '\n' && r != '\0') {
		*p = r;
	    }
	}
    }

    return buf;
}


/***********************************************************************/
// unscramble: Unscramble (decrypt) the buffer

char *unscramble (int key, char *restrict buf, int bufsize)
{
    return scramble(key, buf, bufsize);
}


/************************************************************************
*                  Miscellaneous function definitions                   *
************************************************************************/

// These functions are documented in the file "utils.h"


/***********************************************************************/
// xmalloc: Allocate a new block of memory, with checking

void *xmalloc (size_t size)
{
    void *p;


    if (size < 1)
	size = 1;

    p = malloc(size);
    if (p == NULL) {
	err_exit_nomem();
    }

    return p;
}


/***********************************************************************/
// xstrdup: Duplicate a string, with checking

char *xstrdup (const char *str)
{
    char *s;


    if (str == NULL)
	str = "";

    s = strdup(str);
    if (s == NULL) {
	err_exit_nomem();
    }

    return s;
}


/***********************************************************************/
// End of file