colors.c / colors.h To convert in-game player name colors to html display. References used: http://www.rapidtables.com/convert/color/hsl-to-rgb.htm http://www.rapidtables.com/convert/color/rgb-to-hsl.htm https://gitlab.com/xonotic/xonstat/blob/master/xonstat/util.py Overview: This component is slightly based on util.py of XonStats, but the only functionality needed is coloring the player's names. Since C programming language does not have standard libraries for color model conversions and regex, some functionality had to be self written. The function of interest is: def html_colors(qstr='', limit=None): This component uses purely C standard library. Advanced string manipulations such as replace and concatenation are avoided. Instead, strings are printed in parts across functions. There is only one instance of dynamic memory allocation. void print_plname(const char *) It both allocates, near the start, and frees memory at the end. darkplaces Player Names & Colors Players can add color themes to their names. They're expressed either decimal or hexidecimal. The decimal format follows A character '^' that is not displayed, followed by a single digit between 0 and 9. The hexidecimal format follows A string '^x' that is not displayed, followed by 3 digits between 0 - 0xF. Python Regex to C Translation The snippets from the original python code: _all_colors = re.compile(r'\^(\d|x[\dA-Fa-f]{3})') _dec_colors = re.compile(r'\^(\d)') _hex_colors = re.compile(r'\^x([\dA-Fa-f])([\dA-Fa-f])([\dA-Fa-f])') _dec_spans = [ "", "", "", "", "", "", "", "", "", "" ] ... def html_colors(qstr='', limit=None): ... html = _dec_colors.sub(lambda match: _dec_spans[int(match.group(1))], qstr) html = _hex_colors.sub(hex_repl, html) ... html = _dec_colors.sub(lambda match: _dec_spans[int(match.group(1))], qstr) The character following a '^' is treated as an index to the array '_dec_spans'. The corresponding element in '_dec_spans' replaces the character '^' and the following digit in the string 'qstr'. html = _hex_colors.sub(hex_repl, html) The output of function 'hex_repl' replaces matching strings in html- '^x' followed by 3 hexadecimal digits. The function 'hex_repl' has more to do with the algorithms of color model conversions than it has to do with regex rules. The control flow to output similar results to the regex substitutions is in the function static void b(char * const str); Unlike the python counterparts, it segments the player name into tokens and prints strings also other strings instead of the sequences not intended to be displayed. Function Walkthrough Sorted by caller to callee. void print_plname(const char *) const char * parameter is the player's name. It is used as a basis for the variable 'copy'. 'copy' will always be the shorter character string. This is function is intended to be used by the client file. This function unconditionally allocates memory (calloc) and frees it at the end. By itself, it only removes extraneous instances of the character '^'. It then calls the function static void b(char * const) where actual output occurs. static void b(char * const) const char * parameter is the player's name. The data pointed at by the pointer is altered by function 'strtok', but the pointer itself is never changed. Abstractly, fragments of the player's name are treated as a command to print specific strings. This function iterates once through the player's name. 'strtok' segments the player's name; sequences between and not including '^'s are treated as substrings. The first character of the substring is checked for a digit inclusively between 0 and 9 for a decimal color code. Exclusively or, checked for an 'x' and a numerical sequence afterwards for a hexidecimal color code. If the substring does not have either, it is printed like an ordinary string. This function may not be adequate when a player's name intentionally contains '^'. static void hexspan(const char *) const char * parameter is ideally a sequence of 3 hexidecimal digits. Actually it is the entire substring from the callee. The first 3 elements are of interest as 3 separate single digit numerical values and are explicitly separated to prevent function 'strtol' from interpreting them as multidigit numbers. These 3 elements are rgb values from the game engine. Xonotic represents RGB values as a sequence of three digits 0 - 0xF. Before conversion is to be done, they must be multiplied by 0xF so the full range of values for RGB, 0 - 255 can be represented. This function prints the an html span tag. This function will first convert rgb to hsl to check if the colors are too dark for the web page, and if so brighten up the colors then reconvert to rgb. static void decspan(const int) const int parameter is a digit, the range being [0, 9]. This function is straightforward. It will print an html tag corresponding to the const int parameter. void hsl2rgb(struct Rgb *, const struct Hls const *) First parameter, 'struct Rgb *' is the result of the conversion. It does not need to be initialized. Second parameter, 'const struct Hls const *' is the values and color model to convert from and because, it must be initialized. The math referenced from: http://www.rapidtables.com/convert/color/hsl-to-rgb.htm The implemenation deviates at the last 3 lines of code where the results are finalized and placed in the output. The webpage does not mention that rounding up is necessary. However it is, otherwise the nonzero rgb values for the following colors Silver (0°,0%,75%) Gray (0°,0%,50%) Maroon (0°,100%,25%) Olive (60°,100%,25%) Green (120°,100%,25%) Purple (300°,100%,25%) Teal (180°,100%,25%) Navy (240°,100%,25%) will be off by one. void rgb2hsl(struct Hls *, const struct Rgb const *) First parameter, 'struct Hls *' is the result of the conversion. It does not need to be initialized. Second parameter, 'const struct Rgb const *' is the values and color model to convert from and because, it must be initialized. The math referenced from: http://www.rapidtables.com/convert/color/rgb-to-hsl.htm The implementation deviates when calculating hue, when Cmax is R'. Instead of modulo, there is a summation by 6 when G' is less than B'.