Task: Update a configuration file

C: #include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define strcomp(X, Y) strcasecmp(X, Y)

struct option
{ const char *name, *value; 
  int flag; };


struct option updlist[] =
{ { "NEEDSPEELING", NULL },
  { "SEEDSREMOVED", "" },
  { "NUMBEROFBANANAS", "1024" },
  { "NUMBEROFSTRAWBERRIES", "62000" },
  { NULL, NULL } };

int output_opt(FILE *to, struct option *opt)
{ if (opt->value == NULL)
    return fprintf(to, "; %s\n", opt->name);
  else if (opt->value[0] == 0)
    return fprintf(to, "%s\n", opt->name);
  else 
    return fprintf(to, "%s %s\n", opt->name, opt->value); }

int update(FILE *from, FILE *to, struct option *updlist) 
{ char line_buf[256], opt_name[128];
  int i;
  for (;;)
  { size_t len, space_span, span_to_hash;
    if (fgets(line_buf, sizeof line_buf, from) == NULL)
      break;
    len = strlen(line_buf);
    space_span = strspn(line_buf, "\t ");
    span_to_hash = strcspn(line_buf, "#");
    if (space_span == span_to_hash)
      goto line_out;
    if (space_span == len)
      goto line_out;
    if ((sscanf(line_buf, "; %127s", opt_name) == 1) ||
        (sscanf(line_buf, "%127s", opt_name) == 1))
    { int flag = 0;
      for (i = 0; updlist[i].name; i++)
      { if (strcomp(updlist[i].name, opt_name) == 0)
        { if (output_opt(to, &updlist[i]) < 0)
            return -1;
          updlist[i].flag = 1;
          flag = 1; } }
      if (flag == 0)
        goto line_out; }
    else
  line_out: 
      if (fprintf(to, "%s", line_buf) < 0)
        return -1;
    continue; }
  { for (i = 0; updlist[i].name; i++)
    { if (!updlist[i].flag)
        if (output_opt(to, &updlist[i]) < 0)
          return -1; } }
  return feof(from) ? 0 : -1; }

int main(void)
{ if (update(stdin, stdout, updlist) < 0)
  { fprintf(stderr, "failed\n");
    return (EXIT_FAILURE); }
  return 0; }







Python: 




import re
import string





DISABLED_PREFIX = ';'





class Option(object):
    

    
    def __init__(self, name, value=None, disabled=False,
                 disabled_prefix=DISABLED_PREFIX):
        
        self.name = str(name)
        self.value = value
        self.disabled = bool(disabled)
        self.disabled_prefix = disabled_prefix

    
    def __str__(self):
        
        disabled = ('', '%s ' % self.disabled_prefix)[self.disabled]
        value = (' %s' % self.value, '')[self.value is None]
        return ''.join((disabled, self.name, value))

    
    def get(self):
        
        enabled = not bool(self.disabled)
        if self.value is None:
            value = enabled
        else:
            value = enabled and self.value
        return value

    



class Config(object):
    
    
    reOPTION = r'^\s*(?P<disabled>%s*)\s*(?P<name>\w+)(?:\s+(?P<value>.+?))?\s*$'

    
    def __init__(self, fname=None, disabled_prefix=DISABLED_PREFIX):
        
        self.disabled_prefix = disabled_prefix
        self.contents = []          
        self.options = {}           
        self.creOPTION = re.compile(self.reOPTION % self.disabled_prefix)
        if fname:
            self.parse_file(fname)

    
    def __str__(self):
        
        return '\n'.join(map(str, self.contents))

    
    def parse_file(self, fname):
        
        with open(fname) as f:
            self.parse_lines(f)
        return self

    
    def parse_lines(self, lines):
        
        for line in lines:
            self.parse_line(line)
        return self

    
    def parse_line(self, line):
        
        s = ''.join(c for c in line.strip() if c in string.printable) 
        moOPTION = self.creOPTION.match(s)
        if moOPTION:
            name = moOPTION.group('name').upper()
            if not name in self.options:
                self.add_option(name, moOPTION.group('value'),
                                moOPTION.group('disabled'))
        else:
            if not s.startswith(self.disabled_prefix):
                self.contents.append(line.rstrip())
        return self

    
    def add_option(self, name, value=None, disabled=False):
        
        name = name.upper()
        opt = Option(name, value, disabled)
        self.options[name] = opt
        self.contents.append(opt)
        return opt

    
    def set_option(self, name, value=None, disabled=False):
        
        name = name.upper()
        opt = self.options.get(name)
        if opt:
            opt.value = value
            opt.disabled = disabled
        else:
            opt = self.add_option(name, value, disabled)
        return opt

    
    def enable_option(self, name, value=None):
        
        return self.set_option(name, value, False)

    
    def disable_option(self, name, value=None):
        
        return self.set_option(name, value, True)

    
    def get_option(self, name):
        
        opt = self.options.get(name.upper())
        value = opt.get() if opt else None
        return value





if __name__ == '__main__':
    import sys
    cfg = Config(sys.argv[1] if len(sys.argv) > 1 else None)
    cfg.disable_option('needspeeling')
    cfg.enable_option('seedsremoved')
    cfg.enable_option('numberofbananas', 1024)
    cfg.enable_option('numberofstrawberries', 62000)
    print cfg