i386/MIT/course/src/src.lab/lib/args.c

   1 #include <inc/args.h>
   2 #include <inc/string.h>
   3
   4 void
   5 argstart(int *argc, char **argv, struct Argstate *args)
   6 {
   7         args->argc = argc;
   8         args->argv = (const char **) argv;
   9         args->curarg = (*argc > 1 && argv ? "" : 0);
  10         args->argvalue = 0;
  11 }
  12
  13 int
  14 argnext(struct Argstate *args)
  15 {
  16         int arg;
  17
  18         args->argvalue = 0;
  19
  20         // Done processing arguments if args->curarg == 0
  21         if (args->curarg == 0)
  22                 return -1;
  23
  24         if (!*args->curarg) {
  25                 // Need to process the next argument
  26                 // Check for end of argument list
  27                 if (*args->argc == 1
  28                     || args->argv[1][0] != '-'
  29                     || args->argv[1][1] == '\0')
  30                         goto endofargs;
  31                 // Shift arguments down one
  32                 args->curarg = args->argv[1] + 1;
  33                 memmove(args->argv + 1, args->argv + 2, sizeof(const char *) * (*args->argc - 1));
  34                 (*args->argc)--;
  35                 // Check for "--": end of argument list
  36                 if (args->curarg[0] == '-' && args->curarg[1] == '\0')
  37                         goto endofargs;
  38         }
  39
  40         arg = (unsigned char) *args->curarg;
  41         args->curarg++;
  42         return arg;
  43
  44     endofargs:
  45         args->curarg = 0;
  46         return -1;
  47 }
  48
  49 char *
  50 argvalue(struct Argstate *args)
  51 {
  52         return (char*) (args->argvalue ? args->argvalue : argnextvalue(args));
  53 }
  54
  55 char *
  56 argnextvalue(struct Argstate *args)
  57 {
  58         if (!args->curarg)
  59                 return 0;
  60         if (*args->curarg) {
  61                 args->argvalue = args->curarg;
  62                 args->curarg = "";
  63         } else if (*args->argc > 1) {
  64                 args->argvalue = args->argv[1];
  65                 memmove(args->argv + 1, args->argv + 2, sizeof(const char *) * (*args->argc - 1));
  66                 (*args->argc)--;
  67         } else {
  68                 args->argvalue = 0;
  69                 args->curarg = 0;
  70         }
  71         return (char*) args->argvalue;
  72 }
  73