Programming

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

typedef struct buffer
{
    // Position of string segment in dat, length of data in dat
    int start, end, len;
    // Position in proc
    int pstart, pend;
    // String data
    char dat[256];
    // String tokens
    char proc[512];
} buffer;

int buffer_read(FILE *fp, buffer *b)
{
  fprintf(stderr,"Input: ");
  if(fgets(b->dat,256,fp)==NULL)
    return(-1);

  b->pstart=1;
  b->pend=1;
  b->start=0;
  b->end=0;
  b->len=strlen(b->dat);
  b->proc[0]='\0';
  b->proc[1]='\0';
  return(0);
}

char **buffer_get_args(buffer *p)
{
  int numargs=0,running=1;
  char **out=NULL;

  while((p->start < p->len) && running)
  {
    int tmp;

    switch(p->dat[p->end])
    {
    // Seperate one argument from another.
    case '\r':
    case '\n':
    case '\t':
    case ' ':
      // Don't add another seperator if already seperated
      if(p->proc[p->pend-1]!='\0')
      {
        // Add a NULL terminator to make it a seperate string
        p->proc[p->pend++]='\0';
        out=(char **)realloc(out,sizeof(char **)*(numargs+1));
        out[numargs++]=p->proc + p->pstart;

        p->pstart=p->pend;
      }

      p->start=(++p->end);
      continue;

    // Seperates groups of arguments from each other
    case ';':
    case '&':
      tmp=p->dat[p->end];

      if(p->pend > p->pstart)
      {
        // Add a NULL terminator to make it a seperate string
        p->proc[p->pend++]='\0';
        out=(char **)realloc(out,sizeof(char **)*(numargs+1));
        out[numargs++]=p->proc + p->pstart;

        p->pstart=p->pend;
      }

      // Ignore multiple of the same
      while(p->dat[p->end] == tmp)
        p->end++;

      p->start=p->end;

      if(tmp == '&')
      {
        p->proc[p->pend++]='&';
        p->proc[p->pend++]='\0';

        out=(char **)realloc(out,sizeof(char **)*(numargs+1));
        out[numargs++]=p->proc + p->pstart;

        p->pstart=p->pend;
      }

      running=0;
      continue;
    // Another character.  Add stuff on.
    default:
      p->proc[p->pend++] = p->dat[p->end];
      break;
    }

    p->end++;
  }

  p->proc[p->pend]='\0';

  if(out != NULL)
  {
    out=(char **)realloc(out,sizeof(char **)*(numargs+1));
    out[numargs++]=NULL;
  }

  return(out);
}

int main(int argc, char *argv[])
{
  buffer input;

  while(buffer_read(stdin,&input)>=0)
  {
    char **args;

    while(args=buffer_get_args(&input))
    {
      int n;
      for(n=0; args[n] != NULL; n++)
        fprintf(stderr," [%s]",args[n]);

      fprintf(stderr,"\n");

      free(args);
    }
  }

  return(0);
}