OT: CS education gone wrong (Was: Re: TDD is BS?)

[Walter Bright]

On 6/21/2013 3:35 PM, Andrei Alexandrescu wrote:
> On 6/21/13 3:22 PM, Adam D. Ruppe wrote:
>> Just for laughs I just slapped together a strstr
>
> Post it and I'll destroy it.

Can I play, too? Mine from the Digital Mars C library. Haven't looked at it 
since 2001.
==================================================

/*_ strstr.c */
/* Copyright (C) 1985-2001 by Digital Mars		*/
/* All Rights Reserved					*/
/* www.digitalmars.com					*/
/* Written by Walter Bright				*/

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

#if 0 /* Smaller but slower under many circumstances. */
char *strstr(const char *s1,const char *s2)
{   size_t len2;
     size_t len1;
     char c2 = *s2;

     len1 = strlen(s1);
     len2 = strlen(s2);
     if (!len2)
	return (char *) s1;
     while (len2 <= len1)
     {
	if (c2 == *s1)
	    if (memcmp(s2,s1,len2) == 0)
		return (char *) s1;
	s1++;
	len1--;
     }
     return NULL;
}
#else
#include <limits.h>    /* defines UCHAR_MAX */
/****************************************************************************
See "Algorithms" Second Edition by Robert Sedgewick.  Boyer-Moore string
search routine.
****************************************************************************/
char *strstr(const char *text, const char * pattern)
{
   const size_t M = strlen(pattern);
   const unsigned long N = strlen(text);
   const char *p_p = pattern;
   const char *t_p;
   size_t skip[UCHAR_MAX + 1];
   size_t i, j;

   if(M == 0)
     return (char *)text;

   if(M > N)   /* If pattern is longer than the text string. */
     return 0;

#if __INTSIZE == 4
   _memintset((int *)skip, M, UCHAR_MAX + 1);
#else
   { size_t *s_p = skip + UCHAR_MAX;
     do
     {
       *s_p = M;
     }while(s_p-- > skip);
   }
#endif

   p_p = pattern;
   do
   {
     skip[*(const unsigned char *)p_p] = M - 1 - (p_p - pattern);
   } while(*++p_p);

   p_p = pattern + M - 1;
   t_p = text + M - 1;

   while(1)
   {
     char c;

     c = *t_p;
     if(c == *p_p)
     {
       if(p_p - pattern == 0)
	return (char *)t_p;

       t_p--; p_p--;
     }
     else
     {
       size_t step = M - (p_p - pattern);

       if (step < skip[(unsigned char)c])
	step = skip[(unsigned char)c];

       /* If we have run out of text to search in. */
       /* Need cast for case of large strings with 16 bit size_t... */
       if((unsigned long)(t_p - text) + step >= N)
	return 0;

       t_p += step;

       p_p = pattern + M - 1;
     }
   }
}
#endif	/* #if 0 */