new string matching API

[Brian Pane]

I put together an abstract API for string matching, plus a
concrete "subclass" that implements a simplified form of
Boyer-Moore.  (The point of the design is to allow different
search implementations to be plugged in as needed.  We could,
for example, add a BNDM implementation for use in apps where
BNDM is a better choice than Boyer-Moore.)
All the places where I'm thinking of using this code are in
the httpd, but I suspect that it may be useful for other APR-based
projects.
Does anyone have strong opinions for or against adding
this to apr-util?
Thanks,
--Brian
#ifndef APR_STRMATCH_H
#define APR_STRMATCH_H
/**
* @file apr_strmatch.h
* @brief APR-UTIL string matching routines
*/
#ifdef __cplusplus
extern "C" {
#endif
/**
* @defgroup APR_Util_StrMatch String matching routines
* @ingroup APR_Util
* @{
*/
#include "apu.h"
#include "apr_pools.h"
typedef struct apr_strmatch_pattern apr_strmatch_pattern;
/**
* Precompiled search pattern
*/
struct apr_strmatch_pattern {
   const char *(*compare)(const apr_strmatch_pattern *this_pattern,
                           const char *s, apr_size_t slen);
   const char *pattern;
   apr_size_t length;
   void *context;  /* hook for subclasses to add precomputed metadata */
};
#if defined(DOXYGEN)
/**
* Search for a precompiled pattern within a string
* @param pattern The pattern
* @param s The string in which to search for the pattern
* @param slen The length of s (excluding null terminator)
* @return A pointer to the first instance of the pattern in s, or
*         NULL if not found
*/
APU_DECLARE(const char *) apr_strmatch(const apr_strmatch_pattern *pattern,
                                      const char *s; apr_size_t s);
#else
#define apr_strmatch(pattern, s, slen) 
(*((pattern)->compare))((pattern), (s), (slen))
#endif

/**
* Precompile a pattern for matching using the Boyer-Moore-Horspool 
algorithm
* @param p The pool from which to allocate the pattern
* @param s The pattern string
* @param case_sensitive Whether the matching should be case-sensitive
* @return a pointer to the compiled pattern, or NULL if compilation fails
*/
APU_DECLARE(const apr_strmatch_pattern *)
        apr_strmatch_precompile(apr_pool_t *p, const char *s,
                                int case_sensitive);

/** @} */
#ifdef __cplusplus
}
#endif
#endif    /* !APR_STRMATCH_H */