[PATCH 2/2] vec: Add array_slice::bsearch

[Richard Biener]

> Am 26.08.2022 um 18:40 schrieb Martin Jambor <mjambor@suse.cz>:
> 
> Hi,
> 
> This adds a method to binary search in a sorted array_slice.
> 
> The implementation is direct copy of vec:bsearch.  Moreover, to only
> copy it once and not twice, I used const_cast in the non-const
> variants to be able to use the const variants.  I hope that is
> acceptable abuse of const_cast but I'll be happy to change that if
> not.
> 
> Bootstrapped and tested along code that actually uses it on
> x86_64-linux.  OK for trunk?

Can you avoid the copying by using array slice bsearch from the vec<> bsearch?


> Thanks,
> 
> Martin
> 
> 
> gcc/ChangeLog:
> 
> 2022-08-08  Martin Jambor  <mjambor@suse.cz>
> 
>    * vec.h (array_slice::bsearch): New methods.
> ---
> gcc/vec.h | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 94 insertions(+)
> 
> diff --git a/gcc/vec.h b/gcc/vec.h
> index b0477e1044c..61ebdc4ca13 100644
> --- a/gcc/vec.h
> +++ b/gcc/vec.h
> @@ -2301,6 +2301,14 @@ public:
>   // True if the array is valid, false if it is an array like INVALID.
>   bool is_valid () const { return m_base || m_size == 0; }
> 
> +  /* Methods for binary search in sorted array_slice.  */
> +  const T *bsearch (const void *key, int (*compar)(const void *,
> +                           const void *)) const;
> +  T *bsearch (const void *key, int (*compar)(const void *, const void *));
> +  const T *bsearch (const void *key,
> +          int (*compar)(const void *, const void *, void *), void *) const;
> +  T *bsearch (const void *key,
> +          int (*compar)(const void *, const void *, void *), void *);
> private:
>   iterator m_base;
>   unsigned int m_size;
> @@ -2361,6 +2369,92 @@ make_array_slice (T *base, unsigned int size)
>   return array_slice<T> (base, size);
> }
> 
> +/* Search the contents of the sorted array_slice with a binary search.  CMP is
> +   the comparison function to pass to bsearch.  */
> +
> +template<typename T>
> +inline const T *
> +array_slice<T>::bsearch (const void *key,
> +             int (*compar) (const void *, const void *)) const
> +{
> +  const void *base = this->m_base;
> +  size_t nmemb = this->size ();
> +  size_t size = sizeof (T);
> +  /* The following is a copy of glibc stdlib-bsearch.h.  */
> +  size_t l, u, idx;
> +  const void *p;
> +  int comparison;
> +
> +  l = 0;
> +  u = nmemb;
> +  while (l < u)
> +    {
> +      idx = (l + u) / 2;
> +      p = (const void *) (((const char *) base) + (idx * size));
> +      comparison = (*compar) (key, p);
> +      if (comparison < 0)
> +    u = idx;
> +      else if (comparison > 0)
> +    l = idx + 1;
> +      else
> +    return (T *)const_cast<void *>(p);
> +    }
> +
> +  return NULL;
> +}
> +
> +template<typename T>
> +inline T *
> +array_slice<T>::bsearch (const void *key,
> +             int (*compar) (const void *, const void *))
> +{
> +  return const_cast<T>(bsearch (key, compar));
> +}
> +
> +/* Search the contents of the sorted array_slice with a binary search.  CMP is
> +   the comparison function to pass to bsearch.  */
> +
> +template<typename T>
> +inline const T *
> +array_slice<T>::bsearch (const void *key,
> +             int (*compar) (const void *, const void *, void *),
> +             void *data) const
> +{
> +  const void *base = this->m_base;
> +  size_t nmemb = this->size ();
> +  size_t size = sizeof (T);
> +  /* The following is a copy of glibc stdlib-bsearch.h.  */
> +  size_t l, u, idx;
> +  const void *p;
> +  int comparison;
> +
> +  l = 0;
> +  u = nmemb;
> +  while (l < u)
> +    {
> +      idx = (l + u) / 2;
> +      p = (const void *) (((const char *) base) + (idx * size));
> +      comparison = (*compar) (key, p, data);
> +      if (comparison < 0)
> +    u = idx;
> +      else if (comparison > 0)
> +    l = idx + 1;
> +      else
> +    return (T *)const_cast<void *>(p);
> +    }
> +
> +  return NULL;
> +}
> +
> +template<typename T>
> +inline T *
> +array_slice<T>::bsearch (const void *key,
> +             int (*compar) (const void *, const void *, void *),
> +             void *data)
> +{
> +  return const_cast<T> (bsearch (key, compar, data));
> +}
> +
> #if (GCC_VERSION >= 3000)
> # pragma GCC poison m_vec m_vecpfx m_vecdata
> #endif
> -- 
> 2.37.2
>