Re: [Xen-devel] [PATCH V2 2/4] xen: Add generic implementation of binary search

[Julien Grall <julien.grall@xxxxxxx>]

Hi Shanker,

On 18/07/16 00:26, Shanker Donthineni wrote:
> This patch adds the generic implementation of binary search algorithm
> whcih is copied from Linux kernel v4.7-rc7. No functional changes.
NIT: ws/whcih/which/

> Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
FWIW:

Reviewed-by: Julien Grall <julien.grall@xxxxxxx>

Regards,

> ---
> Changes since v1:
>  Removed the header file xen/include/xen/bsearch.h.
>  Defined function bsearch() prototype in the header file xen/lib.h.
>
>  xen/common/Makefile   |  1 +
>  xen/common/bsearch.c  | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  xen/include/xen/lib.h |  3 +++
>  3 files changed, 55 insertions(+)
>  create mode 100644 xen/common/bsearch.c
>
> diff --git a/xen/common/Makefile b/xen/common/Makefile
> index dbf00c6..f8123c2 100644
> --- a/xen/common/Makefile
> +++ b/xen/common/Makefile
> @@ -43,6 +43,7 @@ obj-y += schedule.o
>  obj-y += shutdown.o
>  obj-y += softirq.o
>  obj-y += sort.o
> +obj-y += bsearch.o
>  obj-y += smp.o
>  obj-y += spinlock.o
>  obj-y += stop_machine.o
> diff --git a/xen/common/bsearch.c b/xen/common/bsearch.c
> new file mode 100644
> index 0000000..7090930
> --- /dev/null
> +++ b/xen/common/bsearch.c
> @@ -0,0 +1,51 @@
> +/*
> + * A generic implementation of binary search for the Linux kernel
> + *
> + * Copyright (C) 2008-2009 Ksplice, Inc.
> + * Author: Tim Abbott <tabbott@xxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; version 2.
> + */
> +
> +#include <xen/lib.h>
> +
> +/*
> + * bsearch - binary search an array of elements
> + * @key: pointer to item being searched for
> + * @base: pointer to first element to search
> + * @num: number of elements
> + * @size: size of each element
> + * @cmp: pointer to comparison function
> + *
> + * This function does a binary search on the given array.  The
> + * contents of the array should already be in ascending sorted order
> + * under the provided comparison function.
> + *
> + * Note that the key need not have the same type as the elements in
> + * the array, e.g. key could be a string and the comparison function
> + * could compare the string with the struct's name field.  However, if
> + * the key and elements in the array are of the same type, you can use
> + * the same comparison function for both sort() and bsearch().
> + */
> +void *bsearch(const void *key, const void *base, size_t num, size_t size,
> +             int (*cmp)(const void *key, const void *elt))
> +{
> +       size_t start = 0, end = num;
> +       int result;
> +
> +       while (start < end) {
> +               size_t mid = start + (end - start) / 2;
> +
> +               result = cmp(key, base + mid * size);
> +               if (result < 0)
> +                       end = mid;
> +               else if (result > 0)
> +                       start = mid + 1;
> +               else
> +                       return (void *)base + mid * size;
> +       }
> +
> +       return NULL;
> +}
> diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
> index b1b0fb2..b90d582 100644
> --- a/xen/include/xen/lib.h
> +++ b/xen/include/xen/lib.h
> @@ -153,4 +153,7 @@ void dump_execstate(struct cpu_user_regs *);
>
>  void init_constructors(void);
>
> +void *bsearch(const void *key, const void *base, size_t num, size_t size,
> +              int (*cmp)(const void *key, const void *elt))
> +
>  #endif /* __LIB_H__ */
--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel