[ovs-dev] [token bucket 2/3] sat-math: Introduce macro version of SAT_MUL.

[Ethan Jackson]

Looks good, thanks.

Ethan

On Wed, May 30, 2012 at 5:16 PM, Ben Pfaff <blp at nicira.com> wrote:
> The macro version can be used in a constant expression, such as an
> initializer for a variable with static lifetime.  (Otherwise, it's better
> to use the function.)
>
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
>  lib/sat-math.h |   12 +++++++-----
>  1 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/lib/sat-math.h b/lib/sat-math.h
> index ae504ba..f4287fc 100644
> --- a/lib/sat-math.h
> +++ b/lib/sat-math.h
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 2008 Nicira, Inc.
> + * Copyright (c) 2008, 2012 Nicira, Inc.
>  *
>  * Licensed under the Apache License, Version 2.0 (the "License");
>  * you may not use this file except in compliance with the License.
> @@ -34,13 +34,15 @@ sat_sub(unsigned int x, unsigned int y)
>     return x >= y ? x - y : 0;
>  }
>
> -/* Saturating multiplication: overflow yields UINT_MAX. */
> +/* Saturating multiplication of "unsigned int"s: overflow yields UINT_MAX. */
> +#define SAT_MUL(X, Y)                                                   \
> +    ((Y) == 0 ? 0                                                       \
> +     : (X) <= UINT_MAX / (Y) ? (unsigned int) (X) * (unsigned int) (Y)  \
> +     : UINT_MAX)
>  static inline unsigned int
>  sat_mul(unsigned int x, unsigned int y)
>  {
> -    return (!y ? 0
> -            : x <= UINT_MAX / y ? x * y
> -            : UINT_MAX);
> +    return SAT_MUL(x, y);
>  }
>
>  #endif /* sat-math.h */
> --
> 1.7.2.5
>
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