[gentoo-portage-dev] [PATCH] isolated-functions.sh: eliminate loop in has()

[gentoo-portage-dev] [PATCH] isolated-functions.sh: eliminate loop in has()

[rindeal]

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From edc6df44de4e0f22322062c7c7e1b973bd89f4cd Mon Sep 17 00:00:00 2001
From: Jan Chren <dev.rindeal@gmail.com>
Date: Fri, 22 Apr 2016 14:21:08 +0200
Subject: [PATCH] isolated-functions.sh: eliminate loop in has()

Looping is slow and clutters debug log.
Still this wouldn't matter that much if has() wasn't one of the most used
functions.

Thus this patch should bring a general improvement.
---
 bin/isolated-functions.sh | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/bin/isolated-functions.sh b/bin/isolated-functions.sh
index e320f71..6900f99 100644
--- a/bin/isolated-functions.sh
+++ b/bin/isolated-functions.sh
@@ -463,14 +463,12 @@ hasv() {
 }

 has() {
-       local needle=$1
+       local needle=$'\a'"$1"$'\a'
        shift
+       local IFS=$'\a'
+       local haystack=$'\a'"$@"$'\a'

-       local x
-       for x in "$@"; do
-               [ "${x}" = "${needle}" ] && return 0
-       done
-       return 1
+       [[ "${haystack}" == *"${needle}"* ]]
 }

 __repo_attr() {
--
2.7.3

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Re: [gentoo-portage-dev] [PATCH] isolated-functions.sh: eliminate loop in has()

[Zac Medico]

On 04/22/2016 06:07 AM, rindeal wrote:
> From edc6df44de4e0f22322062c7c7e1b973bd89f4cd Mon Sep 17 00:00:00 2001
> From: Jan Chren <dev.rindeal@gmail.com <mailto:dev.rindeal@gmail.com>>
> Date: Fri, 22 Apr 2016 14:21:08 +0200
> Subject: [PATCH] isolated-functions.sh: eliminate loop in has()
> 
> Looping is slow and clutters debug log.
> Still this wouldn't matter that much if has() wasn't one of the most
> used functions.
> 
> Thus this patch should bring a general improvement.
> ---
>  bin/isolated-functions.sh | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/bin/isolated-functions.sh b/bin/isolated-functions.sh
> index e320f71..6900f99 100644
> --- a/bin/isolated-functions.sh
> +++ b/bin/isolated-functions.sh
> @@ -463,14 +463,12 @@ hasv() {
>  }
> 
>  has() {
> -       local needle=$1
> +       local needle=$'\a'"$1"$'\a'
>         shift
> +       local IFS=$'\a'
> +       local haystack=$'\a'"$@"$'\a'
> 
> -       local x
> -       for x in "$@"; do
> -               [ "${x}" = "${needle}" ] && return 0
> -       done
> -       return 1
> +       [[ "${haystack}" == *"${needle}"* ]]
>  }
> 
>  __repo_attr() {
> --
> 2.7.3

We used to have a similar implementation, but it was changed to a loop
in order to be 100% compatible with PMS. As far as I know, the only way
to implement it in a way that truely respects whitespace in elements is
with a loop.

BTW, your version would have to use this in order to respect word
broundaries:

    [[ " ${haystack} " == *" ${needle} "* ]]

However, that still doesn't completely respect whitespace. Consider:

    has " b c " a b c d e

I'm not aware of any cases in which we actually need to respect
whitespace in the has function, but according to PMS is should respect
whitespace IIRC.
-- 
Thanks,
Zac

Re: [gentoo-portage-dev] [PATCH] isolated-functions.sh: eliminate loop in has()

[Anthony G. Basile]

On 4/22/16 9:07 AM, rindeal wrote:
>>From edc6df44de4e0f22322062c7c7e1b973bd89f4cd Mon Sep 17 00:00:00 2001
> From: Jan Chren <dev.rindeal@gmail.com>
> Date: Fri, 22 Apr 2016 14:21:08 +0200
> Subject: [PATCH] isolated-functions.sh: eliminate loop in has()
> 
> Looping is slow and clutters debug log.
> Still this wouldn't matter that much if has() wasn't one of the most used
> functions.

do you have any benchmarks?  what you say makes sense but i'm not sure
of the implementation details of "$A" == "*${B}*" so its hard to say.

> 
> Thus this patch should bring a general improvement.
> ---
>  bin/isolated-functions.sh | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/bin/isolated-functions.sh b/bin/isolated-functions.sh
> index e320f71..6900f99 100644
> --- a/bin/isolated-functions.sh
> +++ b/bin/isolated-functions.sh
> @@ -463,14 +463,12 @@ hasv() {
>  }
> 
>  has() {
> -       local needle=$1
> +       local needle=$'\a'"$1"$'\a'

why the ascii bell?  just because you'd never expect it in a parameter
to has?

>         shift
> +       local IFS=$'\a'
> +       local haystack=$'\a'"$@"$'\a'

you want "$*" here not "$@"

> 
> -       local x
> -       for x in "$@"; do
> -               [ "${x}" = "${needle}" ] && return 0
> -       done
> -       return 1
> +       [[ "${haystack}" == *"${needle}"* ]]
>  }
> 
>  __repo_attr() {
> --
> 2.7.3
> 


-- 
Anthony G. Basile, Ph. D.
Chair of Information Technology
D'Youville College
Buffalo, NY 14201
(716) 829-8197