[% setvar title Standard support for opening i/o handles on scalars and arrays-of-scalars %]
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Standard support for opening i/o handles on scalars and arrays-of-scalars
Maintainer: Eryq (Erik Dorfman) <email@example.com> Date: 23 Aug 2000 Last Modified: 24 Sep 2000 Mailing List: firstname.lastname@example.org Number: 186 Version: 3 Status: Frozen
Support the ability to open an i/o handle on a scalar, and also on an array-of-scalars. Implement this in C (for speed), and provide it in a "standard" extension module (for universal availability).
It's extremely useful to be able to open an i/o handle on a common in-core data structure, such as a scalar or an array-of-lines. Such a capability breaks down the artificial boundary between core-based and disk-based data processing, allowing a developer to...
The CPAN modules IO::Scalar, IO::ScalarArray, and IO::Lines currently provide some of this functionality, but their pure-Perl implementation (chosen for portability) is not as fast or memory-efficient as a native implementation could be. Additionally, since they are not part of the standard Perl distribution, many developers are either unaware of their existence or unwilling to obtain and install them.
This RFC proposes that support for "in-core i/o" be folded into the Perl distribution as a standard extension module, making use of native C code for speed.
As described above. The following i/o handle classes are proposed as minimally necessary; they are taken from existing Perl5 CPAN modules with the same names:
An i/o handle which can be opened on a scalar (string) variable. We simply treat the bytes of the scalar as a "virtual file".
An i/o handle which can be opened on an array of scalar (string) variables. Here, the "virtual file" is defined as the concatenation of the scalars in the array. One very common way to obtain such a data structure is to slurp a file into an array.
If Perl6 follows Java's example of distinguishing "bytes" from
"characters", then it should be understood that the proposed i/o handles
manipulate bytes, not characters. That is, the Java equivalents
are classes like
Character-based i/o should be handled by some additional conversion mechanism which is wrapped around byte-based i/o; this mechanism should be applicable to any i/o stream. A look at the Java implementation of byte-oriented "input/output streams" versus character-oriented "readers and writers" is worthwhile for this.