使用 Perl XS 和 PerlIO 制作旧库 [英] Making an old library work with Perl XS and PerlIO

问题描述

我是一个 XS 初学者，我正在考虑更改一个现有的 XS 模块，该模块大量使用 15 年以上的底层 C 库(实际上该模块基本上只是粘到这个库上).问题是我希望能够使用 PerlIO 字符串技巧，例如:

I am rather an XS beginner and I am looking into changing an existing XS module which uses a 15+ year old underlying C library heavily (in fact the module is basically just glue to this library). The problem is that I would like to be able to use PerlIO string trickery like:

open($fh, '<', \$string);

然后将 $fh 传递给库需要 FILE 的 XS 粘合.问题是 XS 有:

and then pass $fh to the XS glue where the library is expecting FILE. The problem is that the XS has:

int
_parse (entry_ref, filename, file, preserve=FALSE)
    SV *    entry_ref;
    char *  filename;
    FILE *  file;
    boolean preserve;

我认为它需要:

PerlIO *  file;

这当然行不通，因为肯定不止于此.当我查看库中的 _parse 代码时，结果是:

This doesn't work of course as there must be more to it than that. When I look at the _parse code in the library, it ends up in:

AST * bt_parse_entry (FILE *    infile,
                      char *    filename,
                      btshort    options,
                      boolean * status)
{
   AST *         entry_ast = NULL;
   static int *  err_counts = NULL;
   static FILE * prev_file = NULL;

用 FILE 再次输入.现在我必须开始的基本问题是 - 这甚至可能在不更改库的情况下进行吗?也就是说，我可以通过更改 XS 来从字符串 PerlIO 行为中获得伪文件句柄吗?

with FILE types again. Now the basic question I have have to start with is - is this even possible without changing the library; that is, can I get pseudo-filehandle from strings PerlIO behaviour just by changing the XS?

推荐答案

Perl API 提供 PerlIO_exportFILE() (实现)，它可以将带有文件描述符的 PerlIO 句柄转换为 stdio FILE 指针.由于 PerlIO::Scalar 是没有文件描述符的内存中"文件句柄转换无法成功.传递 PerlIO::Scalar 句柄的唯一可移植方式是将其刷新到临时文件.不太便携的方法是使用支持回调的 stdio，如 BSD 实现，funopen(3).

The Perl API provides PerlIO_exportFILE() (Implementation) which can convert a PerlIO handle with a file descriptor to a stdio FILE pointer. Since PerlIO::Scalar is an "in-memory" file handle without a file descriptor the conversion cannot succeed. The only portable way to pass a PerlIO::Scalar handle would be to flush it to a temporary file. The less portable way would be to use a stdio that supports callbacks, like the BSD implementation, funopen(3).

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