ExtUtils-ParseXS-3.16

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名前
説明

名前¶

perlxstypemap - Perl XS C/Perl type mapping

perlxstypemap - Perl XS C/Perl 型マッピング

説明¶

The more you think about interfacing between two languages, the more you'll realize that the majority of programmer effort has to go into converting between the data structures that are native to either of the languages involved. This trumps other matter such as differing calling conventions because the problem space is so much greater. There are simply more ways to shove data into memory than there are ways to implement a function call.

二つの言語の間のインターフェースについて考えれば考えるほど、プログラマの努力の大半はどちらかの言語にネイティブなデータ構造の変換に費やされることに気付くことになります。これは呼び出し規則の違いといったものより重要です; 問題空間が遥かに大きいからです。単純に、関数呼び出しを実装する方法よりデータをメモリに納める方法の方が遥かに多いです。

Perl XS' attempt at a solution to this is the concept of typemaps. At an abstract level, a Perl XS typemap is nothing but a recipe for converting from a certain Perl data structure to a certain C data structure and vice versa. Since there can be C types that are sufficiently similar to warrant converting with the same logic, XS typemaps are represented by a unique identifier, henceforth called an <XS type> in this document. You can then tell the XS compiler that multiple C types are to be mapped with the same XS typemap.

これに対する Perl XS での解決の試みは、typemap という概念です。抽象レベルでは、Perl の XS typemap はある種の Perl データ構造からある種の C データ構造、およびその逆への変換のためのレシピ以外の何者でもありません。同じロジックでの変換を保証することと十分に似ている C 型もあるので、 XS typemap はユニークな識別子として表現され、以降この文書では「XS 型」 <XS type> と呼ばれます。それから複数の C 型が同じ XS typemap にマッピングされるように XS コンパイラに伝えることができます。

In your XS code, when you define an argument with a C type or when you are using a CODE: and an OUTPUT: section together with a C return type of your XSUB, it'll be the typemapping mechanism that makes this easy.

XS コード中で、C 型の引数を定義したり、XSUB の C 返り型と CODE: と OUTPUT: の節を共に使ったりする場合、これらを簡単にするために typemap 機構があります。

typemap の構造¶

In more practical terms, the typemap is a collection of code fragments which are used by the xsubpp compiler to map C function parameters and values to Perl values. The typemap file may consist of three sections labelled TYPEMAP, INPUT, and OUTPUT. An unlabelled initial section is assumed to be a TYPEMAP section. The INPUT section tells the compiler how to translate Perl values into variables of certain C types. The OUTPUT section tells the compiler how to translate the values from certain C types into values Perl can understand. The TYPEMAP section tells the compiler which of the INPUT and OUTPUT code fragments should be used to map a given C type to a Perl value. The section labels TYPEMAP, INPUT, or OUTPUT must begin in the first column on a line by themselves, and must be in uppercase.

より実際的な用語としては、typemap は C 関数の引数と値を Perl の値にマッピングするために xsubpp コンパイラによって使われるコード片の集合 (collection)です。 typemap ファイルは TYPEMAP, INPUT, OUTPUT というラベルの付いた三つのセクションから構成されます。ラベルのついていない初期化セクションは、TYPEMAP であるかのように仮定されます。 INPUT セクションは、コンパイラに対して Perl の値をどのように (幾つかある) C の型に変換するかを指示します。 OUTPUT セクションは、コンパイラに対してどのようにして C の型を Perl が認識できる値に変換するのかを指示します。 TYPEMAP セクションは、コンパイラに対して指示された C の型を Perl の値にマッピングするのに使うべき INPUT セクションもしくは OUTPUT セクションにあるコード片を指示します。セクションラベル TYPEMAP, INPUT, OUTPUT は行の先頭におかれ、大文字でなければなりません。

Each type of section can appear an arbitrary number of times and does not have to appear at all. For example, a typemap may commonly lack INPUT and OUTPUT sections if all it needs to do is associate additional C types with core XS types like T_PTROBJ. Lines that start with a hash # are considered comments and ignored in the TYPEMAP section, but are considered significant in INPUT and OUTPUT. Blank lines are generally ignored.

Traditionally, typemaps needed to be written to a separate file, conventionally called typemap in a CPAN distribution. With ExtUtils::ParseXS (the XS compiler) version 3.12 or better which comes with perl 5.16, typemaps can also be embedded directly into XS code using a HERE-doc like syntax:

  TYPEMAP: <<HERE
  ...
  HERE

where HERE can be replaced by other identifiers like with normal Perl HERE-docs. All details below about the typemap textual format remain valid.

where HERE can be replaced by other identifiers like with normal Perl HERE-docs. All details below about the typemap textual format remain valid. (TBT)

The TYPEMAP section should contain one pair of C type and XS type per line as follows. An example from the core typemap file:

The TYPEMAP section should contain one pair of C type and XS type per line as follows. An example from the core typemap file: (TBT)

  TYPEMAP
  # all variants of char* is handled by the T_PV typemap
  char *          T_PV
  const char *    T_PV
  unsigned char * T_PV
  ...

The INPUT and OUTPUT sections have identical formats, that is, each unindented line starts a new in- or output map respectively. A new in- or output map must start with the name of the XS type to map on a line by itself, followed by the code that implements it indented on the following lines. Example:

  INPUT
  T_PV
    $var = ($type)SvPV_nolen($arg)
  T_PTR
    $var = INT2PTR($type,SvIV($arg))

We'll get to the meaning of those Perlish-looking variables in a little bit.

We'll get to the meaning of those Perlish-looking variables in a little bit. (TBT)

Finally, here's an example of the full typemap file for mapping C strings of the char * type to Perl scalars/strings:

Finally, here's an example of the full typemap file for mapping C strings of the char * type to Perl scalars/strings: (TBT)

  TYPEMAP
  char *  T_PV
  
  INPUT
  T_PV
    $var = ($type)SvPV_nolen($arg)
  
  OUTPUT
  T_PV
    sv_setpv((SV*)$arg, $var);

Here's a more complicated example: suppose that you wanted struct netconfig to be blessed into the class Net::Config. One way to do this is to use underscores (_) to separate package names, as follows:

もっと複雑な例を挙げましょう。 struct netconfig を Net::Config というクラスに bless したいと考えていると仮定しましょう。これを行うやり方の一つは、アンダースコア(_)を以下の様にパッケージ名を区切るために使うというものです。

  typedef struct netconfig * Net_Config;

And then provide a typemap entry T_PTROBJ_SPECIAL that maps underscores to double-colons (::), and declare Net_Config to be of that type:

それからアンダースコアをダブルコロン(::)にマップする typemap エントリー T_PTROBJ_SPECIAL を用意して、Net_Config をその型として宣言します。

  TYPEMAP
  Net_Config      T_PTROBJ_SPECIAL
  
  INPUT
  T_PTROBJ_SPECIAL
    if (sv_derived_from($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")){
      IV tmp = SvIV((SV*)SvRV($arg));
      $var = INT2PTR($type, tmp);
    }
    else
      croak(\"$var is not of type ${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")
  
  OUTPUT
  T_PTROBJ_SPECIAL
    sv_setref_pv($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\",
                 (void*)$var);

The INPUT and OUTPUT sections substitute underscores for double-colons on the fly, giving the desired effect. This example demonstrates some of the power and versatility of the typemap facility.

INPUT セクションと OUTPUT セクションはアンダースコアをダブルコロンへその場で置換して、期待される効果をもたらします。この例では typemap 機構の威力と適用範囲の広さを例示します。

The INT2PTR macro (defined in perl.h) casts an integer to a pointer of a given type, taking care of the possible different size of integers and pointers. There are also PTR2IV, PTR2UV, PTR2NV macros, to map the other way, which may be useful in OUTPUT sections.

(perl.h に定義されている) INT2PTR マクロは、整数から与えられた型のポインタへのキャストを、整数とポインタとのサイズが異なる可能性を考慮しつつ行います。また、OUTPUT セクションで有用かもしれない、他の方法でマッピングする、 PTR2IV, PTR2UV, PTR2NV マクロもあります。

配布の中の typemap ファイルの役割¶

The default typemap in the lib/ExtUtils directory of the Perl source contains many useful types which can be used by Perl extensions. Some extensions define additional typemaps which they keep in their own directory. These additional typemaps may reference INPUT and OUTPUT maps in the main typemap. The xsubpp compiler will allow the extension's own typemap to override any mappings which are in the default typemap. Instead of using an additional typemap file, typemaps may be embedded verbatim in XS with a heredoc-like syntax. See the documentation on the TYPEMAP: XS keyword.

Perl のソースの lib/ExtUtils ディレクトリにあるデフォルトの typemap は Perl のエクステンションから使うことのできるたくさんの便利な型があります。一部のエクステンションではそれに固有のディレクトリに、typemap に対する追加の定義を置いています。これらの追加された typemap はメインの typemap にある INPUT や OUTPUT のマッピングを参照することができます。 xsubpp コンパイラは、エクステンションに固有の typemap がデフォルトの typemap にあるマッピングをオーバーライドすることを許しています。追加の typemap ファイルを使う代わりに、typemap はヒヤドキュメント風の文法を使って XS にそのまま組み込むことができます。 TYPEMAP: XS キーワードの文書を参照してください。

For CPAN distributions, you can assume that the XS types defined by the perl core are already available. Additionally, the core typemap has default XS types for a large number of C types. For example, if you simply return a char * from your XSUB, the core typemap will have this C type associated with the T_PV XS type. That means your C string will be copied into the PV (pointer value) slot of a new scalar that will be returned from your XSUB to to Perl.

If you're developing a CPAN distribution using XS, you may add your own file called typemap to the distribution. That file may contain typemaps that either map types that are specific to your code or that override the core typemap file's mappings for common C types.

CPAN 配布間で typemap を共有する¶

Starting with ExtUtils::ParseXS version 3.13_01 (comes with perl 5.16 and better), it is rather easy to share typemap code between multiple CPAN distributions. The general idea is to share it as a module that offers a certain API and have the dependent modules declare that as a built-time requirement and import the typemap into the XS. An example of such a typemap-sharing module on CPAN is ExtUtils::Typemaps::Basic. Two steps to getting that module's typemaps available in your code:

(perl 5.16 以降に同梱されている) ExtUtils::ParseXS バージョン 3.13_01 から、 it is rather easy to share typemap code between multiple CPAN distributions. The general idea is to share it as a module that offers a certain API and have the dependent modules declare that as a built-time requirement and import the typemap into the XS. An example of such a typemap-sharing module on CPAN is ExtUtils::Typemaps::Basic. Two steps to getting that module's typemaps available in your code: (TBT)

Declare ExtUtils::Typemaps::Basic as a build-time dependency in Makefile.PL (use BUILD_REQUIRES), or in your Build.PL (use build_requires).

Makefile.PL (BUILD_REQUIRES を使う) または Build.PL (build_requires を使う) で、ビルド時依存として ExtUtils::Typemaps::Basic を宣言する。
Include the following line in the XS section of your XS file: (don't break the line)

XS ファイルの XS 節に以下の行を含めてください: (行は分割しないでください)
```
  INCLUDE_COMMAND: $^X -MExtUtils::Typemaps::Cmd
                   -e "print embeddable_typemap(q{Basic})"
```

typemap エントリを書く¶

Each INPUT or OUTPUT typemap entry is a double-quoted Perl string that will be evaluated in the presence of certain variables to get the final C code for mapping a certain C type.

それぞれの INPUT または OUTPUT typemap エントリは、特定の C 型にマッピングするための最終的な C コードを得るために、特定の変数の存在が評価される、ダブルクォートで囲まれた Perl 文字列です。

This means that you can embed Perl code in your typemap (C) code using constructs such as ${ perl code that evaluates to scalar reference here }. A common use case is to generate error messages that refer to the true function name even when using the ALIAS XS feature:

つまり、${ ここにスカラリファレンスに評価される perl コード } のような構文を使って、typemap (C) コードの中に Perl コードを組み込めるということです。一般的な使用法は、ALIAS XS 機能を使っているときでも、真の関数名を参照するエラーメッセージを生成することです:

  ${ $ALIAS ? \q[GvNAME(CvGV(cv))] : \qq[\"$pname\"] }

For many typemap examples, refer to the core typemap file that can be found in the perl source tree at lib/ExtUtils/typemap.

多くの typemap の例で、perl ソースツリーの lib/ExtUtils/typemap にあるコア typemap ファイルを参照しています。

The Perl variables that are available for interpolation into typemaps are the following:

typemap へ展開可能な Perl 変数は以下のものです:

$var - the name of the input or output variable, eg. RETVAL for return values.

$var - 入力または出力の変数名; 例えば返り値の RETVAL。
$type - the raw C type of the parameter, any : replaced with _.

$type - 引数の生の C 型; : は _ に置換されます。
$ntype - the supplied type with * replaced with Ptr. e.g. for a type of Foo::Bar, $ntype is Foo::Bar

$ntype - 提供された型 ; * は Ptr に置換されます。例えば Foo::Bar の型では、$ntype は Foo::Bar です。
$arg - the stack entry, that the parameter is input from or output to, e.g. ST(0)

$arg - スタックエントリ; 引数は入力または出力; 例えば ST(0)
$argoff - the argument stack offset of the argument. ie. 0 for the first argument, etc.

$argoff - 引数の引数スタックオフセット。つまり、最初の引数は 0、など。
$pname - the full name of the XSUB, with including the PACKAGE name, with any PREFIX stripped. This is the non-ALIAS name.

$pname - XSUB 完全名; PACKAGE 名を含み、PREFIX は除去されます。これは非-ALIAS 名です。
$Package - the package specified by the most recent PACKAGE keyword.

$Package - もっとも最近の PACKAGE キーワードで指定されたパッケージ。
$ALIAS - non-zero if the current XSUB has any aliases declared with ALIAS.

$ALIAS - 現在の XSUB が ALIAS で宣言された別名を持っていれば非 0。

コア typemap の完全な一覧¶

Each C type is represented by an entry in the typemap file that is responsible for converting perl variables (SV, AV, HV, CV, etc.) to and from that type. The following sections list all XS types that come with perl by default.

T_SV

This simply passes the C representation of the Perl variable (an SV*) in and out of the XS layer. This can be used if the C code wants to deal directly with the Perl variable.

This simply passes the C representation of the Perl variable (an SV*) in and out of the XS layer. This can be used if the C code wants to deal directly with the Perl variable. (TBT)

T_SVREF

Used to pass in and return a reference to an SV.

SV へのリファレンスを渡したり返したりするために使われます。

Note that this typemap does not decrement the reference count when returning the reference to an SV*. See also: T_SVREF_REFCOUNT_FIXED

Note that this typemap does not decrement the reference count when returning the reference to an SV*. See also: T_SVREF_REFCOUNT_FIXED (TBT)

T_SVREF_FIXED

Used to pass in and return a reference to an SV. This is a fixed variant of T_SVREF that decrements the refcount appropriately when returning a reference to an SV*. Introduced in perl 5.15.4.

Used to pass in and return a reference to an SV. This is a fixed variant of T_SVREF that decrements the refcount appropriately when returning a reference to an SV*. Introduced in perl 5.15.4. (TBT)

T_AVREF

From the perl level this is a reference to a perl array. From the C level this is a pointer to an AV.

perl レベルでは perl 配列へのリファレンスです。 C レベルでは AV へのポインタです。

Note that this typemap does not decrement the reference count when returning an AV*. See also: T_AVREF_REFCOUNT_FIXED

この typemap は AV* を返すときに参照カウントをデクリメントしないことに注意してください。 T_AVREF_REFCOUNT_FIXED も参照してください。

T_AVREF_REFCOUNT_FIXED

From the perl level this is a reference to a perl array. From the C level this is a pointer to an AV. This is a fixed variant of T_AVREF that decrements the refcount appropriately when returning an AV*. Introduced in perl 5.15.4.

T_HVREF

From the perl level this is a reference to a perl hash. From the C level this is a pointer to an HV.

From the perl level this is a reference to a perl hash. From the C level this is a pointer to an HV. (TBT)

Note that this typemap does not decrement the reference count when returning an HV*. See also: T_HVREF_REFCOUNT_FIXED

Note that this typemap does not decrement the reference count when returning an HV*. See also: T_HVREF_REFCOUNT_FIXED (TBT)

T_HVREF_REFCOUNT_FIXED

From the perl level this is a reference to a perl hash. From the C level this is a pointer to an HV. This is a fixed variant of T_HVREF that decrements the refcount appropriately when returning an HV*. Introduced in perl 5.15.4.

T_CVREF

From the perl level this is a reference to a perl subroutine (e.g. $sub = sub { 1 };). From the C level this is a pointer to a CV.

From the perl level this is a reference to a perl subroutine (e.g. $sub = sub { 1 };). From the C level this is a pointer to a CV. (TBT)

Note that this typemap does not decrement the reference count when returning an HV*. See also: T_HVREF_REFCOUNT_FIXED

Note that this typemap does not decrement the reference count when returning an HV*. See also: T_HVREF_REFCOUNT_FIXED (TBT)

T_CVREF_REFCOUNT_FIXED

From the perl level this is a reference to a perl subroutine (e.g. $sub = sub { 1 };). From the C level this is a pointer to a CV.

From the perl level this is a reference to a perl subroutine (e.g. $sub = sub { 1 };). From the C level this is a pointer to a CV. (TBT)

This is a fixed variant of T_HVREF that decrements the refcount appropriately when returning an HV*. Introduced in perl 5.15.4.

This is a fixed variant of T_HVREF that decrements the refcount appropriately when returning an HV*. Introduced in perl 5.15.4. (TBT)

T_SYSRET

The T_SYSRET typemap is used to process return values from system calls. It is only meaningful when passing values from C to perl (there is no concept of passing a system return value from Perl to C).

System calls return -1 on error (setting ERRNO with the reason) and (usually) 0 on success. If the return value is -1 this typemap returns undef. If the return value is not -1, this typemap translates a 0 (perl false) to "0 but true" (which is perl true) or returns the value itself, to indicate that the command succeeded.

The POSIX module makes extensive use of this type.

POSIX モジュールはこの型を広範囲に使います。

T_UV

An unsigned integer.

符号なし整数。

T_IV

A signed integer. This is cast to the required integer type when passed to C and converted to an IV when passed back to Perl.

符号付き整数。 This is cast to the required integer type when passed to C and converted to an IV when passed back to Perl. (TBT)

T_INT

A signed integer. This typemap converts the Perl value to a native integer type (the int type on the current platform). When returning the value to perl it is processed in the same way as for T_IV.

符号付き整数。 This typemap converts the Perl value to a native integer type (the int type on the current platform). When returning the value to perl it is processed in the same way as for T_IV. (TBT)

Its behaviour is identical to using an int type in XS with T_IV.

この振る舞いは XS で T_IV 付きで int を使うのと同じです。

T_ENUM

An enum value. Used to transfer an enum component from C. There is no reason to pass an enum value to C since it is stored as an IV inside perl.

列挙値。 C から列挙要素を転送するために使われます。 C に列挙値を渡す理由はありません; perl の内部では IV として保管されているからです。

T_BOOL

A boolean type. This can be used to pass true and false values to and from C.

真偽値型。これは C との間で真と偽の値を渡すために使えます。

T_U_INT

This is for unsigned integers. It is equivalent to using T_UV but explicitly casts the variable to type unsigned int. The default type for unsigned int is T_UV.

これは符号なし整数のためのものです。 It is equivalent to using T_UV but explicitly casts the variable to type unsigned int. The default type for unsigned int is T_UV. (TBT)

T_SHORT

Short integers. This is equivalent to T_IV but explicitly casts the return to type short. The default typemap for short is T_IV.

short 整数。 This is equivalent to T_IV but explicitly casts the return to type short. The default typemap for short is T_IV. (TBT)

T_U_SHORT

Unsigned short integers. This is equivalent to T_UV but explicitly casts the return to type unsigned short. The default typemap for unsigned short is T_UV.

符号なし short 整数。 This is equivalent to T_UV but explicitly casts the return to type unsigned short. The default typemap for unsigned short is T_UV. (TBT)

T_U_SHORT is used for type U16 in the standard typemap.

T_U_SHORT は標準 typemap での U16 型で使われます。

T_LONG

Long integers. This is equivalent to T_IV but explicitly casts the return to type long. The default typemap for long is T_IV.

long 整数。 This is equivalent to T_IV but explicitly casts the return to type long. The default typemap for long is T_IV. (TBT)

T_U_LONG

Unsigned long integers. This is equivalent to T_UV but explicitly casts the return to type unsigned long. The default typemap for unsigned long is T_UV.

符号なし long 整数。 This is equivalent to T_UV but explicitly casts the return to type unsigned long. The default typemap for unsigned long is T_UV. (TBT)

T_U_LONG is used for type U32 in the standard typemap.

T_U_LONG は標準 typemap での U32 型で使われます。

T_CHAR

Single 8-bit characters.

単一の 8 ビット文字。

T_U_CHAR

An unsigned byte.

符号なしバイト。

T_FLOAT

A floating point number. This typemap guarantees to return a variable cast to a float.

浮動小数点数。この typemap は float にキャストした変数を返すことを保証します。

T_NV

A Perl floating point number. Similar to T_IV and T_UV in that the return type is cast to the requested numeric type rather than to a specific type.

Perl の浮動小数点数。 Similar to T_IV and T_UV in that the return type is cast to the requested numeric type rather than to a specific type. (TBT)

T_DOUBLE

A double precision floating point number. This typemap guarantees to return a variable cast to a double.

倍精度浮動小数点数。 This typemap guarantees to return a variable cast to a double. (TBT)

T_PV

A string (char *).

文字列 (char *)。

T_PTR

A memory address (pointer). Typically associated with a void * type.

メモリアドレス(ポインタ)。典型的には void * 型に結びつけられます。

T_PTRREF

Similar to T_PTR except that the pointer is stored in a scalar and the reference to that scalar is returned to the caller. This can be used to hide the actual pointer value from the programmer since it is usually not required directly from within perl.

The typemap checks that a scalar reference is passed from perl to XS.

typemap はスカラリファレンスが perl から XS に渡されたことをチェックします。

T_PTROBJ

Similar to T_PTRREF except that the reference is blessed into a class. This allows the pointer to be used as an object. Most commonly used to deal with C structs. The typemap checks that the perl object passed into the XS routine is of the correct class (or part of a subclass).

The pointer is blessed into a class that is derived from the name of type of the pointer but with all '*' in the name replaced with 'Ptr'.

The pointer is blessed into a class that is derived from the name of type of the pointer but with all '*' in the name replaced with 'Ptr'. (TBT)

T_REF_IV_REF

NOT YET

未記述

T_REF_IV_PTR

Similar to T_PTROBJ in that the pointer is blessed into a scalar object. The difference is that when the object is passed back into XS it must be of the correct type (inheritance is not supported).

Similar to T_PTROBJ in that the pointer is blessed into a scalar object. The difference is that when the object is passed back into XS it must be of the correct type (inheritance is not supported). (TBT)

The pointer is blessed into a class that is derived from the name of type of the pointer but with all '*' in the name replaced with 'Ptr'.

The pointer is blessed into a class that is derived from the name of type of the pointer but with all '*' in the name replaced with 'Ptr'. (TBT)

T_PTRDESC

NOT YET

未記述

T_REFREF

Similar to T_PTRREF, except the pointer stored in the referenced scalar is dereferenced and copied to the output variable. This means that T_REFREF is to T_PTRREF as T_OPAQUE is to T_OPAQUEPTR. All clear?

Only the INPUT part of this is implemented (Perl to XSUB) and there are no known users in core or on CPAN.

これは INPUT 部 (Perl から XSUB) のみが実装されていて、コアや CPAN で使っているコードは知られていません。

T_REFOBJ

NOT YET

未記述

T_OPAQUEPTR

This can be used to store bytes in the string component of the SV. Here the representation of the data is irrelevant to perl and the bytes themselves are just stored in the SV. It is assumed that the C variable is a pointer (the bytes are copied from that memory location). If the pointer is pointing to something that is represented by 8 bytes then those 8 bytes are stored in the SV (and length() will report a value of 8). This entry is similar to T_OPAQUE.

In principle the unpack() command can be used to convert the bytes back to a number (if the underlying type is known to be a number).

In principle the unpack() command can be used to convert the bytes back to a number (if the underlying type is known to be a number). (TBT)

This entry can be used to store a C structure (the number of bytes to be copied is calculated using the C sizeof function) and can be used as an alternative to T_PTRREF without having to worry about a memory leak (since Perl will clean up the SV).

T_OPAQUE

This can be used to store data from non-pointer types in the string part of an SV. It is similar to T_OPAQUEPTR except that the typemap retrieves the pointer directly rather than assuming it is being supplied. For example, if an integer is imported into Perl using T_OPAQUE rather than T_IV the underlying bytes representing the integer will be stored in the SV but the actual integer value will not be available. i.e. The data is opaque to perl.

The data may be retrieved using the unpack function if the underlying type of the byte stream is known.

The data may be retrieved using the unpack function if the underlying type of the byte stream is known. (TBT)

T_OPAQUE supports input and output of simple types. T_OPAQUEPTR can be used to pass these bytes back into C if a pointer is acceptable.

T_OPAQUE supports input and output of simple types. T_OPAQUEPTR can be used to pass these bytes back into C if a pointer is acceptable. (TBT)

Implicit array

xsubpp supports a special syntax for returning packed C arrays to perl. If the XS return type is given as

xsubpp supports a special syntax for returning packed C arrays to perl. If the XS return type is given as (TBT)

  array(type, nelem)

xsubpp will copy the contents of nelem * sizeof(type) bytes from RETVAL to an SV and push it onto the stack. This is only really useful if the number of items to be returned is known at compile time and you don't mind having a string of bytes in your SV. Use T_ARRAY to push a variable number of arguments onto the return stack (they won't be packed as a single string though).

This is similar to using T_OPAQUEPTR but can be used to process more than one element.

This is similar to using T_OPAQUEPTR but can be used to process more than one element. (TBT)

T_PACKED

Calls user-supplied functions for conversion. For OUTPUT (XSUB to Perl), a function named XS_pack_$ntype is called with the output Perl scalar and the C variable to convert from. $ntype is the normalized C type that is to be mapped to Perl. Normalized means that all * are replaced by the string Ptr. The return value of the function is ignored.

Conversely for INPUT (Perl to XSUB) mapping, the function named XS_unpack_$ntype is called with the input Perl scalar as argument and the return value is cast to the mapped C type and assigned to the output C variable.

An example conversion function for a typemapped struct foo_t * might be:

typemap された構造体 foo_t * のための変換関数の例は次のようなものです:

  static void
  XS_pack_foo_tPtr(SV *out, foo_t *in)
  {
    dTHX; /* alas, signature does not include pTHX_ */
    HV* hash = newHV();
    hv_stores(hash, "int_member", newSViv(in->int_member));
    hv_stores(hash, "float_member", newSVnv(in->float_member));
    /* ... */

    /* mortalize as thy stack is not refcounted */
    sv_setsv(out, sv_2mortal(newRV_noinc((SV*)hash)));
  }

The conversion from Perl to C is left as an exercise to the reader, but the prototype would be:

Perl から C への変換は読者の演習として残されていますが、プロトタイプは次のようになります:

  static foo_t *
  XS_unpack_foo_tPtr(SV *in);

Instead of an actual C function that has to fetch the thread context using dTHX, you can define macros of the same name and avoid the overhead. Also, keep in mind to possibly free the memory allocated by XS_unpack_foo_tPtr.

T_PACKEDARRAY

T_PACKEDARRAY is similar to T_PACKED. In fact, the INPUT (Perl to XSUB) typemap is indentical, but the OUTPUT typemap passes an additional argument to the XS_pack_$ntype function. This third parameter indicates the number of elements in the output so that the function can handle C arrays sanely. The variable needs to be declared by the user and must have the name count_$ntype where $ntype is the normalized C type name as explained above. The signature of the function would be for the example above and foo_t **:

T_PACKEDARRAY は T_PACKED に似ています。 In fact, the INPUT (Perl to XSUB) typemap is indentical, but the OUTPUT typemap passes an additional argument to the XS_pack_$ntype function. This third parameter indicates the number of elements in the output so that the function can handle C arrays sanely. The variable needs to be declared by the user and must have the name count_$ntype where $ntype is the normalized C type name as explained above. The signature of the function would be for the example above and foo_t **: (TBT)

  static void
  XS_pack_foo_tPtrPtr(SV *out, foo_t *in, UV count_foo_tPtrPtr);

The type of the third parameter is arbitrary as far as the typemap is concerned. It just has to be in line with the declared variable.

The type of the third parameter is arbitrary as far as the typemap is concerned. It just has to be in line with the declared variable. (TBT)

Of course, unless you know the number of elements in the sometype ** C array, within your XSUB, the return value from foo_t ** XS_unpack_foo_tPtrPtr(...) will be hard to decypher. Since the details are all up to the XS author (the typemap user), there are several solutions, none of which particularly elegant. The most commonly seen solution has been to allocate memory for N+1 pointers and assign NULL to the (N+1)th to facilitate iteration.

Alternatively, using a customized typemap for your purposes in the first place is probably preferrable.

あるいは、最初の場所であなたの目的のためのカスタマイズされた typemap を使う方がおそらく好ましいです。

T_DATAUNIT

NOT YET

未記述

T_CALLBACK

NOT YET

未記述

T_ARRAY

This is used to convert the perl argument list to a C array and for pushing the contents of a C array onto the perl argument stack.

This is used to convert the perl argument list to a C array and for pushing the contents of a C array onto the perl argument stack. (TBT)

The usual calling signature is

この通常の呼び出しシグネチャは

  @out = array_func( @in );

Any number of arguments can occur in the list before the array but the input and output arrays must be the last elements in the list.

Any number of arguments can occur in the list before the array but the input and output arrays must be the last elements in the list. (TBT)

When used to pass a perl list to C the XS writer must provide a function (named after the array type but with 'Ptr' substituted for '*') to allocate the memory required to hold the list. A pointer should be returned. It is up to the XS writer to free the memory on exit from the function. The variable ix_$var is set to the number of elements in the new array.

When returning a C array to Perl the XS writer must provide an integer variable called size_$var containing the number of elements in the array. This is used to determine how many elements should be pushed onto the return argument stack. This is not required on input since Perl knows how many arguments are on the stack when the routine is called. Ordinarily this variable would be called size_RETVAL.

Additionally, the type of each element is determined from the type of the array. If the array uses type intArray * xsubpp will automatically work out that it contains variables of type int and use that typemap entry to perform the copy of each element. All pointer '*' and 'Array' tags are removed from the name to determine the subtype.

T_STDIO

This is used for passing perl filehandles to and from C using FILE * structures.

This is used for passing perl filehandles to and from C using FILE * structures. (TBT)

T_INOUT

This is used for passing perl filehandles to and from C using PerlIO * structures. The file handle can used for reading and writing. This corresponds to the +< mode, see also T_IN and T_OUT.

This is used for passing perl filehandles to and from C using PerlIO * structures. The file handle can used for reading and writing. This corresponds to the +< mode, see also T_IN and T_OUT. (TBT)

See perliol for more information on the Perl IO abstraction layer. Perl must have been built with -Duseperlio.

See perliol for more information on the Perl IO abstraction layer. Perl must have been built with -Duseperlio. (TBT)

There is no check to assert that the filehandle passed from Perl to C was created with the right open() mode.

There is no check to assert that the filehandle passed from Perl to C was created with the right open() mode. (TBT)

Hint: The perlxstut tutorial covers the T_INOUT, T_IN, and T_OUT XS types nicely.

Hint: The perlxstut tutorial covers the T_INOUT, T_IN, and T_OUT XS types nicely. (TBT)

T_IN

Same as T_INOUT, but the filehandle that is returned from C to Perl can only be used for reading (mode <).

Same as T_INOUT, but the filehandle that is returned from C to Perl can only be used for reading (mode <). (TBT)

T_OUT

Same as T_INOUT, but the filehandle that is returned from C to Perl is set to use the open mode +>.

Same as T_INOUT, but the filehandle that is returned from C to Perl is set to use the open mode +>. (TBT)