对于通过参数返回一个函数创建类型映射 [英] Create a typemap for a function that returns through arguments

问题描述

我转换C API> Java和我有下面的函数原型。

I am converting C api > Java, and I have the following function prototype.

/*
 Retrieves an individual field value from the current Line
 \param reader pointer to Text Reader object.
 \param field_num relative field [aka column] index: first field has index 0.
 \param type on completion this variable will contain the value type.
 \param value on completion this variable will contain the current field value.
 \return 0 on failure: any other value on success.
 */

extern int gaiaTextReaderFetchField (gaiaTextReaderPtr reader, int field_num, int *type, const char **value);

我想获得返回的状态不如预期，返回类型为int和价值作为一个字符串（不被释放）

I would like to get the status returned as expected, return the "type" as an int and "value" as a string (not to be deallocated)

从技术文档我发现你创建一对夫妇可以保留返回值结构的。

From documentation I have found that you create a couple of structs that can retain the returned values.

可能有人请帮助我这第一个？

Could someone please help make this first one with me?

推荐答案

假设你的函数声明存在于一个名为header.h，你可以这样做：

Assuming your function declaration exists in a file called header.h you can do something like:

%module test

%{
#include "header.h"
%}

%inline %{
  %immutable;
  struct FieldFetch {
    int status;
    int type;
    char *value;
  };
  %mutable;

  struct FieldFetch gaiaTextReaderFetchField(gaiaTextReaderPtr reader, int field_num) {
    struct FieldFetch result;
    result.status = gaiaTextReaderFetchField(reader, field_num, &result.type, &result.value);
    return result;
  }
%}

%ignore gaiaTextReaderFetchField;
%include "header.h"

这隐藏了真正的 gaiaTextReaderFetchField ，而是替代返回两个输出参数，并以（不可修改）结构调用的结果的版本。

This hides the "real" gaiaTextReaderFetchField and instead substitutes a version that returns both of the output parameters and the result of the call in an (unmodifiable) struct.

（你可以做的返回状态为0会导致异常，而不是被抛出，如果您愿意，使用％javaexception ，而不是将其放置在结构）

(You could make the return status being 0 cause an exception to be thrown instead if you'd rather, using %javaexception instead of placing it in the struct)

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