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[英]How do I pass a file/blob from JavaScript to emscripten/WebAssembly (C++)?
[英]How do I pass objects from Javascript to C++ using Emscripten
我想将一个Javascript对象从JS传递回C ++类/方法。 我有以下简单的代码片段,它不起作用:
// Access JS objects in C++ like C++ objects
#include "emscripten/val.h" //Causing errors !
using namespace emscripten;
int main() {
val Math = val::global("Math");
return Math.call("abs", -10); // returns 10
}
我使用以下代码在Windows上使用emscripten进行编译:
cmd> emcc Access_Objects.cpp
我得到了很大的错误记录:
In file included from Access_Objects.cpp:2:
In file included from C:\Program Files\Emscripten\emscripten\1.16.0\system\inclu
de\emscripten/val.h:4:
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:2
4:5: error:
unknown type name 'constexpr'
constexpr bool has_unbound_type_names = true;
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:2
4:15: error:
expected unqualified-id
constexpr bool has_unbound_type_names = true;
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:5
6:21: error:
use of undeclared identifier 'has_unbound_type_names'
if (has_unbound_type_names || std::is_polymorphic<C>::value) {
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:6
7:17: error:
use of undeclared identifier 'has_unbound_type_names'
if (has_unbound_type_names || std::is_polymorphic<C>::value) {
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:8
2:40: error:
a space is required between consecutive right angle brackets (use '> >')
struct TypeID<std::unique_ptr<T>> {
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:9
8:42: error:
a space is required between consecutive right angle brackets (use '> >')
struct TypeID<AllowedRawPointer<T>> {
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
82:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(char);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
82:9: error:
expected member name or ';' after declaration specifiers
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(char);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:23: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
~~~~~~~~~ ^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
83:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(signed char);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
83:9: error:
expected member name or ';' after declaration specifiers
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(signed char);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:23: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
~~~~~~~~~ ^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
84:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(unsigned char);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
84:9: error:
expected member name or ';' after declaration specifiers
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(unsigned char);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:23: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
~~~~~~~~~ ^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
85:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(signed short);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
85:9: error:
expected member name or ';' after declaration specifiers
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(signed short);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:23: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
~~~~~~~~~ ^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
86:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(unsigned short);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
86:9: error:
expected member name or ';' after declaration specifiers
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(unsigned short);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:23: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
~~~~~~~~~ ^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
87:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(signed int);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
87:9: error:
expected member name or ';' after declaration specifiers
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(signed int);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:23: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
~~~~~~~~~ ^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
88:9: error:
unknown type name 'constexpr'
EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE(unsigned int);
^
C:\Program Files\Emscripten\emscripten\1.16.0\system\include\emscripten/wire.h:1
74:13: note:
expanded from macro 'EMSCRIPTEN_DEFINE_NATIVE_BINDING_TYPE'
constexpr static WireType toWireType(const type& v) { \
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
ERROR root: compiler frontend failed to generate LLVM bitcode, halting
错误是在'wire.h'中引起的,它包含在'emscripten / val.h'中。
我该如何解决这些错误? 或者有没有其他方法将对象从JS传递给C ++?
还有其他方法可以在JS和C ++之间进行交互。 我发现最稳定的方法是通过包装JS函数来构建自己的库,以便可以从C ++中调用它们。
如果你想从C ++调用Javascript的Math.abs(),你可以编辑“src / library.JS”。 在那里,您将找到一个C ++中可用的函数名称的巨型映射。 如果你想调用你的新函数“JS_Math_abs”,你会添加:
JS_Math_abs: function(value) {
return Math.abs(value);
},
然后,您将修改C ++代码以指定输入和输出类型。 加:
extern "C" {
extern int JS_Math_abs(int);
}
不要误解我的意思,这种方法比val应该更烦人(它是否正常工作),但它最终也应该更有效率。 一旦你有了需要包装的主库,你会发现它非常稳定。 但是,在大多数情况下,使用像abs()这样的函数的C ++版本很容易。
您可以在此处找到有关创建自己的库的更多信息: http : //kripken.github.io/emscripten-site/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html#interacting-with-code-call-javascript-从本机
如上所述,您需要将-std = c ++ 11作为其使用c ++ 11传递给编译器
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