=head1 NAME

SPVM::Document::Extension - C/C++ Binding using SPVM Extension(BETA before 1.0)

=head1 Tutorial

=head2 Runtime Compile Native Function

If you use the feature Runtime Compile Native Function, you can write program using C language in runtime.
This is similar with L<Extension::C>, but L<SPVM> implement this feature by default.
  
  # SPVM/TestCase/Extension.spvm
  package TestCase::Extension {
    native sub sum : int ($num1 : int, $num2 : int);
  }
  
  // SPVM/TestCase/Extension.native/Extension.c
  #include <spvm_api.h>
  
  int32_t SPVM__TestCase__Extension__sum(SPVM_API* api, SPVM_API_VALUE* args) {
    
    int32_t total = args[0].int_value + args[1].int_value;
    
    return total;
  }

At first, you specify C<native> descripter at SPVM subroutine.

  package TestCase::Extension {
    # native descripter
    native sub sum : int ($num1 : int, $num2 : int);
  }

Next, you create "SPVM/TestCase/Extension/Extension.c" file
  
  SPVM/TestCase/Extension.spvm
  SPVM/TestCase/Extension.native/Extension.c

Next, you write C language. You include C<spvm_api.h>.

  #include <spvm_api.h>

C Function name must be replace C<:> with <_> and add C<SPVM__> to top of SPVM subroutine name. SPVM subroutine absolute name is
C<TestCase::Extension::sum>. C function name is C<SPVM__TestCase__Extension__sum>.

  int32_t SPVM__TestCase__Extension__sum(SPVM_API* api, SPVM_API_VALUE* args) {

    int32_t total = args[0].int_value + args[1].int_value;
    
    return total;
  }

First argument is C<api>. This is the pointer to C<SPVM_API>. Second argument is C<args>. This is array of C<SPVM_API_VALUE>.

SPVM_API_VALUE is union of C language. If you want to get int value, you do the followng.

  args[0].int_value

You can get all type of value by the following member.

  args[0].byte_value
  args[0].short_value
  args[0].int_value
  args[0].long_value
  args[0].float_value
  args[0].double_value
  args[0].object_value

Type of return value is corresponding the folloing type.

  [SPVM]              [C]
  byte                int8_t
  short               int16_t
  int                 int32_t
  long                int64_t
  float               float
  double              double
  [Object value]      SPVM_API_OBJECT*