JVM_UNSAFE_NATIVE_MEMCOPY

Copies native memory to managed memory allocated by third-party APIs, such as the Windows FormatMessage API. You cannot address managed memory except with this JVM_UNSAFE_NATIVE_MEMCOPY library routine.

Warning: When using this library routine, take great care to pass valid parameters. An invalid parameter can cause instability in your environment.

Syntax:

call “JVM_UNSAFE_NATIVE_MEMCOPY” using
   by value nativePointer
   by value memoryLength
   by value managedPointer
   returning status-code
end-call

Parameters:

nativePointer

A native-pointer.

memoryLength

The length expressed as PIC S9(9) COMP-5.

managedPointer

A pointer where native-pointer is the user typedef:

$IF JVM32 DEFINED  
01 native-pointer is typedef pic x(4) comp-5.
$ELSE
01 native-pointer is typedef pic x(8) comp-5.
$END

status-code

The returned status code.

On Entry:

nativePointer: The address if the native memory.
memoryLength: The length of the native memory block.
managedPointer: The address of the managed memory block.

On Exit:

status-code

0	success
1	a bad length has been given

Example:

This example demonstrates how the FormatMessage API can be used from a JVM compiled COBOL program.

      $set ans85 mf defaultbyte"00" case
      $ if jvmgen set
      $ set remove"internal" remove"event"
      $end
       copy "windows.cpy".
 
       program-id. geterror.
       special-names.
          call-convention 74 is winapi.
       data division.
       working-storage section.
 
      $if jvmgen set
      $ if NOP64 set
        01 native-pointer     is typedef pic x(4) comp-5.
      $ else
        01 native-pointer     is typedef pic x(8) comp-5.
      $ end
      $else
        01 native-pointer     is typedef pointer.
      $end
 
       01 format-message-group.
        03 last-error                   DWORD.
        03 message-pointer              native-pointer.
        03 format-type                  DWORD.
        03 bytes-returned               DWORD.
        03 last-error-display           pic 9(2).
 
       local-storage section.
       01 ls-message-buffer                pic x(1024).
 
       linkage section.
       01 lnk-message-buffer               pic x(1024).
       procedure division.
      $if jvmgen set
           call "cob32api"
      $end
 
           display "First 20 system error messages"
 
           perform display-error varying last-error from 0 by 1
              until last-error = 20
 
           stop run.
 
       display-error.
           move 0 to format-type
           add FORMAT-MESSAGE-ALLOCATE-BUFFER to format-type
           add FORMAT-MESSAGE-FROM-SYSTEM to format-type
 
           call winapi FormatMessage
              using by value     format-type
                    by value     0 size 4       *> lpSource ignored
                    by value     last-error     *> error number
                    by value     0 size 4       *> LangID ignored
                    by reference message-pointer*> pointer to mess.
                    by value     0 size 4       *> min size of buffer
                    by value     0 size 4       *> arguments ignored
              returning bytes-returned
           end-call
 
           if bytes-returned > 0 and
                   bytes-returned < length of ls-message-buffer
 
      $if jvmgen set
      *> use the managed memory instead of the native memory
              set address of lnk-message-buffer to
                      address of ls-message-buffer
      
      *> Copy the native memory to to the managed memory
              call "JVM_UNSAFE_NATIVE_MEMCOPY" using
                 by value message-pointer
                 by value bytes-returned
                 by value address of ls-message-buffer
              end-call
      $else
              set address of lnk-message-buffer to message-pointer
      $end
              move last-error to last-error-display
              display " " last-error-display " =  "
                      lnk-message-buffer (1:bytes-returned - 2) *> remove x"ODOA"
 
              call winapi "LocalFree"
                using by value message-pointer
             end-call
 
           end-if.