Use data conversion

Two forms of data conversion are supported by IBM MQ Automation Classes for ActiveX - numeric encoding, and character set conversion.

Numeric encoding

If you set the MQMessage Encoding property, the following methods convert between different numeric encoding systems:

ReadDecimal2 method
ReadDecimal4 method
ReadDouble method
ReadDouble4 method
ReadFloat method
ReadInt2 method
ReadInt4 method
ReadLong method
ReadShort method
ReadUInt2 method
WriteDecimal2 method
WriteDecimal4 method
WriteDouble method
WriteDouble4 method
WriteFloat method
WriteInt2 method
WriteInt4 method
WriteLong method
WriteShort method
WriteUInt2 method

The Encoding property can be set and interpreted using the supplied IBM MQ constants. Figure 1 shows an example of these:

Figure 1. Supplied IBM MQ constants for encoding

/* Encodings for Binary Integers */
MQENC_INTEGER_UNDEFINED
MQENC_INTEGER_NORMAL
MQENC_INTEGER_REVERSED

/* Encodings for Decimals */
MQENC_DECIMAL_UNDEFINED
MQENC_DECIMAL_NORMAL
MQENC_DECIMAL_REVERSED

/* Encodings for Floating-Point Numbers */
MQENC_FLOAT_UNDEFINED
MQENC_FLOAT_IEEE_NORMAL
MQENC_FLOAT_IEEE_REVERSED
MQENC_FLOAT_S390

For example, to send an integer from an Intel system to a System/390 operating system in System/390 encoding:

Dim msg As New MQMessage  'Define an IBM MQ message for our use..
Print msg. Encoding   'Currently 546 (or X'222')
                                            'Set the encoding property
                                             to 785 (or X'311')
msg. Encoding = MQENC_INTEGER_NORMAL OR MQENC_DECIMAL_NORMAL
                           OR MQENC_FLOAT_S390
Print msg. Encoding   'Print it to see the change
Dim local_num As long 'Define a long integer
local_num = 1234                            'Set it
msg. WriteLong (local_num)       'Write the number into the message

Character set conversion

Character set conversion is necessary when you send a message from one system to another system where the code pages are different. Code page conversion is used by:

ReadString method
ReadNullTerminatedString method
WriteString method
WriteNullTerminatedString method
MessageData Property

You must set the MQMessage CharacterSet property to a supported character set value (CCSID).

IBM MQ Automation Classes for ActiveX uses conversion tables to perform character set conversion.

For example, to convert strings automatically to code page 437:

Dim msg As New MQMessage                 'Define an IBM MQ message
msg.CharacterSet = 437                 'Set code page required
msg.WriteString "A character string"'Put character string in message

The WriteString method receives the string data ( A character string in the example) as a Unicode string. It then converts this data from Unicode into code page 437 using the conversion table 34B001B5.TBL.

Characters in the Unicode string that are not supported by code page 437 are given the standard substitution character from code page 437.

Similarly, when we use the ReadString method, the incoming message has a character set established by the IBM MQ Message Descriptor (MQMD) value and there is a conversion from this code page into Unicode before it is passed back to your scripting language.