Link3270 ADS descriptor

The ADS descriptor contains a header with general information about the map, and a field descriptor for every field that appears in the ADS, corresponding to every named field in the map definition macro. It can be located in the mapset from an offset field in DFHMAPDS.

ADS descriptor header

The ADS descriptor header contains general information about the map and a pointer to the first of a variable number of chained field descriptions.

Offset
Hex
Type
Len
Name
(0)
STRUCTURE
38
ADS-DESCRIPTOR
(0)
HALFWORD
2
ADSD-LENGTH
(2)
CHARACTER
4
ADSD-EYECATCHER
(6)
HALFWORD
2
ADSD-MAP-INDEX
(8)
HALFWORD
2
ADSD-FIELD-COUNT
(A)
HALFWORD
2
ADSD-STRUCTURE-LENGTH
(C)
HALFWORD
2
ADSD-ATTRIBUTE-NUMBER
(E)
CHARACTER
12
ADSD-ATTRIBUTE-TYPE-CODES
(1A)
CHARACTER
1
ADSD-MAP-JUSTIFY-HOR
(1B)
CHARACTER
1
ADSD-MAP-JUSTIFY-VER
(1C)
HALFWORD
2
ADSD-MAP-STARTING-LINE
(1E)
HALFWORD
2
ADSD-MAP-STARTING-COLUMN
(20)
HALFWORD
2
ADSD-MAP-LINES
(22)
HALFWORD
2
ADSD-MAP-COLUMNS
(24)
CHARACTER
1
ADSD-WRITE-CONTROL-CHARACTER
(25)
CHARACTER
1
(reserved)
(26)
STRUCTURE

ADSD-FIRST-FIELD
ADSD-LENGTH
The length of the ADS descriptor.
ADSD-EYECATCHER
An eye-catcher ('ADSD') to identify this as an ADS descriptor.
ADSD-MAP-INDEX
The index number of the map within the mapset.
ADSD-FIELD-COUNT
The number of fields within the ADS; that is, the number of named fields in the map definition. A separate field is counted for each element of an array defined with the OCCURS parameter, but subfields of group fields (GRPNAME) are not counted. The field count may be zero, in which case there are no field descriptors following the header.
ADSD-STRUCTURE-LENGTH
The length of the application data structure.
ADSD-ATTRIBUTE-NUMBER
The number of extended attributes in fields used in the map; that is, the number of attributes specified in DSATTS in the map definition.
ADSD-ATTRIBUTE-TYPE-CODES
a 1-character code for the attribute types in each field, in order, derived from DSATTS:
ADSD-MAP-JUSTIFY-HOR
The horizontal justification for the map, either L (LEFT) or R (RIGHT) from the JUSTIFY operand on the map definition.
ADSD-MAP-JUSTIFY-VER
The vertical justification for the map, from the JUSTIFY operand on the map definition. This can have the values F (FIRST), L (LAST), B (BOTTOM), or blank (no vertical JUSTIFY operand).
ADSD-MAP-STARTING-LINE
The starting line for the map, from the LINE operand on the DFHMDI macro, (LINE = NEXT gives a value of 255; LINE = SAME gives a value of 254.)
ADSD-MAP-STARTING-COLUMN
The starting column for the map, from the COLUMN operand on the DFHMDI macro. (COLUMN = NEXT gives a value of 255; COLUMN = SAME gives a value of 254.)
ADSD-MAP-LINES
The number of lines in the map from the SIZE operand.
ADSD-MAP-COLUMNS
The number of columns in the map from the SIZE operand.
ADSD-WRITE-CONTROL-CHAR
The 3270 encoded WCC derived from the CONTROL operand.
ADSD-FIRST-FIELD
The first field descriptor. The address of the first field descriptor in the ADSD (zero if ADSD-FIELD-COUNT is zero).

ADS field descriptor

After the header, the ADS descriptor contains a variable number of field descriptors. Each field descriptor has the following format:

Offset
Hex
Type
Len
Name
(0)
STRUCTURE
42
ADS-FIELD-DESCRIPTOR
(0)
CHARACTER
32
ADSD-FIELD-NAME
(20)
HALFWORD
2
ADSD-FIELD-NAME-LEN
(22)
HALFWORD
2
ADSD-OCCURS-INDEX
(24)
HALFWORD
2
ADSD-FIELD-OFFSET
(26)
HALFWORD
2
ADSD-FIELD-DATA-LEN
(28)
CHARACTER
1
ADSD-FIELD-JUSTIFY
(29)
CHARACTER
1
ADSD-FIELD-FILL-CHAR
(2A)
CHARACTER

ADSD-NEXT-FIELD
ADSD-FIELD-NAME
The unsuffixed field name padded with blanks on the right.
ADSD-FIELD-NAME-LEN
The number of characters in the field name.
ADSD-OCCURS-INDEX
When OCCURS is specified for a field definition there is a separate field descriptor for each element of the array, and ADSD-OCCURS-INDEX indicates the array index for the particular field. If OCCURS is not specified, then ADSD-OCCURS-INDEX is 0.
ADSD-FIELD-OFFSET
The offset of the field within the ADS. The offset is to the beginning of the (fullword) length field, and you must add 2 (for the length field) + 1 (for the 3270 attribute) + ADSD-ATTRIBUTE-NUMBER to obtain the offset of the data part of the field.
ADSD-FIELD-DATA-LEN
The length of the field in the ADS.
ADSD-FIELD-JUSTIFY
A 1-character field indicating whether the data is to be justified left 'L' or right 'R' if the supplied length is less than the length in the ADS.
ADSD-FIELD-FILL-CHAR
The character (blank or '0') to be used to pad the remainder of the field in the ADS.
ADSD-NEXT-FIELD
The next field descriptor. The address of ADSD-NEXT-FIELD can be used to update a pointer for the field descriptor.

Related concepts
The Link3270 bridge mechanism
Related tasks
Using the Link3270 bridge
Writing the Link3270 client
Related reference
Link3270 message formats
Link3270 message header (BRIH)
Inbound Link3270 vectors
Outbound Link3270 vectors
Link3270 diagnostics
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