Spectrum ROM: Routine at 171E

171E: THE 'STREAM DATA' SUBROUTINE

Used by the routines at CLOSE and OPEN.

This subroutine returns in the BC register pair the stream data for a given stream.

Output
BC	Offset from the stream data table (STRMS)
HL	Address of the offset in the stream data table

STR_DATA

171E

CALL FIND_INT1

The given stream number is taken off the calculator stack.

1721

CP $10

Give an error if the stream number is greater than +0F.

1723

JR C,STR_DATA1

This entry point is used by the routines at OPEN and CAT_ETC.

Report O - Invalid stream.

REPORT_O_2

1725

RST $08

Call the error handling routine.

1726

DEFB $17

Continue with valid stream numbers.

STR_DATA1

1727

ADD A,$03

Range now +03 to +12.

1729

RLCA

And now +06 to +24.

172A

LD HL,$5C10

The base address of the stream data area.

172D

LD C,A

Move the stream code to the BC register pair.

172E

LD B,$00

1730

ADD HL,BC

Index into the data area and fetch the the two data bytes into the BC register pair.

1731

LD C,(HL)

1732

INC HL

1733

LD B,(HL)

1734

DEC HL

Make the pointer address the first of the data bytes before returning.

1735

RET