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Inside Macintosh: Devices /

Chapter 2 - Slot Manager / Slot Manager Reference

Slot Manager Routines / Getting Information From sResources

SReadByte

You can use the SReadByte function to determine the value of the low-order byte of an sResource entry.

FUNCTION SReadByte (spBlkPtr: SpBlockPtr): OSErr;

spBlkPtr

A pointer to a Slot Manager parameter block.

<--	spResult	LongInt	The contents of the entry byte.
-->	spsPointer	Ptr	A pointer to an sResource (described in "The sResource," beginning on page 2-7).
-->	spID	SignedByte	The ID of the sResource entry.
X	spOffsetData	LongInt
X	spByteLanes	SignedByte

DESCRIPTION

The SReadByte function returns the low-order byte of the offset field of an entry in an sResource. You provide a pointer to the sResource in the spsPointer field and the ID of the entry in the spID field. The SReadByte function returns the value in the low-order byte of the spResult field.

SPECIAL CONSIDERATIONS

This function may alter the values of the spOffsetData and spByteLanes fields of the parameter block. Your application should not depend on the values returned in these fields.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SReadByte function are

Trap macro	Selector
_SlotManager	$0000

You must set up register D0 with the routine selector and register A0 with the address of the Slot Manager parameter block. When _SlotManager returns, register D0 contains the result code.

Registers on entry
A0	Address of the parameter block
D0	$0000

Registers on exit
D0	Result code

RESULT CODES

noErr	0	No error
smNoMoresRsrcs	-344	Requested sResource not found