Skip to content

Latest commit

 

History

History
72 lines (53 loc) · 2.28 KB

InitStruct.md

File metadata and controls

72 lines (53 loc) · 2.28 KB
Raw

NAME

InitStruct - initialize memory from a table

SYNOPSIS

    InitStruct(initTable, memory, size);
               A1         A2      D0

    void InitStruct(struct InitStruct *, APTR, ULONG);

FUNCTION

Clear a memory area, then set up default values according to the data and offset values in the initTable. Typically only assembly programs take advantage of this function, and only with the macros defined in "exec/initializers.i".

The initialization table has byte commands to

|a ||byte| |given||byte| |once | load |count||word| into |next ||rptr| offset, |repetitively | |long|

Not all combinations are supported. The offset, when specified, is relative to the memory pointer provided (Memory), and is initially zero. The initialization data (InitTable) contains byte commands whose 8 bits are interpreted as follows:

ddssnnnn dd the destination type (and size): 00 no offset, use next destination, nnnn is count 01 no offset, use next destination, nnnn is repeat 10 destination offset is in the next byte, nnnn is count 11 destination offset is in the next 24-bits, nnnn is count ss the size and location of the source: 00 long, from the next two aligned words 01 word, from the next aligned word 10 byte, from the next byte 11 ERROR - will cause an ALERT (see below) nnnn the count or repeat: count the (number+1) of source items to copy repeat the source is copied (number+1) times.

initTable commands are always read from the next even byte. Given destination offsets are always relative to the memory pointer (A2).

The command %00000000 ends the InitTable stream: use %00010001 if you really want to copy one longword without a new offset.

24 bit APTR not supported for 68020 compatibility -- use long.

INPUTS

initTable - the beginning of the commands and data to init Memory with. Must be on an even boundary unless only byte initialization is done. End table with "dc.b 0" or "dc.w 0". memory - the beginning of the memory to initialize. Must be on an even boundary if size is specified. size - the size of memory, which is used to clear it before initializing it via the initTable. If Size is zero, memory is not cleared before initializing.

size must be an even number.

SEE ALSO

exec/initializers.i