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NAME
- InitStruct
-
initialize memory from a table
SYNOPSIS
InitStruct(initTable, memory, size);
void InitStruct(struct InitStruct *, APTR, ULONG);
A1 A2 D0
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
ddssnnnn
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.
The Kickstart 1.0 era legacy 24 bit APTR (with the byte command using %11 as the size and location of the source) is not supported for 68020 compatibility on Kickstart 1.1-1.3, causing an Alert of type AN_InitAPtr.
Do not use the byte command %11. Use the byte command %00 instead, which will copy a 32 bit word (long).
The initialization table has byte commands to
|a ||byte| |given||byte| |once |
load |count||word| into |next ||rptr| offset, |repetitively |
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:
|long|
ddssnnnn
dd the destination type (and size):
ss the size and location of the source:
nnnn the count or repeat:
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
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
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 on Kickstart 1.1-1.3 (see below)
01 word, from the next aligned word
10 byte, from the next byte
11 ERROR - will cause an ALERT on Kickstart 1.1-1.3 (see below)
count the (number+1) of source items to copy
repeat the source is copied (number+1) times.
repeat the source is copied (number+1) times.
The command %00000000 ends the InitTable stream: use %00010001 if you really want to copy one longword without a new offset.
The Kickstart 1.0 era legacy 24 bit APTR (with the byte command using %11 as the size and location of the source) is not supported for 68020 compatibility on Kickstart 1.1-1.3, causing an Alert of type AN_InitAPtr.
Do not use the byte command %11. Use the byte command %00 instead, which will copy a 32 bit word (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.
NOTES
The macros defined in the <exec/initializers.h> header file which correspond to the assembly language macros in the "exec/initializers.i" file are only suitable for use with integer constants. The INITLONG() macro does not work with pointer values.
Illegal size and location of the source no longer cause an Alert on Kickstart 2.0 and beyond. InitStruct() will instead stop further processing of the initialization data and return.
Illegal size and location of the source no longer cause an Alert on Kickstart 2.0 and beyond. InitStruct() will instead stop further processing of the initialization data and return.
SEE ALSO
"exec/initializers.i", <exec/initializers.h>