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51 lines
1.1 KiB
ArmAsm
51 lines
1.1 KiB
ArmAsm
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; Karri Kaksonen, 2010
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;
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; This function reads count bytes from the place where the address counter is.
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; Use lseek to place the address counter where you want to read from.
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;
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; The file descriptor is ignored in this implementation. The read operation
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; reads bytes from a raw cart and does not understand the concept of files.
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; So if you read over the end of file you get data from the next file.
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;
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; The count-parameter can be positive (Atari style) or negative (BLL style).
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; In any case the read routine will work correctly.
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;
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; int __fastcall__ read(int fd,void *buf,int count)
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;
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.importzp _FileDestPtr
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.import lynxread0
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.import pushax,ldaxysp,ldax0sp,incsp6
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.export _read
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.segment "CODE"
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.proc _read: near
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.segment "CODE"
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jsr pushax
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ldy #$03
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jsr ldaxysp
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sta _FileDestPtr
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stx _FileDestPtr+1
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jsr ldax0sp
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phx ; The BLL kit uses negative counts
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plx ; while the basic Lynx uses positive
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bmi @1 ; make all counts negative
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eor #$FF
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pha
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txa
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eor #$FF
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bra @2
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@1: pha
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txa
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@2: tay
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plx
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jsr lynxread0
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jsr ldax0sp
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jmp incsp6
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.endproc
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