115 lines
3.3 KiB
Plaintext
115 lines
3.3 KiB
Plaintext
;;********************************************************************************
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;; @module ringbuffer
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;; @details
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;; Size of the ringbuffer is RBUF_MEM_END - RBUF_MEM_START - 2, since two bytes
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;; are used by the read and write pointer
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;; The `RBUF_NAME` variable must be defined, the functions will then be exported
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;; as `rb_<RBUF_NAME>_<function>` where `<function>` = `init`, `read` or `write`
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;;
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;; @note
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;; Doxygen can not generate proper documentation for this module, because
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;; all names are defined using macros
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;; @requires
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;; RBUF_MEM_START: First address of ringbuffer memory space
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;; RBUF_MEM_END: Last address of ringbuffer memory space
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;; RBUF_NAME: Name of the ringbuffer
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;; @ingroup utility
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;;********************************************************************************
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.code
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.ifndef RBUF_MEM_START
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.fatal "RBUF_MEM_START not defined"
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.endif
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.ifndef RBUF_MEM_END
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.fatal "RBUF_MEM_END not defined"
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.endif
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; can not detect if RBUF_NAME is defined, if it is not you will get
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; "String constant expected" Error on the line below
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.define _RBUF_NAME .concat("rb_", RBUF_NAME)
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RB_WRITE = RBUF_MEM_START ; write pointer, relative to RB_WRITE
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RB_READ = RBUF_MEM_START + 1 ; read ponter, relative to RB_START
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RB_START = RBUF_MEM_START + 2
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RB_LENGTH = RBUF_MEM_END - RBUF_MEM_START - 2
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.if RB_LENGTH < 1
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.fatal "buffer size too small, must be at least 1"
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.endif
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.if RB_LENGTH > $ff
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.fatal "buffer size too large, must be <= $ff"
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.endif
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;;********************************************************************************
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;; @function Initialize the buffer
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;;********************************************************************************
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.ident(.concat(_RBUF_NAME, "_init")):
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.scope
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stz RB_WRITE
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stz RB_READ
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rts
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.endscope
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;;********************************************************************************
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;; @function Read a value from the buffer
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;; @details
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;; If there is no value to be read, the Pz will be set
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;; @returns A: value
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;; @modifies A, X
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;;********************************************************************************
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.ident(.concat(_RBUF_NAME, "_read")):
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.scope
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ldx RB_READ
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cpx RB_WRITE
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beq @rb_read_rts ; if buffer empty
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lda RB_START,x
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inx ; increment RB_READ pointer, not using macro bec. of unknown Pz
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cpx #RB_LENGTH
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beq @read_wrap
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stx RB_READ
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@rb_read_rts:
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rts
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@read_wrap: ; ptr == RB_LENGTH -> ptr = 0
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stz RB_READ
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; make sure Pz is not set
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ldx #$01
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rts
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.endscope
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;;********************************************************************************
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;; @function Write a value to the buffer
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;; @param A: value to store
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;; @modifies X
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;;********************************************************************************
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.ident(.concat(_RBUF_NAME, "_write")):
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.scope
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; lda kp_VALUES, x ; load the char in a
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ldx RB_WRITE
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sta RB_START,x
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inx ; increment write pointer
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cpx #RB_LENGTH
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beq @write_wrap
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stx RB_WRITE
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@check_buf_full: ; increment read if buffer is full
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cpx RB_READ
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beq @read_inc
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rts
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@write_wrap: ; ptr == RB_LENGTH -> ptr = 0
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stz RB_WRITE
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ldx #0
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bra @check_buf_full
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@read_inc:
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ldx RB_READ
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inx
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cpx #RB_LENGTH
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beq @read_wrap
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stx RB_READ
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rts
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@read_wrap: ; ptr == RB_LENGTH -> ptr = 0
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stz RB_READ
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rts
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.endscope
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.undefine _RBUF_NAME
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.undefine RBUF_NAME
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