Slightly neater version (using alias properly)
;;; Copyright (c) 2008 Traversal Technology
;;;
;;; Permission is hereby granted, free of charge, to any person obtaining a
;;; copy of this software and associated documentation files (the "Software"),
;;; to deal in the Software without restriction, including without limitation
;;; the rights to use, copy, modify, merge, publish, distribute, sublicense,
;;; and/or sell copies of the Software, and to permit persons to whom the
;;; Software is furnished to do so, subject to the following conditions:
;;;
;;; The above copyright notice and this permission notice shall be included in
;;; all copies or substantial portions of the Software.
;;;
;;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
;;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
;;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
;;; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
;;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
;;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
;;; DEALINGS IN THE SOFTWARE.
;;;
;;; Author: Mark Marshall
include hqio
; HERE!
let G_VID_SCREEN_WIDTH = 0x100
let G_VID_GLYPH_HEIGHT_M1 = 0x101
frame test
alias p0 = r31
protect r10..r30
move 640, r1
move r1, [G_VID_SCREEN_WIDTH]
move 15, r1
move r1, [G_VID_GLYPH_HEIGHT_M1]
move ((123000000)/65536)+1, r6
shiftu r6, 16, r6
add r6, -11072, r6 ; ((123000000)%65536)
move 0x12, r7
move 0x34, r8
noop
jump draw_glyph, r9
noop
noop
jump 510
noop
endframe
;;; ------------------------------------------------------------------------
;;; draw_glyph(r6: pixel_addr, r7: fg_color, r8: bg_color, r9: continuation)
frame draw_glyph
alias p0..p3 = r6..r9
alias q0..q3 = r0..r3
protect r4..r5
protect r10..r31
; p0 = pixel address
; p1 = fg color
; p2 = bg color
; p3 = return address
;
; q0 = general scratch register
; q1 = y counter
; q2 = mask (and x counter) / second scratch
; q3 = font data
;
; Global data:
;
; G_VID_SCREEN_WIDTH
; The offset to add to the pixel_address to move down one line
; G_VID_GLYPH_HEIGHT_M1
; The height of a font character (minus 1)
;
; It is assumed that the glyph data is contained in consecutive
; 8-bit chunks of the data being read from memory. The least
; signifigant 8-bits are the first (top) line. For each line,
; the most significant bit is assumed to be the left-most bit.
; This matches the VGA (and common sense?).
draw_glyph:
; We use Q1 as our height counter, starting from 0
move 0, q1
glyph_loop:
; Every fourth scan line we need to read a new uint32 of
; glyph data. The code is smaller if I only have one loop,
; as opposed to the two in Tims original C version.
and q1, 3, q0
jnzero q0, glyph_no_get
; Shift the glyph data.
shiftu q3, -8, q3
move [MEM_READQ_DATA], q3
glyph_no_get:
; We now check to see if thre are at least 9 free spaces
; in the command Q. If there are fewer than 9 we loop.
;
; R2 is the mask that we will use below, we might as well
; load that up now in the delay slot after the memory read.
glyph_loop_cmd:
move [MEM_CMDQ_FREE], q0
move 0x80, q2
sub q0, 9, q0
jneg q0, glyph_loop_cmd
noop
; Set the current pixel address.
move p0, [MEM_SEND_ADDR_MEM]
; We now loop over the eight horizontal pixels of the
; glyph data. To count this loop we are using the mask
; that has been initialised to 0x80. Once we have shifted
; it right until it is zero we are done.
glyph_loop_x:
; And the mask with the glyph data, and load R0 with either
; the foreground color or the background color.
and q3, q2, q0
jzero q0, glyph_bg
move p2, q0
move p1, q0
glyph_bg:
; Shift the mask and loop if non-zero. The store to video
; mem is done in the delay slot.
shiftu q2, -1, q2
jnzero q2, glyph_loop_x
move q0, [MEM_SEND_DATA_1111]
; Read the screen width and the glyph height
move [G_VID_SCREEN_WIDTH], q0
move [G_VID_GLYPH_HEIGHT_M1], q2
; Move pixel addr to the next line down
add p0, q0, p0
; If our height counter is equal to the glyph height then
; we are done
sub q1, q2, q0
jnzero q0, glyph_loop
add q1, 1, q1
jump p3
noop
endframe
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