Commit | Line | Data |
---|---|---|
a221d644 | 1 | ;;; -*-asm-*- |
4278b406 | 2 | ;;; (c) 2021 Mark Wooding |
a221d644 MW |
3 | ;;; |
4 | ;;; Best not to ask why. | |
5 | ||
4278b406 MW |
6 | ;;;----- Licensing notice --------------------------------------------------- |
7 | ;;; | |
8 | ;;; This file is part of ZX Fizzbuzz. | |
9 | ;;; | |
10 | ;;; ZX Fizzbuzz is free software: you can redistribute it and/or modify it | |
11 | ;;; under the terms of the GNU Lesser General Public License as published | |
12 | ;;; by the Free Software Foundation; either version 3 of the License, or | |
13 | ;;; (at your option) any later version. | |
14 | ;;; | |
15 | ;;; ZX Fizzbuzz is distributed in the hope that it will be useful, but | |
16 | ;;; WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | ;;; Lesser General Public License for more details. | |
19 | ;;; | |
20 | ;;; You should have received a copy of the GNU Lesser General Public | |
21 | ;;; License along with ZX Fizzbuzz. If not, see | |
22 | ;;; <https://www.gnu.org/licenses/>. | |
23 | ||
a221d644 MW |
24 | ;; Look at the buffer and decide what to do. |
25 | again: ld e, 0 | |
26 | ||
27 | ;; First, decide whether it's a multiple of three. This is a bit | |
28 | ;; fiddly. | |
29 | ld a, (len) | |
30 | ld b, a | |
31 | ld hl, buf | |
32 | xor a | |
33 | ||
34 | ;; Main `mod 3' loop. Load a byte and add it into the accumulator in | |
35 | ;; decimal. | |
36 | mod3: ld c, (hl) | |
37 | inc hl | |
38 | add a, c | |
39 | daa | |
40 | jr nc, mod3_1 | |
41 | call squish | |
42 | add a, 1 | |
43 | daa | |
44 | mod3_1: djnz mod3 | |
45 | ||
46 | call squish | |
47 | call squish | |
48 | ||
64b6fca5 | 49 | and a |
a221d644 MW |
50 | jr z, prfizz |
51 | cp 3 | |
52 | jr z, prfizz | |
53 | cp 6 | |
54 | jr z, prfizz | |
55 | cp 9 | |
56 | jr nz, nofizz | |
57 | ||
58 | prfizz: ld hl, fizz | |
59 | call print | |
60 | inc e | |
61 | ||
62 | ;; Next, decide whether it's a multiple of five. This is easier. | |
63 | nofizz: ld a, (buf) | |
64 | and 0x0f | |
65 | jr z, prbuzz | |
66 | cp 5 | |
67 | jr nz, nobuzz | |
68 | ||
69 | prbuzz: ld hl, buzz | |
70 | call print | |
71 | jr prnl | |
72 | ||
73 | ;; Not a multiple of five. Skip ahead if it was a multiple of three. | |
74 | nobuzz: ld a, e | |
64b6fca5 | 75 | and a |
a221d644 MW |
76 | jr nz, prnl |
77 | ||
78 | ;; OK, so just print the value. | |
a221d644 | 79 | ld hl, buf - 1 |
0bf6b60e | 80 | ld bc, (len) |
a221d644 MW |
81 | add hl, bc |
82 | ld b, c | |
83 | ||
84 | ld a, (hl) | |
85 | ld d, a | |
86 | srl a | |
87 | srl a | |
88 | srl a | |
89 | srl a | |
90 | jr z, skiplz | |
64b6fca5 MW |
91 | fixdig |
92 | print_a | |
a221d644 MW |
93 | skiplz: ld a, d |
94 | and 0x0f | |
64b6fca5 MW |
95 | fixdig |
96 | print_a | |
a221d644 MW |
97 | dec b |
98 | jr z, prnl | |
99 | ||
100 | prdig: dec hl | |
101 | ld a, (hl) | |
102 | ld d, a | |
103 | srl a | |
104 | srl a | |
105 | srl a | |
106 | srl a | |
64b6fca5 MW |
107 | fixdig |
108 | print_a | |
a221d644 MW |
109 | ld a, d |
110 | and 0x0f | |
64b6fca5 MW |
111 | fixdig |
112 | print_a | |
a221d644 MW |
113 | djnz prdig |
114 | ||
115 | ;; Print the newline. | |
64b6fca5 MW |
116 | prnl: ld a, spc |
117 | print_a | |
a221d644 MW |
118 | |
119 | ;; Increment the counter. | |
120 | ld hl, buf | |
121 | ld a, (len) | |
122 | ld b, a | |
123 | scf | |
124 | incr: ld a, (hl) | |
125 | adc a, 0 | |
126 | daa | |
127 | ld (hl), a | |
128 | jp nc, again | |
129 | inc hl | |
130 | djnz incr | |
131 | ||
132 | ;; Carry out. | |
a221d644 | 133 | ld (hl), 1 |
b4fd0180 MW |
134 | ld hl, len |
135 | inc (hl) | |
a221d644 MW |
136 | jp again |
137 | ||
138 | squish: | |
139 | ;; Add the two halves of a. | |
140 | ld c, a | |
141 | and 0x0f | |
142 | srl c | |
143 | srl c | |
144 | srl c | |
145 | srl c | |
146 | add a, c | |
147 | daa | |
148 | ret | |
149 | ||
150 | print: | |
151 | ;; Print the string at hl. | |
152 | ld a, (hl) | |
64b6fca5 | 153 | endstrp |
a221d644 | 154 | ret z |
64b6fca5 | 155 | print_a |
a221d644 MW |
156 | inc hl |
157 | jr print | |
158 | ||
64b6fca5 MW |
159 | ;; Initial state. The buffer notionally continues for another 254 |
160 | ;; bytes, but there's no point in including them in the image. | |
0bf6b60e | 161 | len: db 1, 0 |
64b6fca5 | 162 | buf: db 1 |