-
Welcome to B4X forum!
B4X is a set of simple and powerful cross platform RAD tools:
- B4A (free) - Android development
- B4J (free) - Desktop and Server development
- B4i - iOS development
- B4R (free) - Arduino, ESP8266 and ESP32 development
Wish Unsigned Byte
- Thread starter Star-Dust
- Start date
- Similar Threads Similar Threads
I second this motion, but in B4A as well. I find it astonishing that through the life of the Basic4 compilers that an unsigned byte is not even thought of. Is this a rebellious choice of the authors? It's certainly painful knowing that I've started a serious project only to hit a road block this ridiculous.
Simply put, I need to have a large array of bytes and actually use each byte as I need as an unsigned byte.
Simply put, I need to have a large array of bytes and actually use each byte as I need as an unsigned byte.
It is a victim at the intersection of Rue de Computer Science and Reality Way, and a carry-over from Java, similar to 0x for hex literals rather than &H.
I am thankful that B4X Bytes at least accept values of 128..255, even if they won't give 'em back.
While we're here: the easiest way I know of to convert them from signed back to unsigned is Bit.And(SignedByte, 0xFF)
(rather than the If convolutions that are sometimes bandied about)
More of a pot hole than a road block ? but I share your pain ? it irritates me daily too, and I would be be quite happy if there was a UByte type, or an option to default Bytes to unsigned. Although that then raises the question of: what also about Shorts, and even Ints and Longs?
edit: actually, I like UByte better, because that way doesn't break existing code like invoking an unsigned default option would
Last edited:
I was able to get temporary relief by doing bit.and(0xff, bytevar) but bit.and(bytevar, 0xff) doesn't seem to work... and I'm just using the result in a quick byte*16 lookup table. Later I'll need to work a lot with CPU bytes in my retro emulator and it looks like I'm going to have to do an insane amount of conversions. We'll see. Yes, major pot hole in the road.
I mean, just because Java uses signed bytes doesn't mean a Basic compiler (to Java) can't offer unsigned and deal with it.
I mean, just because Java uses signed bytes doesn't mean a Basic compiler (to Java) can't offer unsigned and deal with it.
That anomaly seems highly unlikely. More likely to be a misreading during the heat of a programming battle long ago, and you've just stuck ever since with what you know works.
Unless somehow a 0xFF was interpreted as a Byte (-1) which would be 0xFFFFFFFF as an Int, and thus not mask anything. But I'm pretty sure both arguments to Bit.And are Ints ie 32 bits (signed, not that it matters...)
Is this true? ?
Question: If B4X will provide unsigned byte, internally it will still use Bit.And() to convert (?) so there will be no performance raise right?
Nope, you're (probably) right. There is a JVM instruction bipush "push a byte onto the stack as an integer value" which presumably means Java (signed) bytes. Unisgned bytes would require an extra instruction or two.
There would be a programmer performance raise, though. ?
Last edited:
Not if the result should be, or is okay to be, an integer.
I need an uns8 * 16 to get a correct integer offset into my font array (bytes)
Offset into 4096 byte font table is Bit.ShiftLeft(Bit.And(CharByte, 0xFF), 4) ?
Actually, now that I'm on a lunch break, I should just pull my finger out and check that Bit.And(bytevar, 0xFF) and Bit.And(0xFF, bytevar) are equivalent. ?
B4X:
For I = 0 To 255
Dim VarByte As Byte = I
Dim OffsetVC As Int = Bit.ShiftLeft(Bit.And(VarByte, 0xFF), 4)
Dim OffsetCV As Int = Bit.ShiftLeft(Bit.And(0xFF, VarByte), 4)
If OffsetVC = OffsetCV Then
Dim Flag As String = "ok"
Else
Dim Flag As String = "WTF?"
End If
Log( _
I & TAB & _
VarByte & TAB & _
OffsetVC & TAB & _
OffsetCV & TAB & _
Flag & TAB & _
Bit.ToHexString(OffsetVC) _
)
Next
Log output:
Waiting for debugger to connect...
Program started.
0 0 0 0 ok 0
1 1 16 16 ok 10
2 2 32 32 ok 20
3 3 48 48 ok 30
4 4 64 64 ok 40
5 5 80 80 ok 50
6 6 96 96 ok 60
7 7 112 112 ok 70
8 8 128 128 ok 80
9 9 144 144 ok 90
10 10 160 160 ok a0
11 11 176 176 ok b0
12 12 192 192 ok c0
13 13 208 208 ok d0
14 14 224 224 ok e0
15 15 240 240 ok f0
16 16 256 256 ok 100
17 17 272 272 ok 110
18 18 288 288 ok 120
19 19 304 304 ok 130
20 20 320 320 ok 140
21 21 336 336 ok 150
22 22 352 352 ok 160
23 23 368 368 ok 170
24 24 384 384 ok 180
25 25 400 400 ok 190
26 26 416 416 ok 1a0
27 27 432 432 ok 1b0
28 28 448 448 ok 1c0
29 29 464 464 ok 1d0
30 30 480 480 ok 1e0
31 31 496 496 ok 1f0
32 32 512 512 ok 200
33 33 528 528 ok 210
34 34 544 544 ok 220
35 35 560 560 ok 230
36 36 576 576 ok 240
37 37 592 592 ok 250
38 38 608 608 ok 260
39 39 624 624 ok 270
40 40 640 640 ok 280
41 41 656 656 ok 290
42 42 672 672 ok 2a0
43 43 688 688 ok 2b0
44 44 704 704 ok 2c0
45 45 720 720 ok 2d0
46 46 736 736 ok 2e0
47 47 752 752 ok 2f0
48 48 768 768 ok 300
49 49 784 784 ok 310
50 50 800 800 ok 320
51 51 816 816 ok 330
52 52 832 832 ok 340
53 53 848 848 ok 350
54 54 864 864 ok 360
55 55 880 880 ok 370
56 56 896 896 ok 380
57 57 912 912 ok 390
58 58 928 928 ok 3a0
59 59 944 944 ok 3b0
60 60 960 960 ok 3c0
61 61 976 976 ok 3d0
62 62 992 992 ok 3e0
63 63 1008 1008 ok 3f0
64 64 1024 1024 ok 400
65 65 1040 1040 ok 410
66 66 1056 1056 ok 420
67 67 1072 1072 ok 430
68 68 1088 1088 ok 440
69 69 1104 1104 ok 450
70 70 1120 1120 ok 460
71 71 1136 1136 ok 470
72 72 1152 1152 ok 480
73 73 1168 1168 ok 490
74 74 1184 1184 ok 4a0
75 75 1200 1200 ok 4b0
76 76 1216 1216 ok 4c0
77 77 1232 1232 ok 4d0
78 78 1248 1248 ok 4e0
79 79 1264 1264 ok 4f0
80 80 1280 1280 ok 500
81 81 1296 1296 ok 510
82 82 1312 1312 ok 520
83 83 1328 1328 ok 530
84 84 1344 1344 ok 540
85 85 1360 1360 ok 550
86 86 1376 1376 ok 560
87 87 1392 1392 ok 570
88 88 1408 1408 ok 580
89 89 1424 1424 ok 590
90 90 1440 1440 ok 5a0
91 91 1456 1456 ok 5b0
92 92 1472 1472 ok 5c0
93 93 1488 1488 ok 5d0
94 94 1504 1504 ok 5e0
95 95 1520 1520 ok 5f0
96 96 1536 1536 ok 600
97 97 1552 1552 ok 610
98 98 1568 1568 ok 620
99 99 1584 1584 ok 630
100 100 1600 1600 ok 640
101 101 1616 1616 ok 650
102 102 1632 1632 ok 660
103 103 1648 1648 ok 670
104 104 1664 1664 ok 680
105 105 1680 1680 ok 690
106 106 1696 1696 ok 6a0
107 107 1712 1712 ok 6b0
108 108 1728 1728 ok 6c0
109 109 1744 1744 ok 6d0
110 110 1760 1760 ok 6e0
111 111 1776 1776 ok 6f0
112 112 1792 1792 ok 700
113 113 1808 1808 ok 710
114 114 1824 1824 ok 720
115 115 1840 1840 ok 730
116 116 1856 1856 ok 740
117 117 1872 1872 ok 750
118 118 1888 1888 ok 760
119 119 1904 1904 ok 770
120 120 1920 1920 ok 780
121 121 1936 1936 ok 790
122 122 1952 1952 ok 7a0
123 123 1968 1968 ok 7b0
124 124 1984 1984 ok 7c0
125 125 2000 2000 ok 7d0
126 126 2016 2016 ok 7e0
127 127 2032 2032 ok 7f0
128 -128 2048 2048 ok 800
129 -127 2064 2064 ok 810
130 -126 2080 2080 ok 820
131 -125 2096 2096 ok 830
132 -124 2112 2112 ok 840
133 -123 2128 2128 ok 850
134 -122 2144 2144 ok 860
135 -121 2160 2160 ok 870
136 -120 2176 2176 ok 880
137 -119 2192 2192 ok 890
138 -118 2208 2208 ok 8a0
139 -117 2224 2224 ok 8b0
140 -116 2240 2240 ok 8c0
141 -115 2256 2256 ok 8d0
142 -114 2272 2272 ok 8e0
143 -113 2288 2288 ok 8f0
144 -112 2304 2304 ok 900
145 -111 2320 2320 ok 910
146 -110 2336 2336 ok 920
147 -109 2352 2352 ok 930
148 -108 2368 2368 ok 940
149 -107 2384 2384 ok 950
150 -106 2400 2400 ok 960
151 -105 2416 2416 ok 970
152 -104 2432 2432 ok 980
153 -103 2448 2448 ok 990
154 -102 2464 2464 ok 9a0
155 -101 2480 2480 ok 9b0
156 -100 2496 2496 ok 9c0
157 -99 2512 2512 ok 9d0
158 -98 2528 2528 ok 9e0
159 -97 2544 2544 ok 9f0
160 -96 2560 2560 ok a00
161 -95 2576 2576 ok a10
162 -94 2592 2592 ok a20
163 -93 2608 2608 ok a30
164 -92 2624 2624 ok a40
165 -91 2640 2640 ok a50
166 -90 2656 2656 ok a60
167 -89 2672 2672 ok a70
168 -88 2688 2688 ok a80
169 -87 2704 2704 ok a90
170 -86 2720 2720 ok aa0
171 -85 2736 2736 ok ab0
172 -84 2752 2752 ok ac0
173 -83 2768 2768 ok ad0
174 -82 2784 2784 ok ae0
175 -81 2800 2800 ok af0
176 -80 2816 2816 ok b00
177 -79 2832 2832 ok b10
178 -78 2848 2848 ok b20
179 -77 2864 2864 ok b30
180 -76 2880 2880 ok b40
181 -75 2896 2896 ok b50
182 -74 2912 2912 ok b60
183 -73 2928 2928 ok b70
184 -72 2944 2944 ok b80
185 -71 2960 2960 ok b90
186 -70 2976 2976 ok ba0
187 -69 2992 2992 ok bb0
188 -68 3008 3008 ok bc0
189 -67 3024 3024 ok bd0
190 -66 3040 3040 ok be0
191 -65 3056 3056 ok bf0
192 -64 3072 3072 ok c00
193 -63 3088 3088 ok c10
194 -62 3104 3104 ok c20
195 -61 3120 3120 ok c30
196 -60 3136 3136 ok c40
197 -59 3152 3152 ok c50
198 -58 3168 3168 ok c60
199 -57 3184 3184 ok c70
200 -56 3200 3200 ok c80
201 -55 3216 3216 ok c90
202 -54 3232 3232 ok ca0
203 -53 3248 3248 ok cb0
204 -52 3264 3264 ok cc0
205 -51 3280 3280 ok cd0
206 -50 3296 3296 ok ce0
207 -49 3312 3312 ok cf0
208 -48 3328 3328 ok d00
209 -47 3344 3344 ok d10
210 -46 3360 3360 ok d20
211 -45 3376 3376 ok d30
212 -44 3392 3392 ok d40
213 -43 3408 3408 ok d50
214 -42 3424 3424 ok d60
215 -41 3440 3440 ok d70
216 -40 3456 3456 ok d80
217 -39 3472 3472 ok d90
218 -38 3488 3488 ok da0
219 -37 3504 3504 ok db0
220 -36 3520 3520 ok dc0
221 -35 3536 3536 ok dd0
222 -34 3552 3552 ok de0
223 -33 3568 3568 ok df0
224 -32 3584 3584 ok e00
225 -31 3600 3600 ok e10
226 -30 3616 3616 ok e20
227 -29 3632 3632 ok e30
228 -28 3648 3648 ok e40
229 -27 3664 3664 ok e50
230 -26 3680 3680 ok e60
231 -25 3696 3696 ok e70
232 -24 3712 3712 ok e80
233 -23 3728 3728 ok e90
234 -22 3744 3744 ok ea0
235 -21 3760 3760 ok eb0
236 -20 3776 3776 ok ec0
237 -19 3792 3792 ok ed0
238 -18 3808 3808 ok ee0
239 -17 3824 3824 ok ef0
240 -16 3840 3840 ok f00
241 -15 3856 3856 ok f10
242 -14 3872 3872 ok f20
243 -13 3888 3888 ok f30
244 -12 3904 3904 ok f40
245 -11 3920 3920 ok f50
246 -10 3936 3936 ok f60
247 -9 3952 3952 ok f70
248 -8 3968 3968 ok f80
249 -7 3984 3984 ok f90
250 -6 4000 4000 ok fa0
251 -5 4016 4016 ok fb0
252 -4 4032 4032 ok fc0
253 -3 4048 4048 ok fd0
254 -2 4064 4064 ok fe0
255 -1 4080 4080 ok ff0
Program terminated (StartMessageLoop was not called).Then some other problem was happening at the time I assumed it was the ordering for Bit.And. I just swapped the order, knowing it was unlikely to have any effect, but my offsets were correct. Anyway....
I also assumed that a Multiply on these modern CPUs might be quicker than 4 Left Shifts. Additionally, the reason I haven't packed the functions together is because I've been trying to figure out where the problem was. I'll tighten and speed things up as I go.
I also assumed that a Multiply on these modern CPUs might be quicker than 4 Left Shifts. Additionally, the reason I haven't packed the functions together is because I've been trying to figure out where the problem was. I'll tighten and speed things up as I go.
Unlikely, decades ago even our minicomputers had barrel shifters which could do any shift in a single CPU cycle. But unless you are programming in assembler this level of concern is irrelevant. You have a virtual machine and optimizing just in time compilers between your code and what the CPU sees so you can't be certain of anything low level.
