45 lines
1.8 KiB
Markdown
45 lines
1.8 KiB
Markdown
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# Bit String
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A library to check and extract values from integers based on a "bit string". Primarily intended for (my) emulator instruction decoding, but maybe someone else can find a use for it?
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## Example
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```zig
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const std = @import("std");
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test "doc test" {
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const value: u8 = 0b10001011;
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try std.testing.expectEqual(true, match("10001011", value));
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try std.testing.expectEqual(false, match("11111011", value));
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try std.testing.expectEqual(true, match("1---1011", value));
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{
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const ret = extract("1000aaaa", value);
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try std.testing.expectEqual(@as(u4, 0b1011), ret.a);
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}
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{
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const ret = extract("1aaa1aaa", value);
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try std.testing.expectEqual(@as(u6, 0b000011), ret.a);
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}
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{
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const ret = extract("1---abcd", value);
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try std.testing.expectEqual(@as(u3, 0b1), ret.a);
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try std.testing.expectEqual(@as(u3, 0b0), ret.b);
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try std.testing.expectEqual(@as(u3, 0b1), ret.c);
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try std.testing.expectEqual(@as(u3, 0b1), ret.d);
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}
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}
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```
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## Syntax
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| Token | Meaning | Description
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| ------- | --------- | -----------
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| `0` | Unset bit | In the equivalent position, the value's bit must be set.
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| `1` | Set bit | In the equivalent position, the value's bit must be set.
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| `a..=z` | Variable | Given the 4-bit bit string, `"1aa0"`, the value `0b1010` would produce the variable `a` with the value `0b01`
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| `-` | Ignored | In the equivalent position, the value's bit does not matter.
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## Notes
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- This library does the majority of it's work at `comptime`. Due to this, you cannot create strings to match against at runtime.
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- Variables do not have to be "sequential". This means the 5-bit bit string `"1aa0a"` with the value `0b10101` will produce the variable `a` with the value `0b011`.
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