Generate a unit structure to represent a set of bit-regions. Intended to be used both as bitflags held in structs/collections as well as representing something like a memory-mapped register in more embedded applications.
This crate is set as #![no_std] so it can freely be used in other such crates.
Regions are given the #repr({type}) attribute based on the {repr}
given to the macro.
The following traits are generated for the new struct:
- Into<{repr}>
- From<{repr}>
- PartialEq
- Display
- toggles print their name if set
- multibit always prints {name}={val}
- Debug
- prints raw value in hex
- + and +=
- - and -=
- * and *=
- / and /=
- ^ and ^=
- | and |=
- & and &=
Example purely to show the API. Creates a stack-based u16 unit-struct with helper methods.
```rust
bitregions! { pub Example u16 { ENFEATURE: 0b0000000000000001, ENDEVICE: 0b0000000000000010, PORTNUM: 0b0000000000011100 | 0..=5, // only 0-5 is valid BUSY: 0b0000000001000000, VALBUFFER: 0b1111111100000000, }
pub fn port_and_value(port: u8, val: u8) -> Example {
let mut r = Example::new(0u16);
r.set_port_num(port);
r.set_val_buffer(val);
r
}
}
fn main() { println!("value buffer mask is: {:#X}", Example::VAL_BUFFER);
// create an example memory mapped io register
// exists on the stack with the value 0.
// see below for using this as a pointer to the register.
let mut ex = Example::new(0u16);
// enable the feature this register governs
ex.set_en_feature();
// wait for the busy bit to clear
// then set busy to block reader (could be more pedantic with ex.set_busy())
while ex.busy() { println!("bus is busy"); }
ex.toggle_busy();
assert_eq!(ex.extract_busy().raw() & Example::BUSY, Example::BUSY);
// set the port to write to. must be 0-5
// otherwise we trigger a debug_assert! (removed in release builds)
// same with the value buffer
ex |= Example::port_and_value(4u8, 0x38u8);
// clear busy bit (could be more pedantic with ex.unset_busy())
ex.toggle_busy();
// wait for a response
while ex.busy() { println!("waiting for response"); }
// read the value out of the buffer (pre-shifted for you)
// then, assert the shift happened correctly by looking at the
// unshifted version returned by the extract_{field} variant.
let resp = ex.val_buffer();
assert_eq!(resp << 8, ex.extract_val_buffer().raw());
// disable the feature this register governs
ex.unset_en_feature();
//
// math and bitwise operations
//
ex += 1u16.into();
ex -= 1u16.into();
ex *= 2u16.into();
ex /= 2u16.into();
ex |= 0xBD.into();
ex &= 0xDB.into();
ex ^= ex.raw().into();
//
// display and debug
//
ex = Example::with_en_feature(); // use a with_{field} ctor
ex.set_port_num(4u8);
ex.set_val_buffer(0xABu8);
let display = format!("{}", ex);
assert_eq!(display, "EN_FEATURE | PORT_NUM=0x4 | VAL_BUFFER=0xAB");
let debug = format!("{:?}", ex);
assert_eq!(debug, "0xAB11");
} ```
A common case for bitmaps/bitflags/etc are memory-mapped registers. Below is an example that creates a lifetimed reference to some memory region this register would represent.
You can optionally provide a default address location using the
{name} {repr} @ {addr} syntax. This variant returns a static, mutable ref.
```rust
bitregions! { pub Example u16 @ 0xDEADBEEF { ENFEATURE: 0b0000000000000001, ENDEVICE: 0b0000000000000010, PORTNUM: 0b0000000000011100 | 0..=5, // only 0-5 is valid BUSY: 0b0000000001000000, VALBUFFER: 0b1111111100000000, } }
const MEMIOADDR: usize = 0xC0FFEE; bitregions! { pub MemIOBase u16 @ MEMIOADDR { SOMEREGION: 0b0000000000000001, } } bitregions! { pub ControlReg u16 @ MEMIOADDR + 0x80 { SOME_REGION: 0b0000000000000001, } }
fn main() { // create "fake memory" so the doc-test works // address is the important thing let mem: [u8; 4096] = [0u8; 4096];
// create a lifetimed reference to the register elsewhere
// in memory (the above slice, in our case, but could be anywhere)
let ex = unsafe { Example::at_addr_mut(&mem[8] as *const _ as usize) };
// everything else works like normal
ex.set_en_feature();
assert!(ex.en_feature());
ex.set_val_buffer(128u8);
println!("{:#X}", ex.val_buffer());
assert_eq!(128, ex.val_buffer());
// you can also initialize the pointer directly
let ptr = unsafe { Example::default_ptr() };
assert_eq!(ptr as *mut _ as usize, 0xDEADBEEF);
// but we cannot use it in the examples or it will segfault :/
// you can set the default address using a literal, ident, or const expression
let memio = unsafe { MemIOBase::default_ptr() };
assert_eq!(memio as *mut _ as usize, MEMIO_ADDR);
let control = unsafe { ControlReg::default_ptr() };
assert_eq!(control as *mut _ as usize, MEMIO_ADDR + 0x80);
} ```
Below is an example which casts a reference of the region's underlying type to our generated struct. This allows you to "add features" to a raw value. While safer than the memory-mapped example but is still unsafe code as you could share a reference into a slice.
```rust
bitregions! { pub Example u16 { ENFEATURE: 0b0000000000000001, ENDEVICE: 0b0000000000000010, PORTNUM: 0b0000000000011100 | 0..=5, // only 0-5 is valid BUSY: 0b0000000001000000, VALBUFFER: 0b1111111100000000, } }
fn main() { // create "fake memory" to illustrate the example // the reference could be to a single u16 or relevant type... let mut mem: [u8; 4096] = [0u8; 4096];
// create the reference -- this is unsafe because we allow
// for a wider range of types than strictly the underlying type.
// you can see in this example we use a &u8 to create (effectively) a &u16
let ex = unsafe { Example::at_ref_mut(&mut mem[8]) };
// everything else works like normal
ex.set_en_feature();
assert!(ex.en_feature());
ex.set_val_buffer(128u8);
println!("{:#X}", ex.val_buffer());
assert_eq!(128, ex.val_buffer());
} ```
When built in debug-mode, setters will assert the given value both fits in the region (4bit number in 2bit region) and is within the (optional) range (3bit region, 0-5 allowed, given 7).
```rust
bitregions! { pub Example u8 { RANGED: 0b00011100 | 1..=6, NON_RANGED: 0b11100000, } }
fn main() { let mut ex = Example::new(0u8);
ex.set_ranged(1u8); // works fine
ex.set_ranged(3u8); // works fine
ex.set_ranged(6u8); // works fine
ex.set_ranged(0u8); // will panic do to range violation
ex.set_ranged(7u8); // will panic do to range violation
ex.set_ranged(8u8); // will panic do to region violation
ex.set_non_ranged(1u8); // works fine
ex.set_non_ranged(3u8); // works fine
ex.set_non_ranged(6u8); // works fine
ex.set_non_ranged(0u8); // works fine
ex.set_non_ranged(7u8); // works fine
ex.set_non_ranged(8u8); // will panic do to region violation
} ```