Trait frame_support::dispatch::fmt::LowerHex

pub trait LowerHex {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

x formatting.

The LowerHex trait should format its output as a number in hexadecimal, with a through f in lower case.

For primitive signed integers (i8 to i128, and isize), negative values are formatted as the two’s complement representation.

The alternate flag, #, adds a 0x in front of the output.

For more information on formatters, see the module-level documentation.

Examples

Basic usage with i32:

let y = 42; // 42 is '2a' in hex

assert_eq!(format!("{y:x}"), "2a");
assert_eq!(format!("{y:#x}"), "0x2a");

assert_eq!(format!("{:x}", -16), "fffffff0");

Implementing LowerHex on a type:

use std::fmt;

struct Length(i32);

impl fmt::LowerHex for Length {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let val = self.0;

        fmt::LowerHex::fmt(&val, f) // delegate to i32's implementation
    }
}

let l = Length(9);

assert_eq!(format!("l as hex is: {l:x}"), "l as hex is: 9");

assert_eq!(format!("l as hex is: {l:#010x}"), "l as hex is: 0x00000009");

Required Methods

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

Errors

This function should return Err if, and only if, the provided Formatter returns Err. String formatting is considered an infallible operation; this function only returns a Result because writing to the underlying stream might fail and it must provide a way to propagate the fact that an error has occurred back up the stack.

Implementors

impl LowerHex for i8

impl LowerHex for i16

impl LowerHex for i32

impl LowerHex for i64

impl LowerHex for i128

impl LowerHex for isize

impl LowerHex for u8

impl LowerHex for u16

impl LowerHex for u32

impl LowerHex for u64

impl LowerHex for u128

impl LowerHex for usize

impl LowerHex for Mnemonic

impl LowerHex for Seed

impl LowerHex for Bytes

impl LowerHex for BytesMut

impl LowerHex for Signature

impl LowerHex for FrameFlags

impl LowerHex for H128

impl LowerHex for H160

impl LowerHex for H256

impl LowerHex for H384

impl LowerHex for H512

impl LowerHex for H768

impl LowerHex for primitive_types::U128

impl LowerHex for U256

impl LowerHex for U512

impl LowerHex for CreateFlags

impl LowerHex for ReadFlags

impl LowerHex for WatchFlags

impl LowerHex for Access

impl LowerHex for AtFlags

impl LowerHex for FallocateFlags

impl LowerHex for MemfdFlags

impl LowerHex for Mode

impl LowerHex for OFlags

impl LowerHex for RenameFlags

impl LowerHex for ResolveFlags

impl LowerHex for SealFlags

impl LowerHex for StatVfsMountFlags

impl LowerHex for StatxFlags

impl LowerHex for DupFlags

impl LowerHex for FdFlags

impl LowerHex for ReadWriteFlags

impl LowerHex for MapFlags

impl LowerHex for MlockAllFlags

impl LowerHex for MlockFlags

impl LowerHex for MprotectFlags

impl LowerHex for MremapFlags

impl LowerHex for MsyncFlags

impl LowerHex for ProtFlags

impl LowerHex for UserfaultfdFlags

impl LowerHex for MountFlags

impl LowerHex for MountPropagationFlags

impl LowerHex for UnmountFlags

impl LowerHex for Flags

impl LowerHex for TimerfdFlags

impl LowerHex for TimerfdTimerFlags

impl LowerHex for IFlags

impl LowerHex for XattrFlags

impl LowerHex for MembarrierQuery

impl LowerHex for PidfdFlags

impl LowerHex for PidfdGetfdFlags

impl LowerHex for FloatingPointEmulationControl

impl LowerHex for FloatingPointExceptionMode

impl LowerHex for SpeculationFeatureControl

impl LowerHex for SpeculationFeatureState

impl LowerHex for UnalignedAccessControl

impl LowerHex for WaitOptions

impl LowerHex for WaitidOptions

impl LowerHex for CapabilityFlags

impl LowerHex for CapabilitiesSecureBits

impl LowerHex for TaggedAddressMode

impl LowerHex for ThreadNameSpaceType

impl LowerHex for UnshareFlags

impl LowerHex for Capabilities

impl LowerHex for Braced

impl LowerHex for Hyphenated

impl LowerHex for Simple

impl LowerHex for Urn

impl LowerHex for Uuid

impl LowerHex for WithdrawReasons

impl<'a, I> LowerHex for Format<'a, I>

where I: Iterator, <I as Iterator>::Item: LowerHex,

impl<'a, T> LowerHex for StyledValue<'a, T>

where T: LowerHex,

impl<'a, T, O> LowerHex for Domain<'a, Const, T, O>

where O: BitOrder, T: BitStore,

impl<'s, T> LowerHex for SliceVec<'s, T>

where T: LowerHex,

impl<A> LowerHex for TinyVec<A>

where A: Array, <A as Array>::Item: LowerHex,

impl<A> LowerHex for ArrayVec<A>

where A: Array, <A as Array>::Item: LowerHex,

impl<A, O> LowerHex for BitArray<A, O>

where O: BitOrder, A: BitViewSized,

impl<O> LowerHex for I16<O>

where O: ByteOrder,

impl<O> LowerHex for I32<O>

where O: ByteOrder,

impl<O> LowerHex for I64<O>

where O: ByteOrder,

impl<O> LowerHex for I128<O>

where O: ByteOrder,

impl<O> LowerHex for U16<O>

where O: ByteOrder,

impl<O> LowerHex for U32<O>

where O: ByteOrder,

impl<O> LowerHex for U64<O>

where O: ByteOrder,

impl<O> LowerHex for zerocopy::byteorder::U128<O>

where O: ByteOrder,

impl<T> LowerHex for &T

where T: LowerHex + ?Sized,

impl<T> LowerHex for &mut T

where T: LowerHex + ?Sized,

impl<T> LowerHex for GenericArray<u8, T>

where T: ArrayLength<u8> + Add, <T as Add>::Output: ArrayLength<u8>,

impl<T> LowerHex for FmtBinary<T>

where T: Binary + LowerHex,

impl<T> LowerHex for FmtDisplay<T>

where T: Display + LowerHex,

impl<T> LowerHex for FmtList<T>

where &'a T: for<'a> IntoIterator, <&'a T as IntoIterator>::Item: for<'a> LowerHex,

impl<T> LowerHex for FmtLowerExp<T>

where T: LowerExp + LowerHex,

impl<T> LowerHex for FmtLowerHex<T>

where T: LowerHex,

impl<T> LowerHex for FmtOctal<T>

where T: Octal + LowerHex,

impl<T> LowerHex for FmtPointer<T>

where T: Pointer + LowerHex,

impl<T> LowerHex for FmtUpperExp<T>

where T: UpperExp + LowerHex,

impl<T> LowerHex for FmtUpperHex<T>

where T: UpperHex + LowerHex,

impl<T> LowerHex for NonZero<T>

where T: ZeroablePrimitive + LowerHex,

impl<T> LowerHex for Saturating<T>

where T: LowerHex,

impl<T> LowerHex for Wrapping<T>

where T: LowerHex,

impl<T, O> LowerHex for BitSlice<T, O>

where T: BitStore, O: BitOrder,

Bit-Slice Rendering

This implementation prints the contents of a &BitSlice in one of binary, octal, or hexadecimal. It is important to note that this does not render the raw underlying memory! They render the semantically-ordered contents of the bit-slice as numerals. This distinction matters if you use type parameters that differ from those presumed by your debugger (which is usually <u8, Msb0>).

The output separates the T elements as individual list items, and renders each element as a base- 2, 8, or 16 numeric string. When walking an element, the bits traversed by the bit-slice are considered to be stored in most-significant-bit-first ordering. This means that index [0] is the high bit of the left-most digit, and index [n] is the low bit of the right-most digit, in a given printed word.

In order to render according to expectations of the Arabic numeral system, an element being transcribed is chunked into digits from the least-significant end of its rendered form. This is most noticeable in octal, which will always have a smaller ceiling on the left-most digit in a printed word, while the right-most digit in that word is able to use the full 0 ..= 7 numeral range.

Examples

use bitvec::prelude::*;

let data = [
  0b000000_10u8,
// digits print LTR
  0b10_001_101,
// significance is computed RTL
  0b01_000000,
];
let bits = &data.view_bits::<Msb0>()[6 .. 18];

assert_eq!(format!("{:b}", bits), "[10, 10001101, 01]");
assert_eq!(format!("{:o}", bits), "[2, 215, 1]");
assert_eq!(format!("{:X}", bits), "[2, 8D, 1]");

The {:#} format modifier causes the standard 0b, 0o, or 0x prefix to be applied to each printed word. The other format specifiers are not interpreted by this implementation, and apply to the entire rendered text, not to individual words.