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/*!
Parsing flags from text.
Format and parse a flags value as text using the following grammar:
- _Flags:_ (_Whitespace_ _Flag_ _Whitespace_)`|`*
- _Flag:_ _Name_ | _Hex Number_
- _Name:_ The name of any defined flag
- _Hex Number_: `0x`([0-9a-fA-F])*
- _Whitespace_: (\s)*
As an example, this is how `Flags::A | Flags::B | 0x0c` can be represented as text:
```text
A | B | 0x0c
```
Alternatively, it could be represented without whitespace:
```text
A|B|0x0C
```
Note that identifiers are *case-sensitive*, so the following is *not equivalent*:
```text
a|b|0x0C
```
*/
#![allow(clippy::let_unit_value)]
use core::fmt::{self, Write};
use crate::{Bits, Flags};
/**
Write a flags value as text.
Any bits that aren't part of a contained flag will be formatted as a hex number.
*/
pub fn to_writer<B: Flags>(flags: &B, mut writer: impl Write) -> Result<(), fmt::Error>
where
B::Bits: WriteHex,
{
// A formatter for bitflags that produces text output like:
//
// A | B | 0xf6
//
// The names of set flags are written in a bar-separated-format,
// followed by a hex number of any remaining bits that are set
// but don't correspond to any flags.
// Iterate over known flag values
let mut first = true;
let mut iter = flags.iter_names();
for (name, _) in &mut iter {
if !first {
writer.write_str(" | ")?;
}
first = false;
writer.write_str(name)?;
}
// Append any extra bits that correspond to flags to the end of the format
let remaining = iter.remaining().bits();
if remaining != B::Bits::EMPTY {
if !first {
writer.write_str(" | ")?;
}
writer.write_str("0x")?;
remaining.write_hex(writer)?;
}
fmt::Result::Ok(())
}
#[cfg(feature = "serde")]
pub(crate) struct AsDisplay<'a, B>(pub(crate) &'a B);
#[cfg(feature = "serde")]
impl<'a, B: Flags> fmt::Display for AsDisplay<'a, B>
where
B::Bits: WriteHex,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
to_writer(self.0, f)
}
}
/**
Parse a flags value from text.
This function will fail on any names that don't correspond to defined flags.
Unknown bits will be retained.
*/
pub fn from_str<B: Flags>(input: &str) -> Result<B, ParseError>
where
B::Bits: ParseHex,
{
let mut parsed_flags = B::empty();
// If the input is empty then return an empty set of flags
if input.trim().is_empty() {
return Ok(parsed_flags);
}
for flag in input.split('|') {
let flag = flag.trim();
// If the flag is empty then we've got missing input
if flag.is_empty() {
return Err(ParseError::empty_flag());
}
// If the flag starts with `0x` then it's a hex number
// Parse it directly to the underlying bits type
let parsed_flag = if let Some(flag) = flag.strip_prefix("0x") {
let bits =
<B::Bits>::parse_hex(flag).map_err(|_| ParseError::invalid_hex_flag(flag))?;
B::from_bits_retain(bits)
}
// Otherwise the flag is a name
// The generated flags type will determine whether
// or not it's a valid identifier
else {
B::from_name(flag).ok_or_else(|| ParseError::invalid_named_flag(flag))?
};
parsed_flags.insert(parsed_flag);
}
Ok(parsed_flags)
}
/**
Write a flags value as text, ignoring any unknown bits.
*/
pub fn to_writer_truncate<B: Flags>(flags: &B, writer: impl Write) -> Result<(), fmt::Error>
where
B::Bits: WriteHex,
{
to_writer(&B::from_bits_truncate(flags.bits()), writer)
}
/**
Parse a flags value from text.
This function will fail on any names that don't correspond to defined flags.
Unknown bits will be ignored.
*/
pub fn from_str_truncate<B: Flags>(input: &str) -> Result<B, ParseError>
where
B::Bits: ParseHex,
{
Ok(B::from_bits_truncate(from_str::<B>(input)?.bits()))
}
/**
Write only the contained, defined, named flags in a flags value as text.
*/
pub fn to_writer_strict<B: Flags>(flags: &B, mut writer: impl Write) -> Result<(), fmt::Error> {
// This is a simplified version of `to_writer` that ignores
// any bits not corresponding to a named flag
let mut first = true;
let mut iter = flags.iter_names();
for (name, _) in &mut iter {
if !first {
writer.write_str(" | ")?;
}
first = false;
writer.write_str(name)?;
}
fmt::Result::Ok(())
}
/**
Parse a flags value from text.
This function will fail on any names that don't correspond to defined flags.
This function will fail to parse hex values.
*/
pub fn from_str_strict<B: Flags>(input: &str) -> Result<B, ParseError> {
// This is a simplified version of `from_str` that ignores
// any bits not corresponding to a named flag
let mut parsed_flags = B::empty();
// If the input is empty then return an empty set of flags
if input.trim().is_empty() {
return Ok(parsed_flags);
}
for flag in input.split('|') {
let flag = flag.trim();
// If the flag is empty then we've got missing input
if flag.is_empty() {
return Err(ParseError::empty_flag());
}
// If the flag starts with `0x` then it's a hex number
// These aren't supported in the strict parser
if flag.starts_with("0x") {
return Err(ParseError::invalid_hex_flag("unsupported hex flag value"));
}
let parsed_flag = B::from_name(flag).ok_or_else(|| ParseError::invalid_named_flag(flag))?;
parsed_flags.insert(parsed_flag);
}
Ok(parsed_flags)
}
/**
Encode a value as a hex string.
Implementors of this trait should not write the `0x` prefix.
*/
pub trait WriteHex {
/// Write the value as hex.
fn write_hex<W: fmt::Write>(&self, writer: W) -> fmt::Result;
}
/**
Parse a value from a hex string.
*/
pub trait ParseHex {
/// Parse the value from hex.
fn parse_hex(input: &str) -> Result<Self, ParseError>
where
Self: Sized;
}
/// An error encountered while parsing flags from text.
#[derive(Debug)]
pub struct ParseError(ParseErrorKind);
#[derive(Debug)]
#[allow(clippy::enum_variant_names)]
enum ParseErrorKind {
EmptyFlag,
InvalidNamedFlag {
#[cfg(not(feature = "std"))]
got: (),
#[cfg(feature = "std")]
got: String,
},
InvalidHexFlag {
#[cfg(not(feature = "std"))]
got: (),
#[cfg(feature = "std")]
got: String,
},
}
impl ParseError {
/// An invalid hex flag was encountered.
pub fn invalid_hex_flag(flag: impl fmt::Display) -> Self {
let _flag = flag;
let got = {
#[cfg(feature = "std")]
{
_flag.to_string()
}
};
ParseError(ParseErrorKind::InvalidHexFlag { got })
}
/// A named flag that doesn't correspond to any on the flags type was encountered.
pub fn invalid_named_flag(flag: impl fmt::Display) -> Self {
let _flag = flag;
let got = {
#[cfg(feature = "std")]
{
_flag.to_string()
}
};
ParseError(ParseErrorKind::InvalidNamedFlag { got })
}
/// A hex or named flag wasn't found between separators.
pub const fn empty_flag() -> Self {
ParseError(ParseErrorKind::EmptyFlag)
}
}
impl fmt::Display for ParseError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match &self.0 {
ParseErrorKind::InvalidNamedFlag { got } => {
let _got = got;
write!(f, "unrecognized named flag")?;
#[cfg(feature = "std")]
{
write!(f, " `{}`", _got)?;
}
}
ParseErrorKind::InvalidHexFlag { got } => {
let _got = got;
write!(f, "invalid hex flag")?;
#[cfg(feature = "std")]
{
write!(f, " `{}`", _got)?;
}
}
ParseErrorKind::EmptyFlag => {
write!(f, "encountered empty flag")?;
}
}
Ok(())
}
}
#[cfg(feature = "std")]
impl std::error::Error for ParseError {}