/rust/registry/src/index.crates.io-6f17d22bba15001f/bitflags-2.4.0/src/parser.rs

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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(())
}

pub(crate) struct AsDisplay<'a, B>(pub(crate) &'a B);

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)
}

/**
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 {}

Coverage Report

Created: 2025-08-28 06:06

Line	Count	Source (jump to first uncovered line)
1		/*!
2		Parsing flags from text.
3
4		Format and parse a flags value as text using the following grammar:
5
6		- _Flags:_ (_Whitespace_ _Flag_ _Whitespace_)`\|`*
7		- _Flag:_ _Name_ \| _Hex Number_
8		- _Name:_ The name of any defined flag
9		- _Hex Number_: `0x`([0-9a-fA-F])*
10		- _Whitespace_: (\s)*
11
12		As an example, this is how `Flags::A \| Flags::B \| 0x0c` can be represented as text:
13
14		```text
15		A \| B \| 0x0c
16		```
17
18		Alternatively, it could be represented without whitespace:
19
20		```text
21		A\|B\|0x0C
22		```
23
24		Note that identifiers are case-sensitive, so the following is not equivalent:
25
26		```text
27		a\|b\|0x0C
28		```
29		*/
30
31		#![allow(clippy::let_unit_value)]
32
33		use core::fmt::{self, Write};
34
35		use crate::{Bits, Flags};
36
37		/**
38		Write a flags value as text.
39