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//! Source locations.
//!
//! Cranelift tracks the original source location of each instruction, and preserves the source
//! location when instructions are transformed.

use std::fmt;

/// A source location.
///
/// This is an opaque 32-bit number attached to each Cranelift IR instruction. Cranelift does not
/// interpret source locations in any way, they are simply preserved from the input to the output.
///
/// The default source location uses the all-ones bit pattern `!0`. It is used for instructions
/// that can't be given a real source location.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct SourceLoc(u32);

impl SourceLoc {
    /// Create a new source location with the given bits.
    pub fn new(bits: u32) -> Self {
        SourceLoc(bits)
    }

    /// Is this the default source location?
    pub fn is_default(self) -> bool {
        self == Default::default()
    }

    /// Read the bits of this source location.
    pub fn bits(self) -> u32 {
        self.0
    }
}

impl Default for SourceLoc {
    fn default() -> Self {
        SourceLoc(!0)
    }
}

impl fmt::Display for SourceLoc {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        if self.is_default() {
            write!(f, "@-")
        } else {
            write!(f, "@{:04x}", self.0)
        }
    }
}

#[cfg(test)]
mod tests {
    use ir::SourceLoc;
    use std::string::ToString;

    #[test]
    fn display() {
        assert_eq!(SourceLoc::default().to_string(), "@-");
        assert_eq!(SourceLoc::new(0).to_string(), "@0000");
        assert_eq!(SourceLoc::new(16).to_string(), "@0010");
        assert_eq!(SourceLoc::new(0xabcdef).to_string(), "@abcdef");
    }
}