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use alloc::borrow::Cow;
use alloc::str;
use core::fmt;

use addr2line::gimli;
use addr2line::Context;

mod freestanding;
use self::freestanding::resolve as resolve_imp;
use self::freestanding::Symbol as SymbolImp;

/// Resolve an address to a symbol, passing the symbol to the specified
/// closure.
///
/// This function will look up the given address in areas such as the local
/// symbol table, dynamic symbol table, or DWARF debug info (depending on the
/// activated implementation) to find symbols to yield.
///
/// The closure may not be called if resolution could not be performed, and it
/// also may be called more than once in the case of inlined functions.
///
/// Symbols yielded represent the execution at the specified `addr`, returning
/// file/line pairs for that address (if available).
///
/// # Example
///
/// ```
/// extern crate backtrace;
///
/// fn main() {
///     backtrace::trace(|frame| {
///         let ip = frame.ip();
///
///         backtrace::resolve(ip, |symbol| {
///             // ...
///         });
///
///         false // only look at the top frame
///     });
/// }
/// ```
pub fn resolve<F: FnMut(&Symbol)>(
    ctxt: Option<&Context<gimli::EndianRcSlice<gimli::RunTimeEndian>>>,
    offset: u64,
    addr: *mut u8,
    mut cb: F,
) -> Result<(), addr2line::gimli::Error> {
    resolve_imp(ctxt, offset, addr, &mut cb)
}

/// A trait representing the resolution of a symbol in a file.
///
/// This trait is yielded as a trait object to the closure given to the
/// `backtrace::resolve` function, and it is virtually dispatched as it's
/// unknown which implementation is behind it.
///
/// A symbol can give contextual information about a function, for example the
/// name, filename, line number, precise address, etc. Not all information is
/// always available in a symbol, however, so all methods return an `Option`.
pub struct Symbol {
    inner: SymbolImp,
}

impl Symbol {
    /// Returns the name of this function.
    ///
    /// The returned structure can be used to query various properties about the
    /// symbol name:
    ///
    /// * The `Display` implementation will print out the demangled symbol.
    /// * The raw `str` value of the symbol can be accessed (if it's valid
    ///   utf-8).
    /// * The raw bytes for the symbol name can be accessed.
    pub fn name(&self) -> Option<Cow<str>> {
        self.inner.name()
    }

    /// Returns the starting address of this function.
    pub fn addr(&self) -> Option<*mut u8> {
        self.inner.addr()
    }

    /// Returns the file name where this function was defined.
    ///
    /// This is currently only available when libbacktrace is being used (e.g.
    /// unix platforms other than OSX) and when a binary is compiled with
    /// debuginfo. If neither of these conditions is met then this will likely
    /// return `None`.
    pub fn filename(&self) -> Option<&str> {
        self.inner.filename()
    }

    /// Returns the line number for where this symbol is currently executing.
    ///
    /// This return value is typically `Some` if `filename` returns `Some`, and
    /// is consequently subject to similar caveats.
    pub fn lineno(&self) -> Option<u32> {
        self.inner.lineno()
    }
}

impl fmt::Debug for Symbol {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut d = f.debug_struct("Symbol");
        if let Some(name) = self.name() {
            d.field("name", &name);
        }
        if let Some(addr) = self.addr() {
            d.field("addr", &addr);
        }
        if let Some(filename) = self.filename() {
            d.field("filename", &filename);
        }
        if let Some(lineno) = self.lineno() {
            d.field("lineno", &lineno);
        }
        d.finish()
    }
}