Struct symbolic::debuginfo::dwarf::gimli::EntriesCursor

pub struct EntriesCursor<'abbrev, 'unit, R>
where
    R: Reader,
{ /* private fields */ }

A cursor into the Debugging Information Entries tree for a compilation unit.

The EntriesCursor can traverse the DIE tree in DFS order using next_dfs(), or skip to the next sibling of the entry the cursor is currently pointing to using next_sibling().

It is also possible to traverse the DIE tree at a lower abstraction level using next_entry(). This method does not skip over null entries, or provide any indication of the current tree depth. In this case, you must use current() to obtain the current entry, and current().has_children() to determine if the entry following the current entry will be a sibling or child. current() will return None if the current entry is a null entry, which signifies the end of the current tree depth.

Implementations

impl<'abbrev, 'unit, R> EntriesCursor<'abbrev, 'unit, R>

where R: Reader,

pub fn current(&self) -> Option<&DebuggingInformationEntry<'abbrev, 'unit, R>>

Get a reference to the entry that the cursor is currently pointing to.

If the cursor is not pointing at an entry, or if the current entry is a null entry, then None is returned.

pub fn next_entry(&mut self) -> Result<Option<()>, Error>

Move the cursor to the next DIE in the tree.

Returns Some if there is a next entry, even if this entry is null. If there is no next entry, then None is returned.

pub fn next_dfs( &mut self, ) -> Result<Option<(isize, &DebuggingInformationEntry<'abbrev, 'unit, R>)>, Error>

Move the cursor to the next DIE in the tree in DFS order.

Upon successful movement of the cursor, return the delta traversal depth and the entry:

• If we moved down into the previous current entry’s children, we get Some((1, entry)).

• If we moved to the previous current entry’s sibling, we get Some((0, entry)).

• If the previous entry does not have any siblings and we move up to its parent’s next sibling, then we get Some((-1, entry)). Note that if the parent doesn’t have a next sibling, then it could go up to the parent’s parent’s next sibling and return Some((-2, entry)), etc.

If there is no next entry, then None is returned.

Here is an example that finds the first entry in a compilation unit that does not have any children.

let unit = get_some_unit();
let abbrevs = get_abbrevs_for_unit(&unit);

let mut first_entry_with_no_children = None;
let mut cursor = unit.entries(&abbrevs);

// Move the cursor to the root.
assert!(cursor.next_dfs().unwrap().is_some());

// Traverse the DIE tree in depth-first search order.
let mut depth = 0;
while let Some((delta_depth, current)) = cursor.next_dfs().expect("Should parse next dfs") {
    // Update depth value, and break out of the loop when we
    // return to the original starting position.
    depth += delta_depth;
    if depth <= 0 {
        break;
    }

    first_entry_with_no_children = Some(current.clone());
}

println!("The first entry with no children is {:?}",
         first_entry_with_no_children.unwrap());

pub fn next_sibling( &mut self, ) -> Result<Option<&DebuggingInformationEntry<'abbrev, 'unit, R>>, Error>

Move the cursor to the next sibling DIE of the current one.

Returns Ok(Some(entry)) when the cursor has been moved to the next sibling, Ok(None) when there is no next sibling.

The depth of the cursor is never changed if this method returns Ok. Once Ok(None) is returned, this method will continue to return Ok(None) until either next_entry or next_dfs is called.

Here is an example that iterates over all of the direct children of the root entry:

let unit = get_some_unit();
let abbrevs = get_abbrevs_for_unit(&unit);

let mut cursor = unit.entries(&abbrevs);

// Move the cursor to the root.
assert!(cursor.next_dfs().unwrap().is_some());

// Move the cursor to the root's first child.
assert!(cursor.next_dfs().unwrap().is_some());

// Iterate the root's children.
loop {
    {
        let current = cursor.current().expect("Should be at an entry");
        println!("{:?} is a child of the root", current);
    }

    if cursor.next_sibling().expect("Should parse next sibling").is_none() {
        break;
    }
}

Trait Implementations

impl<'abbrev, 'unit, R> Clone for EntriesCursor<'abbrev, 'unit, R>

where R: Clone + Reader,

fn clone(&self) -> EntriesCursor<'abbrev, 'unit, R>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'abbrev, 'unit, R> Debug for EntriesCursor<'abbrev, 'unit, R>

where R: Debug + Reader,

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

Formats the value using the given formatter.