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    731

    use std::{ ptr, mem, str, slice, fmt };
    use std::ops::{ Index, IndexMut, Deref };
    use std::iter::FromIterator;

    use crate::codegen::{ DumpGenerator, Generator, PrettyGenerator };
    use crate::value::JsonValue;

    const KEY_BUF_LEN: usize = 32;
    static NULL: JsonValue = JsonValue::Null;

    // FNV-1a implementation
    //
    // While the `Object` is implemented as a binary tree, not a hash table, the
    // order in which the tree is balanced makes absolutely no difference as long
    // as there is a deterministic left / right ordering with good spread.
    // Comparing a hashed `u64` is faster than comparing `&str` or even `&[u8]`,
    // for larger objects this yields non-trivial performance benefits.
    //
    // Additionally this "randomizes" the keys a bit. Should the keys in an object
    // be inserted in alphabetical order (an example of such a use case would be
    // using an object as a store for entries by ids, where ids are sorted), this
    // will prevent the tree from being constructed in a way where the same branch
    // of each node is always used, effectively producing linear lookup times. Bad!
    //
    // Example:
    //
    // ```
    // println!("{}", hash_key(b"10000056"));
    // println!("{}", hash_key(b"10000057"));
    // println!("{}", hash_key(b"10000058"));
    // println!("{}", hash_key(b"10000059"));
    // ```
    //
    // Produces:
    //
    // ```
    // 15043794053238616431  <-- 2nd
    // 15043792953726988220  <-- 1st
    // 15043800650308385697  <-- 4th
    // 15043799550796757486  <-- 3rd
    // ```
    #[inline]
    fn hash_key(key: &[u8]) -> u64 {
        let mut hash: u64 = 0xcbf29ce484222325;
        for byte in key {
            hash ^= *byte as u64;
            hash = hash.wrapping_mul(0x100000001b3);
        }
        hash
    }

    struct Key {
        // Internal buffer to store keys that fit within `KEY_BUF_LEN`,
        // otherwise this field will contain garbage.
        pub buf: [u8; KEY_BUF_LEN],

        // Length of the key in bytes.
        pub len: usize,

        // Cached raw pointer to the key, so that we can cheaply construct
        // a `&str` slice from the `Node` without checking if the key is
        // allocated separately on the heap, or in the `key_buf`.
        pub ptr: *mut u8,

        // A hash of the key, explanation below.
        pub hash: u64,
    }

    impl Key {
        #[inline]
        fn new(hash: u64, len: usize) -> Self {
            Key {
                buf: [0; KEY_BUF_LEN],
                len: len,
                ptr: ptr::null_mut(),
                hash: hash
            }
        }

        #[inline]
        fn as_bytes(&self) -> &[u8] {
            unsafe {
                slice::from_raw_parts(self.ptr, self.len)
            }
        }

        #[inline]
        fn as_str(&self) -> &str {
            unsafe {
                str::from_utf8_unchecked(self.as_bytes())
            }
        }

        // The `buf` on the `Key` can only be filled after the struct
        // is already on the `Vec`'s heap (along with the `Node`).
        // For that reason it's not set in `Key::new` but only after
        // the `Node` is created and allocated.
        #[inline]
        fn attach(&mut self, key: &[u8]) {
            if self.len <= KEY_BUF_LEN {
                unsafe {
                    ptr::copy_nonoverlapping(
                        key.as_ptr(),
                        self.buf.as_mut_ptr(),
                        self.len
                    );
                }
                self.ptr = self.buf.as_mut_ptr();
            } else {
                let mut heap = key.to_vec();
                self.ptr = heap.as_mut_ptr();
                mem::forget(heap);
            }
        }

        // Since we store `Node`s on a vector, it will suffer from reallocation.
        // Whenever that happens, `key.ptr` for short keys will turn into dangling
        // pointers and will need to be re-cached.
        #[inline]
        fn fix_ptr(&mut self) {
            if self.len <= KEY_BUF_LEN {
                self.ptr = self.buf.as_mut_ptr();
            }
        }
    }

    // Implement `Sync` and `Send` for `Key` despite the use of raw pointers. The struct
    // itself should be memory safe.
    unsafe impl Sync for Key {}
    unsafe impl Send for Key {}

    // Because long keys _can_ be stored separately from the `Key` on heap,
    // it's essential to clean up the heap allocation when the `Key` is dropped.
    impl Drop for Key {
        fn drop(&mut self) {
            unsafe {
                if self.len > KEY_BUF_LEN {
                    // Construct a `Vec` out of the `key_ptr`. Since the key is
                    // always allocated from a slice, the capacity is equal to length.
                    let heap = Vec::from_raw_parts(
                        self.ptr,
                        self.len,
                        self.len
                    );

                    // Now that we have an owned `Vec<u8>`, drop it.
                    drop(heap);
                }
            }
        }
    }

    // Just like with `Drop`, `Clone` needs a custom implementation that accounts
    // for the fact that key _can_ be separately heap allocated.
    impl Clone for Key {
        fn clone(&self) -> Self {
            if self.len > KEY_BUF_LEN {
                let mut heap = self.as_bytes().to_vec();
                let ptr = heap.as_mut_ptr();
                mem::forget(heap);

                Key {
                    buf: [0; KEY_BUF_LEN],
                    len: self.len,
                    ptr: ptr,
                    hash: self.hash,
                }
            } else {
                Key {
                    buf: self.buf,
                    len: self.len,
                    ptr: ptr::null_mut(), // requires a `fix_ptr` call after `Node` is on the heap
                    hash: self.hash,
                }
            }
        }
    }

    #[derive(Clone)]
    struct Node {
        // String-esque key abstraction
        pub key: Key,

        // Value stored.
        pub value: JsonValue,

        // Store vector index pointing to the `Node` for which `key_hash` is smaller
        // than that of this `Node`.
        // Will default to 0 as root node can't be referenced anywhere else.
        pub left: usize,

        // Same as above but for `Node`s with hash larger than this one. If the
        // hash is the same, but keys are different, the lookup will default
        // to the right branch as well.
        pub right: usize,
    }

    impl fmt::Debug for Node {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            fmt::Debug::fmt(&(self.key.as_str(), &self.value, self.left, self.right), f)
        }
    }

    impl PartialEq for Node {
        fn eq(&self, other: &Node) -> bool {
            self.key.hash       == other.key.hash       &&
            self.key.as_bytes() == other.key.as_bytes() &&
            self.value          == other.value
        }
    }

    impl Node {
        #[inline]
        fn new(value: JsonValue, hash: u64, len: usize) -> Node {
            Node {
                key: Key::new(hash, len),
                value: value,
                left: 0,
                right: 0,
            }
        }
    }

    /// A binary tree implementation of a string -> `JsonValue` map. You normally don't
    /// have to interact with instances of `Object`, much more likely you will be
    /// using the `JsonValue::Object` variant, which wraps around this struct.
    #[derive(Debug)]
    pub struct Object {
        store: Vec<Node>
    }

    impl Object {
        /// Create a new, empty instance of `Object`. Empty `Object` performs no
        /// allocation until a value is inserted into it.
        #[inline(always)]
        pub fn new() -> Self {
            Object {
                store: Vec::new()
            }
        }

        /// Create a new `Object` with memory preallocated for `capacity` number
        /// of entries.
        #[inline(always)]
        pub fn with_capacity(capacity: usize) -> Self {
            Object {
                store: Vec::with_capacity(capacity)
            }
        }

        #[inline]
        fn node_at_index_mut(&mut self, index: usize) -> *mut Node {
            unsafe { self.store.as_mut_ptr().offset(index as isize) }
        }

        #[inline(always)]
        fn add_node(&mut self, key: &[u8], value: JsonValue, hash: u64) -> usize {
            let index = self.store.len();

            if index < self.store.capacity() {
                // Because we've just checked the capacity, we can avoid
                // using `push`, and instead do unsafe magic to memcpy
                // the new node at the correct index without additional
                // capacity or bound checks.
                unsafe {
                    let node = Node::new(value, hash, key.len());
                    self.store.set_len(index + 1);

                    // To whomever gets concerned: I got better results with
                    // copy than write. Difference in benchmarks wasn't big though.
                    ptr::copy_nonoverlapping(
                        &node as *const Node,
                        self.store.as_mut_ptr().offset(index as isize),
                        1,
                    );

                    // Since the Node has been copied, we need to forget about
                    // the owned value, else we may run into use after free.
                    mem::forget(node);
                }

                unsafe { self.store.get_unchecked_mut(index).key.attach(key) };
            } else {
                self.store.push(Node::new(value, hash, key.len()));

                unsafe { self.store.get_unchecked_mut(index).key.attach(key) };

                // Index up to the index (old length), we don't need to fix
                // anything on the Node that just got pushed.
                for node in self.store.iter_mut().take(index) {
                    node.key.fix_ptr();
                }
            }

            index
        }

        /// Insert a new entry, or override an existing one. Note that `key` has
        /// to be a `&str` slice and not an owned `String`. The internals of
        /// `Object` will handle the heap allocation of the key if needed for
        /// better performance.
        #[inline]
        pub fn insert(&mut self, key: &str, value: JsonValue) {
            self.insert_index(key, value);
        }

        pub(crate) fn insert_index(&mut self, key: &str, value: JsonValue) -> usize {
            let key = key.as_bytes();
            let hash = hash_key(key);

            if self.store.len() == 0 {
                self.store.push(Node::new(value, hash, key.len()));
                self.store[0].key.attach(key);
                return 0;
            }

            let mut node = unsafe { &mut *self.node_at_index_mut(0) };
            let mut parent = 0;

            loop {
                if hash == node.key.hash && key == node.key.as_bytes() {
                    node.value = value;
                    return parent;
                } else if hash < node.key.hash {
                    if node.left != 0 {
                        parent = node.left;
                        node = unsafe { &mut *self.node_at_index_mut(node.left) };
                        continue;
                    }
                    let index = self.add_node(key, value, hash);
                    self.store[parent].left = index;

                    return index;
                } else {
                    if node.right != 0 {
                        parent = node.right;
                        node = unsafe { &mut *self.node_at_index_mut(node.right) };
                        continue;
                    }
                    let index = self.add_node(key, value, hash);
                    self.store[parent].right = index;

                    return index;
                }
            }
        }

        #[inline]
        pub(crate) fn override_at(&mut self, index: usize, value: JsonValue) {
            self.store[index].value = value;
        }

        #[inline]
        #[deprecated(since="0.11.11", note="Was only meant for internal use")]
        pub fn override_last(&mut self, value: JsonValue) {
            if let Some(node) = self.store.last_mut() {
                node.value = value;
            }
        }

        pub fn get(&self, key: &str) -> Option<&JsonValue> {
            if self.store.len() == 0 {
                return None;
            }

            let key = key.as_bytes();
            let hash = hash_key(key);

            let mut node = unsafe { self.store.get_unchecked(0) };

            loop {
                if hash == node.key.hash && key == node.key.as_bytes() {
                    return Some(&node.value);
                } else if hash < node.key.hash {
                    if node.left == 0 {
                        return None;
                    }
                    node = unsafe { self.store.get_unchecked(node.left) };
                } else {
                    if node.right == 0 {
                        return None;
                    }
                    node = unsafe { self.store.get_unchecked(node.right) };
                }
            }
        }

        pub fn get_mut(&mut self, key: &str) -> Option<&mut JsonValue> {
            if self.store.len() == 0 {
                return None;
            }

            let key = key.as_bytes();
            let hash = hash_key(key);

            let mut index = 0;
            {
                let mut node = unsafe { self.store.get_unchecked(0) };

                loop {
                    if hash == node.key.hash && key == node.key.as_bytes() {
                        break;
                    } else if hash < node.key.hash {
                        if node.left == 0 {
                            return None;
                        }
                        index = node.left;
                        node = unsafe { self.store.get_unchecked(node.left) };
                    } else {
                        if node.right == 0 {
                            return None;
                        }
                        index = node.right;
                        node = unsafe { self.store.get_unchecked(node.right) };
                    }
                }
            }

            let node = unsafe { self.store.get_unchecked_mut(index) };

            Some(&mut node.value)
        }

        /// Attempts to remove the value behind `key`, if successful
        /// will return the `JsonValue` stored behind the `key`.
        pub fn remove(&mut self, key: &str) -> Option<JsonValue> {
            if self.store.len() == 0 {
                return None;
            }

            let key = key.as_bytes();
            let hash = hash_key(key);
            let mut index = 0;

            {
                let mut node = unsafe { self.store.get_unchecked(0) };

                // Try to find the node
                loop {
                    if hash == node.key.hash && key == node.key.as_bytes() {
                        break;
                    } else if hash < node.key.hash {
                        if node.left == 0 {
                            return None;
                        }
                        index = node.left;
                        node = unsafe { self.store.get_unchecked(node.left) };
                    } else {
                        if node.right == 0 {
                            return None;
                        }
                        index = node.right;
                        node = unsafe { self.store.get_unchecked(node.right) };
                    }
                }
            }

            // Removing a node would screw the tree badly, it's easier to just
            // recreate it. This is a very costly operation, but removing nodes
            // in JSON shouldn't happen very often if at all. Optimizing this
            // can wait for better times.
            let mut new_object = Object::with_capacity(self.store.len() - 1);
            let mut removed = None;

            for (i, node) in self.store.iter_mut().enumerate() {
                if i == index {
                    // Rust doesn't like us moving things from `node`, even if
                    // it is owned. Replace fixes that.
                    removed = Some(mem::replace(&mut node.value, JsonValue::Null));
                } else {
                    let value = mem::replace(&mut node.value, JsonValue::Null);

                    new_object.insert(node.key.as_str(), value);
                }
            }

            mem::swap(self, &mut new_object);

            removed
        }

        #[inline(always)]
        pub fn len(&self) -> usize {
            self.store.len()
        }

        #[inline(always)]
        pub fn is_empty(&self) -> bool {
            self.store.is_empty()
        }

        /// Wipe the `Object` clear. The capacity will remain untouched.
        pub fn clear(&mut self) {
            self.store.clear();
        }

        #[inline(always)]
        pub fn iter(&self) -> Iter {
            Iter {
                inner: self.store.iter()
            }
        }

        #[inline(always)]
        pub fn iter_mut(&mut self) -> IterMut {
            IterMut {
                inner: self.store.iter_mut()
            }
        }

        /// Prints out the value as JSON string.
        pub fn dump(&self) -> String {
            let mut gen = DumpGenerator::new();
            gen.write_object(self).expect("Can't fail");
            gen.consume()
        }

        /// Pretty prints out the value as JSON string. Takes an argument that's
        /// number of spaces to indent new blocks with.
        pub fn pretty(&self, spaces: u16) -> String {
            let mut gen = PrettyGenerator::new(spaces);
            gen.write_object(self).expect("Can't fail");
            gen.consume()
        }
    }

    // Custom implementation of `Clone`, as new heap allocation means
    // we have to fix key pointers everywhere!
    impl Clone for Object {
        fn clone(&self) -> Self {
            let mut store = self.store.clone();

            for node in store.iter_mut() {
                node.key.fix_ptr();
            }

            Object {
                store: store
            }
        }
    }

    impl<K: AsRef<str>, V: Into<JsonValue>> FromIterator<(K, V)> for Object {
        fn from_iter<I: IntoIterator<Item=(K, V)>>(iter: I) -> Self {
            let iter = iter.into_iter();
            let mut object = Object::with_capacity(iter.size_hint().0);

            for (key, value) in iter {
                object.insert(key.as_ref(), value.into());
            }

            object
        }
    }

    // Because keys can inserted in different order, the safe way to
    // compare `Object`s is to iterate over one and check if the other
    // has all the same keys.
    impl PartialEq for Object {
        fn eq(&self, other: &Object) -> bool {
            if self.len() != other.len() {
                return false;
            }

            for (key, value) in self.iter() {
                match other.get(key) {
                    Some(ref other_val) => if *other_val != value { return false; },
                    None                => return false
                }
            }

            true
        }
    }

    pub struct Iter<'a> {
        inner: slice::Iter<'a, Node>
    }

    impl<'a> Iter<'a> {
        /// Create an empty iterator that always returns `None`
        pub fn empty() -> Self {
            Iter {
                inner: [].iter()
            }
        }
    }

    impl<'a> Iterator for Iter<'a> {
        type Item = (&'a str, &'a JsonValue);

        #[inline(always)]
        fn next(&mut self) -> Option<Self::Item> {
            self.inner.next().map(|node| (node.key.as_str(), &node.value))
        }
    }

    impl<'a> DoubleEndedIterator for Iter<'a> {
        #[inline(always)]
        fn next_back(&mut self) -> Option<Self::Item> {
            self.inner.next_back().map(|node| (node.key.as_str(), &node.value))
        }
    }

    impl<'a> ExactSizeIterator for Iter<'a> {
        fn len(&self) -> usize {
            self.inner.len()
        }
    }

    pub struct IterMut<'a> {
        inner: slice::IterMut<'a, Node>
    }

    impl<'a> IterMut<'a> {
        /// Create an empty iterator that always returns `None`
        pub fn empty() -> Self {
            IterMut {
                inner: [].iter_mut()
            }
        }
    }

    impl<'a> Iterator for IterMut<'a> {
        type Item = (&'a str, &'a mut JsonValue);

        #[inline(always)]
        fn next(&mut self) -> Option<Self::Item> {
            self.inner.next().map(|node| (node.key.as_str(), &mut node.value))
        }
    }

    impl<'a> DoubleEndedIterator for IterMut<'a> {
        #[inline(always)]
        fn next_back(&mut self) -> Option<Self::Item> {
            self.inner.next_back().map(|node| (node.key.as_str(), &mut node.value))
        }
    }

    impl<'a> ExactSizeIterator for IterMut<'a> {
        fn len(&self) -> usize {
            self.inner.len()
        }
    }

    /// Implements indexing by `&str` to easily access object members:
    ///
    /// ## Example
    ///
    /// ```
    /// # #[macro_use]
    /// # extern crate json;
    /// # use json::JsonValue;
    /// #
    /// # fn main() {
    /// let value = object!{
    ///     foo: "bar"
    /// };
    ///
    /// if let JsonValue::Object(object) = value {
    ///   assert!(object["foo"] == "bar");
    /// }
    /// # }
    /// ```
    // TODO: doc
    impl<'a> Index<&'a str> for Object {
        type Output = JsonValue;

        fn index(&self, index: &str) -> &JsonValue {
            match self.get(index) {
                Some(value) => value,
                _ => &NULL
            }
        }
    }

    impl Index<String> for Object {
        type Output = JsonValue;

        fn index(&self, index: String) -> &JsonValue {
            self.index(index.deref())
        }
    }

    impl<'a> Index<&'a String> for Object {
        type Output = JsonValue;

        fn index(&self, index: &String) -> &JsonValue {
            self.index(index.deref())
        }
    }

    /// Implements mutable indexing by `&str` to easily modify object members:
    ///
    /// ## Example
    ///
    /// ```
    /// # #[macro_use]
    /// # extern crate json;
    /// # use json::JsonValue;
    /// #
    /// # fn main() {
    /// let value = object!{};
    ///
    /// if let JsonValue::Object(mut object) = value {
    ///   object["foo"] = 42.into();
    ///
    ///   assert!(object["foo"] == 42);
    /// }
    /// # }
    /// ```
    impl<'a> IndexMut<&'a str> for Object {
        fn index_mut(&mut self, index: &str) -> &mut JsonValue {
            if self.get(index).is_none() {
                self.insert(index, JsonValue::Null);
            }
            self.get_mut(index).unwrap()
        }
    }

    impl IndexMut<String> for Object {
        fn index_mut(&mut self, index: String) -> &mut JsonValue {
            self.index_mut(index.deref())
        }
    }

    impl<'a> IndexMut<&'a String> for Object {
        fn index_mut(&mut self, index: &String) -> &mut JsonValue {
            self.index_mut(index.deref())
        }
    }