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// Copyright 2019 Google LLC // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. use super::{Builder, Pushable, Value, VectorBuilder}; /// Builds a Flexbuffer map, returned by a [Builder](struct.Builder.html). /// /// ## Side effect when dropped: /// When this is dropped, or `end_map` is called, the map is /// commited to the buffer. If this map is the root of the flexbuffer, then the /// root is written and the flexbuffer is complete. /// ## Panics: /// - Duplicate keys will result in a panic in both debug and release mode. /// - Keys with internal nulls results in a panic in debug mode and result in silent truncaction /// in release mode. pub struct MapBuilder<'a> { pub(super) builder: &'a mut Builder, // If the root is this map then start == None. Otherwise start is the // number of values in the 'values stack' before adding this map. pub(super) start: Option<usize>, } impl<'a> MapBuilder<'a> { /// Push `p` onto this map with key `key`. /// This will panic (in debug mode) if `key` contains internal nulls. #[inline] pub fn push<P: Pushable>(&mut self, key: &str, p: P) { self.builder.push_key(key); self.builder.push(p); } /// Starts a nested vector that will be pushed onto this map /// with key `key` when it is dropped. /// /// This will panic (in debug mode) if `key` contains internal nulls. #[inline] pub fn start_vector(&mut self, key: &str) -> VectorBuilder { // Push the key that refers to this nested vector. self.builder.push_key(key); // Nested vector. let start = Some(self.builder.values.len()); VectorBuilder { builder: &mut self.builder, start, } } /// Starts a nested map which that will be pushed onto this map /// with key `key` when it is dropped. /// /// This will panic (in debug mode) if `key` contains internal nulls. #[inline] pub fn start_map(&mut self, key: &str) -> MapBuilder { // Push the key that refers to this nested vector. self.builder.push_key(key); // Nested map. let start = Some(self.builder.values.len()); MapBuilder { builder: &mut self.builder, start, } } /// `end_map` sorts the map by key and writes it to the buffer. This happens anyway /// when the map builder is dropped. #[inline] pub fn end_map(self) {} } impl<'a> Drop for MapBuilder<'a> { #[inline] fn drop(&mut self) { self.builder.end_map_or_vector(true, self.start); } } // Read known keys / strings as iterators over bytes -- skipping utf8 validation and strlen. pub(super) fn get_key(buffer: &[u8], address: usize) -> impl Iterator<Item = &u8> { buffer[address..].iter().take_while(|&&b| b != b'\0') } // `values` is assumed to be of the format [key1, value1, ..., keyN, valueN]. // The keys refer to cstrings in `buffer`. When this function returns, // `values` is sorted in place by key. pub(super) fn sort_map_by_keys(values: &mut [Value], buffer: &[u8]) { debug_assert_eq!(values.len() % 2, 0); debug_assert!(values.iter().step_by(2).all(Value::is_key)); let raw_pairs = values.as_mut_ptr() as *mut [Value; 2]; let pairs_len = values.len() / 2; // Unsafe code needed to treat the slice as key-value pairs when sorting in place. This is // preferred over custom sorting or adding another dependency. By construction, this part // of the values stack must be alternating (key, value) pairs. The public API must not be // able to trigger the above debug_assets that protect this unsafe usage. let pairs: &mut [[Value; 2]] = unsafe { std::slice::from_raw_parts_mut(raw_pairs, pairs_len) }; #[rustfmt::skip] pairs.sort_unstable_by(|[key1, _], [key2, _]| { if let Value::Key(a1) = *key1 { if let Value::Key(a2) = *key2 { let s1 = get_key(buffer, a1); let s2 = get_key(buffer, a2); let ord = s1.cmp(s2); if ord == std::cmp::Ordering::Equal { let dup: String = get_key(buffer, a1).map(|&b| b as char).collect(); panic!("Duplicated key in map {:?}", dup); } return ord; } } unreachable!(); }); }