1 // Copyright 2019 Google LLC 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 use super::{Builder, MapBuilder, Pushable}; 16 17 /// Builds a Flexbuffer vector, returned by a [Builder](struct.Builder.html). 18 /// 19 /// ## Side effect when dropped: 20 /// When this is dropped, or `end_vector` is called, the vector is 21 /// commited to the buffer. If this vector is the root of the flexbuffer, then the 22 /// root is written and the flexbuffer is complete. The FlexBufferType of this vector 23 /// is determined by the pushed values when this is dropped. The most compact vector type is 24 /// automatically chosen. 25 pub struct VectorBuilder<'a> { 26 pub(crate) builder: &'a mut Builder, 27 // If the root is this vector then start == None. Otherwise start is the 28 // number of values in the 'values stack' before adding this vector. 29 pub(crate) start: Option<usize>, 30 } 31 impl<'a> VectorBuilder<'a> { 32 /// Pushes `p` onto the vector. 33 #[inline] push<P: Pushable>(&mut self, p: P)34 pub fn push<P: Pushable>(&mut self, p: P) { 35 self.builder.push(p); 36 } 37 /// Starts a nested vector that will be pushed onto this vector when it is dropped. 38 #[inline] start_vector(&mut self) -> VectorBuilder39 pub fn start_vector(&mut self) -> VectorBuilder { 40 let start = Some(self.builder.values.len()); 41 VectorBuilder { 42 builder: &mut self.builder, 43 start, 44 } 45 } 46 /// Starts a nested map that will be pushed onto this vector when it is dropped. 47 #[inline] start_map(&mut self) -> MapBuilder48 pub fn start_map(&mut self) -> MapBuilder { 49 let start = Some(self.builder.values.len()); 50 MapBuilder { 51 builder: &mut self.builder, 52 start, 53 } 54 } 55 /// `end_vector` determines the type of the vector and writes it to the buffer. 56 /// This will happen automatically if the VectorBuilder is dropped. 57 #[inline] end_vector(self)58 pub fn end_vector(self) {} 59 } 60 impl<'a> Drop for VectorBuilder<'a> { 61 #[inline] drop(&mut self)62 fn drop(&mut self) { 63 self.builder.end_map_or_vector(false, self.start); 64 } 65 } 66