Add `CyanSWF`, the streaming file writer object
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/*
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* Created on Sat Sep 19 2020
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*
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* This file is a part of TerrabaseDB
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* Copyright (c) 2020, Sayan Nandan <ohsayan at outlook dot com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*
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*/
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//! # `CyanSWF`
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//! `CyanSWF` short for Cyan "StreamingWriteFile" is a minimal implementation
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//! of a file to which writes are _streamed_.
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//!
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//! What this essentially means — is that,
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//! instead of taking a whole object and then writing it to the disk, like what persistent
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//! storage did till v0.4.2, `CyanSWF` takes a part, encodes into its _kinda binary_
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//! equivalent, and then writes that to disk. It then takes the next part, encodes it, and then writes it to disk.
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//! The advantage of using this method is that the entire object does not need to be encoded at once
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//! which has an additional memory and CPU time overhead.
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//!
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//! TODO: At this moment, this is specific to the core `HashMap`. However, in the future
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//! a more generic implementation is to be made.
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use crate::diskstore::TResult;
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use std::fs::File;
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/// The magic number that separates every piece of data from the other
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const CYANSWF_MAGIC: u8 = 0xCA;
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/// The streaming file writer
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pub struct CyanSWF {
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/// The file to which data would be streamed into
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file: File,
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}
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impl CyanSWF {
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/// Create a new `CyanSWF` instance
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pub fn new(filename_and_path: &str) -> TResult<Self> {
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let file = File::create(filename_and_path)?;
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Ok(CyanSWF { file })
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}
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}
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