aconfig_storage_file/src/flag_table.rs

/*
 * Copyright (C) 2024 The Android Open Source Project
 *
 * 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
 *
 *      http://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.
 */

//! flag table module defines the flag table file format and methods for serialization
//! and deserialization

use crate::{
    get_bucket_index, read_str_from_bytes, read_u16_from_bytes, read_u32_from_bytes,
    read_u8_from_bytes,
};
use crate::{AconfigStorageError, StorageFileType, StoredFlagType};
use anyhow::anyhow;
use serde::{Deserialize, Serialize};
use std::fmt;

/// Flag table header struct
#[derive(PartialEq, Serialize, Deserialize)]
pub struct FlagTableHeader {
    pub version: u32,
    pub container: String,
    pub file_type: u8,
    pub file_size: u32,
    pub num_flags: u32,
    pub bucket_offset: u32,
    pub node_offset: u32,
}

/// Implement debug print trait for header
impl fmt::Debug for FlagTableHeader {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        writeln!(
            f,
            "Version: {}, Container: {}, File Type: {:?}, File Size: {}",
            self.version,
            self.container,
            StorageFileType::try_from(self.file_type),
            self.file_size
        )?;
        writeln!(
            f,
            "Num of Flags: {}, Bucket Offset:{}, Node Offset: {}",
            self.num_flags, self.bucket_offset, self.node_offset
        )?;
        Ok(())
    }
}

impl FlagTableHeader {
    /// Serialize to bytes
    pub fn into_bytes(&self) -> Vec<u8> {
        let mut result = Vec::new();
        result.extend_from_slice(&self.version.to_le_bytes());
        let container_bytes = self.container.as_bytes();
        result.extend_from_slice(&(container_bytes.len() as u32).to_le_bytes());
        result.extend_from_slice(container_bytes);
        result.extend_from_slice(&self.file_type.to_le_bytes());
        result.extend_from_slice(&self.file_size.to_le_bytes());
        result.extend_from_slice(&self.num_flags.to_le_bytes());
        result.extend_from_slice(&self.bucket_offset.to_le_bytes());
        result.extend_from_slice(&self.node_offset.to_le_bytes());
        result
    }

    /// Deserialize from bytes
    pub fn from_bytes(bytes: &[u8]) -> Result<Self, AconfigStorageError> {
        let mut head = 0;
        let table = Self {
            version: read_u32_from_bytes(bytes, &mut head)?,
            container: read_str_from_bytes(bytes, &mut head)?,
            file_type: read_u8_from_bytes(bytes, &mut head)?,
            file_size: read_u32_from_bytes(bytes, &mut head)?,
            num_flags: read_u32_from_bytes(bytes, &mut head)?,
            bucket_offset: read_u32_from_bytes(bytes, &mut head)?,
            node_offset: read_u32_from_bytes(bytes, &mut head)?,
        };
        if table.file_type != StorageFileType::FlagMap as u8 {
            return Err(AconfigStorageError::BytesParseFail(anyhow!(
                "binary file is not a flag map"
            )));
        }
        Ok(table)
    }
}

/// Flag table node struct
#[derive(PartialEq, Clone, Serialize, Deserialize)]
pub struct FlagTableNode {
    pub package_id: u32,
    pub flag_name: String,
    pub flag_type: StoredFlagType,
    // within package flag index of this flag type
    pub flag_index: u16,
    pub next_offset: Option<u32>,
}

/// Implement debug print trait for node
impl fmt::Debug for FlagTableNode {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        writeln!(
            f,
            "Package Id: {}, Flag: {}, Type: {:?}, Index: {}, Next: {:?}",
            self.package_id, self.flag_name, self.flag_type, self.flag_index, self.next_offset
        )?;
        Ok(())
    }
}

impl FlagTableNode {
    /// Serialize to bytes
    pub fn into_bytes(&self) -> Vec<u8> {
        let mut result = Vec::new();
        result.extend_from_slice(&self.package_id.to_le_bytes());
        let name_bytes = self.flag_name.as_bytes();
        result.extend_from_slice(&(name_bytes.len() as u32).to_le_bytes());
        result.extend_from_slice(name_bytes);
        result.extend_from_slice(&(self.flag_type as u16).to_le_bytes());
        result.extend_from_slice(&self.flag_index.to_le_bytes());
        result.extend_from_slice(&self.next_offset.unwrap_or(0).to_le_bytes());
        result
    }

    /// Deserialize from bytes
    pub fn from_bytes(bytes: &[u8]) -> Result<Self, AconfigStorageError> {
        let mut head = 0;
        let node = Self {
            package_id: read_u32_from_bytes(bytes, &mut head)?,
            flag_name: read_str_from_bytes(bytes, &mut head)?,
            flag_type: StoredFlagType::try_from(read_u16_from_bytes(bytes, &mut head)?)?,
            flag_index: read_u16_from_bytes(bytes, &mut head)?,
            next_offset: match read_u32_from_bytes(bytes, &mut head)? {
                0 => None,
                val => Some(val),
            },
        };
        Ok(node)
    }

    /// Calculate node bucket index
    pub fn find_bucket_index(package_id: u32, flag_name: &str, num_buckets: u32) -> u32 {
        let full_flag_name = package_id.to_string() + "/" + flag_name;
        get_bucket_index(full_flag_name.as_bytes(), num_buckets)
    }
}

#[derive(PartialEq, Serialize, Deserialize)]
pub struct FlagTable {
    pub header: FlagTableHeader,
    pub buckets: Vec<Option<u32>>,
    pub nodes: Vec<FlagTableNode>,
}

/// Implement debug print trait for flag table
impl fmt::Debug for FlagTable {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        writeln!(f, "Header:")?;
        write!(f, "{:?}", self.header)?;
        writeln!(f, "Buckets:")?;
        writeln!(f, "{:?}", self.buckets)?;
        writeln!(f, "Nodes:")?;
        for node in self.nodes.iter() {
            write!(f, "{:?}", node)?;
        }
        Ok(())
    }
}

/// Flag table struct
impl FlagTable {
    /// Serialize to bytes
    pub fn into_bytes(&self) -> Vec<u8> {
        [
            self.header.into_bytes(),
            self.buckets.iter().map(|v| v.unwrap_or(0).to_le_bytes()).collect::<Vec<_>>().concat(),
            self.nodes.iter().map(|v| v.into_bytes()).collect::<Vec<_>>().concat(),
        ]
        .concat()
    }

    /// Deserialize from bytes
    pub fn from_bytes(bytes: &[u8]) -> Result<Self, AconfigStorageError> {
        let header = FlagTableHeader::from_bytes(bytes)?;
        let num_flags = header.num_flags;
        let num_buckets = crate::get_table_size(num_flags)?;
        let mut head = header.into_bytes().len();
        let buckets = (0..num_buckets)
            .map(|_| match read_u32_from_bytes(bytes, &mut head).unwrap() {
                0 => None,
                val => Some(val),
            })
            .collect();
        let nodes = (0..num_flags)
            .map(|_| {
                let node = FlagTableNode::from_bytes(&bytes[head..])?;
                head += node.into_bytes().len();
                Ok(node)
            })
            .collect::<Result<Vec<_>, AconfigStorageError>>()
            .map_err(|errmsg| {
                AconfigStorageError::BytesParseFail(anyhow!("fail to parse flag table: {}", errmsg))
            })?;

        let table = Self { header, buckets, nodes };
        Ok(table)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{
        test_utils::create_test_flag_table, DEFAULT_FILE_VERSION, MAX_SUPPORTED_FILE_VERSION,
    };

    // this test point locks down the table serialization
    #[test]
    fn test_serialization() {
        for file_version in 1..=MAX_SUPPORTED_FILE_VERSION {
            let flag_table = create_test_flag_table(file_version);

            let header: &FlagTableHeader = &flag_table.header;
            let reinterpreted_header = FlagTableHeader::from_bytes(&header.into_bytes());
            assert!(reinterpreted_header.is_ok());
            assert_eq!(header, &reinterpreted_header.unwrap());

            let nodes: &Vec<FlagTableNode> = &flag_table.nodes;
            for node in nodes.iter() {
                let reinterpreted_node = FlagTableNode::from_bytes(&node.into_bytes()).unwrap();
                assert_eq!(node, &reinterpreted_node);
            }

            let flag_table_bytes = flag_table.into_bytes();
            let reinterpreted_table = FlagTable::from_bytes(&flag_table_bytes);
            assert!(reinterpreted_table.is_ok());
            assert_eq!(&flag_table, &reinterpreted_table.unwrap());
            assert_eq!(flag_table_bytes.len() as u32, header.file_size);
        }
    }

    // this test point locks down that version number should be at the top of serialized
    // bytes
    #[test]
    fn test_version_number() {
        let flag_table = create_test_flag_table(DEFAULT_FILE_VERSION);
        let bytes = &flag_table.into_bytes();
        let mut head = 0;
        let version_from_file = read_u32_from_bytes(bytes, &mut head).unwrap();
        assert_eq!(version_from_file, DEFAULT_FILE_VERSION);
    }

    // this test point locks down file type check
    #[test]
    fn test_file_type_check() {
        let mut flag_table = create_test_flag_table(DEFAULT_FILE_VERSION);
        flag_table.header.file_type = 123u8;
        let error = FlagTable::from_bytes(&flag_table.into_bytes()).unwrap_err();
        assert_eq!(
            format!("{:?}", error),
            format!("BytesParseFail(binary file is not a flag map)")
        );
    }
}