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use std::fs::{metadata, File};
use std::io::{self};
use std::path::PathBuf;
#[cfg(unix)]
use std::os::unix::fs::MetadataExt; // For Unix-like systems
#[cfg(windows)]
use std::os::windows::fs::MetadataExt; // For Windows
pub const ACTIVE_LOG_FILENAME: &str = "db";
pub const DEFAULT_READ_BUF_SIZE: usize = 1024 * 1024; // 1 MB
pub const FIELD_SEPARATOR: u8 = b'\x1C';
pub const ESCAPE_CHARACTER: u8 = b'\x1D';
// Special sequences. Note: these must have the same length!
// Since the log is read both forwards and backwards, we must have a signal
// character (ESCAPE_CHARACTER) on both sides of the special sequence.
pub const SEQ_RECORD_SEP: &[u8] = &[
ESCAPE_CHARACTER,
FIELD_SEPARATOR,
FIELD_SEPARATOR,
ESCAPE_CHARACTER,
];
pub const SEQ_LIT_ESCAPE: &[u8] = &[
ESCAPE_CHARACTER,
ESCAPE_CHARACTER,
ESCAPE_CHARACTER,
ESCAPE_CHARACTER,
];
pub const SEQ_LIT_FIELD_SEP: &[u8] = &[
ESCAPE_CHARACTER,
ESCAPE_CHARACTER,
FIELD_SEPARATOR,
ESCAPE_CHARACTER,
];
#[derive(Debug, Eq, PartialEq)]
pub enum SpecialSequence {
RecordSeparator,
LiteralFieldSeparator,
LiteralEscape,
}
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum MemtableEvictPolicy {
LeastWritten,
LeastRead,
LeastReadOrWritten,
}
#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
pub enum IndexableValue {
Int(i64),
String(String),
}
#[derive(Debug, Clone)]
pub enum RecordFieldType {
Int,
Float,
String,
Bytes,
}
#[derive(Debug, Clone)]
pub enum RecordValue {
Null,
Int(i64),
Float(f64),
String(String),
Bytes(Vec<u8>),
}
impl RecordValue {
pub fn serialize(&self) -> Vec<u8> {
match self {
RecordValue::Null => {
vec![0] // Tag for Null
}
RecordValue::Int(i) => {
let mut bytes = vec![1]; // Tag for Int
let data_bytes = escape_bytes(&i.to_be_bytes());
bytes.extend(&data_bytes);
bytes
}
RecordValue::Float(f) => {
let mut bytes = vec![2]; // Tag for Float
let data_bytes = escape_bytes(&f.to_be_bytes());
bytes.extend(&data_bytes);
bytes
}
RecordValue::String(s) => {
let mut bytes = vec![3]; // Tag for String
let length = s.len() as u64;
let length_bytes = escape_bytes(&length.to_be_bytes());
bytes.extend(&length_bytes);
let data_bytes = escape_bytes(s.as_bytes());
bytes.extend(&data_bytes);
bytes
}
RecordValue::Bytes(b) => {
let mut bytes = vec![4]; // Tag for Bytes
let length = b.len() as u64;
let length_bytes = escape_bytes(&length.to_be_bytes());
bytes.extend(&length_bytes);
let data_bytes = escape_bytes(b);
bytes.extend(&data_bytes);
bytes
}
}
}
/// Deserialize a RecordValue from a byte slice.
/// Returns the deserialized RecordValue and the number of bytes consumed.
pub fn deserialize(bytes: &[u8]) -> (RecordValue, usize) {
match bytes[0] {
0 => (RecordValue::Null, 1),
1 => {
let mut int_bytes = [0; 8];
int_bytes.copy_from_slice(&bytes[1..1 + 8]);
(RecordValue::Int(i64::from_be_bytes(int_bytes)), 1 + 8)
}
2 => {
let mut float_bytes = [0; 8];
float_bytes.copy_from_slice(&bytes[1..1 + 8]);
(RecordValue::Float(f64::from_be_bytes(float_bytes)), 1 + 8)
}
3 => {
let length_bytes = &bytes[1..1 + 8];
let length = u64::from_be_bytes(length_bytes.try_into().unwrap()) as usize;
(
RecordValue::String(
String::from_utf8(bytes[1 + 8..1 + 8 + length].to_vec()).unwrap(),
),
1 + 8 + length,
)
}
4 => {
let length_bytes = &bytes[1..1 + 8];
let length = u64::from_be_bytes(length_bytes.try_into().unwrap()) as usize;
(
RecordValue::Bytes(bytes[1 + 8..1 + 8 + length].to_vec()),
1 + 8 + length,
)
}
_ => panic!("Invalid tag: {}", bytes[0]),
}
}
pub fn as_indexable(&self) -> Option<IndexableValue> {
match self {
RecordValue::Int(i) => Some(IndexableValue::Int(*i)),
RecordValue::String(s) => Some(IndexableValue::String(s.clone())),
_ => None,
}
}
}
#[derive(Debug, Clone)]
pub struct Record {
pub values: Vec<RecordValue>,
}
impl Record {
pub fn serialize(&self) -> Vec<u8> {
let mut bytes = Vec::new();
for value in &self.values {
bytes.extend(value.serialize());
}
bytes
}
pub fn deserialize(bytes: &[u8]) -> Record {
let mut values = Vec::new();
let mut start = 0;
while start < bytes.len() {
let (rv, consumed) = RecordValue::deserialize(&bytes[start..]);
values.push(rv);
start += consumed;
}
Record { values }
}
}
pub fn escape_bytes(buf: &[u8]) -> Vec<u8> {
let mut result = Vec::new();
for byte in buf {
match byte {
&FIELD_SEPARATOR => {
result.extend(SEQ_LIT_FIELD_SEP);
}
&ESCAPE_CHARACTER => {
result.extend(SEQ_LIT_ESCAPE);
}
_ => result.push(*byte),
}
}
result
}
pub fn is_file_same_as_path(file: &File, path: &PathBuf) -> io::Result<bool> {
// Get the metadata for the open file handle
let file_metadata = file.metadata()?;
// Get the metadata for the file at the specified path
let path_metadata = metadata(path)?;
// Platform-specific comparison
#[cfg(unix)]
{
Ok(
file_metadata.dev() == path_metadata.dev()
&& file_metadata.ino() == path_metadata.ino(),
)
}
#[cfg(windows)]
{
Ok(file_metadata.file_index() == path_metadata.file_index()
&& file_metadata.volume_serial_number() == path_metadata.volume_serial_number())
}
}
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