polars_io/file_cache/
metadata.rs

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1use std::path::Path;
2use std::sync::Arc;
3
4use serde::{Deserialize, Serialize};
5
6#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
7pub(super) enum FileVersion {
8    Timestamp(u64),
9    ETag(String),
10    Uninitialized,
11}
12
13#[derive(Debug)]
14pub enum LocalCompareError {
15    LastModifiedMismatch { expected: u64, actual: u64 },
16    SizeMismatch { expected: u64, actual: u64 },
17    DataFileReadError(std::io::Error),
18}
19
20pub type LocalCompareResult = Result<(), LocalCompareError>;
21
22/// Metadata written to a file used to track state / synchronize across processes.
23#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
24pub(super) struct EntryMetadata {
25    pub(super) uri: Arc<str>,
26    pub(super) local_last_modified: u64,
27    pub(super) local_size: u64,
28    pub(super) remote_version: FileVersion,
29    /// TTL since last access, in seconds.
30    pub(super) ttl: u64,
31}
32
33impl std::fmt::Display for LocalCompareError {
34    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
35        match self {
36            Self::LastModifiedMismatch { expected, actual } => write!(
37                f,
38                "last modified time mismatch: expected {}, found {}",
39                expected, actual
40            ),
41            Self::SizeMismatch { expected, actual } => {
42                write!(f, "size mismatch: expected {}, found {}", expected, actual)
43            },
44            Self::DataFileReadError(err) => {
45                write!(f, "failed to read local file metadata: {}", err)
46            },
47        }
48    }
49}
50
51impl EntryMetadata {
52    pub(super) fn new(uri: Arc<str>, ttl: u64) -> Self {
53        Self {
54            uri,
55            local_last_modified: 0,
56            local_size: 0,
57            remote_version: FileVersion::Uninitialized,
58            ttl,
59        }
60    }
61
62    pub(super) fn compare_local_state(&self, data_file_path: &Path) -> LocalCompareResult {
63        let metadata = match std::fs::metadata(data_file_path) {
64            Ok(v) => v,
65            Err(e) => return Err(LocalCompareError::DataFileReadError(e)),
66        };
67
68        let local_last_modified = super::utils::last_modified_u64(&metadata);
69        let local_size = metadata.len();
70
71        if local_last_modified != self.local_last_modified {
72            Err(LocalCompareError::LastModifiedMismatch {
73                expected: self.local_last_modified,
74                actual: local_last_modified,
75            })
76        } else if local_size != self.local_size {
77            Err(LocalCompareError::SizeMismatch {
78                expected: self.local_size,
79                actual: local_size,
80            })
81        } else {
82            Ok(())
83        }
84    }
85
86    pub(super) fn try_write<W: std::io::Write>(&self, writer: &mut W) -> serde_json::Result<()> {
87        serde_json::to_writer(writer, self)
88    }
89
90    pub(super) fn try_from_reader<R: std::io::Read>(reader: &mut R) -> serde_json::Result<Self> {
91        serde_json::from_reader(reader)
92    }
93}
polars_io/file_cache/metadata.rs

polars_io/file_cache/
metadata.rs
