parquet/file/metadata/
footer_tail.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use crate::errors::{ParquetError, Result};
19use crate::file::{FOOTER_SIZE, PARQUET_MAGIC, PARQUET_MAGIC_ENCR_FOOTER};
20
21/// Parsed Parquet footer tail (last 8 bytes of a Parquet file)
22///
23/// There are 8 bytes at the end of the Parquet footer with the following layout:
24/// * 4 bytes for the metadata length
25/// * 4 bytes for the magic bytes 'PAR1' or 'PARE' (encrypted footer)
26///
27/// ```text
28/// +-----+------------------+
29/// | len | 'PAR1' or 'PARE' |
30/// +-----+------------------+
31/// ```
32///
33/// # Examples
34/// ```
35/// # use parquet::file::metadata::FooterTail;
36/// // a non encrypted footer with 28 bytes of metadata
37/// let last_8_bytes: [u8; 8] = [0x1C, 0x00, 0x00, 0x00, b'P', b'A', b'R', b'1'];
38/// let footer_tail = FooterTail::try_from(last_8_bytes).unwrap();
39/// assert_eq!(footer_tail.metadata_length(), 28);
40/// assert_eq!(footer_tail.is_encrypted_footer(), false);
41/// ```
42///
43/// ```
44/// # use parquet::file::metadata::FooterTail;
45/// // an encrypted footer with 512 bytes of metadata
46/// let last_8_bytes = vec![0x00, 0x02, 0x00, 0x00, b'P', b'A', b'R', b'E'];
47/// let footer_tail = FooterTail::try_from(&last_8_bytes[..]).unwrap();
48/// assert_eq!(footer_tail.metadata_length(), 512);
49/// assert_eq!(footer_tail.is_encrypted_footer(), true);
50/// ```
51///
52#[derive(Debug, Clone, Copy, PartialEq, Eq)]
53pub struct FooterTail {
54    metadata_length: usize,
55    encrypted_footer: bool,
56}
57
58impl FooterTail {
59    /// Try to decode the footer tail from the given 8 bytes
60    pub fn try_new(slice: &[u8; FOOTER_SIZE]) -> Result<FooterTail> {
61        let magic = &slice[4..];
62        let encrypted_footer = if magic == PARQUET_MAGIC_ENCR_FOOTER {
63            true
64        } else if magic == PARQUET_MAGIC {
65            false
66        } else {
67            return Err(general_err!("Invalid Parquet file. Corrupt footer"));
68        };
69        // get the metadata length from the footer
70        let metadata_len = u32::from_le_bytes(slice[..4].try_into().unwrap());
71
72        Ok(FooterTail {
73            // u32 won't be larger than usize in most cases
74            metadata_length: metadata_len.try_into()?,
75            encrypted_footer,
76        })
77    }
78
79    /// The length of the footer metadata in bytes
80    pub fn metadata_length(&self) -> usize {
81        self.metadata_length
82    }
83
84    /// Whether the footer metadata is encrypted
85    pub fn is_encrypted_footer(&self) -> bool {
86        self.encrypted_footer
87    }
88}
89
90impl TryFrom<[u8; FOOTER_SIZE]> for FooterTail {
91    type Error = ParquetError;
92
93    fn try_from(value: [u8; FOOTER_SIZE]) -> Result<Self> {
94        Self::try_new(&value)
95    }
96}
97
98impl TryFrom<&[u8]> for FooterTail {
99    type Error = ParquetError;
100
101    fn try_from(value: &[u8]) -> Result<Self> {
102        if value.len() != FOOTER_SIZE {
103            return Err(general_err!(
104                "Invalid footer length {}, expected {FOOTER_SIZE}",
105                value.len()
106            ));
107        }
108        let slice: &[u8; FOOTER_SIZE] = value.try_into().unwrap();
109        Self::try_new(slice)
110    }
111}
parquet/file/metadata/footer_tail.rs

parquet/file/metadata/
footer_tail.rs
