Refactor: extract FooterTail from ParquetMetadataReader

parquet/src/file/metadata/footer_tail.rs

@@ -0,0 +1,111 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+use crate::errors::{ParquetError, Result};
+use crate::file::{FOOTER_SIZE, PARQUET_MAGIC, PARQUET_MAGIC_ENCR_FOOTER};
+
+/// Parsed Parquet footer tail (last 8 bytes of a Parquet file)
+///
+/// There are 8 bytes at the end of the Parquet footer with the following layout:
+/// * 4 bytes for the metadata length
+/// * 4 bytes for the magic bytes 'PAR1' or 'PARE' (encrypted footer)
+///
+/// ```text
+/// +-----+------------------+
+/// | len | 'PAR1' or 'PARE' |
+/// +-----+------------------+
+/// ```
+///
+/// # Examples
+/// ```
+/// # use parquet::file::metadata::FooterTail;
+/// // a non encrypted footer with 28 bytes of metadata
+/// let last_8_bytes: [u8; 8] = [0x1C, 0x00, 0x00, 0x00, b'P', b'A', b'R', b'1'];
+/// let footer_tail = FooterTail::try_from(last_8_bytes).unwrap();
+/// assert_eq!(footer_tail.metadata_length(), 28);
+/// assert_eq!(footer_tail.is_encrypted_footer(), false);
+/// ```
+///
+/// ```
+/// # use parquet::file::metadata::FooterTail;
+/// // an encrypted footer with 512 bytes of metadata
+/// let last_8_bytes = vec![0x00, 0x02, 0x00, 0x00, b'P', b'A', b'R', b'E'];
+/// let footer_tail = FooterTail::try_from(&last_8_bytes[..]).unwrap();
+/// assert_eq!(footer_tail.metadata_length(), 512);
+/// assert_eq!(footer_tail.is_encrypted_footer(), true);
+/// ```
+///
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct FooterTail {
+    metadata_length: usize,
+    encrypted_footer: bool,
+}
+
+impl FooterTail {
+    /// Try to decode the footer tail from the given 8 bytes
+    pub fn try_new(slice: &[u8; FOOTER_SIZE]) -> Result<FooterTail> {
+        let magic = &slice[4..];
+        let encrypted_footer = if magic == PARQUET_MAGIC_ENCR_FOOTER {
+            true
+        } else if magic == PARQUET_MAGIC {
+            false
+        } else {
+            return Err(general_err!("Invalid Parquet file. Corrupt footer"));
+        };
+        // get the metadata length from the footer
+        let metadata_len = u32::from_le_bytes(slice[..4].try_into().unwrap());
+        Ok(crate::file::metadata::FooterTail {
+            // u32 won't be larger than usize in most cases
+            metadata_length: metadata_len as usize,
+            encrypted_footer,
+        })
+    }
+
+    /// The length of the footer metadata in bytes
+    pub fn metadata_length(&self) -> usize {
+        self.metadata_length
+    }
+
+    /// Whether the footer metadata is encrypted
+    pub fn is_encrypted_footer(&self) -> bool {
+        self.encrypted_footer
+    }
+}
+
+impl TryFrom<[u8; FOOTER_SIZE]> for FooterTail {
+    type Error = ParquetError;
+
+    fn try_from(value: [u8; FOOTER_SIZE]) -> Result<Self> {
+        Self::try_new(&value)
+    }
+}
+
+impl TryFrom<&[u8]> for FooterTail {
+    type Error = ParquetError;
+
+    fn try_from(value: &[u8]) -> Result<Self> {
+        if value.len() != FOOTER_SIZE {
+            return Err(general_err!(
+                "Invalid footer length {}, expected {}",
+                value.len(),
+                FOOTER_SIZE
+            ));
+        }
+        let slice: &[u8; FOOTER_SIZE] = value.try_into().unwrap();
+        Self::try_new(slice)
+    }
+}

parquet/src/file/metadata/mod.rs

@@ -90,6 +90,7 @@
 //!
 //!                         * Same name, different struct
 //! ```
+mod footer_tail;
 mod memory;
 mod push_decoder;
 pub(crate) mod reader;
@@ -120,8 +121,9 @@ use crate::schema::types::{
 };
 #[cfg(feature = "encryption")]
 use crate::thrift::{TCompactSliceInputProtocol, TSerializable};
+pub use footer_tail::FooterTail;
 pub use push_decoder::ParquetMetaDataPushDecoder;
-pub use reader::{FooterTail, PageIndexPolicy, ParquetMetaDataReader};
+pub use reader::{PageIndexPolicy, ParquetMetaDataReader};
 use std::ops::Range;
 use std::sync::Arc;
 pub use writer::ParquetMetaDataWriter;

parquet/src/file/metadata/reader.rs

@@ -26,11 +26,13 @@ use crate::encryption::{
 use bytes::Bytes;
 
 use crate::errors::{ParquetError, Result};
-use crate::file::metadata::{ColumnChunkMetaData, FileMetaData, ParquetMetaData, RowGroupMetaData};
+use crate::file::metadata::{
+    ColumnChunkMetaData, FileMetaData, FooterTail, ParquetMetaData, RowGroupMetaData,
+};
 use crate::file::page_index::index::Index;
 use crate::file::page_index::index_reader::{acc_range, decode_column_index, decode_offset_index};
 use crate::file::reader::ChunkReader;
-use crate::file::{FOOTER_SIZE, PARQUET_MAGIC, PARQUET_MAGIC_ENCR_FOOTER};
+use crate::file::FOOTER_SIZE;
 use crate::format::{ColumnOrder as TColumnOrder, FileMetaData as TFileMetaData};
 #[cfg(feature = "encryption")]
 use crate::format::{EncryptionAlgorithm, FileCryptoMetaData as TFileCryptoMetaData};
@@ -103,26 +105,6 @@ impl From<bool> for PageIndexPolicy {
     }
 }
 
-/// Describes how the footer metadata is stored
-///
-/// This is parsed from the last 8 bytes of the Parquet file
-pub struct FooterTail {
-    metadata_length: usize,
-    encrypted_footer: bool,
-}
-
-impl FooterTail {
-    /// The length of the footer metadata in bytes
-    pub fn metadata_length(&self) -> usize {
-        self.metadata_length
-    }
-
-    /// Whether the footer metadata is encrypted
-    pub fn is_encrypted_footer(&self) -> bool {
-        self.encrypted_footer
-    }
-}
-
 impl ParquetMetaDataReader {
     /// Create a new [`ParquetMetaDataReader`]
     pub fn new() -> Self {
@@ -873,39 +855,15 @@ impl ParquetMetaDataReader {
         }
     }
 
-    /// Decodes the end of the Parquet footer
-    ///
-    /// There are 8 bytes at the end of the Parquet footer with the following layout:
-    /// * 4 bytes for the metadata length
-    /// * 4 bytes for the magic bytes 'PAR1' or 'PARE' (encrypted footer)
-    ///
-    /// ```text
-    /// +-----+------------------+
-    /// | len | 'PAR1' or 'PARE' |
-    /// +-----+------------------+
-    /// ```
+    /// Decodes a [`FooterTail`] from the provided 8-byte slice.
     pub fn decode_footer_tail(slice: &[u8; FOOTER_SIZE]) -> Result<FooterTail> {
-        let magic = &slice[4..];
-        let encrypted_footer = if magic == PARQUET_MAGIC_ENCR_FOOTER {
-            true
-        } else if magic == PARQUET_MAGIC {
-            false
-        } else {
-            return Err(general_err!("Invalid Parquet file. Corrupt footer"));
-        };
-        // get the metadata length from the footer
-        let metadata_len = u32::from_le_bytes(slice[..4].try_into().unwrap());
-        Ok(FooterTail {
-            // u32 won't be larger than usize in most cases
-            metadata_length: metadata_len as usize,
-            encrypted_footer,
-        })
+        FooterTail::try_new(slice)
     }
 
     /// Decodes the Parquet footer, returning the metadata length in bytes
     #[deprecated(since = "54.3.0", note = "Use decode_footer_tail instead")]
     pub fn decode_footer(slice: &[u8; FOOTER_SIZE]) -> Result<usize> {
-        Self::decode_footer_tail(slice).map(|f| f.metadata_length)
+        Self::decode_footer_tail(slice).map(|f| f.metadata_length())
     }
 
     /// Decodes [`ParquetMetaData`] from the provided bytes.
@@ -1369,6 +1327,7 @@ mod async_tests {
     use std::io::{Read, Seek, SeekFrom};
     use std::ops::Range;
     use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::sync::Arc;
     use tempfile::NamedTempFile;
 
     use crate::arrow::ArrowWriter;