Migrated code from arrow2 to here

.github/workflows/coverage.yml

@@ -0,0 +1,21 @@
+name: Coverage
+
+on: [pull_request, push]
+
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install Rust
+        run: rustup toolchain install stable --component llvm-tools-preview
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - uses: Swatinem/rust-cache@v1
+      - name: Generate code coverage
+        run: cargo llvm-cov --features full --lcov --output-path lcov.info
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v1
+        with:
+          files: lcov.info
+          fail_ci_if_error: true

.github/workflows/test.yml

@@ -12,4 +12,4 @@ jobs:
         run: rustup update stable
       - uses: Swatinem/rust-cache@v1
       - name: Run
-        run: cargo test
+        run: cargo test --features full

Cargo.toml

@@ -2,7 +2,7 @@
 name = "avro-schema"
 version = "0.2.2"
 license = "Apache-2.0"
-description = "Implementation of Apache Avro spec"
+description = "Apache Avro specification"
 homepage = "https://github.com/DataEngineeringLabs/avro-schema"
 repository = "https://github.com/DataEngineeringLabs/avro-schema"
 authors = ["Jorge C. Leitao <[email protected]>"]
@@ -12,3 +12,23 @@ edition = "2018"
 [dependencies]
 serde_json = { version = "1.0", default-features = false, features = ["std"] }
 serde = { version = "1.0", default-features = false }
+
+fallible-streaming-iterator = { version = "0.1" }
+
+libflate = { version = "1.1.1", optional = true }
+snap = { version = "1", optional = true }
+crc = { version = "2", optional = true }
+
+# for async
+futures = { version = "0.3", optional = true }
+async-stream = { version = "0.3.2", optional = true }
+
+[features]
+default = []
+full = ["compression", "async"]
+compression = [
+    "libflate",
+    "snap",
+    "crc",
+]
+async = ["futures", "async-stream"]

README.md

@@ -1,9 +1,14 @@
 # Avro-schema - Avro schema in Rust
 
+[![test](https://github.com/DataEngineeringLabs/avro-schema/actions/workflows/test.yml/badge.svg)](https://github.com/DataEngineeringLabs/avro-schema/actions/workflows/test.yml)
+[![codecov](https://codecov.io/gh/DataEngineeringLabs/avro-schema/branch/main/graph/badge.svg)](https://codecov.io/gh/DataEngineeringLabs/avro-schema)
+
 This crate contains the complete implementation of the schemas of
 the [Avro specification](https://avro.apache.org/docs/current/spec.html) in
 native Rust.
 
+See API documentation with examples on how to read and write.
+
 ## License
 
 Licensed under either of

src/error.rs

@@ -0,0 +1,22 @@
+//! Contains [`Error`]
+
+/// Error from this crate
+#[derive(Debug, Clone, Copy)]
+pub enum Error {
+    /// Generic error when the file is out of spec
+    OutOfSpec,
+    /// When reading or writing with compression but the feature flag "compression" is not active.
+    RequiresCompression,
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
+impl From<std::io::Error> for Error {
+    fn from(_: std::io::Error) -> Self {
+        Error::OutOfSpec
+    }
+}

src/file.rs

@@ -0,0 +1,60 @@
+//! Contains structs found in Avro files
+use crate::schema::Record;
+
+/// Avro file's Metadata
+#[derive(Debug, Clone, PartialEq, Hash)]
+pub struct FileMetadata {
+    /// The Record represented in the file's Schema
+    pub record: Record,
+    /// The files' compression
+    pub compression: Option<Compression>,
+    /// The files' marker, present in every block
+    pub marker: [u8; 16],
+}
+
+/// A compressed Avro block.
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct CompressedBlock {
+    /// The number of rows
+    pub number_of_rows: usize,
+    /// The compressed data
+    pub data: Vec<u8>,
+}
+
+impl CompressedBlock {
+    /// Creates a new CompressedBlock
+    pub fn new(number_of_rows: usize, data: Vec<u8>) -> Self {
+        Self {
+            number_of_rows,
+            data,
+        }
+    }
+}
+
+/// An uncompressed Avro block.
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct Block {
+    /// The number of rows
+    pub number_of_rows: usize,
+    /// The uncompressed data
+    pub data: Vec<u8>,
+}
+
+impl Block {
+    /// Creates a new Block
+    pub fn new(number_of_rows: usize, data: Vec<u8>) -> Self {
+        Self {
+            number_of_rows,
+            data,
+        }
+    }
+}
+
+/// Valid compressions
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+pub enum Compression {
+    /// Deflate
+    Deflate,
+    /// Snappy
+    Snappy,
+}

src/lib.md

@@ -4,3 +4,84 @@ This is a library containing declarations of the
 [Avro specification](https://avro.apache.org/docs/current/spec.html)
 in Rust's struct and enums together with serialization and deserialization
 implementations based on `serde_json`.
+
+It also contains basic functionality to read and deserialize Avro's file's metadata
+and blocks.
+
+Example of reading a file:
+
+```rust
+use std::convert::TryInto;
+use std::fs::File;
+use std::io::BufReader;
+
+use avro_schema::error::Error;
+use avro_schema::read::fallible_streaming_iterator::FallibleStreamingIterator;
+
+fn read_avro(path: &str) -> Result<(), Error> {
+    let file = &mut BufReader::new(File::open(path)?);
+
+    let metadata = avro_schema::read::read_metadata(file)?;
+
+    println!("{:#?}", metadata);
+
+    let mut blocks =
+        avro_schema::read::BlockStreamingIterator::new(file, metadata.compression, metadata.marker);
+
+    while let Some(block) = blocks.next()? {
+        let _fields = &metadata.record.fields;
+        let length = block.number_of_rows;
+        let mut block: &[u8] = block.data.as_ref();
+        // at this point you can deserialize the block based on `_fields` according
+        // to avro's specification. Note that `Block` is already decompressed.
+        // for example, if there was a single field with f32, we would use
+        for _ in 0..length {
+            let (item, remaining) = block.split_at(4);
+            block = remaining;
+            let _value = f32::from_le_bytes(item.try_into().unwrap());
+            // if there were more fields, we would need to consume (or skip) the remaining
+            // here. You can use `avro_schema::read::decode::zigzag_i64` for integers :D
+        }
+    }
+
+    Ok(())
+}
+```
+
+Example of writing a file
+
+```rust
+use std::fs::File;
+
+use avro_schema::error::Error;
+use avro_schema::file::Block;
+use avro_schema::schema::{Field, Record, Schema};
+
+fn write_avro(compression: Option<avro_schema::file::Compression>) -> Result<(), Error> {
+    let mut file = File::create("test.avro")?;
+
+    let record = Record::new("", vec![Field::new("value", Schema::Float)]);
+
+    avro_schema::write::write_metadata(&mut file, record, compression)?;
+
+    // given some data:
+    let array = vec![1.0f32, 2.0];
+
+    // we need to create a `Block`
+    let mut data: Vec<u8> = vec![];
+    for item in array.iter() {
+        let bytes = item.to_le_bytes();
+        data.extend(bytes);
+    }
+    let mut block = Block::new(array.len(), data);
+
+    // once completed, we compress it
+    let mut compressed_block = avro_schema::file::CompressedBlock::default();
+    let _ = avro_schema::write::compress(&mut block, &mut compressed_block, compression)?;
+
+    // and finally write it to the file
+    avro_schema::write::write_block(&mut file, &compressed_block)?;
+
+    Ok(())
+}
+```

src/lib.rs

@@ -1,7 +1,17 @@
 #![doc = include_str!("lib.md")]
 #![forbid(unsafe_code)]
+#![forbid(missing_docs)]
 
-mod de;
-mod schema;
-mod se;
-pub use schema::*;
+pub mod error;
+pub mod file;
+pub mod schema;
+
+pub mod read;
+#[cfg(feature = "async")]
+#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+pub mod read_async;
+
+pub mod write;
+#[cfg(feature = "async")]
+#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+pub mod write_async;

src/read/block.rs

@@ -0,0 +1,96 @@
+//! APIs to read from Avro format to arrow.
+use std::io::Read;
+
+use fallible_streaming_iterator::FallibleStreamingIterator;
+
+use crate::{error::Error, file::CompressedBlock};
+
+use super::decode;
+
+fn read_size<R: Read>(reader: &mut R) -> Result<(usize, usize), Error> {
+    let rows = match decode::internal_zigzag_i64(reader) {
+        Ok(a) => a,
+        Err(error) => match error {
+            decode::DecodeError::EndOfFile => return Ok((0, 0)),
+            decode::DecodeError::OutOfSpec => return Err(Error::OutOfSpec),
+        },
+    };
+    let bytes = decode::zigzag_i64(reader)?;
+    Ok((rows as usize, bytes as usize))
+}
+
+/// Reads a [`CompressedBlock`] from the `reader`.
+/// # Error
+/// This function errors iff either the block cannot be read or the sync marker does not match
+fn read_block<R: Read>(
+    reader: &mut R,
+    block: &mut CompressedBlock,
+    marker: [u8; 16],
+) -> Result<(), Error> {
+    let (rows, bytes) = read_size(reader)?;
+    block.number_of_rows = rows;
+    if rows == 0 {
+        return Ok(());
+    };
+
+    block.data.clear();
+    block
+        .data
+        .try_reserve(bytes)
+        .map_err(|_| Error::OutOfSpec)?;
+    reader.take(bytes as u64).read_to_end(&mut block.data)?;
+
+    let mut block_marker = [0u8; 16];
+    reader.read_exact(&mut block_marker)?;
+
+    if block_marker != marker {
+        return Err(Error::OutOfSpec);
+    }
+    Ok(())
+}
+
+/// [`FallibleStreamingIterator`] of [`CompressedBlock`].
+pub struct CompressedBlockStreamingIterator<R: Read> {
+    buf: CompressedBlock,
+    reader: R,
+    marker: [u8; 16],
+}
+
+impl<R: Read> CompressedBlockStreamingIterator<R> {
+    /// Creates a new [`CompressedBlockStreamingIterator`].
+    pub fn new(reader: R, marker: [u8; 16], scratch: Vec<u8>) -> Self {
+        Self {
+            reader,
+            marker,
+            buf: CompressedBlock::new(0, scratch),
+        }
+    }
+
+    /// The buffer of [`CompressedBlockStreamingIterator`].
+    pub fn buffer(&mut self) -> &mut CompressedBlock {
+        &mut self.buf
+    }
+
+    /// Deconstructs itself
+    pub fn into_inner(self) -> (R, Vec<u8>) {
+        (self.reader, self.buf.data)
+    }
+}
+
+impl<R: Read> FallibleStreamingIterator for CompressedBlockStreamingIterator<R> {
+    type Error = Error;
+    type Item = CompressedBlock;
+
+    fn advance(&mut self) -> Result<(), Error> {
+        read_block(&mut self.reader, &mut self.buf, self.marker)?;
+        Ok(())
+    }
+
+    fn get(&self) -> Option<&Self::Item> {
+        if self.buf.number_of_rows > 0 {
+            Some(&self.buf)
+        } else {
+            None
+        }
+    }
+}