1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168

//! # (De)serializing Arrows IPC format.
//!
//! Arrow IPC is a [binary format format](https://arrow.apache.org/docs/python/ipc.html).
//! It is the recommended way to serialize and deserialize Polars DataFrames as this is most true
//! to the data schema.
//!
//! ## Example
//!
//! ```rust
//! use polars_core::prelude::*;
//! use polars_io::prelude::*;
//! use std::io::Cursor;
//!
//!
//! let s0 = Series::new("days", &[0, 1, 2, 3, 4]);
//! let s1 = Series::new("temp", &[22.1, 19.9, 7., 2., 3.]);
//! let mut df = DataFrame::new(vec![s0, s1]).unwrap();
//!
//! // Create an in memory file handler.
//! // Vec<u8>: Read + Write
//! // Cursor<T>: Seek
//!
//! let mut buf: Cursor<Vec<u8>> = Cursor::new(Vec::new());
//!
//! // write to the in memory buffer
//! IpcWriter::new(&mut buf).finish(&mut df).expect("ipc writer");
//!
//! // reset the buffers index after writing to the beginning of the buffer
//! buf.set_position(0);
//!
//! // read the buffer into a DataFrame
//! let df_read = IpcReader::new(buf).finish().unwrap();
//! assert!(df.frame_equal(&df_read));
//! ```
use super::{finish_reader, ArrowReader, ArrowResult, RecordBatch};
use crate::prelude::*;
use crate::utils::to_arrow_compatible_df;
use arrow::ipc::{
    reader::FileReader as ArrowIPCFileReader, writer::FileWriter as ArrowIPCFileWriter,
};
use polars_core::prelude::*;
use std::io::{Read, Seek, Write};
use std::sync::Arc;

/// Read Arrows IPC format into a DataFrame
///
/// # Example
/// ```
/// use polars_core::prelude::*;
/// use std::fs::File;
/// use polars_io::ipc::IpcReader;
/// use polars_io::SerReader;
///
/// fn example() -> Result<DataFrame> {
///     let file = File::open("file.ipc").expect("file not found");
///
///     IpcReader::new(file)
///         .finish()
/// }
/// ```
pub struct IpcReader<R> {
    /// File or Stream object
    reader: R,
    /// Aggregates chunks afterwards to a single chunk.
    rechunk: bool,
}

impl<R> ArrowReader for ArrowIPCFileReader<R>
where
    R: Read + Seek,
{
    fn next_record_batch(&mut self) -> ArrowResult<Option<RecordBatch>> {
        self.next().map_or(Ok(None), |v| v.map(Some))
    }

    fn schema(&self) -> Arc<Schema> {
        Arc::new((&*self.schema()).into())
    }
}

impl<R> SerReader<R> for IpcReader<R>
where
    R: Read + Seek,
{
    fn new(reader: R) -> Self {
        IpcReader {
            reader,
            rechunk: true,
        }
    }
    fn set_rechunk(mut self, rechunk: bool) -> Self {
        self.rechunk = rechunk;
        self
    }

    fn finish(self) -> Result<DataFrame> {
        let rechunk = self.rechunk;
        let ipc_reader = ArrowIPCFileReader::try_new(self.reader)?;
        finish_reader(ipc_reader, rechunk, None, None, None)
    }
}

/// Write a DataFrame to Arrow's IPC format
///
/// # Example
///
/// ```
/// use polars_core::prelude::*;
/// use polars_io::ipc::IpcWriter;
/// use std::fs::File;
/// use polars_io::SerWriter;
///
/// fn example(df: &mut DataFrame) -> Result<()> {
///     let mut file = File::create("file.ipc").expect("could not create file");
///
///     IpcWriter::new(&mut file)
///         .finish(df)
/// }
///
/// ```
pub struct IpcWriter<'a, W> {
    writer: &'a mut W,
}

impl<'a, W> SerWriter<'a, W> for IpcWriter<'a, W>
where
    W: Write,
{
    fn new(writer: &'a mut W) -> Self {
        IpcWriter { writer }
    }

    fn finish(self, df: &DataFrame) -> Result<()> {
        let df = to_arrow_compatible_df(df);
        let mut ipc_writer = ArrowIPCFileWriter::try_new(self.writer, &df.schema().to_arrow())?;

        let iter = df.iter_record_batches();

        for batch in iter {
            ipc_writer.write(&batch)?
        }
        let _ = ipc_writer.finish()?;
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use crate::prelude::*;
    use std::io::Cursor;

    #[test]
    fn write_and_read_ipc() {
        // Vec<T> : Write + Read
        // Cursor<Vec<_>>: Seek
        let mut buf: Cursor<Vec<u8>> = Cursor::new(Vec::new());
        let mut df = create_df();

        IpcWriter::new(&mut buf)
            .finish(&mut df)
            .expect("ipc writer");

        buf.set_position(0);

        let df_read = IpcReader::new(buf).finish().unwrap();
        assert!(df.frame_equal(&df_read));
    }
}