cdrs 2.2.0

Cassandra DB driver written in Rust
Documentation 
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use r2d2;
use std::cell::RefCell;
use std::io::{Cursor, Read};
use std::ops::Deref;

use super::*;
use crate::compression::Compression;
use crate::error;
use crate::frame::frame_response::ResponseBody;
use crate::frame::FromCursor;
use crate::transport::CDRSTransport;
use crate::types::data_serialization_types::decode_timeuuid;
use crate::types::{from_bytes, from_u16_bytes, CStringList, UUID_LEN};

pub fn from_connection<M, T>(
  conn: &r2d2::PooledConnection<M>,
  compressor: &Compression,
) -> error::Result<Frame>
where
  T: CDRSTransport + 'static,
  M: r2d2::ManageConnection<Connection = RefCell<T>, Error = error::Error> + Sized,
{
  parse_frame(conn.deref(), compressor)
}

pub fn parse_frame(cursor_cell: &RefCell<Read>, compressor: &Compression) -> error::Result<Frame> {
  let mut version_bytes = [0; Version::BYTE_LENGTH];
  let mut flag_bytes = [0; Flag::BYTE_LENGTH];
  let mut opcode_bytes = [0; Opcode::BYTE_LENGTH];
  let mut stream_bytes = [0; STREAM_LEN];
  let mut length_bytes = [0; LENGTH_LEN];
  let mut cursor = cursor_cell.borrow_mut();

  // NOTE: order of reads matters
  cursor.read_exact(&mut version_bytes)?;
  cursor.read_exact(&mut flag_bytes)?;
  cursor.read_exact(&mut stream_bytes)?;
  cursor.read_exact(&mut opcode_bytes)?;
  cursor.read_exact(&mut length_bytes)?;

  let version = Version::from(version_bytes.to_vec());
  let flags = Flag::get_collection(flag_bytes[0]);
  let stream = from_u16_bytes(&stream_bytes);
  let opcode = Opcode::from(opcode_bytes[0]);
  let length = from_bytes(&length_bytes) as usize;

  let mut body_bytes = Vec::with_capacity(length);
  unsafe {
    body_bytes.set_len(length);
  }

  cursor.read_exact(&mut body_bytes)?;

  let full_body = if flags.iter().any(|flag| flag == &Flag::Compression) {
    compressor.decode(body_bytes)?
  } else {
    Compression::None.decode(body_bytes)?
  };

  // Use cursor to get tracing id, warnings and actual body
  let mut body_cursor = Cursor::new(full_body.as_slice());

  let tracing_id = if flags.iter().any(|flag| flag == &Flag::Tracing) {
    let mut tracing_bytes = Vec::with_capacity(UUID_LEN);
    unsafe {
      tracing_bytes.set_len(UUID_LEN);
    }
    body_cursor.read_exact(&mut tracing_bytes)?;

    decode_timeuuid(tracing_bytes.as_slice()).ok()
  } else {
    None
  };

  let warnings = if flags.iter().any(|flag| flag == &Flag::Warning) {
    CStringList::from_cursor(&mut body_cursor)?.into_plain()
  } else {
    vec![]
  };

  let mut body = vec![];

  body_cursor.read_to_end(&mut body)?;

  let frame = Frame {
    version: version,
    flags: flags,
    opcode: opcode,
    stream: stream,
    body: body,
    tracing_id: tracing_id,
    warnings: warnings,
  };

  convert_frame_into_result(frame)
}

fn convert_frame_into_result(frame: Frame) -> error::Result<Frame> {
  match frame.opcode {
    Opcode::Error => frame.get_body().and_then(|err| match err {
      ResponseBody::Error(err) => Err(error::Error::Server(err)),
      _ => unreachable!(),
    }),
    _ => Ok(frame),
  }
}