Add support for writing Flatbuffers

Need to figure out stream parsing yet

marketdata.fbs

@@ -22,7 +22,7 @@ table LevelUpdate {
 }
 
 table Message {
-    ts_nanos:uint64;
+    ts_nanos:int64;
     symbol:string;
     body:MessageBody;
 }

src/capnp_runner.rs

@@ -17,6 +17,7 @@ fn __take_until<'a>(tag: &'static str, input: &'a [u8]) -> IResult<&'a [u8], &'a
 }
 
 fn parse_symbol(sym: &[u8; 8]) -> &str {
+    // TODO: Use the `jetscii` library for all that SIMD goodness
     // IEX guarantees ASCII, so we're fine using an unsafe conversion
     let (_, sym_bytes) = __take_until(" ", &sym[..]).unwrap();
     unsafe { from_utf8_unchecked(sym_bytes) }

src/flatbuffers_runner.rs

@@ -0,0 +1,113 @@
+use std::io::Write;
+use std::str::from_utf8_unchecked;
+
+use capnp::data::new_builder;
+use flatbuffers::buffer_has_identifier;
+use nom::{bytes::complete::take_until, IResult};
+
+use crate::iex::{IexMessage, IexPayload};
+use crate::marketdata_generated::md_shootout;
+
+fn __take_until<'a>(tag: &'static str, input: &'a [u8]) -> IResult<&'a [u8], &'a [u8]> {
+    take_until(tag)(input)
+}
+
+fn parse_symbol(sym: &[u8; 8]) -> &str {
+    // TODO: Use the `jetscii` library for all that SIMD goodness
+    // IEX guarantees ASCII, so we're fine using an unsafe conversion
+    let (_, sym_bytes) = __take_until(" ", &sym[..]).unwrap();
+    unsafe { from_utf8_unchecked(sym_bytes) }
+}
+
+pub struct FlatbuffersWriter<'a> {
+    builder: flatbuffers::FlatBufferBuilder<'a>,
+    message_buffer: Vec<flatbuffers::WIPOffset<md_shootout::Message<'a>>>,
+}
+
+impl<'a> FlatbuffersWriter<'a> {
+    pub fn new() -> FlatbuffersWriter<'static> {
+        FlatbuffersWriter {
+            builder: flatbuffers::FlatBufferBuilder::new(),
+            message_buffer: Vec::new(),
+        }
+    }
+
+    pub fn serialize(&mut self, payload: &IexPayload, output: &mut Vec<u8>) {
+
+        // Because FlatBuffers can't handle nested vectors (specifically, we can't track
+        // both the variable-length vector of messages, and the variable-length strings
+        // within those messages), we have to cache the messages as they get built
+        // so they can be added all at once later.
+
+        for iex_msg in &payload.messages {
+            let msg_args = match iex_msg {
+                IexMessage::TradeReport(tr) => {
+                    // The `Args` objects used are wrappers over an underlying `Builder`.
+                    // We trust release builds to optimize out the wrapper, but would be
+                    // interesting to know whether that's actually the case.
+                    let trade = md_shootout::Trade::create(
+                        &mut self.builder,
+                        &md_shootout::TradeArgs {
+                            price: tr.price,
+                            size_: tr.size,
+                        },
+                    );
+
+                    /*
+                    let mut trade_builder = md_shootout::TradeBuilder::new(self.builder);
+                    trade_builder.add_price(tr.price);
+                    trade_builder.add_size_(tr.size);
+                    let trade = trade_builder.finish();
+                    */
+                    let sym_str = self.builder.create_string(parse_symbol(&tr.symbol));
+                    Some(md_shootout::MessageArgs {
+                        ts_nanos: tr.timestamp,
+                        symbol: Some(sym_str),
+                        body_type: md_shootout::MessageBody::Trade,
+                        // Why the hell do I need the `as_union_value` function to convert to UnionWIPOffset???
+                        body: Some(trade.as_union_value()),
+                    })
+                }
+                IexMessage::PriceLevelUpdate(plu) => {
+                    let level_update = md_shootout::LevelUpdate::create(
+                        &mut self.builder,
+                        &md_shootout::LevelUpdateArgs {
+                            price: plu.price,
+                            size_: plu.size,
+                            flags: plu.event_flags,
+                            side: if plu.msg_type == 0x38 { md_shootout::Side::Buy } else { md_shootout::Side::Sell },
+                        },
+                    );
+
+                    let sym_str = self.builder.create_string(parse_symbol(&plu.symbol));
+                    Some(md_shootout::MessageArgs {
+                        ts_nanos: plu.timestamp,
+                        symbol: Some(sym_str),
+                        body_type: md_shootout::MessageBody::LevelUpdate,
+                        body: Some(level_update.as_union_value()),
+                    })
+                }
+                _ => None
+            };
+
+            msg_args.map(|a| {
+                let msg = md_shootout::Message::create(&mut self.builder, &a);
+                self.message_buffer.push(msg);
+            });
+        }
+
+        let messages = self.builder.create_vector(&self.message_buffer[..]);
+
+        // Now that we've finished building all the messages, time to set up the final buffer
+        let mut multimsg_builder = md_shootout::MultiMessageBuilder::new(&mut self.builder);
+        multimsg_builder.add_seq_no(payload.first_seq_no);
+        multimsg_builder.add_messages(messages);
+        let multimsg = multimsg_builder.finish();
+        self.builder.finish(multimsg, None);
+        ;
+        output.write(self.builder.finished_data());
+
+        self.builder.reset();
+        self.message_buffer.clear();
+    }
+}

src/main.rs

@@ -19,6 +19,7 @@ pub mod marketdata_capnp;
 pub mod marketdata_generated; // Flatbuffers
 
 mod capnp_runner;
+mod flatbuffers_runner;
 mod iex;
 mod parsers;
 
@@ -47,9 +48,11 @@ fn main() {
     let mut summarizer = Summarizer::default();
     let mut parser = IexParser::new(&buf[..]);
 
+    let mut output_buf: Vec<u8> = Vec::new();
+
+    /*
     let mut capnp_writer = capnp_runner::CapnpWriter::new();
     let capnp_reader = capnp_runner::CapnpReader::new();
-    let mut output_buf = Vec::new();
 
     for iex_payload in parser {
         //let iex_payload = parser.next().unwrap();
@@ -65,6 +68,13 @@ fn main() {
     assert_eq!(read_buf.pos, read_buf.inner.len());
     dbg!(parsed_msgs);
     dbg!(summarizer);
+    */
+
+    let mut fb_writer = flatbuffers_runner::FlatbuffersWriter::new();
+
+    for iex_payload in parser {
+        fb_writer.serialize(&iex_payload, &mut output_buf);
+    }
 }
 
 #[derive(Debug)]

src/marketdata_generated.rs

@@ -2,20 +2,21 @@
 
 
 
-use std::mem;
-use std::cmp::Ordering;
-
 extern crate flatbuffers;
+
+use std::cmp::Ordering;
+use std::mem;
+
 use self::flatbuffers::EndianScalar;
 
 #[allow(unused_imports, dead_code)]
 pub mod md_shootout {
-
-  use std::mem;
     use std::cmp::Ordering;
+    use std::mem;
+
+    use self::flatbuffers::EndianScalar;
 
     extern crate flatbuffers;
-  use self::flatbuffers::EndianScalar;
 
     #[allow(non_camel_case_types)]
 #[repr(u8)]
@@ -383,8 +384,8 @@ impl<'a> Message<'a> {
     pub const VT_BODY: flatbuffers::VOffsetT = 10;
 
   #[inline]
-  pub fn ts_nanos(&self) -> u64 {
-    self._tab.get::<u64>(Message::VT_TS_NANOS, Some(0)).unwrap()
+  pub fn ts_nanos(&self) -> i64 {
+      self._tab.get::<i64>(Message::VT_TS_NANOS, Some(0)).unwrap()
   }
   #[inline]
   pub fn symbol(&self) -> Option<&'a str> {
@@ -421,7 +422,7 @@ impl<'a> Message<'a> {
 }
 
 pub struct MessageArgs<'a> {
-    pub ts_nanos: u64,
+    pub ts_nanos: i64,
     pub symbol: Option<flatbuffers::WIPOffset<&'a  str>>,
     pub body_type: MessageBody,
     pub body: Option<flatbuffers::WIPOffset<flatbuffers::UnionWIPOffset>>,
@@ -443,8 +444,8 @@ pub struct MessageBuilder<'a: 'b, 'b> {
 }
 impl<'a: 'b, 'b> MessageBuilder<'a, 'b> {
   #[inline]
-  pub fn add_ts_nanos(&mut self, ts_nanos: u64) {
-    self.fbb_.push_slot::<u64>(Message::VT_TS_NANOS, ts_nanos, 0);
+  pub fn add_ts_nanos(&mut self, ts_nanos: i64) {
+      self.fbb_.push_slot::<i64>(Message::VT_TS_NANOS, ts_nanos, 0);
   }
   #[inline]
   pub fn add_symbol(&mut self, symbol: flatbuffers::WIPOffset<&'b  str>) {