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//! A library for manipulating [Foxglove MCAP](https://github.com/foxglove/mcap) files,
//! both reading:
//!
//! ```no_run
//! use std::fs;
//!
//! use anyhow::{Context, Result};
//! use camino::Utf8Path;
//! use memmap::Mmap;
//!
//! fn map_mcap<P: AsRef<Utf8Path>>(p: P) -> Result<Mmap> {
//! let fd = fs::File::open(p.as_ref()).context("Couldn't open MCAP file")?;
//! unsafe { Mmap::map(&fd) }.context("Couldn't map MCAP file")
//! }
//!
//! fn read_it() -> Result<()> {
//! let mapped = map_mcap("in.mcap")?;
//!
//! for message in mcap::MessageStream::new(&mapped)? {
//! println!("{:?}", message?);
//! // Or whatever else you'd like to do...
//! }
//! Ok(())
//! }
//! ```
//! or writing:
//! ```no_run
//! use std::{collections::BTreeMap, fs, io::BufWriter};
//!
//! use anyhow::Result;
//!
//! use mcap::{Channel, records::MessageHeader, Writer};
//!
//! fn write_it() -> Result<()> {
//! // To set the profile or compression options, see mcap::WriteOptions.
//! let mut out = Writer::new(
//! BufWriter::new(fs::File::create("out.mcap")?)
//! )?;
//!
//! // Channels and schemas are automatically assigned ID as they're serialized,
//! // and automatically deduplicated with `Arc` when deserialized.
//! let my_channel = Channel {
//! topic: String::from("cool stuff"),
//! schema: None,
//! message_encoding: String::from("application/octet-stream"),
//! metadata: BTreeMap::default()
//! };
//!
//! let channel_id = out.add_channel(&my_channel)?;
//!
//! out.write_to_known_channel(
//! &MessageHeader {
//! channel_id,
//! sequence: 25,
//! log_time: 6,
//! publish_time: 24
//! },
//! &[1, 2, 3]
//! )?;
//! out.write_to_known_channel(
//! &MessageHeader {
//! channel_id,
//! sequence: 32,
//! log_time: 23,
//! publish_time: 25
//! },
//! &[3, 4, 5]
//! )?;
//!
//! out.finish()?;
//!
//! Ok(())
//! }
//! ```
pub mod read;
pub mod records;
pub mod write;
mod io_utils;
use std::{borrow::Cow, collections::BTreeMap, fmt, sync::Arc};
use thiserror::Error;
#[derive(Debug, Error)]
pub enum McapError {
#[error("Bad magic number")]
BadMagic,
#[error("Footer record couldn't be found at the end of the file, before the magic bytes")]
BadFooter,
#[error("Attachment CRC failed (expeted {saved:08X}, got {calculated:08X}")]
BadAttachmentCrc { saved: u32, calculated: u32 },
#[error("Chunk CRC failed (expected {saved:08X}, got {calculated:08X}")]
BadChunkCrc { saved: u32, calculated: u32 },
#[error("Data section CRC failed (expected {saved:08X}, got {calculated:08X})")]
BadDataCrc { saved: u32, calculated: u32 },
#[error("Summary section CRC failed (expected {saved:08X}, got {calculated:08X})")]
BadSummaryCrc { saved: u32, calculated: u32 },
#[error("Index offset and length didn't point to the expected record type")]
BadIndex,
#[error("Attachment length ({header}) exceeds space in record ({available})")]
BadAttachmentLength { header: u64, available: u64 },
#[error("Chunk length ({header}) exceeds space in record ({available})")]
BadChunkLength { header: u64, available: u64 },
#[error("Schema length ({header}) exceeds space in record ({available})")]
BadSchemaLength { header: u32, available: u32 },
#[error("Channel `{0}` has mulitple records that don't match.")]
ConflictingChannels(String),
#[error("Schema `{0}` has mulitple records that don't match.")]
ConflictingSchemas(String),
#[error("Record parse failed")]
Parse(#[from] binrw::Error),
#[error("I/O error from writing, or reading a compression stream")]
Io(#[from] std::io::Error),
#[error("Schema has an ID of 0")]
InvalidSchemaId,
#[error("MCAP file ended in the middle of a record")]
UnexpectedEof,
#[error("Chunk ended in the middle of a record")]
UnexpectedEoc,
#[error("Message {0} referenced unknown channel {1}")]
UnknownChannel(u32, u16),
#[error("Channel `{0}` referenced unknown schema {1}")]
UnknownSchema(String, u16),
#[error("Found record with opcode {0:02X} in a chunk")]
UnexpectedChunkRecord(u8),
#[error("Unsupported compression format `{0}`")]
UnsupportedCompression(String),
}
pub type McapResult<T> = Result<T, McapError>;
/// Magic bytes for the MCAP format
pub const MAGIC: &[u8] = &[0x89, b'M', b'C', b'A', b'P', 0x30, b'\r', b'\n'];
/// Compression options for chunks of channels, schemas, and messages in an MCAP file
#[derive(Debug, Copy, Clone)]
pub enum Compression {
#[cfg(feature = "zstd")]
Zstd,
#[cfg(feature = "lz4")]
Lz4,
}
/// Describes a schema used by one or more [Channel]s in an MCAP file
///
/// The [`CoW`](std::borrow::Cow) can either borrow directly from the mapped file,
/// or hold its own buffer if it was decompressed from a chunk.
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct Schema<'a> {
pub name: String,
pub encoding: String,
pub data: Cow<'a, [u8]>,
}
impl fmt::Debug for Schema<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Schema")
.field("name", &self.name)
.field("encoding", &self.encoding)
.finish_non_exhaustive()
}
}
/// Describes a channel which [Message]s are published to in an MCAP file
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Channel<'a> {
pub topic: String,
pub schema: Option<Arc<Schema<'a>>>,
pub message_encoding: String,
pub metadata: BTreeMap<String, String>,
}
/// An event in an MCAP file, published to a [Channel]
///
/// The [`CoW`](std::borrow::Cow) can either borrow directly from the mapped file,
/// or hold its own buffer if it was decompressed from a chunk.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Message<'a> {
pub channel: Arc<Channel<'a>>,
pub sequence: u32,
pub log_time: u64,
pub publish_time: u64,
pub data: Cow<'a, [u8]>,
}
/// An attachment and its metadata in an MCAP file
#[derive(Debug, PartialEq, Eq)]
pub struct Attachment<'a> {
pub log_time: u64,
pub create_time: u64,
pub name: String,
pub media_type: String,
pub data: Cow<'a, [u8]>,
}
pub use read::{MessageStream, Summary};
pub use write::{WriteOptions, Writer};