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//! Iterate over blobs from a memory map
use self::fileformat::BlobHeader;
use crate::blob::{decode_blob, BlobDecode, BlobType, ByteOffset};
use crate::block::{HeaderBlock, PrimitiveBlock};
use crate::error::{new_blob_error, new_protobuf_error, BlobError, Result};
use crate::proto::{fileformat, osmformat};
use crate::MAX_BLOB_HEADER_SIZE;
use byteorder::ByteOrder;
use protobuf::Message;
use std::fs::File;
use std::path::Path;
/// A read-only memory map.
#[derive(Debug)]
pub struct Mmap {
mmap: memmap2::Mmap,
}
impl Mmap {
/// Creates a memory map from a given file.
///
/// # Safety
/// The underlying file should not be modified while holding the memory map.
/// See [memmap-rs issue 25](https://github.com/danburkert/memmap-rs/issues/25) for more
/// information on the safety of memory maps.
///
/// # Example
/// ```
/// use osmpbf::*;
///
/// # fn foo() -> Result<()> {
/// let f = std::fs::File::open("tests/test.osm.pbf")?;
/// let mmap = unsafe { Mmap::from_file(&f)? };
/// # Ok(())
/// # }
/// # foo().unwrap();
/// ```
pub unsafe fn from_file(file: &File) -> Result<Mmap> {
memmap2::Mmap::map(file)
.map(|m| Mmap { mmap: m })
.map_err(|e| e.into())
}
/// Creates a memory map from a given path.
///
/// # Safety
/// The underlying file should not be modified while holding the memory map.
/// See [memmap-rs issue 25](https://github.com/danburkert/memmap-rs/issues/25) for more
/// information on the safety of memory maps.
///
/// # Example
/// ```
/// use osmpbf::*;
///
/// # fn foo() -> Result<()> {
/// let mmap = unsafe { Mmap::from_path("tests/test.osm.pbf")? };
/// # Ok(())
/// # }
/// # foo().unwrap();
/// ```
pub unsafe fn from_path<P: AsRef<Path>>(path: P) -> Result<Mmap> {
let file = File::open(&path)?;
memmap2::Mmap::map(&file)
.map(|m| Mmap { mmap: m })
.map_err(|e| e.into())
}
/// Returns an iterator over the blobs in this memory map.
pub fn blob_iter(&self) -> MmapBlobReader {
MmapBlobReader::new(self)
}
fn as_slice(&self) -> &[u8] {
&self.mmap
}
}
/// A PBF blob from a memory map.
#[derive(Clone, Debug)]
pub struct MmapBlob<'a> {
header: BlobHeader,
data: &'a [u8],
offset: ByteOffset,
}
impl<'a> MmapBlob<'a> {
/// Decodes the blob and tries to obtain the inner content (usually a [`HeaderBlock`] or a
/// [`PrimitiveBlock`]). This operation might involve an expensive decompression step.
pub fn decode(&'a self) -> Result<BlobDecode<'a>> {
let blob = fileformat::Blob::parse_from_bytes(self.data)
.map_err(|e| new_protobuf_error(e, "blob content"))?;
match self.header.type_() {
"OSMHeader" => {
let block = Box::new(HeaderBlock::new(decode_blob(&blob)?));
Ok(BlobDecode::OsmHeader(block))
}
"OSMData" => {
let block: osmformat::PrimitiveBlock = decode_blob(&blob)?;
Ok(BlobDecode::OsmData(PrimitiveBlock::new(block)))
}
x => Ok(BlobDecode::Unknown(x)),
}
}
/// Returns the type of a blob without decoding its content.
pub fn get_type(&self) -> BlobType {
match self.header.type_() {
"OSMHeader" => BlobType::OsmHeader,
"OSMData" => BlobType::OsmData,
x => BlobType::Unknown(x),
}
}
/// Returns the byte offset of the blob from the start of its memory map.
pub fn offset(&self) -> ByteOffset {
self.offset
}
}
/// A reader for memory mapped PBF files that allows iterating over [`MmapBlob`]s.
#[derive(Clone, Debug)]
pub struct MmapBlobReader<'a> {
mmap: &'a Mmap,
offset: usize,
last_blob_ok: bool,
}
impl<'a> MmapBlobReader<'a> {
/// Creates a new `MmapBlobReader`.
///
/// # Example
/// ```
/// use osmpbf::*;
///
/// # fn foo() -> Result<()> {
///
/// let mmap = unsafe { Mmap::from_path("tests/test.osm.pbf")? };
/// let reader = MmapBlobReader::new(&mmap);
///
/// # Ok(())
/// # }
/// # foo().unwrap();
/// ```
pub fn new(mmap: &Mmap) -> MmapBlobReader {
MmapBlobReader {
mmap,
offset: 0,
last_blob_ok: true,
}
}
/// Move the cursor to the given byte offset.
///
/// # Example
/// ```
/// use osmpbf::*;
///
/// # fn foo() -> Result<()> {
///
/// let mmap = unsafe { Mmap::from_path("tests/test.osm.pbf")? };
/// let mut reader = MmapBlobReader::new(&mmap);
///
/// let first_blob = reader.next().unwrap()?;
/// let second_blob = reader.next().unwrap()?;
///
/// reader.seek(first_blob.offset());
/// let first_blob_again = reader.next().unwrap()?;
///
/// assert_eq!(first_blob.offset(), first_blob_again.offset());
///
/// # Ok(())
/// # }
/// # foo().unwrap();
/// ```
pub fn seek(&mut self, pos: ByteOffset) {
self.offset = pos.0 as usize;
}
}
impl<'a> Iterator for MmapBlobReader<'a> {
type Item = Result<MmapBlob<'a>>;
fn next(&mut self) -> Option<Self::Item> {
let slice = &self.mmap.as_slice()[self.offset..];
match slice.len() {
0 => return None,
1..=3 => {
self.last_blob_ok = false;
return Some(Err(new_blob_error(BlobError::InvalidHeaderSize)));
}
_ => {}
}
let header_size = byteorder::BigEndian::read_u32(slice) as usize;
if header_size as u64 >= MAX_BLOB_HEADER_SIZE {
self.last_blob_ok = false;
return Some(Err(new_blob_error(BlobError::HeaderTooBig {
size: header_size as u64,
})));
}
if slice.len() < 4 + header_size {
self.last_blob_ok = false;
let io_error = ::std::io::Error::new(
::std::io::ErrorKind::UnexpectedEof,
"content too short for header",
);
return Some(Err(io_error.into()));
}
let header = match BlobHeader::parse_from_bytes(&slice[4..(4 + header_size)]) {
Ok(x) => x,
Err(e) => {
self.last_blob_ok = false;
return Some(Err(new_protobuf_error(e, "blob header")));
}
};
let data_size = header.datasize() as usize;
let chunk_size = 4 + header_size + data_size;
if slice.len() < chunk_size {
self.last_blob_ok = false;
let io_error = ::std::io::Error::new(
::std::io::ErrorKind::UnexpectedEof,
"content too short for block data",
);
return Some(Err(io_error.into()));
}
let prev_offset = self.offset;
self.offset += chunk_size;
Some(Ok(MmapBlob {
header,
data: &slice[(4 + header_size)..chunk_size],
offset: ByteOffset(prev_offset as u64),
}))
}
}