98 lines
2.3 KiB
Rust
98 lines
2.3 KiB
Rust
//file format "sniff"
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use binrw::{binrw, BinReaderExt, io::TakeSeekExt};
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pub enum Error{
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InvalidHeader(binrw::Error),
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UnexpectedEOF,
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InvalidBlockId(BlockId),
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Seek(std::io::Error),
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}
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/* spec
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//begin global header
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//global metadata (32 bytes)
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b"SNFB"
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u32 format_version
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u64 priming_bytes
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//how many bytes of the file must be read to guarantee all of the expected
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//format-specific metadata is available to facilitate streaming the remaining contents
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//used by the database to guarantee that it serves at least the bare minimum
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u128 resource_uuid
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//identifies the file from anywhere for any other file
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//global block layout (variable size)
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u64 num_blocks
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for block_id in 0..num_blocks{
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u64 first_byte
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}
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//end global header
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//begin blocks
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//each block is compressed with zstd or gz or something
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*/
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#[binrw]
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#[brw(little)]
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#[derive(Clone,Copy)]
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pub(crate) enum FourCC{
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#[brw(magic=b"SNFM")]
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Map,
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#[brw(magic=b"SNFB")]
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Bot,
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#[brw(magic=b"SNFD")]
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Demo,
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}
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#[binrw]
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#[brw(little)]
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struct Header{
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/// Type of file
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fourcc:FourCC,
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/// Type version
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version:u32,
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/// Minimum data required to know the location of all streamable resources for this specific file
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priming:u64,
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/// uuid for this file
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resource:u128,
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//don't need try_calc: the struct will force field initialization anyways and it can be calculated there
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block_count:u32,
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#[br(count=block_count+1)]
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block_location:Vec<u64>,
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}
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#[binrw]
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#[brw(little)]
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#[derive(Clone,Copy,Hash,id::Id,Eq,PartialEq)]
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pub struct BlockId(u32);
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pub(crate) struct File<R:BinReaderExt>{
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header:Header,
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//reference to the data
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data:R,
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}
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impl<R:BinReaderExt> File<R>{
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pub(crate) fn new(mut input:R)->Result<File<R>,Error>{
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Ok(File{
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header:input.read_le().map_err(Error::InvalidHeader)?,
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data:input,
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})
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}
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pub(crate) fn block_reader(&mut self,block_id:BlockId)->Result<binrw::io::TakeSeek<&mut R>,Error>{
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if self.header.block_location.len() as u32<=block_id.get(){
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return Err(Error::InvalidBlockId(block_id))
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}
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let block_start=self.header.block_location[block_id.get() as usize];
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let block_end=self.header.block_location[block_id.get() as usize+1];
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self.data.seek(std::io::SeekFrom::Start(block_start)).map_err(Error::Seek)?;
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Ok((&mut self.data).take_seek(block_end-block_start))
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}
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pub(crate) fn fourcc(&self)->FourCC{
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self.header.fourcc
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}
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}
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