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use std::borrow::Borrow; use std::sync::Arc; use std::sync::Mutex; use std::fs::File; use std::io::Read; use std::io::Seek; use std::io::SeekFrom; use std::ops::Range; use std::ops::Deref; use std::io; use std::collections::HashMap; use std::fmt; const DEBUG: bool = false; const CHUNK_SIZE: usize = 0x8000; #[derive(Debug, Clone, PartialEq, Eq)] pub enum FileViewError { IOError, OutOfBoundsError, RangeTooBigError } #[derive(Debug, Clone)] pub struct FileView { inner: Arc<Mutex<FileViewInner>>, pub length: u64 } #[derive(Debug)] struct FileViewInner { file: File, buffers: HashMap<u64, FileViewChunkWrapper> } #[derive(Debug, Clone)] struct FileViewChunkWrapper { readers: u64, inner: Arc<FileViewChunk> } struct FileViewChunk { offset: u64, data: Vec<u8> } #[derive(Clone)] pub struct FileViewMapping { inner: Arc<FileViewMappingInner> } struct FileViewMappingInner { file_view: FileView, start_offset: usize, end_offset: usize, length: usize, buffers: Vec<Arc<FileViewChunk>> } pub struct FileViewMappingChunks<'a> { mapping: &'a FileViewMapping, index: usize } impl<'a> std::iter::Iterator for FileViewMappingChunks<'a> { type Item = &'a [u8]; fn next(&mut self) -> Option<&'a [u8]> { let index = self.index; self.index += 1; if index < self.mapping.inner.buffers.len() { let begin = if index == 0 { self.mapping.inner.start_offset } else { 0 }; let end = if index == self.mapping.inner.buffers.len()-1 { self.mapping.inner.end_offset } else { CHUNK_SIZE }; Some(&self.mapping.inner.buffers[index].data[begin..end]) } else { None } } } impl FileViewMapping { pub fn chunks(&self) -> FileViewMappingChunks { FileViewMappingChunks { mapping: &self, index: 0 } } pub fn to_vec(&self) -> Vec<u8> { let mut v = Vec::with_capacity(self.inner.length); for chunk in self.chunks() { v.extend_from_slice(chunk) } v } } impl Drop for FileViewChunk { fn drop(&mut self) { if DEBUG { println!("dropping {:?}", &self); } } } impl FileView { pub fn new(file: File) -> Result<Self, FileViewError> { Ok(FileView { length: file.metadata()?.len(), inner: Arc::new(Mutex::new(FileViewInner { file: file, buffers: HashMap::new() })) }) } fn handle_dropped_mapping(&self, mapping: &FileViewMappingInner) { let inner = &mut *self.inner.lock().unwrap(); let mut stale_buffer_ids = vec!(); for chunk in &mapping.buffers { let wrapper = inner.buffers.get_mut(&chunk.offset).unwrap(); wrapper.readers -= 1; if wrapper.readers == 0 { stale_buffer_ids.push(chunk.offset) } } for stale_buffer_id in stale_buffer_ids { inner.buffers.remove(&stale_buffer_id).unwrap(); } } pub fn read<R: Borrow<Range<u64>>>(&self, range: R) -> Result<FileViewMapping, FileViewError> { let inner = &mut *self.inner.lock().unwrap(); let range = range.borrow(); if DEBUG { println!("read({:x}-{:x}) (self.length={:x})", range.start, range.end, self.length) } if range.end > self.length { return Err(FileViewError::OutOfBoundsError); } let u64_len = range.end - range.start; if u64_len > std::usize::MAX as u64 { return Err(FileViewError::RangeTooBigError) } let len = u64_len as usize; let start_offset = (range.start % CHUNK_SIZE as u64) as usize; let mut end_offset; let base_address = range.start - range.start % CHUNK_SIZE as u64; let mut buffers = vec!(); let mut address = base_address; inner.file.seek(SeekFrom::Start(base_address))?; loop { if inner.buffers.contains_key(&address) { inner.file.seek(SeekFrom::Current(CHUNK_SIZE as i64))?; let chunk = inner.buffers.get_mut(&address).unwrap(); chunk.readers += 1; buffers.push(chunk.inner.clone()) } else { let mut buffer = vec!(0; CHUNK_SIZE); inner.file.read(&mut buffer)?; let chunk = Arc::new(FileViewChunk { offset: address, data: buffer }); inner.buffers.insert(address, FileViewChunkWrapper { readers: 1, inner: chunk.clone() }); buffers.push(chunk); } end_offset = (range.end - address) as usize; address += CHUNK_SIZE as u64; if address >= range.end { break; } } Ok(FileViewMapping { inner: Arc::new(FileViewMappingInner { file_view: self.clone(), start_offset: start_offset, end_offset: end_offset, length: len, buffers: buffers }) }) } } impl Drop for FileViewMappingInner { fn drop(&mut self) { if DEBUG { println!("dropping {:?}", &self); } self.file_view.handle_dropped_mapping(&self); } } impl fmt::Debug for FileViewMappingInner { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "FileViewMappingInner {{ start_offset: {:x}, length: {:x} }}", self.start_offset, self.length) } } impl fmt::Debug for FileViewChunk { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "FileViewChunk {{ begin: {:x}, end: {:x} }}", self.offset, self.offset + CHUNK_SIZE as u64) } } impl From<io::Error> for FileViewError { fn from(_: io::Error) -> Self { FileViewError::IOError } }