1 files changed, 99 insertions, 0 deletions

diff --git a/src/zip/file_driver.rs b/src/zip/file_driver.rs
new file mode 100644
index 0000000..47b4242
--- /dev/null
+++ b/src/zip/file_driver.rs
@@ -0,0 +1,99 @@
+use crate::driver::FileDriver;
+use crate::zip::{ZipError, ZipFileInfo, ZipResult};
+use std::io::{
+    Error as IoError, ErrorKind as IoErrorKind, Read, Result as IoResult, Seek, SeekFrom, Take,
+    Write,
+};
+
+pub struct ZipFile<'d, Io> {
+    io: &'d mut Io,
+    info: &'d ZipFileInfo,
+
+    bounds: (u64, u64),
+    cursor: u64,
+}
+
+impl<'d, Io> FileDriver for ZipFile<'d, Io> {
+    type Io = Io;
+    type FileInfo = ZipFileInfo;
+
+    fn info(&self) -> &Self::FileInfo {
+        self.info
+    }
+}
+
+impl<'d, Io: Read + Seek> ZipFile<'d, Io> {
+    pub fn new(io: &'d mut Io, info: &'d ZipFileInfo) -> ZipResult<Self> {
+        io.seek(SeekFrom::Start(info.header_pointer))?;
+        let buf = {
+            let mut buf = [0; 30];
+            io.read(&mut buf)?;
+            buf
+        };
+        if u32::from_le_bytes(buf[..4].try_into().unwrap()) != 0x04034b50 {
+            return Err(ZipError::InvalidFileHeaderSignature.into());
+        }
+        let data_pointer = info.header_pointer
+            + 30
+            + u16::from_le_bytes(buf[26..28].try_into().unwrap()) as u64
+            + u16::from_le_bytes(buf[28..30].try_into().unwrap()) as u64;
+        io.seek(SeekFrom::Start(data_pointer))?;
+
+        Ok(Self {
+            io,
+            info,
+
+            bounds: (data_pointer, data_pointer + info.compressed_size),
+            cursor: data_pointer,
+        })
+    }
+}
+
+impl<'d, Io: Read> Read for ZipFile<'d, Io> {
+    fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
+        let upper = buf.len().min((self.bounds.1 - self.cursor) as usize);
+        self.cursor += upper as u64;
+        self.io.read(&mut buf[..upper])
+    }
+}
+
+impl<'d, Io: Write> Write for ZipFile<'d, Io> {
+    fn write(&mut self, buf: &[u8]) -> IoResult<usize> {
+        todo!()
+    }
+
+    fn flush(&mut self) -> IoResult<()> {
+        todo!()
+    }
+}
+
+impl<'d, Io: Seek> Seek for ZipFile<'d, Io> {
+    fn seek(&mut self, pos: SeekFrom) -> IoResult<u64> {
+        self.cursor = match pos {
+            SeekFrom::Start(offset) => self.bounds.0 + offset,
+            SeekFrom::End(offset) => {
+                let cursor = self.bounds.1.saturating_add_signed(offset);
+                if cursor < self.bounds.0 {
+                    return Err(IoError::new(
+                        IoErrorKind::InvalidInput,
+                        ZipError::NegativeFileOffset,
+                    ));
+                }
+                cursor
+            }
+            SeekFrom::Current(offset) => {
+                let cursor = self.cursor.saturating_add_signed(offset);
+                if cursor < self.bounds.0 {
+                    return Err(IoError::new(
+                        IoErrorKind::InvalidInput,
+                        ZipError::NegativeFileOffset,
+                    ));
+                }
+                cursor
+            }
+        }
+        .min(self.bounds.1);
+
+        Ok(self.io.seek(SeekFrom::Start(self.cursor))? - self.bounds.0)
+    }
+}