Add basic BGI unpack support

src/utils/bit_stream.rs

@@ -0,0 +1,76 @@
+use crate::ext::io::*;
+use anyhow::Result;
+use std::io::Write;
+
+pub struct BitStream<'a> {
+    m_input: MemReaderRef<'a>,
+    m_bits: u32,
+    m_cached_bits: u32,
+}
+
+impl<'a> BitStream<'a> {
+    pub fn new(input: MemReaderRef<'a>) -> Self {
+        BitStream {
+            m_input: input,
+            m_bits: 0,
+            m_cached_bits: 0,
+        }
+    }
+
+    pub fn get_bits(&mut self, count: u32) -> Result<u32> {
+        while self.m_cached_bits < count {
+            let byte = self.m_input.read_u8()?;
+            self.m_bits = (self.m_bits << 8) | byte as u32;
+            self.m_cached_bits += 8;
+        }
+        let mask = (1 << count) - 1;
+        self.m_cached_bits -= count;
+        let result = (self.m_bits >> self.m_cached_bits) & mask;
+        Ok(result)
+    }
+}
+
+pub struct BitWriter<'a, T: Write> {
+    writer: &'a mut T,
+    buffer: u32,
+    buffer_size: u32,
+}
+
+impl<'a, T: Write> BitWriter<'a, T> {
+    pub fn new(writer: &'a mut T) -> Self {
+        BitWriter {
+            writer,
+            buffer: 0,
+            buffer_size: 0,
+        }
+    }
+
+    pub fn flush(&mut self) -> Result<()> {
+        if self.buffer_size > 0 {
+            self.writer.write_u8((self.buffer & 0xFF) as u8)?;
+            self.buffer = 0;
+            self.buffer_size = 0;
+        }
+        Ok(())
+    }
+
+    pub fn put_bits(&mut self, byte: u32, token_width: u8) -> Result<()> {
+        for i in 0..token_width {
+            self.put_bit((byte & (1 << (token_width - 1 - i))) != 0)?;
+        }
+        Ok(())
+    }
+
+    pub fn put_bit(&mut self, bit: bool) -> Result<()> {
+        self.buffer <<= 1;
+        if bit {
+            self.buffer |= 1;
+        }
+        self.buffer_size += 1;
+        if self.buffer_size == 8 {
+            self.writer.write_u8((self.buffer & 0xFF) as u8)?;
+            self.buffer_size -= 8;
+        }
+        Ok(())
+    }
+}

src/utils/mod.rs

@@ -1,3 +1,5 @@
+#[cfg(feature = "utils-bit-stream")]
+pub mod bit_stream;
 pub mod counter;
 pub mod encoding;
 #[cfg(windows)]