1 files changed, 102 insertions, 0 deletions
diff --git a/ocaml/lib/bitstream.ml b/ocaml/lib/bitstream.ml
new file mode 100644
index 0000000..cfe094c
--- /dev/null
+++ b/ocaml/lib/bitstream.ml
@@ -0,0 +1,102 @@
+(** Bitstream utilities for jam/cue serialization *)
+
+(** A bitstream writer *)
+type writer = {
+  buf: bytes ref;          (** Buffer for bits *)
+  mutable bit_pos: int;    (** Current bit position *)
+}
+
+(** A bitstream reader *)
+type reader = {
+  buf: bytes;              (** Buffer to read from *)
+  mutable bit_pos: int;    (** Current bit position *)
+  len: int;                (** Length in bits *)
+}
+
+(** Create a new bitstream writer *)
+let writer_create () = {
+  buf = ref (Bytes.create 1024);
+  bit_pos = 0;
+}
+
+(** Grow the writer buffer if needed *)
+let writer_ensure (w : writer) (bits_needed : int) : unit =
+  let bytes_needed : int = (w.bit_pos + bits_needed + 7) / 8 in
+  let buf_ref : bytes ref = w.buf in
+  let current_buf : bytes = !buf_ref in
+  if bytes_needed > (Bytes.length current_buf) then begin
+    let old_buf : bytes = current_buf in
+    let new_size : int = max (bytes_needed * 2) (Bytes.length old_buf * 2) in
+    let new_buf : bytes = Bytes.create new_size in
+    Bytes.blit old_buf 0 new_buf 0 (Bytes.length old_buf);
+    buf_ref := new_buf
+  end
+
+(** Write a single bit *)
+let write_bit w bit =
+  writer_ensure w 1;
+  let byte_pos = w.bit_pos / 8 in
+  let bit_off = w.bit_pos mod 8 in
+  if bit then begin
+    let buf = !(w.buf) in
+    let old_byte = Bytes.get_uint8 buf byte_pos in
+    Bytes.set_uint8 buf byte_pos (old_byte lor (1 lsl bit_off))
+  end;
+  w.bit_pos <- w.bit_pos + 1
+
+(** Write multiple bits from a Z.t value *)
+let write_bits w value nbits =
+  writer_ensure w nbits;
+  for i = 0 to nbits - 1 do
+    let bit = Z.testbit value i in
+    write_bit w bit
+  done
+
+(** Get the final bytes from a writer *)
+let writer_to_bytes (w : writer) : bytes =
+  let byte_len = (w.bit_pos + 7) / 8 in
+  let buf_ref : bytes ref = w.buf in
+  let buf : bytes = !buf_ref in
+  Bytes.sub buf 0 byte_len
+
+(** Create a bitstream reader *)
+let reader_create buf =
+  {
+    buf;
+    bit_pos = 0;
+    len = Bytes.length buf * 8;
+  }
+
+(** Read a single bit *)
+let read_bit r =
+  if r.bit_pos >= r.len then
+    raise (Invalid_argument "read_bit: end of stream");
+  let byte_pos = r.bit_pos / 8 in
+  let bit_off = r.bit_pos mod 8 in
+  let byte_val = Bytes.get_uint8 r.buf byte_pos in
+  r.bit_pos <- r.bit_pos + 1;
+  (byte_val lsr bit_off) land 1 = 1
+
+(** Read multiple bits as a Z.t *)
+let read_bits r nbits =
+  let result = ref Z.zero in
+  for i = 0 to nbits - 1 do
+    if read_bit r then
+      result := Z.logor !result (Z.shift_left Z.one i)
+  done;
+  !result
+
+(** Peek at a bit without advancing *)
+let peek_bit r =
+  if r.bit_pos >= r.len then
+    raise (Invalid_argument "peek_bit: end of stream");
+  let byte_pos = r.bit_pos / 8 in
+  let bit_off = r.bit_pos mod 8 in
+  let byte_val = Bytes.get_uint8 r.buf byte_pos in
+  (byte_val lsr bit_off) land 1 = 1
+
+(** Get current bit position *)
+let reader_pos r = r.bit_pos
+
+(** Check if at end of stream *)
+let reader_at_end r = r.bit_pos >= r.len