/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * bitstream_writer.h — MSB-first bit packer with Exp-Golomb coding.
 *
 * Used by h264_nal_synth to emit AnnexB SPS / PPS NAL units the
 * daemon prepends to libva-provided slice data before feeding
 * libavcodec.  The writer is the minimum primitives the H.264
 * SPS/PPS RBSPs need:
 *
 *   put_u(v, n)   — n-bit unsigned, MSB first
 *   put_ue(v)     — Exp-Golomb unsigned (CAVLC ue(v))
 *   put_se(v)     — Exp-Golomb signed   (CAVLC se(v))
 *   align()       — rbsp_trailing_bits: stop_one + zero-pad to byte
 *
 * No allocations — the caller hands in a fixed buffer and the writer
 * tracks (byte, bit) cursor in it.  Overruns are detected and made
 * sticky via an error flag; callers check bsw_overflowed at the end.
 */
#ifndef DAEDALUS_BITSTREAM_WRITER_H
#define DAEDALUS_BITSTREAM_WRITER_H

#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>

struct bs_writer {
	uint8_t *buf;
	size_t cap;
	size_t pos_bytes;
	int pos_bit;     /* 0..7, MSB-first within the current byte */
	bool overflow;
};

void bsw_init(struct bs_writer *bs, uint8_t *buf, size_t cap);
void bsw_put_u(struct bs_writer *bs, uint32_t v, int n);
void bsw_put_ue(struct bs_writer *bs, uint32_t v);
void bsw_put_se(struct bs_writer *bs, int32_t v);

/* Align to next byte boundary by appending rbsp_trailing_bits:
 * a single '1' followed by '0's up to the byte boundary.  After
 * this call bsw_bytes is the RBSP length. */
void bsw_align_rbsp(struct bs_writer *bs);

/* Byte count of payload written so far.  If pos_bit != 0, returns
 * pos_bytes (incomplete bits are not counted; finalise with
 * bsw_align_rbsp first). */
size_t bsw_bytes(const struct bs_writer *bs);

static inline bool bsw_overflowed(const struct bs_writer *bs)
{
	return bs->overflow;
}

#endif /* DAEDALUS_BITSTREAM_WRITER_H */