BitStream.hpp

Go to the documentation of this file.

/*
    Copyright (c) 2009-2010 Christopher A. Taylor.  All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.
    * Neither the name of LibCat nor the names of its contributors may be used
      to endorse or promote products derived from this software without
      specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
*/

// Not currently being maintained.

// FIXME: Big-endian code is untested
// FIXME: Not suitable for storing large buffers > 500 MB in size

#ifndef CAT_BIT_STREAM_HPP
#define CAT_BIT_STREAM_HPP

#include <cat/Platform.hpp>

namespace cat {



namespace bs_bit
{
    template<u32 N_BITS> struct set
    {
        u32 bits;
        set(u32 c_bits) : bits(c_bits) { }
    };

    template<u32 N_BITS> struct get
    {
        u32 &ref;
        get(u32 &c_ref) : ref(c_ref) { }
    };
}

namespace bs_byte
{
    struct set
    {
        u32 bytes;
        const void *ref;

        set(u32 b, const void *r) : ref(r), bytes(b) { }
    };

    struct get
    {
        u32 bytes;
        void *ref;

        get(u32 b, void *r) : ref(r), bytes(b) { }
    };
}



class BitStream
{
    bool fixed_buffer;
    u8 *buffer;
    u32 buffer_bytes;
    bool read_underrun;

    // grow to be able to write a number of bits
    void grow(u32 bits);

public:
    u32 read_offset, write_offset; // in bits

public:
    BitStream(u32 bytes = 0, void *vbuffer = 0);
    ~BitStream();

    // free unused buffer space
    void shrink();

public:
    u8 *get() { return buffer; }

    bool aligned() { return read_offset % 8 == 0; }
    u8 *peek() { return buffer + read_offset / 8; }

public:
    // returns true iff the buffer is valid
    bool valid() { return buffer != 0; }

    // returns count of remaining readable bits
    int unread() { return write_offset - read_offset; }

    // returns true if a recent read operation would have overrun the buffer
    bool underrun();

    // skip ahead a number of bits
    void skip(u32 bits);

public:
    // insertion
    void write1(u8 data); // data MUST be 1 or 0

    template<class T> void write(T data)
    {
        grow(sizeof(T) * 8);

        u32 byte_offset = write_offset / 8;
        u32 shift = write_offset % 8;

        if (shift)
        {
            buffer[byte_offset] |= (u8)(data << shift);
            data = data >> (8 - shift);
            ++byte_offset;
        }

        *(T*)(buffer + byte_offset) = data;

        write_offset += sizeof(T) * 8;
    }
    template<> void write(s8 data) { write((u8)data); }
    template<> void write(s16 data) { write((u16)data); }
    template<> void write(s32 data) { write((u32)data); }
    template<> void write(s64 data) { write((u64)data); }
    template<> void write(float data) { write(*(u32*)&data); }
    template<> void write(double data) { write(*(u64*)&data); }

    void writeBits(u32 data, int count);
    void writeBytes(const void *data, u32 byte_count);

public:
    // stream-mode insertion
    BitStream &operator<<(const char *data) { writeBytes(data, (u32)strlen(data)); return *this; }

    template<class T> BitStream &operator<<(T data) { write(data); return *this; }

    template<u32 N_BITS> BitStream &operator<<(const bs_bit::set<N_BITS> &n) { writeBits(n.bits, N_BITS); return *this; }
    template<> BitStream &operator<<(const bs_bit::set<1> &n) { write1((u8)n.bits); return *this; }
    template<> BitStream &operator<<(const bs_bit::set<8> &n) { write((u8)n.bits); return *this; }
    template<> BitStream &operator<<(const bs_bit::set<16> &n) { write((u16)n.bits); return *this; }
    template<> BitStream &operator<<(const bs_bit::set<32> &n) { write((u32)n.bits); return *this; }

    BitStream &operator<<(const bs_byte::set &n) { writeBytes(n.ref, n.bytes); return *this; }

public:
    // extraction
    u8 read1();

    template<class T> void read(T &data)
    {
        const u32 bits = sizeof(T) * 8;

        if (read_offset + bits > write_offset)
        {
            read_underrun = true;
            return;
        }

        u32 byte_offset = read_offset / 8;
        u32 shift = read_offset % 8;

        if (shift)
            data = (*(T*)(buffer + byte_offset + 1) << (8 - shift)) | (buffer[byte_offset] >> shift);
        else
            data = *(T*)(buffer + byte_offset);

        read_offset += bits;
    }
    template<> void read(float &data) { read((u32&)data); }
    template<> void read(double &data) { write(*(u64*)&data); }
    template<class T> T read() { T temp; read(temp); return temp; }

    u32 readBits(u32 count);
    void readBytes(void *data, u32 byte_count);

public:
    // stream-mode extraction
    template<class T> BitStream &operator>>(T &data) { read(data); return *this; }

    template<u32 N_BITS> BitStream &operator>>(const bs_bit::get<N_BITS> &n) { n.ref = readBits(N_BITS); return *this; }
    template<> BitStream &operator>>(const bs_bit::get<1> &n) { n.ref = read1(); return *this; }
    template<> BitStream &operator>>(const bs_bit::get<8> &n) { n.ref = read<u8>(); return *this; }
    template<> BitStream &operator>>(const bs_bit::get<16> &n) { n.ref = read<u16>(); return *this; }
    template<> BitStream &operator>>(const bs_bit::get<32> &n) { read(n.ref); return *this; }

    BitStream &operator>>(const bs_byte::get &n) { readBytes(n.ref, n.bytes); return *this; }
};


} // namespace cat

#endif // CAT_BIT_STREAM_HPP