foobar2000/helpers/bitreader_helper.h

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namespace bitreader_helper {

        inline static size_t extract_bit(const t_uint8 * p_stream,size_t p_offset) {
                return (p_stream[p_offset>>3] >> (7-(p_offset&7)))&1;
        }

        static size_t extract_int(const t_uint8 * p_stream,size_t p_base,size_t p_width) {
                size_t ret = 0;
                size_t offset = p_base;
                for(size_t bit=0;bit<p_width;bit++) {
                        ret <<= 1;
                        ret |= extract_bit(p_stream,offset++);
                }
                return ret;
        }

class bitreader
{
public:
        inline bitreader(const t_uint8 * p_ptr,t_size p_base)
                : m_ptr(p_ptr), m_bitptr(p_base)
        {
        }

        inline void skip(t_size p_bits)
        {
                m_bitptr += p_bits;
        }

        template<typename t_ret>
        t_ret read_t(t_size p_bits) {
                t_ret ret = 0;
                for(t_size bit=0;bit<p_bits;bit++)
                {
                        ret <<= 1;
                        ret |= (m_ptr[m_bitptr>>3] >> (7-(m_bitptr&7)))&1;
                        m_bitptr++;
                }
                return ret;
        }

        t_size read(t_size p_bits) {return read_t<t_size>(p_bits);}

        inline t_size get_bitptr() const {return m_bitptr;}

        inline bool read_bit() {
                bool state = ( (m_ptr[m_bitptr>>3] >> (7-(m_bitptr&7)))&1 ) != 0;
                m_bitptr++;
                return state;
        }

private:

        const t_uint8 * m_ptr;
        t_size m_bitptr;
};

class bitreader_fromfile
{
public:
        inline bitreader_fromfile(service_ptr_t<file> const& p_file) : m_file(p_file), m_buffer_ptr(0) {}
        
        t_size read(t_size p_bits,abort_callback & p_abort) {
                t_size ret = 0;
                for(t_size bit=0;bit<p_bits;bit++) {
                        if (m_buffer_ptr == 0)
                                m_file->read_object(&m_buffer,1,p_abort);

                        ret <<= 1;
                        ret |= (m_buffer >> (7-m_buffer_ptr))&1;
                        m_buffer_ptr = (m_buffer_ptr+1) & 7;
                }
                return ret;
        }

        void skip(t_size p_bits,abort_callback & p_abort) {
                for(t_size bit=0;bit<p_bits;bit++) {
                        if (m_buffer_ptr == 0) m_file->read_object(&m_buffer,1,p_abort);
                        m_buffer_ptr = (m_buffer_ptr+1) & 7;
                }
        }

        inline void byte_align() {m_buffer_ptr = 0;}

private:
        service_ptr_t<file> m_file;
        t_size m_buffer_ptr;
        t_uint8 m_buffer;
};

class bitreader_limited
{
public:
        inline bitreader_limited(const t_uint8 * p_ptr,t_size p_base,t_size p_remaining) : m_reader(p_ptr,p_base), m_remaining(p_remaining) {}

        inline t_size get_bitptr() const {return m_reader.get_bitptr();}

        inline t_size get_remaining() const {return m_remaining;}

        inline void skip(t_size p_bits) {
                if (p_bits > m_remaining) throw exception_io_data_truncation();
                m_remaining -= p_bits;
                m_reader.skip(p_bits);
        }

        t_size read(t_size p_bits)
        {
                if (p_bits > m_remaining) throw exception_io_data_truncation();
                m_remaining -= p_bits;
                return m_reader.read(p_bits);
        }

private:
        bitreader m_reader;
        t_size m_remaining;
};

inline static t_size extract_bits(const t_uint8 * p_buffer,t_size p_base,t_size p_count) {
        return bitreader(p_buffer,p_base).read(p_count);
}

}

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