/* 
 * Mr. 4th Dimention - Allen Webster
 *  Four Tech
 *
 * public domain -- no warranty is offered or implied; use this code at your own risk
 * 
 * 30.10.2015
 * 
 * Buffer data object
 *  type - Multi Gap Buffer
 *
 * This scheme was originally introduced to me by Martin Cohen,
 * who calls it a "Fixed Width Gap Buffer".
 * 
 */

// TOP

typedef struct{
    char *data;
    int size1, gap_size, size2;
    int start_pos;
} Fixed_Width_Gap_Buffer;

#define fixed_width_buffer_size Kbytes(8)
#define fixed_width_buffer_half_size Kbytes(4)

typedef struct{
    Fixed_Width_Gap_Buffer *gaps;
    int chunk_count;
    int chunk_max;
    int size;
} Multi_Gap_Buffer;

inline_4tech int
buffer_good(Multi_Gap_Buffer *buffer){
    int good;
    good = (buffer->gaps != 0);
    return(good);
}

inline_4tech int
buffer_size(Multi_Gap_Buffer *buffer){
    int size;
    size = buffer->size;
    return(size);
}

typedef struct{
    Multi_Gap_Buffer *buffer;
    char *data;
    int size;
    int chunk_i;
    int chunk_count;
} Multi_Gap_Buffer_Init;


internal_4tech Multi_Gap_Buffer_Init
buffer_begin_init(Multi_Gap_Buffer *buffer, char *data, int size){
    Multi_Gap_Buffer_Init init;
    init.buffer = buffer;
    init.data = data;
    init.size = size;
    init.chunk_i = 0;
    init.chunk_count = div_ceil_4tech(size, fixed_width_buffer_half_size);
    return(init);
}

internal_4tech int
buffer_init_need_more(Multi_Gap_Buffer_Init *init){
    int result;
    result = 1;
    if (init->buffer->gaps && init->chunk_i == init->chunk_count)
        result = 0;
    return(result);
}

internal_4tech int
buffer_init_page_size(Multi_Gap_Buffer_Init *init){
    Multi_Gap_Buffer *buffer;
    int result;
    buffer = init->buffer;
    if (buffer->gaps) result = fixed_width_buffer_size;
    else result = init->chunk_count * 2 * sizeof(*buffer->gaps);
    return(result);
}

internal_4tech void
buffer_init_provide_page(Multi_Gap_Buffer_Init *init, void *page, int page_size){
    Multi_Gap_Buffer *buffer;
    buffer = init->buffer;
    
    if (buffer->gaps){
        assert_4tech(page_size >= fixed_width_buffer_size);
        buffer->gaps[init->chunk_i].data = (char*)page;
        ++init->chunk_i;
    }
    else{
        buffer->gaps = (Fixed_Width_Gap_Buffer*)page;
        buffer->chunk_max = page_size / sizeof(*buffer->gaps);
    }
}

internal_4tech int
buffer_end_init(Multi_Gap_Buffer_Init *init){
    Multi_Gap_Buffer *buffer;
    Fixed_Width_Gap_Buffer *gap;
    int result;
    int i, count;
    char *data;
    int pos, size, total_size, start_pos;
    int osize1, size1, size2;

    result = 0;
    buffer = init->buffer;
    if (buffer->gaps){
        if (buffer->chunk_max >= div_ceil_4tech(init->size, fixed_width_buffer_half_size)){
            buffer->chunk_count = init->chunk_count;
            result = 1;
            
            data = init->data;
            total_size = init->size;
            gap = buffer->gaps;
            count = init->chunk_count;
            size = fixed_width_buffer_half_size;
            pos = 0;
            start_pos = 0;
            
            for (i = 0; i < count; ++i, ++gap, pos += size){
                if (pos + size > total_size) size = total_size - pos;
                
                if (gap->data){
                    size2 = size >> 1;
                    size1 = osize1 = size - size2;
                    
                    if (size1 > 0){
                        size1 = eol_convert_in(gap->data, data + pos, size1);
                        if (size2 > 0){
                            size2 = eol_convert_in(gap->data + size1, data + pos + osize1, size2);
                        }
                    }
                    
                    gap->size1 = size1;
                    gap->size2 = size2;
                    gap->gap_size = fixed_width_buffer_size - size1 - size2;
                    memmove_4tech(gap->data + size1 + gap->gap_size, gap->data + size1, size2);

                    gap->start_pos = start_pos;
                    start_pos += size1 + size2;
                }
                else{
                    result = 0;
                    break;
                }
            }
            buffer->size = start_pos;
        }
    }
    
    return(result);
}

// BOTTOM