49 lines
1.2 KiB
Plaintext
49 lines
1.2 KiB
Plaintext
How to do a B*Tree insert:
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add_to_page(cursor, data, ptr){
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if( data_fits_on_page ){ add data to page; return; }
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if( page==root ){
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split currentpage+(data+ptr) into lowerpart, center, upperpart
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newpage1 = lowerpart;
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newpage2 = upperpart;
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page = ptr(newpage1) + center + ptr(newpage2);
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return;
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}
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if( move_some_data_left || move_some_data_right ){
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add data to page
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return
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}
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split currentpage+(data+ptr) into lowerpart, center, upperpart
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newpage = upperpart
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currentpage = lowerpart
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pop cursor one level
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add_to_page(cursor, center, ptr(newpage));
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}
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unlink_entry(cursor, olddata){
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if( !is_a_leaf ){
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n = next_entry()
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if( n fits pageof(cursor) ){
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if( olddata!=nil ) copy dataof(cursor) into olddata
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copy dataof(n) into dataof(cursor)
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unlink_entry(n, nil)
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return
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}
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n = prev_entry()
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if( n fits pageof(cursor) ){
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if( olddata!=nil ) copy dataof(cursor) into olddata
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copy dataof(n) into dataof(cursor)
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unlink_entry(n, nil)
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return
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}
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unlink_entry(n, leafdata)
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move cursor data and ptr into olddata, oldptr
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add_to_page(cursor, leafdata, oldptr)
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return
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}
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move cursor data into olddata
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if( !underfull(pageof(cursor)) ) return
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}
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