| 摘要 |
Data compression and decompression utilising eg the Ziv-Lempel algorithm is simplified by utilising a tree structure for the dictionary in which alternative symbols at a given position in a symbol sequence (a,b,c) are linked by linking pointers R of a first type and successive symbols (ab,bc,ca,aba,abb,abc) are linked by linking pointers D of a second type. For example the sequence ab may continue with any one of the symbols a,b and c grouped together by R pointers in a list below the final symbol of the sequence ab. Each symbol is defined by an associated pair of D and R pointers, in conjunction with a parent pointer P which identifies its parent. Symbols having no D pointers extending therefrom are pruned from the tree and transferred to a free list as shown in Figure 8(b). |
