| 摘要 |
In a block compressed data file, desired given non-compressed data is identified in a subset of a compressed data file and only the subset of the compressed data file containing the desired data is decompressed. Three operating modes according to application access level permission are allowed. The direct-read mode is used for application read-only permission. The file shadowing mode is used for application read/write permission when it is likely that the application will only read from the file without writing to it. The file putback mode is used for application read/write permission when it is likely the application will write to the file. Data caching of decompressed data blocks from a file avoids repetitious decompressing of a data block requested at different times. Block access of the compressed data file occurs through a table of offsets, either stored in the compressed data file itself or constructed from scratch.
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