Conversion device, memory system, decompression device, and method

A decompression device comprising:

• a demultiplexer configured to extract first to Nth substreams from a first compressed stream including the first to Nth substreams, where N is an integer greater than or equal to two, the first to Nth substreams being placed in order in the first compressed stream and including first variable-length codes to Nth variable-length codes into which first symbols to Nth symbols of a symbol string have been converted by subjecting the first symbols to the Nth symbols to entropy coding;
• first to Nth extractors configured to extract the first variable-length codes to the Nth variable-length codes from the first to Nth substreams;
• first to Nth decoders configured to convert the first variable-length codes to the Nth variable-length codes into the first symbols to the Nth symbols by subjecting the first variable-length codes to the Nth variable-length codes to entropy decoding;
• and
• a deinterleave unit configured to:
• output the symbol string by reordering the first symbols to the Nth symbols, into which the first variable-length codes to the Nth variable-length codes have been converted, when a first output format is specified from outside, and
• reorder the first variable-length codes to the Nth variable-length codes extracted from the first to Nth substreams in accordance with the symbol string and output a second compressed stream in which the reordered first variable-length codes to Nth variable-length codes are placed, when a second output format different from the first output format is specified from outside.

A method of controlling a nonvolatile memory, the method comprising:

• dividing a symbol string into first symbols to Nth symbols;
• converting the first symbols to the Nth symbols into first variable-length codes to Nth variable-length codes by subjecting the first symbols to the Nth symbols to entropy coding;
• outputting a first compressed stream in which first to Nth substreams including the first variable-length codes to the Nth variable-length codes are placed in order;
• storing the first compressed stream in the nonvolatile memory;
• reading the first compressed stream from the nonvolatile memory;
• extracting the first to Nth substreams from the read first compressed stream;
• extracting the first variable-length codes to the Nth variable-length codes from the first to Nth substreams, and converting the extracted first variable-length codes to Nth variable-length codes into the first symbols to the Nth symbols by subjecting the extracted first variable-length codes to Nth variable-length codes to entropy decoding;
• outputting the symbol string by reordering the first symbols to the Nth symbols, into which the first variable-length codes to the Nth variable-length codes have been converted;
• and
• reordering the first variable-length codes to the Nth variable-length codes in accordance with the symbol string and outputting a second compressed stream in which the reordered first variable-length codes to Nth variable-length codes are placed, wherein
• the outputting the symbol string includes outputting the symbol string when a first output format is specified from outside, and
• the outputting the second compressed stream includes outputting the second compressed stream when a second output format different from the first output format is specified from outside.