Abstract: According to one embodiment, a data compression device includes N data compression circuits each including a dictionary buffer, and a dictionary buffer concatenation control circuit. The dictionary buffer concatenation control circuit controls switching between a first mode in which the N data compression circuits operate independently and a second mode in which the N data compression circuits cooperate. The dictionary buffer concatenation control circuit inputs, in the first mode, mutually different uncompressed data to the N data compression circuits, concatenates, in the second mode, N dictionary buffers by storing oldest dictionary data of an i-th dictionary buffer in an (i+1)-th dictionary buffer, and inputs the same uncompressed data to N data compression circuits.

Abstract: According to one embodiment, a data decompression device decompresses a compressed data string obtained by dictionary-based compression, the compressed data string including first compressed data having a first offset. A dictionary circuit includes at least one first dictionary storing first decompressed data corresponding to the first compressed data, and at least one second dictionary storing the first decompressed data. An assignment circuit assigns the first compressed data to at least one dictionary of the at least one first dictionary or the at least one second dictionary.

Abstract: According to one embodiment, a data compression circuit includes a plurality of intermediate match candidate generation circuits. Each of the plurality of intermediate match candidate generation circuits generates an intermediate match candidate by incrementing, based on a match length received from a corresponding intermediate match candidate selection circuit, a match length corresponding to an intermediate match candidate generated in a previous cycle when a distance corresponding to the received match length matches a distance corresponding to the intermediate match candidate generated in the previous cycle and the received match length is greater than a threshold value.

Abstract: According to one embodiment, a data compression circuit includes a plurality of intermediate match candidate generation circuits. Each of the plurality of intermediate match candidate generation circuits generates an intermediate match candidate by incrementing, based on a match length received from a corresponding intermediate match candidate selection circuit, a match length corresponding to an intermediate match candidate generated in a previous cycle when a distance corresponding to the received match length matches a distance corresponding to the intermediate match candidate generated in the previous cycle and the received match length is greater than a threshold value.

Abstract: According to one embodiment, a dictionary compressor for compressing input first data includes a buffer and a search unit. The buffer stores data input to the dictionary compressor prior to the first data. The search unit acquires, from the first data, partial data strings each having a first data length and having head positions in the first data, respectively, that are sequentially shifted by a second data length shorter than the first data length. The search unit performs search processes in parallel and acquires search results respectively corresponding to the search processes, the search processes searching the buffer to acquire respective match data strings that at least partially match the partial data strings, respectively.

Abstract: According to one embodiment, a memory system includes a frequency value update unit, a first intra-group rearranging unit, a second intra-group rearranging unit, and a routing unit. The frequency value update unit adds a first value to each of one or more first frequency values that are associated with one or more first symbols, respectively, in one or more entries in a table. The first intra-group rearranging unit rearranges first entries, which belong to a first group, using frequency values in the first entries. The second intra-group rearranging unit rearranges second entries, which belong to a second group lower than the first group, using frequency values. The routing unit rearranges at least one of the first entries and at least one of the second entries.

Abstract: According to one embodiment, a dictionary buffer stores dictionary data including a first substring and data before the first substring. A substring generator generates, from second input data, second substrings. A transformer transforms each of the second substrings into a hash value. A read processor reads the dictionary data, using a hash value transformed from a third substring among the second substrings. An acquisition unit compares a data string including the third substring and data before the third substring with the read dictionary data, and acquire first and second match lengths of the third and fourth substrings. A coded data generator generates coded data based on the acquired first and second match lengths.

Abstract: According to one embodiment, a compression circuit generates substrings from input data for (3+M) cycles, the input data being N bytes per cycle, a byte length of each substring being greater than or equal to (N×(1+M)+1); obtains a set of matches, each of the matches including at least one past input data which input past and corresponds to at least a part of each of the substrings; selects a subset of matches from the set of matches including the input data of one cycle; and outputs the subset of matches. M is zero or a natural number. N is a positive integer which is two or more.

Abstract: A compression device includes an analyzer circuit, a control circuit, a compressor circuit, and a selector circuit. The analyzer circuit is configured to analyze first data that is input thereto and generate one or more parameter values regarding data compression and/or decompression. The control circuit is configured to generate at least one compression mode information indicating whether or not compression is to be performed, based on the one or more parameter values. The compressor circuit is configured to compress the first data into second data according to the compression mode information. The selector circuit is configured to output the first data if not compressed or the second data if the first data is compressed, together with the compression mode information.

Abstract: According to one embodiment, a memory system includes a frequency value update unit, a first intra-group rearranging unit, a second intra-group rearranging unit, and a routing unit. The frequency value update unit adds a first value to each of one or more first frequency values that are associated with one or more first symbols, respectively, in one or more entries in a table. The first intra-group rearranging unit rearranges first entries, which belong to a first group, using frequency values in the first entries. The second intra-group rearranging unit rearranges second entries, which belong to a second group lower than the first group, using frequency values. The routing unit rearranges at least one of the first entries and at least one of the second entries.

Abstract: According to one embodiment, a compression device includes a first storage unit, a second storage unit, a calculation unit, and a comparison unit. The first storage unit stores addresses associated with hash values, respectively. The second storage unit includes storage areas specified by the addresses, respectively. The calculation unit determines a hash function to be used for first data in accordance with at least a part of the first data, and calculates a hash value using the hash function and at least a part of second data included in the first data. The comparison unit acquires third data from a storage area in the second storage unit specified by a first address, and compares the second data with the third data. The first address is stored in the first storage unit and is associated with the hash value.

Abstract: According to one embodiment, a dictionary compressor for compressing input first data includes a buffer and a search unit. The buffer stores data input to the dictionary compressor prior to the first data. The search unit acquires, from the first data, partial data strings each having a first data length and having head positions in the first data, respectively, that are sequentially shifted by a second data length shorter than the first data length. The search unit performs search processes in parallel and acquires search results respectively corresponding to the search processes, the search processes searching the buffer to acquire respective match data strings that at least partially match the partial data strings, respectively.

Abstract: According to one embodiment, a data decompression device includes: a detection circuit configured to detect a boundary between a header and a payload in a compressed stream, based on boundary information in the header; a separation circuit configured to separate the header and the payload; a first decompression circuit configured to decompress a compressed coding table in the header; and a second decompression circuit configured to decompress the payload, based on an output of the first decompression circuit.

Abstract: According to one embodiment, a memory system includes a frequency value update unit, a first intra-group rearranging unit, a second intra-group rearranging unit, and a routing unit. The frequency value update unit adds a first value to each of one or more first frequency values that are associated with one or more first symbols, respectively, in one or more entries in a table. The first intra-group rearranging unit rearranges first entries, which belong to a first group, using frequency values in the first entries. The second intra-group rearranging unit rearranges second entries, which belong to a second group lower than the first group, using frequency values. The routing unit rearranges at least one of the first entries and at least one of the second entries.

Abstract: According to one embodiment, a data compression device includes a dictionary match determination unit, an extended matching generator, a match selector and a match connector. The dictionary match determination unit searches for first past input data matching first new input data. The extended matching generator compares second past input data subsequent to the first past input data with second new input data subsequent to the first new input data. The match selector generates compressed data by replacing a part of the input data with match information output from the dictionary match determination unit or the extended matching generator. The match connector replaces a plurality of match information in the compressed data with single match information.

Abstract: According to one embodiment, a dictionary buffer stores dictionary data including a first substring and data before the first substring. A substring generator generates, from second input data, second substrings. A transformer transforms each of the second substrings into a hash value. A read processor reads the dictionary data, using a hash value transformed from a third substring among the second substrings. An acquisition unit compares a data string including the third substring and data before the third substring with the read dictionary data, and acquire first and second match lengths of the third and fourth substrings. A coded data generator generates coded data based on the acquired first and second match lengths.

Abstract: According to one embodiment, a memory system includes a compressor configured to output second data obtained by compressing input first data and a non-volatile memory to which third data based on the second data output from the compressor is written. The compressor includes a dictionary coding unit configured to perform dictionary coding on the first data, an entropy coding unit configured to perform entropy coding on the result of the dictionary coding, a first calculation unit configured to calculate compression efficiencies of the dictionary coding and the entropy coding, and a first control unit configured to control an operation of at least one of the dictionary coding unit and the entropy coding unit based on the compression efficiencies and a power reduction level.

Abstract: A memory system includes a non-volatile memory and a controller. The controller is configured to, during a writing operation, generate a first error-detecting code from data that is input, perform a predetermined conversion on the data into first conversion data, generate a second error-detecting code from the first conversion data, and store the data, the first error-detecting code, and the second-error detecting code in the non-volatile memory. The controller is configured to during a read operation, read the data, the first error-detecting code, and the second error-detecting code from the non-volatile memory, perform a first error detection on the data using the first error-detecting code, perform the predetermined conversion on the data into second conversion data, perform a second error detection on the second conversion data using the second error-detecting code, and output the second conversion data based on results of the first and second error detections.

Abstract: A memory system includes a non-volatile memory and a controller. The controller is configured to, during a writing operation, generate a first error-detecting code from data that is input, perform a predetermined conversion on the data into first conversion data, generate a second error-detecting code from the first conversion data, and store the data, the first error-detecting code, and the second-error detecting code in the non-volatile memory. The controller is configured to during a read operation, read the data, the first error-detecting code, and the second error-detecting code from the non-volatile memory, perform a first error detection on the data using the first error-detecting code, perform the predetermined conversion on the data into second conversion data, perform a second error detection on the second conversion data using the second error-detecting code, and output the second conversion data based on results of the first and second error detections.

Abstract: According to one embodiment, a data decompression device includes: a detection circuit configured to detect a boundary between a header and a payload in a compressed stream, based on boundary information in the header; a separation circuit configured to separate the header and the payload; a first decompression circuit configured to decompress a compressed coding table in the header; and a second decompression circuit configured to decompress the payload, based on an output of the first decompression circuit.