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System and method for storing partial blocks of file data in a file cache system by merging partial updated blocks with file block to be written

  • US 5,555,391 A
  • Filed: 12/23/1993
  • Issued: 09/10/1996
  • Est. Priority Date: 12/23/1993
  • Status: Expired due to Term
First Claim
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1. A system for updating a selected portion of a file stored in a non-volatile storage within a file cache system coupled to a host computer system, comprising:

  • buffer means for storing a first selected portion and a second selected portion of a file received from the non-volatile storage, wherein said file is composed of a plurality of segments, each segment contains a plurality of blocks, each block contains a plurality of words, the unit of data transfer between the host computer system and the file cache system is one or more blocks specified by a number of blocks count, the size of a portion of said file to be updated is not equal to an integral multiple of the size of a block and said portion of said file to be updated may be stored in multiple contiguous blocks, said first selected portion of said file is delineated by a first word index within a first selected block of said file, said second selected portion of said file is delineated by a last word index within a last selected block of said file, said first selected block is the same as said last selected block for file updates of less than or equal to one block, and said portion of said file to be updated does not include but is contiguously between said first selected portion and said second selected portion of said file,write FIFO means, coupled to the host computer system, for storing said portion of file to be updated received from the host computer system,write control means, coupled to said write FIFO means, for controlling the selective transfer of said first selected portion of said file from said buffer means, said portion of said file to be updated from said write FIFO means, and said second selected portion of said file from said buffer means to the non-volatile storage by generating a plurality of selection control signals according to said first word index, said last word index, and said number of blocks count, andselection means coupled to said buffer means and the non-volatile storage, and connected to said write FIFO means and said write control means, for selecting said first selected portion of said file or said second selected portion of said file from said buffer means, or said portion of said file to be updated from said write FIFO means for transfer into the non-volatile storage according to said selection control signals received from said write control means.

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