ReadFile operation

[MKC002]

I found ReadFile operation is slow. Is there ay way to make it fast? Or is there any assemble code available to read from file/disk

[enhzflep]

Often times, when disk-io needs to be sped-up there are gains to be made in the way that the data is accessed -but not so much (if any gain) available in the function used to get that data. For example - if you have (say)a million pieces of data stored in a file, it's a better(faster) option to use ReadFile just once and read in the 1,000,000 pieces of data than it is to call the function 1,000,000 times to read 1 piece of data. Provided you're running in an OS with protected memory (i.e not DOS), no - not practically. You could attempt to write some low level code, but I'd suspect that the folk that wrote that part of windows would be more capable of speed than you. ;P Are you able to elaborate on the conditions in which you're using ReadFile, and the reasons you've come to the conclusion it's slow? It's very likely that algorithmic improvements can be made. :)

[Lost User]

How do you measure "slow"? At the very best a ReadFile() operation will operate at the transfer speed of the disk and its interface. At the very worst there are lots of factors that may affect it.

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[David Crow]

Disk I/O in itself is slow, regardless of the API used. What exactly are you needing to do?

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[MKC002]

I read data from a drive at different locations. I can not read large data because of some memory issue. Why it's slow because i check one software which reads it fast.

[Rolf Kristensen]

Usually when reading from a file, then one reads in small chunks like one byte at a time. If using a wrapper around ReadFile like fstream, then it will perform readahead caching by reading large chunks from the file into memory. When reading small chunks from fstream, then it will actually read directly from the internal cache inside fstream.