delete bits from binary file

[zoran]

Is there a way to remove few bits from start of binary file. All file functions are byte based, not bit based. My files are large (GB size) so I would prefer not to read/write files as characters as this takes a long time.

[RavensFan]

I don't know what you mean by removing a few bits from the beginning of a file.

Files only store data in the units of bytes.  It can't read or write individual bits.

[Bob_Schor]

What do you really want to do?  Suppose I have a file that is four bytes (32 bits) in length, and you want to remove 3 bits.  What happens?  Do all of the bits "slide down" by three?  Or is only the first byte affected?

If your file really is a bit-stream and you want to remove "a few" bits, you are pretty much going to have to read and rewrite every single byte.  However, if you read the file as a U64, or 8 bytes at a time, you can "slide down" your bits on the U64, potentially cutting down the number of separate I/O calls by a factor of 8.  You'll, of course, need to fill in the "missing bits" from the next-higher chunk, and will also need to worry about handling the final few "odd" bytes in the file ...

Glad I don't have to do this -- sounds messy.

Bob Schor

[crossrulz]

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Bob_Schor wrote:

Glad I don't have to do this -- sounds messy.

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It is.  I once had to interface with a UUT that used a 12-bit PCM stream.  Why 12-bit?  Saves bandwidth over 16-bit.  Enough to really matter in real situations?  No.  Complicated as $*^&? YES!  Worth doing?  Not in my opinion.