S
smnoff
How does one get the source code for memcpy()?
N
Naresh
smnoff said:
V
Vladimir Oka
smnoff said:
By going to:
www.google.com
or, if one is slightly more informed:
www.gnu.org
or, even better still (advanced users only):
www.gnu.org/software/libc/
or, (for experts only):
by actually writing it
C
Chris Dollin
smnoff said:
Why does one want the source code for memcpy?
[Not that there aren't reasons, but I'm curious as to what they are.]
Note that there is no "the" source code for memcpy. There will be
many sources: some cunningly optimised for a particular environment,
some written to make the intended effect clear; some written in ISO C,
some written in GNU C, some written in assembler ...
Was the Vax C runtime library written in C or Bliss or whatever?
S
Suman
R
Richard Heathfield
Suman said:
A very portable implementation.
I'd expect machine-specific implementations to box a bit more cleverly,
though - e.g. copying a word at a time rather than a byte as far as
possible, or using dedicated machine instructions where that's relevant.
A very portable implementation.
I'd expect machine-specific implementations to box a bit more cleverly,
though - e.g. copying a word at a time rather than a byte as far as
possible, or using dedicated machine instructions where that's relevant.
T
Tim Prince
Some even check for specific CPU hardware variants, to work aroundRichard said:
performance issues with certain instruction sequences. Implementations
for SSE surely will look for aligned runs which can be dealt with by
16-byte loads and stores.
S
Suman
<OT?>Richard said:
<url:
http://cvs.opensolaris.org/source/xref/on/usr/src/lib/libc/i386/gen/memcpy.s
/>
</OT>
M
Malcolm
Though not strictly conforming.Richard Heathfield said:
Arbitrary data must be cast to unsigned char, not plain char.
M
Malcolm
The string library functions are generally pretty easy to implement withsmnoff said:
reasonable efficiency.
memcpy() can be just a bte-copying loop, for instnace.
They are standard library functions for convenience, and because a clever
machine-specific implementation can take advantage of 32-bit copies and the
like. Sometimes the function call might even be inlined by the compiler.
P
pete
Richard said:
I think the pointer types should be (unsigned char *) instead.
R
Richard Heathfield
pete said:
On reflection, <aol>.
On reflection, <aol>.