On Thu, Nov 14, 2013 at 09:45:12AM -0800, H. Peter Anvin wrote:
> On 11/14/2013 12:38 AM, Christian Ruppert wrote:
> > diff --git a/lib/decompress_copy.c b/lib/decompress_copy.c
> > new file mode 100644
> > index 0000000..8a41090
> > --- /dev/null
> > +++ b/lib/decompress_copy.c
> > @@ -0,0 +1,47 @@
> > +#include <linux/decompress/mm.h>
> > +
> > +#define NOZIP_BUFSZ (16 * 1024)
> > +STATIC int INIT nozip(unsigned char *buf, int len,
> > + int(*fill)(void*, unsigned int),
> > + int(*flush)(void*, unsigned int),
> > + unsigned char *outbuf,
> > + int *pos,
> > + void(*error)(char *x))
> > +{
> > + char *b;
> > +
> > + if (buf)
> > + b = buf;
> > + else
> > + b = malloc(NOZIP_BUFSZ);
> > +
> > + if (!b) {
> > + error("Out of memory while allocating buffer");
> > + return -1;
> > + }
> > +
> > + if (flush) {
> > + if (!len)
> > + len = fill(b, NOZIP_BUFSZ);
> > +
> > + len = flush(b, len);
> > + } else {
> > + if (!len)
> > + len = fill(outbuf, NOZIP_BUFSZ);
> > + else {
> > + int i;
> > + for (i = 0; i < len; i++)
> > + outbuf[i] = b[i];
>
> Clever way of doing memcpy(). I know some other compression
> implementations open-code memmove(), but using it for the entire data
> set in the most common case is atrocious. If we need to get a default
> implementation of memmove() we should just do that.
Actually, the x86 architecture already contains a basic implementation
of memcpy in its self-decompressor. Correct me if I'm wrong but I guess
memmove is not required since I don't expect the output of a generic
decompression function to overlap with its input.
We can simply use that function if we agree that
. either nozip is x86 specific
. or every architecture using this code must bring along its own memcpy
implementation in its self-decompressor.
Do you think that would be OK?
Greetings,
Christian
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