Re: [RFC PATCH v2 1/4] decompressor: Add LZ4 decompressor module

Kyungsik Lee
2013-02-27T04:38:29Z

On Tue, Feb 26, 2013 at 02:12:06PM +0100, David Sterba wrote:
> On Tue, Feb 26, 2013 at 03:24:27PM +0900, Kyungsik Lee wrote:
> > This patch adds support for LZ4 decompression in the Linux Kernel.
> > LZ4 Decompression APIs for kernel are based on LZ4 implementation
> > by Yann Collet.
> >
> > LZ4 homepage : http://fastcompression.blogspot.com/p/lz4.html
> > LZ4 source repository : http://code.google.com/p/lz4/
>
> What SVN version did you use?
It's based on r88.

> > +/*
> > + * LZ4_COMPRESSBOUND()
> > + * Provides the maximum size that LZ4 may output in a "worst case" scenario
> > + * (input data not compressible)
> > + */
> > +#define LZ4_COMPRESSBOUND(isize) (isize + ((isize)/255) + 16)
>
> For safety reasons I suggest to add a temporary variable to avoid double
> evaluation of isize.
Yes, Good point.
> > --- /dev/null
> > +++ b/lib/lz4/lz4_decompress.c
> > + }
> > + cpy = op + length - (STEPSIZE - 4);
> > + if (cpy > oend - COPYLENGTH) {
> > +
> > + /* Error: request to write beyond destination buffer */
> > + if (cpy > oend)
> > + goto _output_error;
> > + LZ4_SECURECOPY(ref, op, (oend - COPYLENGTH));
> > + while (op < cpy)
> > + *op++ = *ref++;
> > + op = cpy;
> > + /*
> > + * Check EOF (should never happen, since last 5 bytes
> > + * are supposed to be literals)
> > + */
> > + if (op == oend)
> > + goto _output_error;
> > + continue;
> > + }
> > + LZ4_SECURECOPY(ref, op, cpy);
> > + op = cpy; /* correction */
> > + }
>
> Does this compile? The } is an extra one, and does not match the
> original sources.
>
It's about indent errors. The } is a pair of braces regarding
"while (1) {". However it compiled. It will be fixed.

> > +#define LZ4_COPYPACKET(s, d) \
> > + do { \
> > + LZ4_COPYSTEP(s, d); \
> > + LZ4_COPYSTEP(s, d); \
> > + } while (0)
> > +
> > +#define LZ4_SECURECOPY LZ4_WILDCOPY
> > +#endif
> > +
> > +#define LZ4_READ_LITTLEENDIAN_16(d, s, p) \
> > + (d = s - get_unaligned_le16(p))
> > +#define LZ4_WILDCOPY(s, d, e) \
> > + do { \
> > + LZ4_COPYPACKET(s, d); \
> > + } while (d < e)
>
> All the \ at the ends of lines would look better aligned in one column.
>
Yes, right. It looks better if it's aligned.

Thanks,
Kyungsik