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    SubjectRe: [RFC] LZO de/compression support - take 6
    On 5/30/07, Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
    >
    > On May 28 2007 20:04, Nitin Gupta wrote:
    > >
    > > * Changelog vs. original LZO:
    > > 1) Used standard/kernel defined data types: (this eliminated _huge_
    > > #ifdef chunks)
    > > lzo_bytep -> unsigned char *
    > > lzo_uint -> size_t
    > > lzo_xint -> size_t
    >
    > Is this safe (as far as compressed LZO stream is concerned) --
    > or is it even needed (could it be unsigned int)?
    >
    > > - m_pos -= (*(const unsigned short *)ip) >> 2;
    > > -#else
    > > - m_pos = op - 1;
    > > - m_pos -= (ip[0] >> 2) + (ip[1] << 6);
    > > -#endif
    > >
    > > + m_pos = op - 1 - (cpu_to_le16(*(const u16 *)ip) >> 2);
    > >
    > > (Andrey suggested le16_to_cpu for above but I think it should be cpu_to_le16).
    > > *** Need testing on big endian machine ***
    >
    > On i386, both cpu_to_le16 and le16_to_cpu do nothing.
    > On sparc for example, cpu_to_leXX and leXX_to_cpu do 'the same' ;-)
    > they swap 1234<->4321.
    >
    > It is the bytestream (ip) that is reinterpreted as uint16_t.
    > And I really doubt that the LZO author has a big-endian machine,
    > given the days of ubiquitous x86.

    > le16_to_cpu it is.
    >

    I just missed the point that leXX_to_cpu() and cpu_to_leXX() are
    identical on BE machine anyway. But then why you think it should be
    le_16_cpu() -- how will this make any difference?

    For your ref (from big_endian.h):
    #define __cpu_to_le16(x) ((__force __le16)__swab16((x)))
    #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))

    - Nitin
    -
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