| Message ID | 1341586080-24117-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Accepted |
| Commit | 84988cf910a6881f2180fdcec516b60f8f0dc8c4 |
| Headers | show |
On Fri, Jul 6, 2012 at 2:48 PM, Peter Maydell <peter.maydell@linaro.org> wrote: > Add functions deposit32(), deposit64(), extract32() and extract64() > to extract and deposit bitfields in 32 and 64 bit words. Based on > ideas by Jia Liu and Avi Kivity. > > Suggested-by: Jia Liu <proljc@gmail.com> > Suggested-by: Avi Kivity <avi@redhat.com> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > Reviewed-by: Eric Blake <eblake@redhat.com> > Reviewed-by: Andreas Färber <afaerber@suse.de> Thanks, applied. > --- > Changes: > v1->v2: added missing brackets > v2->v3: renamed field32,field64 to extract32,extract64 > added deposit32,deposit64 at Avi's suggestion > fixed assertion as per Jay Foad's suggestion > v3->v4: fixed gtk-doc comment formats, expanded doc comments slightly > > I took the liberty of leaving Eric and Andreas' Reviewed-by: tags > on since there are no code changes in v4, only doc comments. > > bitops.h | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 90 insertions(+), 0 deletions(-) > > diff --git a/bitops.h b/bitops.h > index 07d1a06..b967ef3 100644 > --- a/bitops.h > +++ b/bitops.h > @@ -269,4 +269,94 @@ static inline unsigned long hweight_long(unsigned long w) > return count; > } > > +/** > + * extract32: > + * @value: the value to extract the bit field from > + * @start: the lowest bit in the bit field (numbered from 0) > + * @length: the length of the bit field > + * > + * Extract from the 32 bit input @value the bit field specified by the > + * @start and @length parameters, and return it. The bit field must > + * lie entirely within the 32 bit word. It is valid to request that > + * all 32 bits are returned (ie @length 32 and @start 0). > + * > + * Returns: the value of the bit field extracted from the input value. > + */ > +static inline uint32_t extract32(uint32_t value, int start, int length) > +{ > + assert(start >= 0 && length > 0 && length <= 32 - start); > + return (value >> start) & (~0U >> (32 - length)); > +} > + > +/** > + * extract64: > + * @value: the value to extract the bit field from > + * @start: the lowest bit in the bit field (numbered from 0) > + * @length: the length of the bit field > + * > + * Extract from the 64 bit input @value the bit field specified by the > + * @start and @length parameters, and return it. The bit field must > + * lie entirely within the 64 bit word. It is valid to request that > + * all 64 bits are returned (ie @length 64 and @start 0). > + * > + * Returns: the value of the bit field extracted from the input value. > + */ > +static inline uint64_t extract64(uint64_t value, int start, int length) > +{ > + assert(start >= 0 && length > 0 && length <= 64 - start); > + return (value >> start) & (~0ULL >> (64 - length)); > +} > + > +/** > + * deposit32: > + * @value: initial value to insert bit field into > + * @start: the lowest bit in the bit field (numbered from 0) > + * @length: the length of the bit field > + * @fieldval: the value to insert into the bit field > + * > + * Deposit @fieldval into the 32 bit @value at the bit field specified > + * by the @start and @length parameters, and return the modified > + * @value. Bits of @value outside the bit field are not modified. > + * Bits of @fieldval above the least significant @length bits are > + * ignored. The bit field must lie entirely within the 32 bit word. > + * It is valid to request that all 64 bits are modified (ie @length > + * 64 and @start 0). > + * > + * Returns: the modified @value. > + */ > +static inline uint32_t deposit32(uint32_t value, int start, int length, > + uint32_t fieldval) > +{ > + uint32_t mask; > + assert(start >= 0 && length > 0 && length <= 32 - start); > + mask = (~0U >> (32 - length)) << start; > + return (value & ~mask) | ((fieldval << start) & mask); > +} > + > +/** > + * deposit32: > + * @value: initial value to insert bit field into > + * @start: the lowest bit in the bit field (numbered from 0) > + * @length: the length of the bit field > + * @fieldval: the value to insert into the bit field > + * > + * Deposit @fieldval into the 64 bit @value at the bit field specified > + * by the @start and @length parameters, and return the modified > + * @value. Bits of @value outside the bit field are not modified. > + * Bits of @fieldval above the least significant @length bits are > + * ignored. The bit field must lie entirely within the 32 bit word. > + * It is valid to request that all 64 bits are modified (ie @length > + * 64 and @start 0). > + * > + * Returns: the modified @value. > + */ > +static inline uint64_t deposit64(uint64_t value, int start, int length, > + uint64_t fieldval) > +{ > + uint64_t mask; > + assert(start >= 0 && length > 0 && length <= 64 - start); > + mask = (~0ULL >> (64 - length)) << start; > + return (value & ~mask) | ((fieldval << start) & mask); > +} > + > #endif > -- > 1.7.1 >
Peter Maydell writes: [...] > +/** > + * extract32: > + * @value: the value to extract the bit field from > + * @start: the lowest bit in the bit field (numbered from 0) > + * @length: the length of the bit field > + * > + * Extract from the 32 bit input @value the bit field specified by the > + * @start and @length parameters, and return it. The bit field must > + * lie entirely within the 32 bit word. It is valid to request that > + * all 32 bits are returned (ie @length 32 and @start 0). > + * > + * Returns: the value of the bit field extracted from the input value. > + */ > +static inline uint32_t extract32(uint32_t value, int start, int length) > +{ > + assert(start >= 0 && length > 0 && length <= 32 - start); > + return (value >> start) & (~0U >> (32 - length)); > +} [...] Wouldn't it be better to use "unsigned int" instead on all the "start" and "length" arguments? Lluis
On 8 July 2012 10:55, Lluís Vilanova <vilanova@ac.upc.edu> wrote: > Wouldn't it be better to use "unsigned int" instead on all the "start" and > "length" arguments? See the arguments about this on one of the previous patch series: http://lists.gnu.org/archive/html/qemu-devel/2012-06/msg04304.html -- PMM
Am 08.07.2012 12:01, schrieb Peter Maydell: > On 8 July 2012 10:55, Lluís Vilanova <vilanova@ac.upc.edu> wrote: >> Wouldn't it be better to use "unsigned int" instead on all the "start" and >> "length" arguments? > See the arguments about this on one of the previous patch series: > http://lists.gnu.org/archive/html/qemu-devel/2012-06/msg04304.html > > -- PMM I just read that arguments and now agree with Blue and with Lluís that 'unsigned' would be better. Cheers, Stefan W.
On 8 July 2012 11:59, Stefan Weil <sw@weilnetz.de> wrote: > Am 08.07.2012 12:01, schrieb Peter Maydell: >> On 8 July 2012 10:55, Lluís Vilanova <vilanova@ac.upc.edu> wrote: >>> Wouldn't it be better to use "unsigned int" instead on all the "start" >>> and "length" arguments? >> >> See the arguments about this on one of the previous patch series: >> http://lists.gnu.org/archive/html/qemu-devel/2012-06/msg04304.html > I just read that arguments and now agree with Blue and with > Lluís that 'unsigned' would be better. ...whereas I still agree with Markus (and with the people who wrote the Linux kernel bitops functions that we borrowed elsewhere in bitops.h) that we should be using plain 'int'. -- PMM
diff --git a/bitops.h b/bitops.h index 07d1a06..b967ef3 100644 --- a/bitops.h +++ b/bitops.h @@ -269,4 +269,94 @@ static inline unsigned long hweight_long(unsigned long w) return count; } +/** + * extract32: + * @value: the value to extract the bit field from + * @start: the lowest bit in the bit field (numbered from 0) + * @length: the length of the bit field + * + * Extract from the 32 bit input @value the bit field specified by the + * @start and @length parameters, and return it. The bit field must + * lie entirely within the 32 bit word. It is valid to request that + * all 32 bits are returned (ie @length 32 and @start 0). + * + * Returns: the value of the bit field extracted from the input value. + */ +static inline uint32_t extract32(uint32_t value, int start, int length) +{ + assert(start >= 0 && length > 0 && length <= 32 - start); + return (value >> start) & (~0U >> (32 - length)); +} + +/** + * extract64: + * @value: the value to extract the bit field from + * @start: the lowest bit in the bit field (numbered from 0) + * @length: the length of the bit field + * + * Extract from the 64 bit input @value the bit field specified by the + * @start and @length parameters, and return it. The bit field must + * lie entirely within the 64 bit word. It is valid to request that + * all 64 bits are returned (ie @length 64 and @start 0). + * + * Returns: the value of the bit field extracted from the input value. + */ +static inline uint64_t extract64(uint64_t value, int start, int length) +{ + assert(start >= 0 && length > 0 && length <= 64 - start); + return (value >> start) & (~0ULL >> (64 - length)); +} + +/** + * deposit32: + * @value: initial value to insert bit field into + * @start: the lowest bit in the bit field (numbered from 0) + * @length: the length of the bit field + * @fieldval: the value to insert into the bit field + * + * Deposit @fieldval into the 32 bit @value at the bit field specified + * by the @start and @length parameters, and return the modified + * @value. Bits of @value outside the bit field are not modified. + * Bits of @fieldval above the least significant @length bits are + * ignored. The bit field must lie entirely within the 32 bit word. + * It is valid to request that all 64 bits are modified (ie @length + * 64 and @start 0). + * + * Returns: the modified @value. + */ +static inline uint32_t deposit32(uint32_t value, int start, int length, + uint32_t fieldval) +{ + uint32_t mask; + assert(start >= 0 && length > 0 && length <= 32 - start); + mask = (~0U >> (32 - length)) << start; + return (value & ~mask) | ((fieldval << start) & mask); +} + +/** + * deposit32: + * @value: initial value to insert bit field into + * @start: the lowest bit in the bit field (numbered from 0) + * @length: the length of the bit field + * @fieldval: the value to insert into the bit field + * + * Deposit @fieldval into the 64 bit @value at the bit field specified + * by the @start and @length parameters, and return the modified + * @value. Bits of @value outside the bit field are not modified. + * Bits of @fieldval above the least significant @length bits are + * ignored. The bit field must lie entirely within the 32 bit word. + * It is valid to request that all 64 bits are modified (ie @length + * 64 and @start 0). + * + * Returns: the modified @value. + */ +static inline uint64_t deposit64(uint64_t value, int start, int length, + uint64_t fieldval) +{ + uint64_t mask; + assert(start >= 0 && length > 0 && length <= 64 - start); + mask = (~0ULL >> (64 - length)) << start; + return (value & ~mask) | ((fieldval << start) & mask); +} + #endif