| Message ID | 1340888154-31903-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 06/28/2012 06:55 AM, Peter Maydell 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>
On 28 June 2012 13:55, 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. NB: I'm planning to put this v3 into a target-arm pullreq at the end of next week, since the LPAE patches depend on it, unless somebody wishes to (a) object (b) commit it before then. thanks -- PMM
Am 28.06.2012 14:55, schrieb Peter Maydell: > 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> > --- > 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 > bikeshed roof is now a slightly darker shade of grey Reviewed-by: Andreas Färber <afaerber@suse.de> Small improvement would be to replace "Returns the" with "Returns: The" in line with how you annotated the arguments, and the function summary should go into its own paragraph between @foo: and Returns:. http://developer.gnome.org/gtk-doc-manual/unstable/documenting_symbols.html.en Andreas
On 6 July 2012 14:41, Andreas Färber <afaerber@suse.de> wrote: > Small improvement would be to replace "Returns the" with "Returns: The" > in line with how you annotated the arguments, and the function summary > should go into its own paragraph between @foo: and Returns:. > > http://developer.gnome.org/gtk-doc-manual/unstable/documenting_symbols.html.en Hmm. I was just following the existing practice in this file, which consistently uses "Returns $whatever" without a colon. memory.h uses "Returns $whatever" rather than "Returns: $whatever" too. But I guess the doc you link to is the official statement of the required syntax. How are these comments? /** * 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. */ /** * 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. */ /** * 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. */ /** * 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. */ -- PMM
Am 06.07.2012 16:01, schrieb Peter Maydell: > On 6 July 2012 14:41, Andreas Färber <afaerber@suse.de> wrote: >> Small improvement would be to replace "Returns the" with "Returns: The" >> in line with how you annotated the arguments, and the function summary >> should go into its own paragraph between @foo: and Returns:. >> >> http://developer.gnome.org/gtk-doc-manual/unstable/documenting_symbols.html.en > > Hmm. I was just following the existing practice in this file, > which consistently uses "Returns $whatever" without a colon. > memory.h uses "Returns $whatever" rather than "Returns: $whatever" > too. But I guess the doc you link to is the official statement > of the required syntax. How are these comments? Looking fine. Didn't know about the "existing practice", I picked up Anthony's object.h style and remembered adjusting that in qom-next. Andreas
diff --git a/bitops.h b/bitops.h index 07d1a06..5a44bb1 100644 --- a/bitops.h +++ b/bitops.h @@ -269,4 +269,70 @@ static inline unsigned long hweight_long(unsigned long w) return count; } +/** + * extract32 - return a specified bit field from a uint32_t value + * @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 + * + * 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 - return a specified bit field from a uint64_t value + * @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 + * + * 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 - Insert into a specified bit field in a uint32_t + * @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 + * + * Returns the input value with the fieldval inserted + * into it at the specified location. + */ +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); +} + +/** + * deposit64 - Insert into a specified bit field in a uint64_t + * @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 + * + * Returns the input value with the fieldval inserted + * into it at the specified location. + */ +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
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> --- 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 bikeshed roof is now a slightly darker shade of grey NB: the deposit functions differ slightly from Avi's proposal: * instead of taking a pointer which we modify, we return the updated value. (This matches the semantics of the TCG deposit op and also seems to me generally nicer) * the implementation permits deposits of the entire word (ie length 32/64) bitops.h | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 66 insertions(+), 0 deletions(-)