[PATCH 4/5] decimal: add conversions to (u)int64_t
Vladimir Davydov
vdavydov.dev at gmail.com
Wed Jul 24 19:17:51 MSK 2019
On Wed, Jul 17, 2019 at 06:33:45PM +0300, Serge Petrenko wrote:
> Update decNumber library, add methods to convert decimals to uint64_t
> and int64_t, add unit tests.
> Also replace decimal_round() function with decimal_round_with_mode() to
> allow setting rounding mode.
Better add decimal_floor(), as decimal_round_with_mode() has a
complicated API IMO.
> We need to round with mode DEC_ROUND_DOWN in to_int64 conversions in
> order to be consistent with double to int conversions.
> It will be needed to compute hints for decimal fields.
>
> Prerequisite #4333
> ---
> src/lib/core/decimal.c | 63 ++++++++++++++++++++++++++++++++--
> src/lib/core/decimal.h | 12 +++++++
> test/unit/decimal.c | 66 ++++++++++++++++++++++++++++++++++-
> test/unit/decimal.result | 74 ++++++++++++++++++++++++++++++++++++++--
> third_party/decNumber | 2 +-
> 5 files changed, 209 insertions(+), 8 deletions(-)
>
> diff --git a/src/lib/core/decimal.c b/src/lib/core/decimal.c
> index 2c69a773c..5a576e6e5 100644
> --- a/src/lib/core/decimal.c
> +++ b/src/lib/core/decimal.c
> @@ -157,6 +157,57 @@ decimal_to_string(const decimal_t *dec)
> return buf;
> }
>
> +static decimal_t *
> +decimal_round_with_mode(decimal_t *dec, int scale, enum rounding mode);
> +
> +decimal_t *
> +decimal_to_int64(decimal_t *dec, int64_t *num)
Why return decimal_t?
Shouldn't 'dec' be marked const?
> +{
> + decimal_t d, z;
> + decNumberZero(&z);
> + d = *dec;
> + dec = &d;
This looks confusing - like you're modifying the given decimal
number below.
> +
> + if (decimal_scale(dec) != 0) {
> + /*
> + * Rounding mode is important here.
> + * We want to be consistent with double
> + * to int conversion so that comparison
> + * hints work correctly.
> + */
> + dec = decimal_round_with_mode(dec, 0, DEC_ROUND_DOWN);
> + }
> + /*
> + * decNumberToInt64 works only with numbers with
> + * zero exponent.
> + */
> + decNumberRescale(dec, dec, &z, &decimal_context);
> + if (decimal_check_status(dec, &decimal_context) == NULL) {
> + return NULL;
> + }
> + *num = decNumberToInt64(dec, &decimal_context);
> + return decimal_check_status(dec, &decimal_context);
> +}
> +
> +decimal_t *
> +decimal_to_uint64(decimal_t *dec, uint64_t *num)
> +{
> + decimal_t d, z;
> + decNumberZero(&z);
> + d = *dec;
> + dec = &d;
> +
> + if (decimal_scale(dec) != 0) {
> + dec = decimal_round_with_mode(dec, 0, DEC_ROUND_DOWN);
> + }
> + decNumberRescale(dec, dec, &z, &decimal_context);
It would be nice to factor out the piece of code shared by
decimal_to_uint64 and decimal_to_int64.
> + if (decimal_check_status(dec, &decimal_context) == NULL) {
> + return NULL;
> + }
> + *num = decNumberToUInt64(dec, &decimal_context);
> + return decimal_check_status(dec, &decimal_context);
> +}
> +
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