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bpo-33781: audioop: enhance rounding double as int (GH-7447) (GH-7452) 

Move the floor() call into fbound() to call floor() on a double
rather than an int. The change should enhance the rounding.

Document also (int)double rounding mode.

(cherry picked from commit 45e4efba7f)
This commit is contained in:
Victor Stinner 2018-06-06 17:12:39 +02:00 committed by GitHub
parent d098098ce1
commit b17d409bc0
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 19 additions and 12 deletions
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31
Modules/audioop.c
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@ -31,11 +31,18 @@ static const unsigned int masks[] = {0, 0xFF, 0xFFFF, 0xFFFFFF, 0xFFFFFFFF};
static int
fbound(double val, double minval, double maxval)
{
if (val > maxval)
if (val > maxval) {
val = maxval;
else if (val < minval + 1)
}
else if (val < minval + 1.0) {
val = minval;
return val;
}
/* Round towards minus infinity (-inf) */
val = floor(val);
/* Cast double to integer: round towards zero */
return (int)val;
}
@ -793,8 +800,8 @@ audioop_mul(PyObject *self, PyObject *args)
if ( size == 1 ) val = (int)*CHARP(cp, i);
else if ( size == 2 ) val = (int)*SHORTP(cp, i);
else if ( size == 4 ) val = (int)*LONGP(cp, i);
fval = (double)val*factor;
val = (int)floor(fbound(fval, minval, maxval));
fval = (double)val * factor;
val = fbound(fval, minval, maxval);
if ( size == 1 ) *CHARP(ncp, i) = (signed char)val;
else if ( size == 2 ) *SHORTP(ncp, i) = (short)val;
else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)val;
@ -837,8 +844,8 @@ audioop_tomono(PyObject *self, PyObject *args)
if ( size == 1 ) val2 = (int)*CHARP(cp, i+1);
else if ( size == 2 ) val2 = (int)*SHORTP(cp, i+2);
else if ( size == 4 ) val2 = (int)*LONGP(cp, i+4);
fval = (double)val1*fac1 + (double)val2*fac2;
val1 = (int)floor(fbound(fval, minval, maxval));
fval = (double)val1 * fac1 + (double)val2 * fac2;
val1 = fbound(fval, minval, maxval);
if ( size == 1 ) *CHARP(ncp, i/2) = (signed char)val1;
else if ( size == 2 ) *SHORTP(ncp, i/2) = (short)val1;
else if ( size == 4 ) *LONGP(ncp, i/2)= (Py_Int32)val1;
@ -881,11 +888,11 @@ audioop_tostereo(PyObject *self, PyObject *args)
else if ( size == 2 ) val = (int)*SHORTP(cp, i);
else if ( size == 4 ) val = (int)*LONGP(cp, i);
fval = (double)val*fac1;
val1 = (int)floor(fbound(fval, minval, maxval));
fval = (double)val * fac1;
val1 = fbound(fval, minval, maxval);
fval = (double)val*fac2;
val2 = (int)floor(fbound(fval, minval, maxval));
fval = (double)val * fac2;
val2 = fbound(fval, minval, maxval);
if ( size == 1 ) *CHARP(ncp, i*2) = (signed char)val1;
else if ( size == 2 ) *SHORTP(ncp, i*2) = (short)val1;
@ -944,7 +951,7 @@ audioop_add(PyObject *self, PyObject *args)
else {
double fval = (double)val1 + (double)val2;
/* truncate in case of overflow */
newval = (int)floor(fbound(fval, minval, maxval));
newval = fbound(fval, minval, maxval);
}
if ( size == 1 ) *CHARP(ncp, i) = (signed char)newval;