forked from minhngoc25a/freetype2
[truetype] Kill very old vector normalization hacks.
Back in the days, vector length calculations were not very accurate
and the vector normalization function, Normalize, had to meticulously
correct the errors for long vectors [commit b7ef2b0968]. It was no
longer necessary after accurate CORDIC algorithms were adopted, but
the code remained. It is time to kill it.
* src/truetype/ttinterp.c (Normalize): Remove error compensation.
(TT_VecLen): Remove any mention of old less accurate implementation.
This commit is contained in:
Alexei Podtelezhnikov
parent
a692170a23
commit
081aba390a
13
ChangeLog
13
ChangeLog
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@ -1,3 +1,16 @@
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2013-01-12 Alexei Podtelezhnikov <apodtele@gmail.com>
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[truetype] Kill very old vector normalization hacks.
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Back in the days, vector length calculations were not very accurate
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and the vector normalization function, Normalize, had to meticulously
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correct the errors for long vectors [commit b7ef2b096867]. It was no
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longer necessary after accurate CORDIC algorithms were adopted, but
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the code remained. It is time to kill it.
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* src/truetype/ttinterp.c (Normalize): Remove error compensation.
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(TT_VecLen): Remove any mention of old less accurate implementation.
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2013-01-11 Werner Lemberg <wl@gnu.org>
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Disable FT_CONFIG_OPTION_OLD_INTERNALS.
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@ -1543,79 +1543,6 @@
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/* return length of given vector */
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#if 0
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static FT_Int32
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TT_VecLen( FT_Int32 x,
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FT_Int32 y )
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{
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FT_Int32 m, hi1, hi2, hi;
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FT_UInt32 l, lo1, lo2, lo;
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/* compute x*x as 64-bit value */
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lo = (FT_UInt32)( x & 0xFFFFU );
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hi = x >> 16;
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l = lo * lo;
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m = hi * lo;
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hi = hi * hi;
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lo1 = l + (FT_UInt32)( m << 17 );
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hi1 = hi + ( m >> 15 ) + ( lo1 < l );
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/* compute y*y as 64-bit value */
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lo = (FT_UInt32)( y & 0xFFFFU );
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hi = y >> 16;
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l = lo * lo;
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m = hi * lo;
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hi = hi * hi;
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lo2 = l + (FT_UInt32)( m << 17 );
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hi2 = hi + ( m >> 15 ) + ( lo2 < l );
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/* add them to get 'x*x+y*y' as 64-bit value */
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lo = lo1 + lo2;
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hi = hi1 + hi2 + ( lo < lo1 );
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/* compute the square root of this value */
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{
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FT_UInt32 root, rem, test_div;
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FT_Int count;
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root = 0;
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{
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rem = 0;
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count = 32;
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do
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{
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rem = ( rem << 2 ) | ( (FT_UInt32)hi >> 30 );
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hi = ( hi << 2 ) | ( lo >> 30 );
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lo <<= 2;
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root <<= 1;
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test_div = ( root << 1 ) + 1;
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if ( rem >= test_div )
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{
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rem -= test_div;
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root += 1;
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}
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} while ( --count );
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}
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return (FT_Int32)root;
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}
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}
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#else
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/* this version uses FT_Vector_Length which computes the same value */
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/* much, much faster.. */
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/* */
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static FT_F26Dot6
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TT_VecLen( FT_F26Dot6 X,
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FT_F26Dot6 Y )
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@ -1629,8 +1556,6 @@
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return FT_Vector_Length( &v );
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}
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#endif
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/*************************************************************************/
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/* */
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@ -2718,7 +2643,6 @@
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FT_UnitVector* R )
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{
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FT_F26Dot6 W;
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FT_Bool S1, S2;
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FT_UNUSED_EXEC;
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@ -2728,80 +2652,18 @@
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Vx *= 0x100;
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Vy *= 0x100;
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W = TT_VecLen( Vx, Vy );
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if ( W == 0 )
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if ( Vx == 0 && Vy == 0 )
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{
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/* XXX: UNDOCUMENTED! It seems that it is possible to try */
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/* to normalize the vector (0,0). Return immediately. */
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return SUCCESS;
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}
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R->x = (FT_F2Dot14)TT_DivFix14( Vx, W );
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R->y = (FT_F2Dot14)TT_DivFix14( Vy, W );
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return SUCCESS;
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}
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W = TT_VecLen( Vx, Vy );
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Vx = TT_DivFix14( Vx, W );
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Vy = TT_DivFix14( Vy, W );
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W = Vx * Vx + Vy * Vy;
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/* Now, we want that Sqrt( W ) = 0x4000 */
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/* Or 0x10000000 <= W < 0x10004000 */
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if ( Vx < 0 )
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{
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Vx = -Vx;
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S1 = TRUE;
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}
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else
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S1 = FALSE;
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if ( Vy < 0 )
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{
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Vy = -Vy;
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S2 = TRUE;
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}
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else
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S2 = FALSE;
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while ( W < 0x10000000L )
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{
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/* We need to increase W by a minimal amount */
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if ( Vx < Vy )
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Vx++;
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else
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Vy++;
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W = Vx * Vx + Vy * Vy;
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}
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while ( W >= 0x10004000L )
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{
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/* We need to decrease W by a minimal amount */
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if ( Vx < Vy )
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Vx--;
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else
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Vy--;
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W = Vx * Vx + Vy * Vy;
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}
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/* Note that in various cases, we can only */
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/* compute a Sqrt(W) of 0x3FFF, eg. Vx = Vy */
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if ( S1 )
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Vx = -Vx;
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if ( S2 )
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Vy = -Vy;
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R->x = (FT_F2Dot14)Vx; /* Type conversion */
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R->y = (FT_F2Dot14)Vy; /* Type conversion */
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R->x = (FT_F2Dot14)TT_DivFix14( Vx, W );
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R->y = (FT_F2Dot14)TT_DivFix14( Vy, W );
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return SUCCESS;
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}
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