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path: root/third_party/freetype/src/base/ftcalc.c
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+/***************************************************************************/
+/* */
+/* ftcalc.c */
+/* */
+/* Arithmetic computations (body). */
+/* */
+/* Copyright 1996-2006, 2008, 2012-2014 by */
+/* David Turner, Robert Wilhelm, and Werner Lemberg. */
+/* */
+/* This file is part of the FreeType project, and may only be used, */
+/* modified, and distributed under the terms of the FreeType project */
+/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
+/* this file you indicate that you have read the license and */
+/* understand and accept it fully. */
+/* */
+/***************************************************************************/
+
+ /*************************************************************************/
+ /* */
+ /* Support for 1-complement arithmetic has been totally dropped in this */
+ /* release. You can still write your own code if you need it. */
+ /* */
+ /*************************************************************************/
+
+ /*************************************************************************/
+ /* */
+ /* Implementing basic computation routines. */
+ /* */
+ /* FT_MulDiv(), FT_MulFix(), FT_DivFix(), FT_RoundFix(), FT_CeilFix(), */
+ /* and FT_FloorFix() are declared in freetype.h. */
+ /* */
+ /*************************************************************************/
+
+
+#include <ft2build.h>
+#include FT_GLYPH_H
+#include FT_TRIGONOMETRY_H
+#include FT_INTERNAL_CALC_H
+#include FT_INTERNAL_DEBUG_H
+#include FT_INTERNAL_OBJECTS_H
+
+
+#ifdef FT_MULFIX_ASSEMBLER
+#undef FT_MulFix
+#endif
+
+/* we need to emulate a 64-bit data type if a real one isn't available */
+
+#ifndef FT_LONG64
+
+ typedef struct FT_Int64_
+ {
+ FT_UInt32 lo;
+ FT_UInt32 hi;
+
+ } FT_Int64;
+
+#endif /* !FT_LONG64 */
+
+
+ /*************************************************************************/
+ /* */
+ /* The macro FT_COMPONENT is used in trace mode. It is an implicit */
+ /* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log */
+ /* messages during execution. */
+ /* */
+#undef FT_COMPONENT
+#define FT_COMPONENT trace_calc
+
+
+ /* transfer sign leaving a positive number */
+#define FT_MOVE_SIGN( x, s ) \
+ FT_BEGIN_STMNT \
+ if ( x < 0 ) \
+ { \
+ x = -x; \
+ s = -s; \
+ } \
+ FT_END_STMNT
+
+ /* The following three functions are available regardless of whether */
+ /* FT_LONG64 is defined. */
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Fixed )
+ FT_RoundFix( FT_Fixed a )
+ {
+ return ( a >= 0 ) ? ( a + 0x8000L ) & ~0xFFFFL
+ : -((-a + 0x8000L ) & ~0xFFFFL );
+ }
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Fixed )
+ FT_CeilFix( FT_Fixed a )
+ {
+ return ( a >= 0 ) ? ( a + 0xFFFFL ) & ~0xFFFFL
+ : -((-a + 0xFFFFL ) & ~0xFFFFL );
+ }
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Fixed )
+ FT_FloorFix( FT_Fixed a )
+ {
+ return ( a >= 0 ) ? a & ~0xFFFFL
+ : -((-a) & ~0xFFFFL );
+ }
+
+#ifndef FT_MSB
+
+ FT_BASE_DEF ( FT_Int )
+ FT_MSB( FT_UInt32 z )
+ {
+ FT_Int shift = 0;
+
+ /* determine msb bit index in `shift' */
+ if ( z & 0xFFFF0000U )
+ {
+ z >>= 16;
+ shift += 16;
+ }
+ if ( z & 0x0000FF00U )
+ {
+ z >>= 8;
+ shift += 8;
+ }
+ if ( z & 0x000000F0U )
+ {
+ z >>= 4;
+ shift += 4;
+ }
+ if ( z & 0x0000000CU )
+ {
+ z >>= 2;
+ shift += 2;
+ }
+ if ( z & 0x00000002U )
+ {
+ /* z >>= 1; */
+ shift += 1;
+ }
+
+ return shift;
+ }
+
+#endif /* !FT_MSB */
+
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( FT_Fixed )
+ FT_Hypot( FT_Fixed x,
+ FT_Fixed y )
+ {
+ FT_Vector v;
+
+
+ v.x = x;
+ v.y = y;
+
+ return FT_Vector_Length( &v );
+ }
+
+
+#ifdef FT_LONG64
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Long )
+ FT_MulDiv( FT_Long a,
+ FT_Long b,
+ FT_Long c )
+ {
+ FT_Int s = 1;
+ FT_Long d;
+
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+ FT_MOVE_SIGN( c, s );
+
+ d = (FT_Long)( c > 0 ? ( (FT_Int64)a * b + ( c >> 1 ) ) / c
+ : 0x7FFFFFFFL );
+
+ return ( s > 0 ) ? d : -d;
+ }
+
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( FT_Long )
+ FT_MulDiv_No_Round( FT_Long a,
+ FT_Long b,
+ FT_Long c )
+ {
+ FT_Int s = 1;
+ FT_Long d;
+
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+ FT_MOVE_SIGN( c, s );
+
+ d = (FT_Long)( c > 0 ? (FT_Int64)a * b / c
+ : 0x7FFFFFFFL );
+
+ return ( s > 0 ) ? d : -d;
+ }
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Long )
+ FT_MulFix( FT_Long a,
+ FT_Long b )
+ {
+#ifdef FT_MULFIX_ASSEMBLER
+
+ return FT_MULFIX_ASSEMBLER( a, b );
+
+#else
+
+ FT_Int s = 1;
+ FT_Long c;
+
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+
+ c = (FT_Long)( ( (FT_Int64)a * b + 0x8000L ) >> 16 );
+
+ return ( s > 0 ) ? c : -c;
+
+#endif /* FT_MULFIX_ASSEMBLER */
+ }
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Long )
+ FT_DivFix( FT_Long a,
+ FT_Long b )
+ {
+ FT_Int s = 1;
+ FT_Long q;
+
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+
+ q = (FT_Long)( b > 0 ? ( ( (FT_UInt64)a << 16 ) + ( b >> 1 ) ) / b
+ : 0x7FFFFFFFL );
+
+ return ( s < 0 ? -q : q );
+ }
+
+
+#else /* !FT_LONG64 */
+
+
+ static void
+ ft_multo64( FT_UInt32 x,
+ FT_UInt32 y,
+ FT_Int64 *z )
+ {
+ FT_UInt32 lo1, hi1, lo2, hi2, lo, hi, i1, i2;
+
+
+ lo1 = x & 0x0000FFFFU; hi1 = x >> 16;
+ lo2 = y & 0x0000FFFFU; hi2 = y >> 16;
+
+ lo = lo1 * lo2;
+ i1 = lo1 * hi2;
+ i2 = lo2 * hi1;
+ hi = hi1 * hi2;
+
+ /* Check carry overflow of i1 + i2 */
+ i1 += i2;
+ hi += (FT_UInt32)( i1 < i2 ) << 16;
+
+ hi += i1 >> 16;
+ i1 = i1 << 16;
+
+ /* Check carry overflow of i1 + lo */
+ lo += i1;
+ hi += ( lo < i1 );
+
+ z->lo = lo;
+ z->hi = hi;
+ }
+
+
+ static FT_UInt32
+ ft_div64by32( FT_UInt32 hi,
+ FT_UInt32 lo,
+ FT_UInt32 y )
+ {
+ FT_UInt32 r, q;
+ FT_Int i;
+
+
+ if ( hi >= y )
+ return (FT_UInt32)0x7FFFFFFFL;
+
+ /* We shift as many bits as we can into the high register, perform */
+ /* 32-bit division with modulo there, then work through the remaining */
+ /* bits with long division. This optimization is especially noticeable */
+ /* for smaller dividends that barely use the high register. */
+
+ i = 31 - FT_MSB( hi );
+ r = ( hi << i ) | ( lo >> ( 32 - i ) ); lo <<= i; /* left 64-bit shift */
+ q = r / y;
+ r -= q * y; /* remainder */
+
+ i = 32 - i; /* bits remaining in low register */
+ do
+ {
+ q <<= 1;
+ r = ( r << 1 ) | ( lo >> 31 ); lo <<= 1;
+
+ if ( r >= y )
+ {
+ r -= y;
+ q |= 1;
+ }
+ } while ( --i );
+
+ return q;
+ }
+
+
+ static void
+ FT_Add64( FT_Int64* x,
+ FT_Int64* y,
+ FT_Int64 *z )
+ {
+ FT_UInt32 lo, hi;
+
+
+ lo = x->lo + y->lo;
+ hi = x->hi + y->hi + ( lo < x->lo );
+
+ z->lo = lo;
+ z->hi = hi;
+ }
+
+
+ /* The FT_MulDiv function has been optimized thanks to ideas from */
+ /* Graham Asher and Alexei Podtelezhnikov. The trick is to optimize */
+ /* a rather common case when everything fits within 32-bits. */
+ /* */
+ /* We compute 'a*b+c/2', then divide it by 'c' (all positive values). */
+ /* */
+ /* The product of two positive numbers never exceeds the square of */
+ /* its mean values. Therefore, we always avoid the overflow by */
+ /* imposing */
+ /* */
+ /* (a + b) / 2 <= sqrt(X - c/2) , */
+ /* */
+ /* where X = 2^32 - 1, the maximum unsigned 32-bit value, and using */
+ /* unsigned arithmetic. Now we replace `sqrt' with a linear function */
+ /* that is smaller or equal for all values of c in the interval */
+ /* [0;X/2]; it should be equal to sqrt(X) and sqrt(3X/4) at the */
+ /* endpoints. Substituting the linear solution and explicit numbers */
+ /* we get */
+ /* */
+ /* a + b <= 131071.99 - c / 122291.84 . */
+ /* */
+ /* In practice, we should use a faster and even stronger inequality */
+ /* */
+ /* a + b <= 131071 - (c >> 16) */
+ /* */
+ /* or, alternatively, */
+ /* */
+ /* a + b <= 129894 - (c >> 17) . */
+ /* */
+ /* FT_MulFix, on the other hand, is optimized for a small value of */
+ /* the first argument, when the second argument can be much larger. */
+ /* This can be achieved by scaling the second argument and the limit */
+ /* in the above inequalities. For example, */
+ /* */
+ /* a + (b >> 8) <= (131071 >> 4) */
+ /* */
+ /* covers the practical range of use. The actual test below is a bit */
+ /* tighter to avoid the border case overflows. */
+ /* */
+ /* In the case of FT_DivFix, the exact overflow check */
+ /* */
+ /* a << 16 <= X - c/2 */
+ /* */
+ /* is scaled down by 2^16 and we use */
+ /* */
+ /* a <= 65535 - (c >> 17) . */
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Long )
+ FT_MulDiv( FT_Long a,
+ FT_Long b,
+ FT_Long c )
+ {
+ FT_Int s = 1;
+
+
+ /* XXX: this function does not allow 64-bit arguments */
+ if ( a == 0 || b == c )
+ return a;
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+ FT_MOVE_SIGN( c, s );
+
+ if ( c == 0 )
+ a = 0x7FFFFFFFL;
+
+ else if ( (FT_ULong)a + b <= 129894UL - ( c >> 17 ) )
+ a = ( (FT_ULong)a * b + ( c >> 1 ) ) / c;
+
+ else
+ {
+ FT_Int64 temp, temp2;
+
+
+ ft_multo64( a, b, &temp );
+
+ temp2.hi = 0;
+ temp2.lo = c >> 1;
+
+ FT_Add64( &temp, &temp2, &temp );
+
+ /* last attempt to ditch long division */
+ a = temp.hi == 0 ? temp.lo / c
+ : ft_div64by32( temp.hi, temp.lo, c );
+ }
+
+ return ( s < 0 ? -a : a );
+ }
+
+
+ FT_BASE_DEF( FT_Long )
+ FT_MulDiv_No_Round( FT_Long a,
+ FT_Long b,
+ FT_Long c )
+ {
+ FT_Int s = 1;
+
+
+ if ( a == 0 || b == c )
+ return a;
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+ FT_MOVE_SIGN( c, s );
+
+ if ( c == 0 )
+ a = 0x7FFFFFFFL;
+
+ else if ( (FT_ULong)a + b <= 131071UL )
+ a = (FT_ULong)a * b / c;
+
+ else
+ {
+ FT_Int64 temp;
+
+
+ ft_multo64( a, b, &temp );
+
+ /* last attempt to ditch long division */
+ a = temp.hi == 0 ? temp.lo / c
+ : ft_div64by32( temp.hi, temp.lo, c );
+ }
+
+ return ( s < 0 ? -a : a );
+ }
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Long )
+ FT_MulFix( FT_Long a,
+ FT_Long b )
+ {
+#ifdef FT_MULFIX_ASSEMBLER
+
+ return FT_MULFIX_ASSEMBLER( a, b );
+
+#elif 0
+
+ /*
+ * This code is nonportable. See comment below.
+ *
+ * However, on a platform where right-shift of a signed quantity fills
+ * the leftmost bits by copying the sign bit, it might be faster.
+ */
+
+ FT_Long sa, sb;
+ FT_ULong ua, ub;
+
+
+ if ( a == 0 || b == 0x10000L )
+ return a;
+
+ /*
+ * This is a clever way of converting a signed number `a' into its
+ * absolute value (stored back into `a') and its sign. The sign is
+ * stored in `sa'; 0 means `a' was positive or zero, and -1 means `a'
+ * was negative. (Similarly for `b' and `sb').
+ *
+ * Unfortunately, it doesn't work (at least not portably).
+ *
+ * It makes the assumption that right-shift on a negative signed value
+ * fills the leftmost bits by copying the sign bit. This is wrong.
+ * According to K&R 2nd ed, section `A7.8 Shift Operators' on page 206,
+ * the result of right-shift of a negative signed value is
+ * implementation-defined. At least one implementation fills the
+ * leftmost bits with 0s (i.e., it is exactly the same as an unsigned
+ * right shift). This means that when `a' is negative, `sa' ends up
+ * with the value 1 rather than -1. After that, everything else goes
+ * wrong.
+ */
+ sa = ( a >> ( sizeof ( a ) * 8 - 1 ) );
+ a = ( a ^ sa ) - sa;
+ sb = ( b >> ( sizeof ( b ) * 8 - 1 ) );
+ b = ( b ^ sb ) - sb;
+
+ ua = (FT_ULong)a;
+ ub = (FT_ULong)b;
+
+ if ( ua + ( ub >> 8 ) <= 8190UL )
+ ua = ( ua * ub + 0x8000U ) >> 16;
+ else
+ {
+ FT_ULong al = ua & 0xFFFFU;
+
+
+ ua = ( ua >> 16 ) * ub + al * ( ub >> 16 ) +
+ ( ( al * ( ub & 0xFFFFU ) + 0x8000U ) >> 16 );
+ }
+
+ sa ^= sb,
+ ua = (FT_ULong)(( ua ^ sa ) - sa);
+
+ return (FT_Long)ua;
+
+#else /* 0 */
+
+ FT_Int s = 1;
+ FT_ULong ua, ub;
+
+
+ if ( a == 0 || b == 0x10000L )
+ return a;
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+
+ ua = (FT_ULong)a;
+ ub = (FT_ULong)b;
+
+ if ( ua + ( ub >> 8 ) <= 8190UL )
+ ua = ( ua * ub + 0x8000UL ) >> 16;
+ else
+ {
+ FT_ULong al = ua & 0xFFFFUL;
+
+
+ ua = ( ua >> 16 ) * ub + al * ( ub >> 16 ) +
+ ( ( al * ( ub & 0xFFFFUL ) + 0x8000UL ) >> 16 );
+ }
+
+ return ( s < 0 ? -(FT_Long)ua : (FT_Long)ua );
+
+#endif /* 0 */
+
+ }
+
+
+ /* documentation is in freetype.h */
+
+ FT_EXPORT_DEF( FT_Long )
+ FT_DivFix( FT_Long a,
+ FT_Long b )
+ {
+ FT_Int s = 1;
+ FT_Long q;
+
+
+ /* XXX: this function does not allow 64-bit arguments */
+
+ FT_MOVE_SIGN( a, s );
+ FT_MOVE_SIGN( b, s );
+
+ if ( b == 0 )
+ {
+ /* check for division by 0 */
+ q = 0x7FFFFFFFL;
+ }
+ else if ( a <= 65535L - ( b >> 17 ) )
+ {
+ /* compute result directly */
+ q = (FT_Long)( ( ( (FT_ULong)a << 16 ) + ( b >> 1 ) ) / b );
+ }
+ else
+ {
+ /* we need more bits; we have to do it by hand */
+ FT_Int64 temp, temp2;
+
+
+ temp.hi = a >> 16;
+ temp.lo = a << 16;
+ temp2.hi = 0;
+ temp2.lo = b >> 1;
+
+ FT_Add64( &temp, &temp2, &temp );
+ q = (FT_Long)ft_div64by32( temp.hi, temp.lo, b );
+ }
+
+ return ( s < 0 ? -q : q );
+ }
+
+
+#endif /* FT_LONG64 */
+
+
+ /* documentation is in ftglyph.h */
+
+ FT_EXPORT_DEF( void )
+ FT_Matrix_Multiply( const FT_Matrix* a,
+ FT_Matrix *b )
+ {
+ FT_Fixed xx, xy, yx, yy;
+
+
+ if ( !a || !b )
+ return;
+
+ xx = FT_MulFix( a->xx, b->xx ) + FT_MulFix( a->xy, b->yx );
+ xy = FT_MulFix( a->xx, b->xy ) + FT_MulFix( a->xy, b->yy );
+ yx = FT_MulFix( a->yx, b->xx ) + FT_MulFix( a->yy, b->yx );
+ yy = FT_MulFix( a->yx, b->xy ) + FT_MulFix( a->yy, b->yy );
+
+ b->xx = xx; b->xy = xy;
+ b->yx = yx; b->yy = yy;
+ }
+
+
+ /* documentation is in ftglyph.h */
+
+ FT_EXPORT_DEF( FT_Error )
+ FT_Matrix_Invert( FT_Matrix* matrix )
+ {
+ FT_Pos delta, xx, yy;
+
+
+ if ( !matrix )
+ return FT_THROW( Invalid_Argument );
+
+ /* compute discriminant */
+ delta = FT_MulFix( matrix->xx, matrix->yy ) -
+ FT_MulFix( matrix->xy, matrix->yx );
+
+ if ( !delta )
+ return FT_THROW( Invalid_Argument ); /* matrix can't be inverted */
+
+ matrix->xy = - FT_DivFix( matrix->xy, delta );
+ matrix->yx = - FT_DivFix( matrix->yx, delta );
+
+ xx = matrix->xx;
+ yy = matrix->yy;
+
+ matrix->xx = FT_DivFix( yy, delta );
+ matrix->yy = FT_DivFix( xx, delta );
+
+ return FT_Err_Ok;
+ }
+
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( void )
+ FT_Matrix_Multiply_Scaled( const FT_Matrix* a,
+ FT_Matrix *b,
+ FT_Long scaling )
+ {
+ FT_Fixed xx, xy, yx, yy;
+
+ FT_Long val = 0x10000L * scaling;
+
+
+ if ( !a || !b )
+ return;
+
+ xx = FT_MulDiv( a->xx, b->xx, val ) + FT_MulDiv( a->xy, b->yx, val );
+ xy = FT_MulDiv( a->xx, b->xy, val ) + FT_MulDiv( a->xy, b->yy, val );
+ yx = FT_MulDiv( a->yx, b->xx, val ) + FT_MulDiv( a->yy, b->yx, val );
+ yy = FT_MulDiv( a->yx, b->xy, val ) + FT_MulDiv( a->yy, b->yy, val );
+
+ b->xx = xx; b->xy = xy;
+ b->yx = yx; b->yy = yy;
+ }
+
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( void )
+ FT_Vector_Transform_Scaled( FT_Vector* vector,
+ const FT_Matrix* matrix,
+ FT_Long scaling )
+ {
+ FT_Pos xz, yz;
+
+ FT_Long val = 0x10000L * scaling;
+
+
+ if ( !vector || !matrix )
+ return;
+
+ xz = FT_MulDiv( vector->x, matrix->xx, val ) +
+ FT_MulDiv( vector->y, matrix->xy, val );
+
+ yz = FT_MulDiv( vector->x, matrix->yx, val ) +
+ FT_MulDiv( vector->y, matrix->yy, val );
+
+ vector->x = xz;
+ vector->y = yz;
+ }
+
+
+#if 0
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( FT_Int32 )
+ FT_SqrtFixed( FT_Int32 x )
+ {
+ FT_UInt32 root, rem_hi, rem_lo, test_div;
+ FT_Int count;
+
+
+ root = 0;
+
+ if ( x > 0 )
+ {
+ rem_hi = 0;
+ rem_lo = x;
+ count = 24;
+ do
+ {
+ rem_hi = ( rem_hi << 2 ) | ( rem_lo >> 30 );
+ rem_lo <<= 2;
+ root <<= 1;
+ test_div = ( root << 1 ) + 1;
+
+ if ( rem_hi >= test_div )
+ {
+ rem_hi -= test_div;
+ root += 1;
+ }
+ } while ( --count );
+ }
+
+ return (FT_Int32)root;
+ }
+
+#endif /* 0 */
+
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( FT_Int )
+ ft_corner_orientation( FT_Pos in_x,
+ FT_Pos in_y,
+ FT_Pos out_x,
+ FT_Pos out_y )
+ {
+ FT_Long result; /* avoid overflow on 16-bit system */
+
+
+ /* deal with the trivial cases quickly */
+ if ( in_y == 0 )
+ {
+ if ( in_x >= 0 )
+ result = out_y;
+ else
+ result = -out_y;
+ }
+ else if ( in_x == 0 )
+ {
+ if ( in_y >= 0 )
+ result = -out_x;
+ else
+ result = out_x;
+ }
+ else if ( out_y == 0 )
+ {
+ if ( out_x >= 0 )
+ result = in_y;
+ else
+ result = -in_y;
+ }
+ else if ( out_x == 0 )
+ {
+ if ( out_y >= 0 )
+ result = -in_x;
+ else
+ result = in_x;
+ }
+ else /* general case */
+ {
+#ifdef FT_LONG64
+
+ FT_Int64 delta = (FT_Int64)in_x * out_y - (FT_Int64)in_y * out_x;
+
+
+ if ( delta == 0 )
+ result = 0;
+ else
+ result = 1 - 2 * ( delta < 0 );
+
+#else
+
+ FT_Int64 z1, z2;
+
+
+ /* XXX: this function does not allow 64-bit arguments */
+ ft_multo64( (FT_Int32)in_x, (FT_Int32)out_y, &z1 );
+ ft_multo64( (FT_Int32)in_y, (FT_Int32)out_x, &z2 );
+
+ if ( z1.hi > z2.hi )
+ result = +1;
+ else if ( z1.hi < z2.hi )
+ result = -1;
+ else if ( z1.lo > z2.lo )
+ result = +1;
+ else if ( z1.lo < z2.lo )
+ result = -1;
+ else
+ result = 0;
+
+#endif
+ }
+
+ /* XXX: only the sign of return value, +1/0/-1 must be used */
+ return (FT_Int)result;
+ }
+
+
+ /* documentation is in ftcalc.h */
+
+ FT_BASE_DEF( FT_Int )
+ ft_corner_is_flat( FT_Pos in_x,
+ FT_Pos in_y,
+ FT_Pos out_x,
+ FT_Pos out_y )
+ {
+ FT_Pos ax = in_x + out_x;
+ FT_Pos ay = in_y + out_y;
+
+ FT_Pos d_in, d_out, d_hypot;
+
+
+ /* The idea of this function is to compare the length of the */
+ /* hypotenuse with the `in' and `out' length. The `corner' */
+ /* represented by `in' and `out' is flat if the hypotenuse's */
+ /* length isn't too large. */
+ /* */
+ /* This approach has the advantage that the angle between */
+ /* `in' and `out' is not checked. In case one of the two */
+ /* vectors is `dominant', this is, much larger than the */
+ /* other vector, we thus always have a flat corner. */
+ /* */
+ /* hypotenuse */
+ /* x---------------------------x */
+ /* \ / */
+ /* \ / */
+ /* in \ / out */
+ /* \ / */
+ /* o */
+ /* Point */
+
+ d_in = FT_HYPOT( in_x, in_y );
+ d_out = FT_HYPOT( out_x, out_y );
+ d_hypot = FT_HYPOT( ax, ay );
+
+ /* now do a simple length comparison: */
+ /* */
+ /* d_in + d_out < 17/16 d_hypot */
+
+ return ( d_in + d_out - d_hypot ) < ( d_hypot >> 4 );
+ }
+
+
+/* END */
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