ref: 4fd9cc73e672de3223a44e9034f788de6641efd0
parent: 4a32dce92a0ff00d824b3ec512b8f6dff28dcaa2
author: Werner Lemberg <[email protected]>
date: Tue Mar 14 15:40:50 EDT 2017
[sfnt] Implement PS names for font instances [2/3]. * src/sfnt/sfdriver.c (fix2float) [TT_CONFIG_OPTION_GX_VAR_SUPPORT]: New function to find the shortest representation of a 16.16 fractional number.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
2017-03-14 Werner Lemberg <[email protected]>
+ [sfnt] Implement PS names for font instances [2/3].
+
+ * src/sfnt/sfdriver.c (fix2float) [TT_CONFIG_OPTION_GX_VAR_SUPPORT]:
+ New function to find the shortest representation of a 16.16
+ fractional number.
+
+2017-03-14 Werner Lemberg <[email protected]>
+
[sfnt] Implement PS names for font instances [1/3].
Add 128bit MurmurHash 3 function.
--- a/src/sfnt/sfdriver.c
+++ b/src/sfnt/sfdriver.c
@@ -601,6 +601,126 @@
}
+#ifdef TT_CONFIG_OPTION_GX_VAR_SUPPORT
+
+ /*
+ * Find the shortest decimal representation of a 16.16 fixed point
+ * number. The function fills `buf' with the result, returning a pointer
+ * to the position after the representation's last byte.
+ */
+
+ static char*
+ fixed2float( FT_Int fixed,
+ char* buf )
+ {+ char* p;
+ char* q;
+ char tmp[5];
+
+ FT_Int int_part;
+ FT_Int frac_part;
+
+ FT_Int i;
+
+
+ p = buf;
+
+ if ( fixed == 0 )
+ {+ *p++ = '0';
+ return p;
+ }
+
+ if ( fixed < 0 )
+ {+ *p++ = '-';
+ fixed = -fixed;
+ }
+
+ int_part = ( fixed >> 16 ) & 0xFFFF;
+ frac_part = fixed & 0xFFFF;
+
+ /* get digits of integer part (in reverse order) */
+ q = tmp;
+ while ( int_part > 0 )
+ {+ *q++ = '0' + int_part % 10;
+ int_part /= 10;
+ }
+
+ /* copy digits in correct order to buffer */
+ while ( q > tmp )
+ *p++ = *--q;
+
+ if ( !frac_part )
+ return p;
+
+ /* save position of point */
+ q = p;
+ *p++ = '.';
+
+ /* apply rounding */
+ frac_part = frac_part * 10 + 5;
+
+ /* get digits of fractional part */
+ for ( i = 0; i < 5; i++ )
+ {+ *p++ = '0' + frac_part / 0x10000L;
+
+ frac_part %= 0x10000L;
+ if ( !frac_part )
+ break;
+
+ frac_part *= 10;
+ }
+
+ /*
+ If the remainder stored in `frac_part' (after the last FOR loop) is
+ smaller than 34480*10, the resulting decimal value minus 0.00001 is
+ an equivalent representation of `fixed'.
+
+ The above FOR loop always finds the larger of the two values; I
+ verified this by iterating over all possible fixed point numbers.
+
+ If the remainder is 17232*10, both values are equally good, and we
+ take the next even number (following IEEE 754's `round to nearest,
+ ties to even' rounding rule).
+
+ If the remainder is smaller than 17232*10, the lower of the two
+ numbers is nearer to the exact result (values 17232 and 34480 were
+ also found by testing all possible fixed point values).
+
+ We use this to find a shorter decimal representation. If not ending
+ with digit zero, we take the representation with less error.
+ */
+ p--;
+ if ( p - q == 5 ) /* five digits? */
+ {+ /* take the representation that has zero as the last digit */
+ if ( frac_part < 34480 * 10 &&
+ *p == '1' )
+ *p = '0';
+
+ /* otherwise use the one with less error */
+ else if ( frac_part == 17232 * 10 &&
+ *p & 1 )
+ *p -= 1;
+
+ else if ( frac_part < 17232 * 10 &&
+ *p != '0' )
+ *p -= 1;
+ }
+
+ /* remove trailing zeros */
+ while ( *p == '0' )
+ *p-- = '\0';
+
+ return p + 1;
+ }
+
+#endif /* TT_CONFIG_OPTION_GX_VAR_SUPPORT */
+
+
static const char*
sfnt_get_ps_name( TT_Face face )
{