diff options
Diffstat (limited to 'engines/glk/glulxe/float.cpp')
-rw-r--r-- | engines/glk/glulxe/float.cpp | 102 |
1 files changed, 101 insertions, 1 deletions
diff --git a/engines/glk/glulxe/float.cpp b/engines/glk/glulxe/float.cpp index c1ffc77be9..36ef2f479b 100644 --- a/engines/glk/glulxe/float.cpp +++ b/engines/glk/glulxe/float.cpp @@ -20,11 +20,111 @@ * */ -#include "glk/glulxe/float.h" +#include "glk/glulxe/glulxe.h" namespace Glk { namespace Glulxe { +uint Glulxe::encode_float(gfloat32 val) { + gfloat32 absval; + uint sign; + int expo; + gfloat32 mant; + uint fbits; + + if (signbit(val)) { + sign = 0x80000000; + absval = -val; + } + else { + sign = 0x0; + absval = val; + } + + if (isinf(val)) { + return sign | 0x7f800000; /* infinity */ + } + + if (isnan(val)) { + return sign | 0x7fc00000; + } + + mant = frexpf(absval, &expo); + + /* Normalize mantissa to be in the range [1.0, 2.0) */ + if (0.5 <= mant && mant < 1.0) { + mant *= 2.0; + expo--; + } + else if (mant == 0.0) { + expo = 0; + } + else { + return sign | 0x7f800000; /* infinity */ + } + + if (expo >= 128) { + return sign | 0x7f800000; /* infinity */ + } + else if (expo < -126) { + /* Denormalized (very small) number */ + mant = ldexpf(mant, 126 + expo); + expo = 0; + } + else if (!(expo == 0 && mant == 0.0)) { + expo += 127; + mant -= 1.0; /* Get rid of leading 1 */ + } + + mant *= 8388608.0; /* 2^23 */ + fbits = (uint)(mant + 0.5); /* round mant to nearest int */ + if (fbits >> 23) { + /* The carry propagated out of a string of 23 1 bits. */ + fbits = 0; + expo++; + if (expo >= 255) { + return sign | 0x7f800000; /* infinity */ + } + } + + return (sign) | ((uint)(expo << 23)) | (fbits); +} + +gfloat32 Glulxe::decode_float(uint val) { + int sign; + int expo; + uint mant; + gfloat32 res; + + /* First byte */ + sign = ((val & 0x80000000) != 0); + expo = (val >> 23) & 0xFF; + mant = val & 0x7FFFFF; + + if (expo == 255) { + if (mant == 0) { + /* Infinity */ + return (sign ? (-INFINITY) : (INFINITY)); + } + else { + /* Not a number */ + return (sign ? (-NAN) : (NAN)); + } + } + + res = (gfloat32)mant / 8388608.0; + + if (expo == 0) { + expo = -126; + } + else { + res += 1.0; + expo -= 127; + } + res = ldexpf(res, expo); + + return (sign ? (-res) : (res)); +} } // End of namespace Glulxe } // End of namespace Glk |