libmach

src/libmach/ieee.c

@@ -0,0 +1,169 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <mach.h>
+
+/*
+ * These routines assume that if the number is representable
+ * in IEEE floating point, it will be representable in the native
+ * double format.  Naive but workable, probably.
+ */
+int
+ieeeftoa64(char *buf, uint n, u32int h, u32int l)
+{
+	double fr;
+	int exp;
+
+	if (n <= 0)
+		return 0;
+
+
+	if(h & (1L<<31)){
+		*buf++ = '-';
+		h &= ~(1L<<31);
+	}else
+		*buf++ = ' ';
+	n--;
+	if(l == 0 && h == 0)
+		return snprint(buf, n, "0.");
+	exp = (h>>20) & ((1L<<11)-1L);
+	if(exp == 0)
+		return snprint(buf, n, "DeN(%.8lux%.8lux)", h, l);
+	if(exp == ((1L<<11)-1L)){
+		if(l==0 && (h&((1L<<20)-1L)) == 0)
+			return snprint(buf, n, "Inf");
+		else
+			return snprint(buf, n, "NaN(%.8lux%.8lux)", h&((1L<<20)-1L), l);
+	}
+	exp -= (1L<<10) - 2L;
+	fr = l & ((1L<<16)-1L);
+	fr /= 1L<<16;
+	fr += (l>>16) & ((1L<<16)-1L);
+	fr /= 1L<<16;
+	fr += (h & (1L<<20)-1L) | (1L<<20);
+	fr /= 1L<<21;
+	fr = ldexp(fr, exp);
+	return snprint(buf, n, "%.18g", fr);
+}
+
+int
+ieeeftoa32(char *buf, uint n, u32int h)
+{
+	double fr;
+	int exp;
+
+	if (n <= 0)
+		return 0;
+
+	if(h & (1L<<31)){
+		*buf++ = '-';
+		h &= ~(1L<<31);
+	}else
+		*buf++ = ' ';
+	n--;
+	if(h == 0)
+		return snprint(buf, n, "0.");
+	exp = (h>>23) & ((1L<<8)-1L);
+	if(exp == 0)
+		return snprint(buf, n, "DeN(%.8lux)", h);
+	if(exp == ((1L<<8)-1L)){
+		if((h&((1L<<23)-1L)) == 0)
+			return snprint(buf, n, "Inf");
+		else
+			return snprint(buf, n, "NaN(%.8lux)", h&((1L<<23)-1L));
+	}
+	exp -= (1L<<7) - 2L;
+	fr = (h & ((1L<<23)-1L)) | (1L<<23);
+	fr /= 1L<<24;
+	fr = ldexp(fr, exp);
+	return snprint(buf, n, "%.9g", fr);
+}
+
+int
+beieeeftoa32(char *buf, uint n, void *s)
+{
+	return ieeeftoa32(buf, n, beswap4(*(u32int*)s));
+}
+
+int
+beieeeftoa64(char *buf, uint n, void *s)
+{
+	return ieeeftoa64(buf, n, beswap4(*(u32int*)s), beswap4(((u32int*)(s))[1]));
+}
+
+int
+leieeeftoa32(char *buf, uint n, void *s)
+{
+	return ieeeftoa32(buf, n, leswap4(*(u32int*)s));
+}
+
+int
+leieeeftoa64(char *buf, uint n, void *s)
+{
+	return ieeeftoa64(buf, n, leswap4(((u32int*)(s))[1]), leswap4(*(u32int*)s));
+}
+
+/* packed in 12 bytes, with s[2]==s[3]==0; mantissa starts at s[4]*/
+int
+beieeeftoa80(char *buf, uint n, void *s)
+{
+	uchar *reg = (uchar*)s;
+	int i;
+	ulong x;
+	uchar ieee[8+8];	/* room for slop */
+	uchar *p, *q;
+
+	memset(ieee, 0, sizeof(ieee));
+	/* sign */
+	if(reg[0] & 0x80)
+		ieee[0] |= 0x80;
+
+	/* exponent */
+	x = ((reg[0]&0x7F)<<8) | reg[1];
+	if(x == 0)		/* number is ±0 */
+		goto done;
+	if(x == 0x7FFF){
+		if(memcmp(reg+4, ieee+1, 8) == 0){ /* infinity */
+			x = 2047;
+		}else{				/* NaN */
+			x = 2047;
+			ieee[7] = 0x1;		/* make sure */
+		}
+		ieee[0] |= x>>4;
+		ieee[1] |= (x&0xF)<<4;
+		goto done;
+	}
+	x -= 0x3FFF;		/* exponent bias */
+	x += 1023;
+	if(x >= (1<<11) || ((reg[4]&0x80)==0 && x!=0))
+		return snprint(buf, n, "not in range");
+	ieee[0] |= x>>4;
+	ieee[1] |= (x&0xF)<<4;
+
+	/* mantissa */
+	p = reg+4;
+	q = ieee+1;
+	for(i=0; i<56; i+=8, p++, q++){	/* move one byte */
+		x = (p[0]&0x7F) << 1;
+		if(p[1] & 0x80)
+			x |= 1;
+		q[0] |= x>>4;
+		q[1] |= (x&0xF)<<4;
+	}
+    done:
+	return beieeeftoa64(buf, n, (void*)ieee);
+}
+
+
+int
+leieeeftoa80(char *buf, uint n, void *s)
+{
+	int i;
+	char *cp;
+	char b[12];
+
+	cp = (char*) s;
+	for(i=0; i<12; i++)
+		b[11-i] = *cp++;
+	return beieeeftoa80(buf, n, b);
+}