runtime: reconstitute runetochar for use by gostringw.

Fixes windows builds (hopefully).

LGTM=bradfitz
R=golang-codereviews, bradfitz, alex.brainman
CC=golang-codereviews
https://golang.org/cl/103470045

1 files changed, 90 insertions, 2 deletions

diff --git a/src/pkg/runtime/string.c b/src/pkg/runtime/string.c
index d5b668bd61..60a0545a9a 100644
--- a/src/pkg/runtime/string.c
+++ b/src/pkg/runtime/string.c
@@ -100,6 +100,94 @@ runtime·gostringnocopy(byte *str)
 	return s;
 }
 
+// TODO: move this elsewhere
+enum
+{
+	Bit1	= 7,
+	Bitx	= 6,
+	Bit2	= 5,
+	Bit3	= 4,
+	Bit4	= 3,
+	Bit5	= 2,
+
+	Tx	= ((1<<(Bitx+1))-1) ^ 0xFF,	/* 1000 0000 */
+	T2	= ((1<<(Bit2+1))-1) ^ 0xFF,	/* 1100 0000 */
+	T3	= ((1<<(Bit3+1))-1) ^ 0xFF,	/* 1110 0000 */
+	T4	= ((1<<(Bit4+1))-1) ^ 0xFF,	/* 1111 0000 */
+
+	Rune1	= (1<<(Bit1+0*Bitx))-1,		/* 0000 0000 0111 1111 */
+	Rune2	= (1<<(Bit2+1*Bitx))-1,		/* 0000 0111 1111 1111 */
+	Rune3	= (1<<(Bit3+2*Bitx))-1,		/* 1111 1111 1111 1111 */
+
+	Maskx	= (1<<Bitx)-1,			/* 0011 1111 */
+
+	Runeerror	= 0xFFFD,
+
+	SurrogateMin = 0xD800,
+	SurrogateMax = 0xDFFF,
+
+	Runemax	= 0x10FFFF,	/* maximum rune value */
+};
+
+static int32
+runetochar(byte *str, int32 rune)  /* note: in original, arg2 was pointer */
+{
+	/* Runes are signed, so convert to unsigned for range check. */
+	uint32 c;
+
+	/*
+	 * one character sequence
+	 *	00000-0007F => 00-7F
+	 */
+	c = rune;
+	if(c <= Rune1) {
+		str[0] = c;
+		return 1;
+	}
+
+	/*
+	 * two character sequence
+	 *	0080-07FF => T2 Tx
+	 */
+	if(c <= Rune2) {
+		str[0] = T2 | (c >> 1*Bitx);
+		str[1] = Tx | (c & Maskx);
+		return 2;
+	}
+
+	/*
+	 * If the Rune is out of range or a surrogate half, convert it to the error rune.
+	 * Do this test here because the error rune encodes to three bytes.
+	 * Doing it earlier would duplicate work, since an out of range
+	 * Rune wouldn't have fit in one or two bytes.
+	 */
+	if (c > Runemax)
+		c = Runeerror;
+	if (SurrogateMin <= c && c <= SurrogateMax)
+		c = Runeerror;
+
+	/*
+	 * three character sequence
+	 *	0800-FFFF => T3 Tx Tx
+	 */
+	if (c <= Rune3) {
+		str[0] = T3 |  (c >> 2*Bitx);
+		str[1] = Tx | ((c >> 1*Bitx) & Maskx);
+		str[2] = Tx |  (c & Maskx);
+		return 3;
+	}
+
+	/*
+	 * four character sequence (21-bit value)
+	 *     10000-1FFFFF => T4 Tx Tx Tx
+	 */
+	str[0] = T4 | (c >> 3*Bitx);
+	str[1] = Tx | ((c >> 2*Bitx) & Maskx);
+	str[2] = Tx | ((c >> 1*Bitx) & Maskx);
+	str[3] = Tx | (c & Maskx);
+	return 4;
+}
+
 String
 runtime·gostringw(uint16 *str)
 {
@@ -109,14 +197,14 @@ runtime·gostringw(uint16 *str)
 
 	n1 = 0;
 	for(i=0; str[i]; i++)
-		n1 += runtime·runetochar(buf, str[i]);
+		n1 += runetochar(buf, str[i]);
 	s = gostringsize(n1+4);
 	n2 = 0;
 	for(i=0; str[i]; i++) {
 		// check for race
 		if(n2 >= n1)
 			break;
-		n2 += runtime·runetochar(s.str+n2, str[i]);
+		n2 += runetochar(s.str+n2, str[i]);
 	}
 	s.len = n2;
 	s.str[s.len] = 0;