a

libc/charstod.c

@@ -0,0 +1,81 @@
+#include <u.h>
+#include <libc.h>
+
+/*
+ * Reads a floating-point number by interpreting successive characters
+ * returned by (*f)(vp).  The last call it makes to f terminates the
+ * scan, so is not a character in the number.  It may therefore be
+ * necessary to back up the input stream up one byte after calling charstod.
+ */
+
+#define ADVANCE *s++ = c; if(s>=e) return NaN(); c = (*f)(vp)
+
+double
+charstod(int(*f)(void*), void *vp)
+{
+	char str[400], *s, *e, *start;
+	int c;
+
+	s = str;
+	e = str + sizeof str - 1;
+	c = (*f)(vp);
+	while(c == ' ' || c == '\t')
+		c = (*f)(vp);
+	if(c == '-' || c == '+'){
+		ADVANCE;
+	}
+	start = s;
+	while(c >= '0' && c <= '9'){
+		ADVANCE;
+	}
+	if(c == '.'){
+		ADVANCE;
+		while(c >= '0' && c <= '9'){
+			ADVANCE;
+		}
+	}
+	if(s > start && (c == 'e' || c == 'E')){
+		ADVANCE;
+		if(c == '-' || c == '+'){
+			ADVANCE;
+		}
+		while(c >= '0' && c <= '9'){
+			ADVANCE;
+		}
+	}else if(s == start && (c == 'i' || c == 'I')){
+		ADVANCE;
+		if(c != 'n' && c != 'N')
+			return NaN();
+		ADVANCE;
+		if(c != 'f' && c != 'F')
+			return NaN();
+		ADVANCE;
+		if(c != 'i' && c != 'I')
+			return NaN();
+		ADVANCE;
+		if(c != 'n' && c != 'N')
+			return NaN();
+		ADVANCE;
+		if(c != 'i' && c != 'I')
+			return NaN();
+		ADVANCE;
+		if(c != 't' && c != 'T')
+			return NaN();
+		ADVANCE;
+		if(c != 'y' && c != 'Y')
+			return NaN();
+		ADVANCE;  /* so caller can back up uniformly */
+		USED(c);
+	}else if(s == str && (c == 'n' || c == 'N')){
+		ADVANCE;
+		if(c != 'a' && c != 'A')
+			return NaN();
+		ADVANCE;
+		if(c != 'n' && c != 'N')
+			return NaN();
+		ADVANCE;  /* so caller can back up uniformly */
+		USED(c);
+	}
+	*s = 0;
+	return strtod(str, &s);
+}