Make our 'ascii_strtod()' helper more generic

We'll want to do sane parsing of strings, but the C library makes it
hard to handle user input sanely and the Qt toDouble() function
interface was designed by a retarded chipmunk.

So just extend our existing hacky "ascii_strtod()" to allow a more
generic interface.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 130 insertions, 0 deletions

diff --git a/strtod.c b/strtod.c
new file mode 100644
index 000000000..4643cfe9d
--- /dev/null
+++ b/strtod.c
@@ -0,0 +1,130 @@
+/*
+ * Sane helper for 'strtod()'.
+ *
+ * Sad that we even need this, but the C library version has
+ * insane locale behavior, and while the Qt "doDouble()" routines
+ * are better in that regard, they don't have an end pointer
+ * (having replaced it with the completely idiotic "ok" boolean
+ * pointer instead).
+ *
+ * I wonder what drugs people are on sometimes.
+ *
+ * Right now we support the following flags to limit the
+ * parsing some ways:
+ *
+ *   STRTOD_NO_SIGN	- don't accept signs
+ *   STRTOD_NO_DOT	- no decimal dots, I'm European
+ *   STRTOD_NO_COMMA	- no comma, please, I'm C locale
+ *   STRTOD_NO_EXPONENT	- no exponent parsing, I'm human
+ *
+ * The "negative" flags are so that the common case can just
+ * use a flag value of 0, and only if you have some special
+ * requirements do you need to state those with explicit flags.
+ *
+ * So if you want the C locale kind of parsing, you'd use the
+ * STRTOD_NO_COMMA flag to disallow a decimal comma. But if you
+ * want a more relaxed "Hey, Europeans are people too, even if
+ * they have locales with commas", just pass in a zero flag.
+ */
+#include <ctype.h>
+#include "dive.h"
+
+double strtod_flags(char *str, char **ptr, unsigned int flags)
+{
+	char *p = str, c, *ep;
+	double val = 0.0;
+	double decimal = 1.0;
+	int sign = 0, esign = 0;
+	int numbers = 0, dot = 0;
+
+	/* skip spaces */
+	while (isspace(c = *p++))
+		/* */;
+
+	/* optional sign */
+	if (!(flags & STRTOD_NO_SIGN)) {
+		switch (c) {
+		case '-':
+			sign = 1;
+			/* fallthrough */
+		case '+':
+			c = *p++;
+		}
+	}
+
+	/* Mantissa */
+	for (;;c = *p++) {
+		if ((c == '.' && !(flags & STRTOD_NO_DOT)) ||
+		    (c == ',' && !(flags & STRTOD_NO_COMMA))) {
+			if (dot)
+				goto done;
+			dot = 1;
+			continue;
+		}
+		if (c >= '0' && c <= '9') {
+			numbers++;
+			if (dot) {
+				decimal /= 10;
+				val += (c - '0') * decimal;
+			} else {
+				val = (val * 10) + (c - '0');
+			}
+			continue;
+		}
+		if (c != 'e' && c != 'E')
+			goto done;
+		if (flags & STRTOD_NO_EXPONENT)
+			goto done;
+		break;
+	}
+
+	if (!numbers)
+		goto done;
+
+	/* Exponent */
+	ep = p;
+	c = *ep++;
+	switch (c) {
+	case '-':
+		esign = 1;
+		/* fallthrough */
+	case '+':
+		c = *ep++;
+	}
+
+	if (c >= '0' && c <= '9') {
+		p = ep;
+		int exponent = c - '0';
+
+		for (;;) {
+			c = *p++;
+			if (c < '0' || c > '9')
+				break;
+			exponent *= 10;
+			exponent += c - '0';
+		}
+
+		/* We're not going to bother playing games */
+		if (exponent > 308)
+			exponent = 308;
+
+		while (exponent-- > 0) {
+			if (esign)
+				val /= 10;
+			else
+				val *= 10;
+		}
+	}
+
+done:
+	if (!numbers)
+		goto no_conversion;
+	if (ptr)
+		*ptr = p-1;
+	return sign ? -val : val;
+
+no_conversion:
+	if (ptr)
+		*ptr = str;
+	return 0.0;
+}