shell: implement optional "BASE#nnnn" numeric literals

function                                             old     new   delta
evaluate_string                                      729     851    +122

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/Config.src

@@ -99,6 +99,11 @@ config FEATURE_SH_MATH_64
 	slightly larger, but will allow computation with very large numbers.
 	This is not in POSIX, so do not rely on this in portable code.
 
+config FEATURE_SH_MATH_BASE
+	bool "Support BASE#nnnn literals"
+	default y
+	depends on FEATURE_SH_MATH
+
 config FEATURE_SH_EXTRA_QUIET
 	bool "Hide message on interactive shell startup"
 	default y

shell/math.c

@@ -513,6 +513,42 @@ static const char op_tokens[] ALIGN1 = {
 };
 #define ptr_to_rparen (&op_tokens[sizeof(op_tokens)-7])
 
+#if ENABLE_FEATURE_SH_MATH_BASE
+static arith_t strto_arith_t(const char *nptr, char **endptr)
+{
+	unsigned base;
+	arith_t n;
+
+# if ENABLE_FEATURE_SH_MATH_64
+	n = strtoull(nptr, endptr, 0);
+# else
+	n = strtoul(nptr, endptr, 0);
+# endif
+	if (**endptr != '#'
+	 || (*nptr < '1' || *nptr > '9')
+	 || (n < 2 || n > 64)
+	) {
+		return n;
+	}
+
+	/* It's "N#nnnn" or "NN#nnnn" syntax, NN can't start with 0,
+	 * NN is in 2..64 range.
+	 */
+	base = (unsigned)n;
+	n = 0;
+	nptr = *endptr + 1;
+	/* bash allows "N#" (empty "nnnn" part) */
+	while (isdigit(*nptr)) {
+		/* bash does not check for overflows */
+		n = n * base + (*nptr++ - '0');
+	}
+	*endptr = (char*)nptr;
+	return n;
+}
+#define strto_arith_t(nptr, endptr, base_is_always_0) \
+	strto_arith_t(nptr, endptr)
+#endif
+
 static arith_t FAST_FUNC
 evaluate_string(arith_state_t *math_state, const char *expr)
 {

shell/math.h

@@ -65,15 +65,19 @@ PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
 
 #if ENABLE_FEATURE_SH_MATH_64
 typedef long long arith_t;
-#define ARITH_FMT "%lld"
+# define ARITH_FMT "%lld"
-#define strto_arith_t strtoull
 #else
 typedef long arith_t;
-#define ARITH_FMT "%ld"
+# define ARITH_FMT "%ld"
-#define strto_arith_t strtoul
+#endif
+
+#if !ENABLE_FEATURE_SH_MATH_BASE
+# if ENABLE_FEATURE_SH_MATH_64
+#  define strto_arith_t strtoull
+# else
+#  define strto_arith_t strtoul
+# endif
 #endif
-//TODO: bash supports "BASE#nnnnn" numeric literals, e.g. 2#1111 = 15.
-//Make strto_arith_t() support that?
 
 typedef const char* FAST_FUNC (*arith_var_lookup_t)(const char *name);
 typedef void        FAST_FUNC (*arith_var_set_t)(const char *name, const char *val);