shell: better comments in BASE#nn code
function old new delta
evaluate_string 932 930 -2
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/math.c b/shell/math.c
index af1ab55..aac5017 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -537,25 +537,23 @@
base = (unsigned)n;
n = 0;
nptr = *endptr + 1;
- /* bash allows "N#" (empty "nnnn" part) */
for (;;) {
unsigned digit = (unsigned)*nptr - '0';
- if (digit >= 10) {
- /* *nptr is not 0..9 */
- if (*nptr > 'z')
- break; /* this rejects e.g. $((64#~)) */
+ if (digit >= 10 /* not 0..9 */
+ && digit <= 'z' - '0' /* needed to reject e.g. $((64#~)) */
+ ) {
/* in bases up to 36, case does not matter for a-z */
digit = (unsigned)(*nptr | 0x20) - ('a' - 10);
if (base > 36 && *nptr <= '_') {
- /* otherwise, A-Z,@,_ are 36..61,62,63 */
- if (*nptr == '@')
- digit = 62;
- else if (*nptr == '_')
+ /* otherwise, A-Z,@,_ are 36-61,62,63 */
+ if (*nptr == '_')
digit = 63;
+ else if (*nptr == '@')
+ digit = 62;
else if (digit < 36) /* A-Z */
digit += 36 - 10;
else
- break; /* error, such as [ or \ */
+ break; /* error: one of [\]^ */
}
//bb_error_msg("ch:'%c'%d digit:%u", *nptr, *nptr, digit);
//if (digit < 10) - example where we need this?
@@ -567,6 +565,12 @@
n = n * base + digit;
nptr++;
}
+ /* Note: we do not set errno on bad chars, we just set a pointer
+ * to the first invalid char. For example, this allows
+ * "N#" (empty "nnnn" part): 64#+1 is a valid expression,
+ * it means 64# + 1, whereas 64#~... is not, since ~ is not a valid
+ * operator.
+ */
*endptr = (char*)nptr;
return n;
}