bc: simplify string-tonumber conversion code

function                                             old     new   delta
bc_program_num                                      1108     983    -125
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-125)           Total: -125 bytes
   text	   data	    bss	    dec	    hex	filename
 985831	    477	   7296	 993604	  f2944	busybox_old
 985706	    477	   7296	 993479	  f28c7	busybox_unstripped

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

1 files changed, 43 insertions, 45 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 71b419d8f..c36486414 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -2199,49 +2199,45 @@ static BcStatus bc_num_binary(BcNum *a, BcNum *b, BcNum *c, size_t scale,
 static bool bc_num_strValid(const char *val, size_t base)
 {
         BcDig b;
-        bool small, radix = false;
-        size_t i, len = strlen(val);
-
-        if (!len) return true;
-
-        small = base <= 10;
-        b = (BcDig)(small ? base + '0' : base - 10 + 'A');
-
-        for (i = 0; i < len; ++i) {
-
-                BcDig c = val[i];
+        bool radix;
 
+        b = (BcDig)(base <= 10 ? base + '0' : base - 10 + 'A');
+        radix = false;
+        for (;;) {
+                BcDig c = *val++;
+                if (c == '\0')
+                        break;
                 if (c == '.') {
-
                         if (radix) return false;
-
                         radix = true;
                         continue;
                 }
-
-                if (c < '0' || (small && c >= b) || (c > '9' && (c < 'A' || c >= b)))
+                if (c < '0' || c >= b || (c > '9' && c < 'A'))
                         return false;
         }
-
         return true;
 }
 
+// Note: n is already "bc_num_zero()"ed,
+// leading zeroes in "val" are removed
 static void bc_num_parseDecimal(BcNum *n, const char *val)
 {
         size_t len, i;
         const char *ptr;
-        bool zero = true;
+        bool zero;
 
-        for (i = 0; val[i] == '0'; ++i);
-
-        val += i;
         len = strlen(val);
-        bc_num_zero(n);
+        if (len == 0)
+                return;
 
-        if (len != 0) {
-                for (i = 0; zero && i < len; ++i) zero = val[i] == '0' || val[i] == '.';
-                bc_num_expand(n, len);
+        zero = true;
+        for (i = 0; val[i]; ++i) {
+                if (val[i] != '0' && val[i] != '.') {
+                        zero = false;
+                        break;
+                }
         }
+        bc_num_expand(n, len);
 
         ptr = strchr(val, '.');
 
@@ -2255,26 +2251,29 @@ static void bc_num_parseDecimal(BcNum *n, const char *val)
         }
 }
 
+// Note: n is already "bc_num_zero()"ed,
+// leading zeroes in "val" are removed
 static void bc_num_parseBase(BcNum *n, const char *val, BcNum *base)
 {
         BcStatus s;
         BcNum temp, mult, result;
         BcDig c = '\0';
-        bool zero = true;
         unsigned long v;
-        size_t i, digits, len = strlen(val);
+        size_t i, digits;
 
-        bc_num_zero(n);
-
-        for (i = 0; zero && i < len; ++i) zero = (val[i] == '.' || val[i] == '0');
-        if (zero) return;
+        for (i = 0; ; ++i) {
+                if (val[i] == '\0')
+                        return;
+                if (val[i] != '.' && val[i] != '0')
+                        break;
+        }
 
         bc_num_init_DEF_SIZE(&temp);
         bc_num_init_DEF_SIZE(&mult);
 
-        for (i = 0; i < len; ++i) {
-
-                c = val[i];
+        for (;;) {
+                c = *val++;
+                if (c == '\0') goto int_err;
                 if (c == '.') break;
 
                 v = (unsigned long) (c <= '9' ? c - '0' : c - 'A' + 10);
@@ -2286,19 +2285,15 @@ static void bc_num_parseBase(BcNum *n, const char *val, BcNum *base)
                 if (s) goto int_err;
         }
 
-        if (i == len) {
-                c = val[i];
-                if (c == 0) goto int_err;
-        }
-
         bc_num_init(&result, base->len);
         //bc_num_zero(&result); - already is
         bc_num_one(&mult);
 
-        for (i += 1, digits = 0; i < len; ++i, ++digits) {
-
-                c = val[i];
-                if (c == 0) break;
+        digits = 0;
+        for (;;) {
+                c = *val++;
+                if (c == '\0') break;
+                digits++;
 
                 v = (unsigned long) (c <= '9' ? c - '0' : c - 'A' + 10);
 
@@ -2318,8 +2313,7 @@ static void bc_num_parseBase(BcNum *n, const char *val, BcNum *base)
 
         if (n->len != 0) {
                 if (n->rdx < digits) bc_num_extend(n, digits - n->rdx);
-        }
-        else
+        } else
                 bc_num_zero(n);
 
 err:
@@ -2498,6 +2492,9 @@ static BcStatus bc_num_parse(BcNum *n, const char *val, BcNum *base,
         if (!bc_num_strValid(val, base_t))
                 return bc_error("bad number string");
 
+        bc_num_zero(n);
+        while (*val == '0') val++;
+
         if (base_t == 10)
                 bc_num_parseDecimal(n, val);
         else
@@ -6387,7 +6384,7 @@ static BcStatus bc_program_asciify(void)
 {
         BcStatus s;
         BcResult *r, res;
-        BcNum *num = NULL, n;
+        BcNum *num, n;
         char *str, *str2, c;
         size_t len = G.prog.strs.len, idx;
         unsigned long val;
@@ -6396,6 +6393,7 @@ static BcStatus bc_program_asciify(void)
                 return bc_error_stack_has_too_few_elements();
         r = bc_vec_top(&G.prog.results);
 
+        num = NULL; // TODO: is this NULL needed?
         s = bc_program_num(r, &num, false);
         if (s) return s;