bc: simple speedups

function                                             old     new   delta
bc_parse_pushName                                     20      56     +36
bc_program_index                                      47      71     +24
bc_parse_pushIndex                                    52      58      +6
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 66/0)               Total: 66 bytes

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

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 2569967d61bf99debc1e4efeeea6fe75474a7e49..cf04e9ff1fe81e735151439e7a9bd9b1a8c8fdc3 100644 (file)
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -3439,17 +3439,38 @@ static void bc_parse_push(char i)
 
 static void bc_parse_pushName(char *name)
 {
+#if 1
+       BcVec *code = &G.prs.func->code;
+       size_t pos = code->len;
+       size_t len = strlen(name) + 1;
+
+       bc_vec_expand(code, pos + len);
+       strcpy(code->v + pos, name);
+       code->len = pos + len;
+#else
+       // Smaller code, but way slow:
        do {
                bc_parse_push(*name);
        } while (*name++);
+#endif
 }
 
+// Indexes < 0xfc are encoded verbatim, else first byte is
+// 0xfc, 0xfd, 0xfe or 0xff, encoding "1..4 bytes",
+// followed by that many bytes, lsb first.
+// (The above describes 32-bit case).
+#define SMALL_INDEX_LIMIT (0x100 - sizeof(size_t))
+
 static void bc_parse_pushIndex(size_t idx)
 {
        size_t mask;
        unsigned amt;
 
        dbg_lex("%s:%d pushing index %zd", __func__, __LINE__, idx);
+       if (idx < SMALL_INDEX_LIMIT) {
+               goto push_idx;
+       }
+
        mask = ((size_t)0xff) << (sizeof(idx) * 8 - 8);
        amt = sizeof(idx);
        do {
@@ -3458,9 +3479,10 @@ static void bc_parse_pushIndex(size_t idx)
                amt--;
        } while (amt != 0);
 
-       bc_parse_push(amt);
+       bc_parse_push(SMALL_INDEX_LIMIT + amt);
 
        while (idx != 0) {
+ push_idx:
                bc_parse_push((unsigned char)idx);
                idx >>= 8;
        }
@@ -5257,6 +5279,11 @@ static size_t bc_program_index(char *code, size_t *bgn)
        size_t res;
 
        amt = *bytes++;
+       if (amt < SMALL_INDEX_LIMIT) {
+               *bgn += 1;
+               return amt;
+       }
+       amt -= SMALL_INDEX_LIMIT;
        *bgn += amt + 1;
 
        amt *= 8;