bc: speed up string printing, fix print ""

function                                             old     new   delta
static.esc                                             -       9      +9
zxc_program_print                                    681     683      +2
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/0 up/down: 11/0)               Total: 11 bytes
   text	   data	    bss	    dec	    hex	filename
 979144	    485	   7296	 986925	  f0f2d	busybox_old
 979062	    485	   7296	 986843	  f0edb	busybox_unstripped

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

2 files changed, 28 insertions, 44 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 1b9cdce5e..bb91216c2 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -5359,7 +5359,7 @@ static char *xc_program_name(char *code, size_t *bgn)
 static void xc_program_printString(const char *str)
 {
 #if ENABLE_DC
-        if (!str[0]) {
+        if (!str[0] && IS_DC) {
                 // Example: echo '[]ap' | dc
                 // should print two bytes: 0x00, 0x0A
                 bb_putchar('\0');
@@ -5367,46 +5367,25 @@ static void xc_program_printString(const char *str)
         }
 #endif
         while (*str) {
-                int c = *str++;
-                if (c != '\\' || !*str)
-                        bb_putchar(c);
-                else {
+                char c = *str++;
+                if (c == '\\') {
+                        static const char esc[] ALIGN1 = "nabfrt""e\\";
+                        char *n;
+
                         c = *str++;
-                        switch (c) {
-                        case 'a':
-                                bb_putchar('\a');
-                                break;
-                        case 'b':
-                                bb_putchar('\b');
-                                break;
-                        case '\\':
-                        case 'e':
-                                bb_putchar('\\');
-                                break;
-                        case 'f':
-                                bb_putchar('\f');
-                                break;
-                        case 'n':
-                                bb_putchar('\n');
-                                G.prog.nchars = SIZE_MAX;
-                                break;
-                        case 'r':
-                                bb_putchar('\r');
-                                break;
-                        case 'q':
-                                bb_putchar('"');
-                                break;
-                        case 't':
-                                bb_putchar('\t');
-                                break;
-                        default:
-                                // Just print the backslash and following character.
+                        n = strchr(esc, c); // note: c can be NUL
+                        if (!n) {
+                                // Just print the backslash and following character
                                 bb_putchar('\\');
                                 ++G.prog.nchars;
-                                bb_putchar(c);
-                                break;
+                        } else {
+                                if (n - esc == 0) // "\n" ?
+                                        G.prog.nchars = SIZE_MAX;
+                                c = "\n\a\b\f\r\t""\\\\""\\"[n - esc];
+                                //   n a b f r t   e \   \<end of line>
                         }
                 }
+                putchar(c);
                 ++G.prog.nchars;
         }
 }
@@ -5631,16 +5610,15 @@ static BC_STATUS zxc_program_print(char inst, size_t idx)
                 str = *xc_program_str(idx);
 
                 if (inst == XC_INST_PRINT_STR) {
-                        for (;;) {
-                                char c = *str++;
-                                if (c == '\0') break;
-                                bb_putchar(c);
-                                ++G.prog.nchars;
-                                if (c == '\n') G.prog.nchars = 0;
-                        }
+                        char *nl;
+                        G.prog.nchars += printf("%s", str);
+                        nl = strrchr(str, '\n');
+                        if (nl)
+                                G.prog.nchars = strlen(nl + 1);
                 } else {
                         xc_program_printString(str);
-                        if (inst == XC_INST_PRINT) bb_putchar('\n');
+                        if (inst == XC_INST_PRINT)
+                                bb_putchar('\n');
                 }
         }
 
diff --git a/testsuite/bc.tests b/testsuite/bc.tests
index 13525ea52..fbcfff2e4 100755
--- a/testsuite/bc.tests
+++ b/testsuite/bc.tests
@@ -149,6 +149,12 @@ testing "bc (!a&&b)" \
         "0\n" \
         "" "(!a&&b)"
 
+# check that dc code is not messing this up (no NUL printing!)
+testing "bc print \"\"" \
+        "bc" \
+        "" \
+        "" "print \"\""
+
 testing "bc print 1,2,3" \
         "bc" \
         "123" \