bc: simplify input pointer manipulation while lexing

function                                             old     new   delta
bc_lex_name                                           70      68      -2
zbc_lex_number                                       177     174      -3
bc_vm_init                                           679     676      -3
bc_lex_whitespace                                     42      39      -3
zbc_parse_text_init                                   55      51      -4
bc_lex_lineComment                                    37      29      -8
bc_lex_assign                                         34      26      -8
zbc_lex_next                                        2039    1965     -74
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/8 up/down: 0/-105)           Total: -105 bytes

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

1 files changed, 55 insertions, 60 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 61fb24304..809b4bfc4 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -714,10 +714,9 @@ typedef struct BcParse {
         smallint lex;      // was BcLexType // first member is most used
         smallint lex_last; // was BcLexType
         bool   lex_newline;
-        size_t lex_i;
         size_t lex_line;
-        size_t lex_len;
         const char *lex_inbuf;
+        const char *lex_end;
         const char *lex_next_at; // last lex_next() was called at this string
         const char *lex_filename;
         FILE *lex_input_fp;
@@ -2748,12 +2747,9 @@ static void bc_lex_lineComment(void)
 {
         BcParse *p = &G.prs;
         // Try: echo -n '#foo' | bc
-        size_t i;
         p->lex = XC_LEX_WHITESPACE;
-        i = p->lex_i;
-        while (i < p->lex_len && p->lex_inbuf[i] != '\n')
-                i++;
-        p->lex_i = i;
+        while (p->lex_inbuf < p->lex_end && *p->lex_inbuf != '\n')
+                p->lex_inbuf++;
 }
 
 static void bc_lex_whitespace(void)
@@ -2761,19 +2757,19 @@ static void bc_lex_whitespace(void)
         BcParse *p = &G.prs;
         p->lex = XC_LEX_WHITESPACE;
         for (;;) {
-                char c = p->lex_inbuf[p->lex_i];
+                char c = *p->lex_inbuf;
                 if (c == '\n') // this is XC_LEX_NLINE, not XC_LEX_WHITESPACE
                         break;
                 if (!isspace(c))
                         break;
-                p->lex_i++;
+                p->lex_inbuf++;
         }
 }
 
 static BC_STATUS zbc_lex_number(char start)
 {
         BcParse *p = &G.prs;
-        const char *buf = p->lex_inbuf + p->lex_i;
+        const char *buf = p->lex_inbuf;
         size_t len, i, ccnt;
         bool pt;
 
@@ -2803,7 +2799,7 @@ static BC_STATUS zbc_lex_number(char start)
         //ccnt is the number of chars in the number string, excluding possible
         //trailing "[\<newline>].[\<newline>]" (with any number of \<NL> repetitions).
         //i is buf[i] index of the first not-yet-parsed char after that.
-        p->lex_i += i;
+        p->lex_inbuf += i;
 
         // This might overestimate the size, if there are "\<NL>"'s
         // in the number. Subtracting number_of_backslashes*2 correctly
@@ -2850,7 +2846,7 @@ static void bc_lex_name(void)
         p->lex = XC_LEX_NAME;
 
         i = 0;
-        buf = p->lex_inbuf + p->lex_i - 1;
+        buf = p->lex_inbuf - 1;
         for (;;) {
                 char c = buf[i];
                 if ((c < 'a' || c > 'z') && !isdigit(c) && c != '_') break;
@@ -2867,7 +2863,7 @@ static void bc_lex_name(void)
         bc_vec_string(&p->lex_strnumbuf, i, buf);
 
         // Increment the index. We minus 1 because it has already been incremented.
-        p->lex_i += i - 1;
+        p->lex_inbuf += i - 1;
 
         //return BC_STATUS_SUCCESS;
 }
@@ -2954,11 +2950,10 @@ static bool bc_lex_more_input(void)
         }
 
         p->lex_inbuf = G.input_buffer.v;
-        p->lex_i = 0;
 //      bb_error_msg("G.input_buffer.len:%d '%s'", G.input_buffer.len, G.input_buffer.v);
-        p->lex_len = G.input_buffer.len - 1; // do not include NUL
+        p->lex_end = p->lex_inbuf + G.input_buffer.len - 1; // do not include NUL
 
-        return p->lex_len != 0;
+        return G.input_buffer.len > 1;
 }
 
 IF_BC(static BC_STATUS zbc_lex_token(void);)
@@ -2983,7 +2978,7 @@ static BC_STATUS zbc_lex_next(void)
         // Comments are also XC_LEX_WHITESPACE tokens and eaten here.
         s = BC_STATUS_SUCCESS;
         do {
-                if (p->lex_i == p->lex_len) {
+                if (p->lex_inbuf == p->lex_end) {
                         p->lex = XC_LEX_EOF;
                         if (!G.prs.lex_input_fp)
                                 RETURN_STATUS(BC_STATUS_SUCCESS);
@@ -2991,9 +2986,9 @@ static BC_STATUS zbc_lex_next(void)
                                 G.prs.lex_input_fp = NULL;
                                 RETURN_STATUS(BC_STATUS_SUCCESS);
                         }
-                        // here it's guaranteed that p->lex_i is below p->lex_len
+                        // here it's guaranteed that p->lex_ibuf is below p->lex_end
                 }
-                p->lex_next_at = p->lex_inbuf + p->lex_i;
+                p->lex_next_at = p->lex_inbuf;
                 dbg_lex("next string to parse:'%.*s'",
                         (int)(strchrnul(p->lex_next_at, '\n') - p->lex_next_at),
                         p->lex_next_at
@@ -3034,8 +3029,7 @@ static BC_STATUS zbc_lex_next_and_skip_NLINE(void)
 static BC_STATUS zbc_lex_text_init(const char *text)
 {
         G.prs.lex_inbuf = text;
-        G.prs.lex_i = 0;
-        G.prs.lex_len = strlen(text);
+        G.prs.lex_end = text + strlen(text);
         G.prs.lex = G.prs.lex_last = XC_LEX_INVALID;
         RETURN_STATUS(zbc_lex_next());
 }
@@ -3047,7 +3041,7 @@ static BC_STATUS zbc_lex_identifier(void)
         BcParse *p = &G.prs;
         BcStatus s;
         unsigned i;
-        const char *buf = p->lex_inbuf + p->lex_i - 1;
+        const char *buf = p->lex_inbuf - 1;
 
         for (i = 0; i < ARRAY_SIZE(bc_lex_kws); ++i) {
                 const char *keyword8 = bc_lex_kws[i].name8;
@@ -3069,7 +3063,7 @@ static BC_STATUS zbc_lex_identifier(void)
                 }
 
                 // We minus 1 because the index has already been incremented.
-                p->lex_i += j - 1;
+                p->lex_inbuf += j - 1;
                 RETURN_STATUS(BC_STATUS_SUCCESS);
         }
 
@@ -3097,11 +3091,11 @@ static BC_STATUS zbc_lex_string(void)
         p->lex = XC_LEX_STR;
 
         nls = 0;
-        i = p->lex_i;
+        i = 0;
         for (;;) {
                 char c = p->lex_inbuf[i];
                 if (c == '\0') {
-                        p->lex_i = i;
+                        p->lex_inbuf += i;
                         RETURN_STATUS(bc_error("unterminated string"));
                 }
                 if (c == '"')
@@ -3110,15 +3104,15 @@ static BC_STATUS zbc_lex_string(void)
                 i++;
         }
 
-        len = i - p->lex_i;
+        len = i;
         // This check makes sense only if size_t is (much) larger than BC_MAX_STRING.
         if (SIZE_MAX > (BC_MAX_STRING | 0xff)) {
                 if (len > BC_MAX_STRING)
                         RETURN_STATUS(bc_error("string too long: must be [1,"BC_MAX_STRING_STR"]"));
         }
-        bc_vec_string(&p->lex_strnumbuf, len, p->lex_inbuf + p->lex_i);
+        bc_vec_string(&p->lex_strnumbuf, len, p->lex_inbuf);
 
-        p->lex_i = i + 1;
+        p->lex_inbuf += i + 1;
         p->lex_line += nls;
         G.err_line = p->lex_line;
 
@@ -3129,8 +3123,8 @@ static BC_STATUS zbc_lex_string(void)
 static void bc_lex_assign(unsigned with_and_without)
 {
         BcParse *p = &G.prs;
-        if (p->lex_inbuf[p->lex_i] == '=') {
-                p->lex_i++;
+        if (*p->lex_inbuf == '=') {
+                p->lex_inbuf++;
                 with_and_without >>= 8; // store "with" value
         } // else store "without" value
         p->lex = (with_and_without & 0xff);
@@ -3145,7 +3139,7 @@ static BC_STATUS zbc_lex_comment(void)
         const char *buf = p->lex_inbuf;
 
         p->lex = XC_LEX_WHITESPACE;
-        i = p->lex_i; /* here buf[p->lex_i] is the '*' of opening comment delimiter */
+        i = 0; /* here lex_inbuf[0] is the '*' of opening comment delimiter */
         for (;;) {
                 char c = buf[++i];
  check_star:
@@ -3156,13 +3150,13 @@ static BC_STATUS zbc_lex_comment(void)
                         goto check_star;
                 }
                 if (c == '\0') {
-                        p->lex_i = i;
+                        p->lex_inbuf += i;
                         RETURN_STATUS(bc_error("unterminated comment"));
                 }
                 nls += (c == '\n');
         }
 
-        p->lex_i = i + 1;
+        p->lex_inbuf += i + 1;
         p->lex_line += nls;
         G.err_line = p->lex_line;
 
@@ -3175,12 +3169,13 @@ static BC_STATUS zbc_lex_token(void)
 {
         BcParse *p = &G.prs;
         BcStatus s = BC_STATUS_SUCCESS;
-        char c = p->lex_inbuf[p->lex_i++], c2;
+        char c = *p->lex_inbuf++;
+        char c2;
 
         // This is the workhorse of the lexer.
         switch (c) {
 //              case '\0': // probably never reached
-//                      p->lex_i--;
+//                      p->lex_inbuf--;
 //                      p->lex = XC_LEX_EOF;
 //                      p->lex_newline = true;
 //                      break;
@@ -3214,11 +3209,11 @@ static BC_STATUS zbc_lex_token(void)
                         bc_lex_assign(BC_LEX_OP_ASSIGN_MODULUS, XC_LEX_OP_MODULUS);
                         break;
                 case '&':
-                        c2 = p->lex_inbuf[p->lex_i];
+                        c2 = *p->lex_inbuf;
                         if (c2 == '&') {
                                 s = zbc_POSIX_does_not_allow_bool_ops_this_is_bad("&&");
                                 if (s) RETURN_STATUS(s);
-                                p->lex_i++;
+                                p->lex_inbuf++;
                                 p->lex = BC_LEX_OP_BOOL_AND;
                         } else {
                                 p->lex = XC_LEX_INVALID;
@@ -3233,9 +3228,9 @@ static BC_STATUS zbc_lex_token(void)
                         bc_lex_assign(BC_LEX_OP_ASSIGN_MULTIPLY, XC_LEX_OP_MULTIPLY);
                         break;
                 case '+':
-                        c2 = p->lex_inbuf[p->lex_i];
+                        c2 = *p->lex_inbuf;
                         if (c2 == '+') {
-                                p->lex_i++;
+                                p->lex_inbuf++;
                                 p->lex = BC_LEX_OP_INC;
                         } else
                                 bc_lex_assign(BC_LEX_OP_ASSIGN_PLUS, XC_LEX_OP_PLUS);
@@ -3244,15 +3239,15 @@ static BC_STATUS zbc_lex_token(void)
                         p->lex = BC_LEX_COMMA;
                         break;
                 case '-':
-                        c2 = p->lex_inbuf[p->lex_i];
+                        c2 = *p->lex_inbuf;
                         if (c2 == '-') {
-                                p->lex_i++;
+                                p->lex_inbuf++;
                                 p->lex = BC_LEX_OP_DEC;
                         } else
                                 bc_lex_assign(BC_LEX_OP_ASSIGN_MINUS, XC_LEX_OP_MINUS);
                         break;
                 case '.':
-                        if (isdigit(p->lex_inbuf[p->lex_i]))
+                        if (isdigit(*p->lex_inbuf))
                                 s = zbc_lex_number(c);
                         else {
                                 p->lex = BC_LEX_KEY_LAST;
@@ -3260,7 +3255,7 @@ static BC_STATUS zbc_lex_token(void)
                         }
                         break;
                 case '/':
-                        c2 = p->lex_inbuf[p->lex_i];
+                        c2 = *p->lex_inbuf;
                         if (c2 == '*')
                                 s = zbc_lex_comment();
                         else
@@ -3301,9 +3296,9 @@ static BC_STATUS zbc_lex_token(void)
                         p->lex = (BcLexType)(c - '[' + BC_LEX_LBRACKET);
                         break;
                 case '\\':
-                        if (p->lex_inbuf[p->lex_i] == '\n') {
+                        if (*p->lex_inbuf == '\n') {
                                 p->lex = XC_LEX_WHITESPACE;
-                                p->lex_i++;
+                                p->lex_inbuf++;
                         } else
                                 s = bc_error_bad_character(c);
                         break;
@@ -3343,11 +3338,11 @@ static BC_STATUS zbc_lex_token(void)
                         p->lex = (BcLexType)(c - '{' + BC_LEX_LBRACE);
                         break;
                 case '|':
-                        c2 = p->lex_inbuf[p->lex_i];
+                        c2 = *p->lex_inbuf;
                         if (c2 == '|') {
                                 s = zbc_POSIX_does_not_allow_bool_ops_this_is_bad("||");
                                 if (s) RETURN_STATUS(s);
-                                p->lex_i++;
+                                p->lex_inbuf++;
                                 p->lex = BC_LEX_OP_BOOL_OR;
                         } else {
                                 p->lex = XC_LEX_INVALID;
@@ -3369,13 +3364,13 @@ static BC_STATUS zbc_lex_token(void)
 static BC_STATUS zdc_lex_register(void)
 {
         BcParse *p = &G.prs;
-        if (G_exreg && isspace(p->lex_inbuf[p->lex_i])) {
+        if (G_exreg && isspace(*p->lex_inbuf)) {
                 bc_lex_whitespace(); // eats whitespace (but not newline)
-                p->lex_i++; // bc_lex_name() expects this
+                p->lex_inbuf++; // bc_lex_name() expects this
                 bc_lex_name();
         } else {
                 bc_vec_pop_all(&p->lex_strnumbuf);
-                bc_vec_push(&p->lex_strnumbuf, &p->lex_inbuf[p->lex_i++]);
+                bc_vec_push(&p->lex_strnumbuf, p->lex_inbuf++);
                 bc_vec_pushZeroByte(&p->lex_strnumbuf);
                 p->lex = XC_LEX_NAME;
         }
@@ -3394,15 +3389,15 @@ static BC_STATUS zdc_lex_string(void)
 
         nls = 0;
         depth = 1;
-        i = p->lex_i;
+        i = 0;
         for (;;) {
                 char c = p->lex_inbuf[i];
                 if (c == '\0') {
-                        p->lex_i = i;
+                        p->lex_inbuf += i;
                         RETURN_STATUS(bc_error("string end could not be found"));
                 }
                 nls += (c == '\n');
-                if (i == p->lex_i || p->lex_inbuf[i - 1] != '\\') {
+                if (i == 0 || p->lex_inbuf[i - 1] != '\\') {
                         if (c == '[') depth++;
                         if (c == ']')
                                 if (--depth == 0)
@@ -3416,11 +3411,11 @@ static BC_STATUS zdc_lex_string(void)
         bc_vec_pushZeroByte(&p->lex_strnumbuf);
         // This check makes sense only if size_t is (much) larger than BC_MAX_STRING.
         if (SIZE_MAX > (BC_MAX_STRING | 0xff)) {
-                if (i - p->lex_i > BC_MAX_STRING)
+                if (i > BC_MAX_STRING)
                         RETURN_STATUS(bc_error("string too long: must be [1,"BC_MAX_STRING_STR"]"));
         }
 
-        p->lex_i = i;
+        p->lex_inbuf += i;
         p->lex_line += nls;
         G.err_line = p->lex_line;
 
@@ -3451,7 +3446,7 @@ static BC_STATUS zdc_lex_token(void)
         }
 
         s = BC_STATUS_SUCCESS;
-        c = p->lex_inbuf[p->lex_i++];
+        c = *p->lex_inbuf++;
         if (c >= '%' && c <= '~'
          && (p->lex = dc_char_to_LEX[c - '%']) != XC_LEX_INVALID
         ) {
@@ -3484,7 +3479,7 @@ static BC_STATUS zdc_lex_token(void)
                         bc_lex_whitespace();
                         break;
                 case '!':
-                        c2 = p->lex_inbuf[p->lex_i];
+                        c2 = *p->lex_inbuf;
                         if (c2 == '=')
                                 p->lex = XC_LEX_OP_REL_NE;
                         else if (c2 == '<')
@@ -3493,13 +3488,13 @@ static BC_STATUS zdc_lex_token(void)
                                 p->lex = XC_LEX_OP_REL_GE;
                         else
                                 RETURN_STATUS(bc_error_bad_character(c));
-                        p->lex_i++;
+                        p->lex_inbuf++;
                         break;
                 case '#':
                         bc_lex_lineComment();
                         break;
                 case '.':
-                        if (isdigit(p->lex_inbuf[p->lex_i]))
+                        if (isdigit(*p->lex_inbuf))
                                 s = zbc_lex_number(c);
                         else
                                 s = bc_error_bad_character(c);
@@ -3651,7 +3646,7 @@ static void bc_parse_reset(void)
                 p->func = bc_program_func_BC_PROG_MAIN();
         }
 
-        p->lex_i = p->lex_len;
+        p->lex_inbuf = p->lex_end;
         p->lex = XC_LEX_EOF;
 
         IF_BC(bc_vec_pop_all(&p->exits);)