Revamp regcurly(), regpiece() use of it

This commit copies portions of new_regcurly(), which has been around
since 5.28, into plain regcurly(), as a baby step in preparation for
converting entirely to the new one.  These functions are used for
parsing {m,n} quantifiers.  Future commits will add capabilities not
available using the old version.

The commit adds an optional parameter, to return to the caller
information it gleans during parsing.

regpiece() is changed by this commit to use this information, instead of
itself reparsing the input.  Part of the reason for this commit is that
changes are planned soon to what is legal syntax.  With this commit in
place, those changes only have to be done once.

This commit also extracts into a function the calculation of the
quantifier bounds.  This allows the logic for that to be done in one
place instead of two.

5 files changed, 170 insertions, 71 deletions

diff --git a/embed.fnc b/embed.fnc
index e633097f9b..5ff0a9bebe 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -2082,6 +2082,8 @@ ES	|void	|dump_regex_sets_structures				    \
 #  endif
 ES	|void|parse_lparen_question_flags|NN RExC_state_t *pRExC_state
 ES	|regnode_offset|reg_node|NN RExC_state_t *pRExC_state|U8 op
+ES	|U32	|get_quantifier_value|NN RExC_state_t *pRExC_state	    \
+				|NN const char * start|NN const char * end
 ES	|regnode_offset|regpiece|NN RExC_state_t *pRExC_state \
 				|NN I32 *flagp|U32 depth
 ES	|bool	|grok_bslash_N	|NN RExC_state_t *pRExC_state		    \
@@ -2343,7 +2345,7 @@ EXTp	|UV	|_to_fold_latin1|const U8 c|NN U8 *p|NN STRLEN *lenp|const unsigned int
 EpX	|SV*	|invlist_clone	|NN SV* const invlist|NULLOK SV* newlist
 #endif
 #if defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_TOKE_C)
-EXpRT	|bool	|regcurly	|NN const char *s
+EXpRT	|bool	|regcurly	|NN const char *s|NN const char *e|NULLOK const char * result[5]
 #endif
 #if defined(PERL_IN_REGEXEC_C)
 ERS	|bool	|isFOO_utf8_lc	|const U8 classnum|NN const U8* character|NN const U8* e
diff --git a/embed.h b/embed.h
index d3a60006d8..159a5e9155 100644
--- a/embed.h
+++ b/embed.h
@@ -1047,6 +1047,7 @@
 #define find_first_differing_byte_pos	S_find_first_differing_byte_pos
 #define get_ANYOFM_contents(a)	S_get_ANYOFM_contents(aTHX_ a)
 #define get_ANYOF_cp_list_for_ssc(a,b)	S_get_ANYOF_cp_list_for_ssc(aTHX_ a,b)
+#define get_quantifier_value(a,b,c)	S_get_quantifier_value(aTHX_ a,b,c)
 #define grok_bslash_N(a,b,c,d,e,f,g)	S_grok_bslash_N(aTHX_ a,b,c,d,e,f,g)
 #define handle_named_backref(a,b,c,d)	S_handle_named_backref(aTHX_ a,b,c,d)
 #define handle_names_wildcard(a,b,c,d)	S_handle_names_wildcard(aTHX_ a,b,c,d)
diff --git a/proto.h b/proto.h
index 333dde15e6..aa156b4cad 100644
--- a/proto.h
+++ b/proto.h
@@ -5761,6 +5761,9 @@ STATIC SV *	S_get_ANYOFM_contents(pTHX_ const regnode * n)
 STATIC SV*	S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state, const regnode_charclass* const node);
 #define PERL_ARGS_ASSERT_GET_ANYOF_CP_LIST_FOR_SSC	\
 	assert(pRExC_state); assert(node)
+STATIC U32	S_get_quantifier_value(pTHX_ RExC_state_t *pRExC_state, const char * start, const char * end);
+#define PERL_ARGS_ASSERT_GET_QUANTIFIER_VALUE	\
+	assert(pRExC_state); assert(start); assert(end)
 STATIC bool	S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state, regnode_offset* nodep, UV *code_point_p, int* cp_count, I32 *flagp, const bool strict, const U32 depth);
 #define PERL_ARGS_ASSERT_GROK_BSLASH_N	\
 	assert(pRExC_state); assert(flagp)
@@ -6149,10 +6152,10 @@ PERL_CALLCONV SV*	Perl_invlist_clone(pTHX_ SV* const invlist, SV* newlist);
 	assert(invlist)
 #endif
 #if defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_TOKE_C)
-PERL_CALLCONV bool	Perl_regcurly(const char *s)
+PERL_CALLCONV bool	Perl_regcurly(const char *s, const char *e, const char * result[5])
 			__attribute__warn_unused_result__;
 #define PERL_ARGS_ASSERT_REGCURLY	\
-	assert(s)
+	assert(s); assert(e)
 
 #endif
 #if defined(PERL_IN_REGEXEC_C)
diff --git a/regcomp.c b/regcomp.c
index 7e8425f392..8e5305cf79 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -362,7 +362,7 @@ struct RExC_state_t {
 
 #define	isNON_BRACE_QUANTIFIER(c)   ((c) == '*' || (c) == '+' || (c) == '?')
 #define	isQUANTIFIER(s,e)  (   isNON_BRACE_QUANTIFIER(*s)                      \
-                            || ((*s) == '{' && regcurly(s)))
+                            || ((*s) == '{' && regcurly(s, e, NULL)))
 
 /*
  * Flags to be passed up and down.
@@ -12541,31 +12541,150 @@ S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
     return ret;
 }
 
-/*
- - regcurly - a little FSA that accepts {\d+,?\d*}
-    Pulled from reg.c.
- */
-#ifndef PERL_IN_XSUB_RE
 bool
-Perl_regcurly(const char *s)
+Perl_regcurly(const char *s, const char *e, const char * result[5])
 {
+    /* This function matches a {m,n} quantifier.  When called with a NULL final
+     * argument, it simply parses the input from 's' up through 'e-1', and
+     * returns a boolean as to whether or not this input is syntactically a
+     * {m,n} quantifier.
+     *
+     * When called with a non-NULL final parameter, and when the function
+     * returns TRUE, it additionally stores information into the array
+     * specified by that parameter about what it found in the parse.  The
+     * parameter must be a pointer into a 5 element array of 'const char *'
+     * elements.  The returned information is as follows:
+     *   result[RBRACE]  points to the closing brace
+     *   result[MIN_S]   points to the first byte of the lower bound
+     *   result[MIN_E]   points to one beyond the final byte of the lower bound
+     *   result[MAX_S]   points to the first byte of the upper bound
+     *   result[MAX_E]   points to one beyond the final byte of the upper bound
+     *
+     * If the quantifier is of the form {m,} (meaning an infinite upper
+     * bound), result[MAX_E] is set to result[MAX_S]; what they actually point
+     * to is irrelevant, just that it's the same place
+     *
+     * If instead the quantifier is of the form {m} there is actually only
+     * one bound, and both the upper and lower result[] elements are set to
+     * point to it.
+     *
+     * This function checks only for syntactic validity; it leaves checking for
+     * semantic validity and raising any diagnostics to the caller.  This
+     * function is called in multiple places to check for syntax, but only from
+     * one for semantics.  It makes it as simple as possible for the
+     * syntax-only callers, while furnishing just enough information for the
+     * semantic caller.
+     */
+
+    const char * min_start = NULL;
+    const char * max_start = NULL;
+    const char * min_end = NULL;
+    const char * max_end = NULL;
+
+    bool has_comma = FALSE;
+
     PERL_ARGS_ASSERT_REGCURLY;
 
-    if (*s++ != '{')
-	return FALSE;
-    if (!isDIGIT(*s))
+    if (s >= e || *s++ != '{')
 	return FALSE;
-    while (isDIGIT(*s))
-	s++;
+
+    if isDIGIT(*s) {
+        min_start = s;
+        do {
+            s++;
+        } while (s < e && isDIGIT(*s));
+        min_end = s;
+    }
+
     if (*s == ',') {
+        has_comma = TRUE;
 	s++;
-	while (isDIGIT(*s))
-	    s++;
+        if isDIGIT(*s) {
+            max_start = s;
+            do {
+                s++;
+            } while (s < e && isDIGIT(*s));
+            max_end = s;
+        }
+    }
+
+    if (s >= e || *s != '}' || ! min_start) {
+        return FALSE;
+    }
+
+    if (result) {
+
+#define RBRACE  0
+#define MIN_S   1
+#define MIN_E   2
+#define MAX_S   3
+#define MAX_E   4
+
+        result[RBRACE] = s;
+
+        result[MIN_S] = min_start;
+        result[MIN_E] = min_end;
+        if (has_comma) {
+            if (max_start) {
+                result[MAX_S] = max_start;
+                result[MAX_E] = max_end;
+            }
+            else {
+                /* Having no value after the comma is signalled by setting
+                 * start and end to the same value.  What that value is isn't
+                 * relevant; NULL is chosen simply because it will fail if the
+                 * caller mistakenly uses it */
+                result[MAX_S] = result[MAX_E] = NULL;
+            }
+        }
+        else {  /* No comma means lower and upper bounds are the same */
+            result[MAX_S] = min_start;
+            result[MAX_E] = min_end;
+        }
     }
 
-    return *s == '}';
+    return TRUE;
 }
-#endif
+
+U32
+S_get_quantifier_value(pTHX_ RExC_state_t *pRExC_state,
+                       const char * start, const char * end)
+{
+    /* This is a helper function for regpiece() to compute, given the
+     * quantifier {m,n}, the value of either m or n, based on the starting
+     * position 'start' in the string, through the byte 'end-1', returning it
+     * if valid, and failing appropriately if not.  It knows the restrictions
+     * imposed on quantifier values */
+
+    UV uv;
+    STATIC_ASSERT_DECL(REG_INFTY <= U32_MAX);
+
+    PERL_ARGS_ASSERT_GET_QUANTIFIER_VALUE;
+
+    if (grok_atoUV(start, &uv, &end)) {
+        if (uv < REG_INFTY) {   /* A valid, small-enough number */
+            return (U32) uv;
+        }
+    }
+    else if (*start == '0') { /* grok_atoUV() fails for only two reasons:
+                                 leading zeros or overflow */
+        RExC_parse++;
+
+        /* Perhaps too generic a msg for what is only failure from having
+         * leading zeros, but this is how it's always behaved. */
+        vFAIL("Invalid quantifier in {,}");
+        NOT_REACHED; /*NOTREACHED*/
+    }
+
+    /* Here, found a quantifier, but was too large; either it overflowed or was
+     * too big a legal number */
+    RExC_parse++;
+    vFAIL2("Quantifier in {,} bigger than %d", REG_INFTY - 1);
+
+    NOT_REACHED; /*NOTREACHED*/
+    return U32_MAX; /* Perhaps some compilers will be expecting a return */
+}
+
 /*
  - regpiece - something followed by possible quantifier * + ? {n,m}
  *
@@ -12588,7 +12707,6 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 {
     regnode_offset ret;
     char op;
-    char *next;
     I32 flags;
     const char * const origparse = RExC_parse;
     I32 min;
@@ -12596,8 +12714,6 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 #ifdef RE_TRACK_PATTERN_OFFSETS
     char *parse_start;
 #endif
-    const char *maxpos = NULL;
-    UV uv;
 
     /* Save the original in case we change the emitted regop to a FAIL. */
     const regnode_offset orig_emit = RExC_emit;
@@ -12620,6 +12736,7 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 
     op = *RExC_parse;
     switch (op) {
+        const char * regcurly_return[5];
 
       case '*':
         nextchar(pRExC_state);
@@ -12638,54 +12755,31 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 
       case '{':  /* A '{' may or may not indicate a quantifier; call regcurly()
                     to determine which */
-        if (regcurly(RExC_parse)) {
-            const char* endptr;
-
-            /* Here is a quantifier, parse for min and max values */
-            maxpos = NULL;
-            next = RExC_parse + 1;
-            while (isDIGIT(*next) || *next == ',') {
-                if (*next == ',') {
-                    if (maxpos)
-                        break;
-                    else
-                        maxpos = next;
-                }
-                next++;
-            }
+        if (regcurly(RExC_parse, RExC_end, regcurly_return)) {
+            const char * min_start = regcurly_return[MIN_S];
+            const char * min_end   = regcurly_return[MIN_E];
+            const char * max_start = regcurly_return[MAX_S];
+            const char * max_end   = regcurly_return[MAX_E];
 
-            assert(*next == '}');
+            assert(min_start);
+            assert(min_end > min_start);
+            min = get_quantifier_value(pRExC_state, min_start, min_end);
 
-            if (!maxpos)
-                maxpos = next;
-            RExC_parse++;
-            if (isDIGIT(*RExC_parse)) {
-                endptr = RExC_end;
-                if (!grok_atoUV(RExC_parse, &uv, &endptr))
-                    vFAIL("Invalid quantifier in {,}");
-                if (uv >= REG_INFTY)
-                    vFAIL2("Quantifier in {,} bigger than %d", REG_INFTY - 1);
-                min = (I32)uv;
-            } else {
-                min = 0;
+            if (max_start == max_end) {     /* Was of the form {m,} */
+                max = REG_INFTY;
             }
-            if (*maxpos == ',')
-                maxpos++;
-            else
-                maxpos = RExC_parse;
-            if (isDIGIT(*maxpos)) {
-                endptr = RExC_end;
-                if (!grok_atoUV(maxpos, &uv, &endptr))
-                    vFAIL("Invalid quantifier in {,}");
-                if (uv >= REG_INFTY)
-                    vFAIL2("Quantifier in {,} bigger than %d", REG_INFTY - 1);
-                max = (I32)uv;
-            } else {
-                max = REG_INFTY;            /* meaning "infinity" */
+            else if (max_start == min_start) {  /* Was of the form {m} */
+                max = min;
             }
+            else {  /* Was of the form {m,n} */
+                assert(max_end >= max_start);
 
-            RExC_parse = next;
+                max = get_quantifier_value(pRExC_state, max_start, max_end);
+            }
+
+            RExC_parse = (char *) regcurly_return[RBRACE];
             nextchar(pRExC_state);
+
             if (max < min) {    /* If can't match, warn and optimize to fail
                                    unconditionally */
                 reginsert(pRExC_state, OPFAIL, orig_emit, depth+1);
@@ -12694,15 +12788,14 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                                     regarglen[OPFAIL] + NODE_STEP_REGNODE;
                 return ret;
             }
-            else if (min == max && *RExC_parse == '?')
-            {
+            else if (min == max && *RExC_parse == '?') {
                 ckWARN2reg(RExC_parse + 1,
                            "Useless use of greediness modifier '%c'",
                            *RExC_parse);
             }
 
             break;
-        } /* End of is regcurly() */
+        } /* End of is {m,n} */
 
         /* Here was a '{', but what followed it didn't form a quantifier. */
         /* FALLTHROUGH */
@@ -12987,7 +13080,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
     /* Disambiguate between \N meaning a named character versus \N meaning
      * [^\n].  The latter is assumed when the {...} following the \N is a legal
      * quantifier, or if there is no '{' at all */
-    if (*p != '{' || regcurly(p)) {
+    if (*p != '{' || regcurly(p, RExC_end, NULL)) {
         RExC_parse = p;
         if (cp_count) {
             *cp_count = -1;
@@ -15376,7 +15469,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
     skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                                             FALSE /* Don't force to /x */ );
     if (   *RExC_parse == '{'
-        && OP(REGNODE_p(ret)) != SBOL && ! regcurly(RExC_parse))
+        && OP(REGNODE_p(ret)) != SBOL && ! regcurly(RExC_parse, RExC_end, NULL))
     {
         if (RExC_strict || new_regcurly(RExC_parse, RExC_end)) {
             RExC_parse++;
diff --git a/toke.c b/toke.c
index cf0a06a44a..fba2382a33 100644
--- a/toke.c
+++ b/toke.c
@@ -3627,7 +3627,7 @@ S_scan_const(pTHX_ char *start)
 	    else if (PL_lex_inpat
 		    && (*s != 'N'
 			|| s[1] != '{'
-			|| regcurly(s + 1)))
+			|| regcurly(s + 1, send, NULL)))
 	    {
 		*d++ = '\\';
 		goto default_action;
@@ -4353,7 +4353,7 @@ S_intuit_more(pTHX_ char *s, char *e)
 
     /* In a pattern, so maybe we have {n,m}. */
     if (*s == '{') {
-	if (regcurly(s)) {
+	if (regcurly(s, e, NULL)) {
 	    return FALSE;
 	}
 	return TRUE;