regcomp.c: Add a constant 0 element before inversion lists

This commit is the first step to separating the header from the body of
inversion lists.  Doing so will allow the compiled-in inversion lists to
be fully read-only.

To invert an inversion list, one simply unshifts a 0 to the front of it
if one is not there, and shifts off the 0 if it does have one.

The current data structure reserves an element at the beginning of each
inversion list that is either 0 or 1.  If 0, it means the inversion list
begins there; if 1, it means the inversion list starts at the next
element.  Inverting involves flipping this bit.

This commit changes the structure so that there is an additional element
just after the element that flips.  This new element is always 0, and
the flipping element now says whether the inversion list begins at the
constant 0 element, or the one after that.

Doing this allows the flipping element to be separated in later commits
from the body of the inversion list, which will always begin with the
constant 0 element.  That means that the body of the inversion list can
be const.

diff --git a/charclass_invlists.h b/charclass_invlists.h
index b5d71af..690526d 100644 (file)
--- a/charclass_invlists.h
+++ b/charclass_invlists.h
@@ -13,11 +13,11 @@ static UV Latin1_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       0,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
-       256,
-       0
+       1039476070, /* Version and data structure type */
+       0,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
+       256
 };
 
 #endif
@@ -28,9 +28,10 @@ static UV AboveLatin1_invlist[] = {
        1,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        256
 };
 
@@ -42,11 +43,11 @@ static UV ASCII_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       0,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
-       128,
-       0
+       1039476070, /* Version and data structure type */
+       0,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
+       128
 };
 
 #endif
@@ -57,9 +58,10 @@ static UV L1Cased_invlist[] = {
        16,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        65,
        91,
        97,
@@ -86,9 +88,10 @@ static UV VertSpace_invlist[] = {
        6,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        10,
        14,
        133,
@@ -105,9 +108,10 @@ static UV PerlSpace_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        9,
        14,
        32,
@@ -122,9 +126,10 @@ static UV XPerlSpace_invlist[] = {
        22,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        9,
        14,
        32,
@@ -157,9 +162,10 @@ static UV PosixAlnum_invlist[] = {
        6,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58,
        65,
@@ -176,9 +182,10 @@ static UV L1PosixAlnum_invlist[] = {
        18,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58,
        65,
@@ -207,9 +214,10 @@ static UV PosixAlpha_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        65,
        91,
        97,
@@ -224,9 +232,10 @@ static UV L1PosixAlpha_invlist[] = {
        16,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        65,
        91,
        97,
@@ -253,9 +262,10 @@ static UV PosixBlank_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        9,
        10,
        32,
@@ -270,9 +280,10 @@ static UV XPosixBlank_invlist[] = {
        18,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        9,
        10,
        32,
@@ -301,13 +312,13 @@ static UV PosixCntrl_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       0,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       0,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        32,
        127,
-       128,
-       0
+       128
 };
 
 #endif
@@ -318,13 +329,13 @@ static UV XPosixCntrl_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       0,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       0,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        32,
        127,
-       160,
-       0
+       160
 };
 
 #endif
@@ -335,9 +346,10 @@ static UV PosixDigit_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58
 };
@@ -350,9 +362,10 @@ static UV PosixGraph_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        33,
        127
 };
@@ -365,9 +378,10 @@ static UV L1PosixGraph_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        33,
        127,
        161,
@@ -382,9 +396,10 @@ static UV PosixLower_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        97,
        123
 };
@@ -397,9 +412,10 @@ static UV L1PosixLower_invlist[] = {
        12,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        97,
        123,
        170,
@@ -422,9 +438,10 @@ static UV PosixPrint_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        32,
        127
 };
@@ -437,9 +454,10 @@ static UV L1PosixPrint_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        32,
        127,
        160,
@@ -454,9 +472,10 @@ static UV PosixPunct_invlist[] = {
        8,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        33,
        48,
        58,
@@ -475,9 +494,10 @@ static UV L1PosixPunct_invlist[] = {
        20,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        33,
        48,
        58,
@@ -508,9 +528,10 @@ static UV PosixSpace_invlist[] = {
        4,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        9,
        14,
        32,
@@ -525,9 +546,10 @@ static UV XPosixSpace_invlist[] = {
        22,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        9,
        14,
        32,
@@ -560,9 +582,10 @@ static UV PosixUpper_invlist[] = {
        2,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        65,
        91
 };
@@ -575,9 +598,10 @@ static UV L1PosixUpper_invlist[] = {
        6,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        65,
        91,
        192,
@@ -594,9 +618,10 @@ static UV PosixWord_invlist[] = {
        8,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58,
        65,
@@ -615,9 +640,10 @@ static UV L1PosixWord_invlist[] = {
        20,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58,
        65,
@@ -648,9 +674,10 @@ static UV PosixXDigit_invlist[] = {
        6,      /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58,
        65,
@@ -667,9 +694,10 @@ static UV XPosixXDigit_invlist[] = {
        12,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        48,
        58,
        65,
@@ -690,9 +718,10 @@ static UV NonL1_Perl_Non_Final_Folds_invlist[] = {
        44,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        700,
        701,
        776,
@@ -745,9 +774,10 @@ static UV _Perl_Multi_Char_Folds_invlist[] = {
        58,     /* Number of elements */
        0,      /* Current iteration position */
        0,      /* Cache of previous search index result */
-       290655244, /* Version and data structure type */
-       1,      /* 0 if this is the first element of the list proper;
-                  1 if the next element is the first */
+       1039476070, /* Version and data structure type */
+       1,      /* 0 if the list starts at 0;
+                  1 if it starts at the element beyond 0 */
+       0,
        223,
        224,
        304,

diff --git a/embed.fnc b/embed.fnc
index 5c27b27..8ad9a13 100644 (file)
--- a/embed.fnc
+++ b/embed.fnc
@@ -1085,7 +1085,7 @@ Ap        |SV*    |regclass_swash |NULLOK const regexp *prog \
                                |NULLOK SV **listsvp|NULLOK SV **altsvp
 #ifdef PERL_IN_REGCOMP_C
 EMsR   |SV*    |_new_invlist_C_array|NN UV* list
-: Not used currently: EXMs     |bool   |_invlistEQ     |NN SV* const a|NN SV* const b|bool complement_b
+: Not used currently: EXMs     |bool   |_invlistEQ     |NN SV* const a|NN SV* const b|const bool complement_b
 #endif
 Ap     |I32    |pregexec       |NN REGEXP * const prog|NN char* stringarg \
                                |NN char* strend|NN char* strbeg|I32 minend \
@@ -1446,9 +1446,13 @@ EiMR     |UV     |invlist_highest|NN SV* const invlist
 #endif
 #if defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_UTF8_C)
 EXmM   |void   |_invlist_intersection  |NN SV* const a|NN SV* const b|NN SV** i
-EXpM   |void   |_invlist_intersection_maybe_complement_2nd|NULLOK SV* const a|NN SV* const b|bool complement_b|NN SV** i
+EXpM   |void   |_invlist_intersection_maybe_complement_2nd \
+               |NULLOK SV* const a|NN SV* const b          \
+               |const bool complement_b|NN SV** i
 EXmM   |void   |_invlist_union |NULLOK SV* const a|NN SV* const b|NN SV** output
-EXpM   |void   |_invlist_union_maybe_complement_2nd|NULLOK SV* const a|NN SV* const b|bool complement_b|NN SV** output
+EXpM   |void   |_invlist_union_maybe_complement_2nd        \
+               |NULLOK SV* const a|NN SV* const b          \
+               |const bool complement_b|NN SV** output
 EXmM   |void   |_invlist_subtract|NN SV* const a|NN SV* const b|NN SV** result
 EXpM   |void   |_invlist_invert|NN SV* const invlist
 EXpM   |void   |_invlist_invert_prop|NN SV* const invlist

diff --git a/inline_invlist.c b/inline_invlist.c
index b56ce60..b194c0d 100644 (file)
--- a/inline_invlist.c
+++ b/inline_invlist.c
@@ -20,20 +20,21 @@
  * insert that at this location.  Then, if an auxiliary program doesn't change
  * correspondingly, it will be discovered immediately */
 #define INVLIST_VERSION_ID_OFFSET 3
-#define INVLIST_VERSION_ID 290655244
+#define INVLIST_VERSION_ID 1039476070
+
+#define INVLIST_ZERO_OFFSET 4  /* 0 or 1 */
+/* The UV at position ZERO contains either 0 or 1.  If 0, the inversion list
+ * contains the code point U+00000, and begins at element [0] in the array,
+ * which always contains 0.  If 1, the inversion list doesn't contain U+0000,
+ * and it begins at element [1].  Inverting an inversion list consists of
+ * adding or removing the 0 at the beginning of it.  By reserving a space for
+ * that 0, inversion can be made very fast: we just flip this UV */
 
 /* For safety, when adding new elements, remember to #undef them at the end of
  * the inversion list code section */
 
-#define INVLIST_ZERO_OFFSET 4  /* 0 or 1; must be last element in header */
-/* The UV at position ZERO contains either 0 or 1.  If 0, the inversion list
- * contains the code point U+00000, and begins here.  If 1, the inversion list
- * doesn't contain U+0000, and it begins at the next UV in the array.
- * Inverting an inversion list consists of adding or removing the 0 at the
- * beginning of it.  By reserving a space for that 0, inversion can be made
- * very fast */
-
-#define HEADER_LENGTH (INVLIST_ZERO_OFFSET + 1)
+#define HEADER_LENGTH (INVLIST_ZERO_OFFSET + 2) /* includes 1 for the constant
+                                                   0 element */
 
 /* An element is in an inversion list iff its index is even numbered: 0, 2, 4,
  * etc */

diff --git a/proto.h b/proto.h
index 9a06590..f5dc0dc 100644 (file)
--- a/proto.h
+++ b/proto.h
@@ -6839,7 +6839,7 @@ PERL_CALLCONV SV* Perl__add_range_to_invlist(pTHX_ SV* invlist, const UV start,
                        __attribute__nonnull__(pTHX_2)
                        __attribute__nonnull__(pTHX_3); */
 
-PERL_CALLCONV void     Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** i)
+PERL_CALLCONV void     Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** i)
                        __attribute__nonnull__(pTHX_2)
                        __attribute__nonnull__(pTHX_4);
 #define PERL_ARGS_ASSERT__INVLIST_INTERSECTION_MAYBE_COMPLEMENT_2ND    \
@@ -6870,7 +6870,7 @@ PERL_CALLCONV void        Perl__invlist_populate_swatch(pTHX_ SV* const invlist, const
                        __attribute__nonnull__(pTHX_2)
                        __attribute__nonnull__(pTHX_3); */
 
-PERL_CALLCONV void     Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** output)
+PERL_CALLCONV void     Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** output)
                        __attribute__nonnull__(pTHX_2)
                        __attribute__nonnull__(pTHX_4);
 #define PERL_ARGS_ASSERT__INVLIST_UNION_MAYBE_COMPLEMENT_2ND   \

diff --git a/regcomp.c b/regcomp.c
index 4885c0b..b2bf63c 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -7047,10 +7047,10 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
  * list.)
  * Taking the complement (inverting) an inversion list is quite simple, if the
  * first element is 0, remove it; otherwise add a 0 element at the beginning.
- * This implementation reserves an element at the beginning of each inversion
- * list to contain 0 when the list contains 0, and contains 1 otherwise.  The
- * actual beginning of the list is either that element if 0, or the next one if
- * 1.
+ * This implementation reserves an element (considered to be the final element
+ * of the header) at the beginning of each inversion list to always contain 0;
+ * there is an additional flag in the header which indicates if the list begins
+ * at the 0, or is offset to begin at the next element.
  *
  * More about inversion lists can be found in "Unicode Demystified"
  * Chapter 13 by Richard Gillam, published by Addison-Wesley.
@@ -7075,11 +7075,11 @@ S__invlist_array_init(pTHX_ SV* const invlist, const bool will_have_0)
 {
     /* Returns a pointer to the first element in the inversion list's array.
      * This is called upon initialization of an inversion list.  Where the
-     * array begins depends on whether the list has the code point U+0000
-     * in it or not.  The other parameter tells it whether the code that
-     * follows this call is about to put a 0 in the inversion list or not.
-     * The first element is either the element with 0, if 0, or the next one,
-     * if 1 */
+     * array begins depends on whether the list has the code point U+0000 in it
+     * or not.  The other parameter tells it whether the code that follows this
+     * call is about to put a 0 in the inversion list or not.  The first
+     * element is either the final part of the header reserved for 0, if TRUE,
+     * or the first element of the non-heading part, if FALSE */
 
     UV* zero = get_invlist_zero_addr(invlist);
 
@@ -7090,7 +7090,8 @@ S__invlist_array_init(pTHX_ SV* const invlist, const bool will_have_0)
 
     /* 1^1 = 0; 1^0 = 1 */
     *zero = 1 ^ will_have_0;
-    return zero + *zero;
+    *(zero + 1) = 0;
+    return 1 + zero + *zero;
 }
 
 PERL_STATIC_INLINE UV*
@@ -7108,10 +7109,12 @@ S_invlist_array(pTHX_ SV* const invlist)
     assert(*get_invlist_zero_addr(invlist) == 0
           || *get_invlist_zero_addr(invlist) == 1);
 
-    /* The array begins either at the element reserved for zero if the
-     * list contains 0 (that element will be set to 0), or otherwise the next
-     * element (in which case the reserved element will be set to 1). */
-    return (UV *) (get_invlist_zero_addr(invlist)
+    /* The array begins either at the header element reserved for zero or the
+     * element after that.  The reserved element is 1 past the zero_addr
+     * element; the latter contains 0 or 1 to indicate how much additionally to
+     * add */
+    assert(0 == *(1 + get_invlist_zero_addr(invlist)));
+    return (UV *) (1 + get_invlist_zero_addr(invlist)
                   + *get_invlist_zero_addr(invlist));
 }
 
@@ -7127,19 +7130,7 @@ S_invlist_set_len(pTHX_ SV* const invlist, const UV len)
     assert(len <= SvLEN(invlist));
 
     SvCUR_set(invlist, TO_INTERNAL_SIZE(len));
-    /* If the list contains U+0000, that element is part of the header,
-     * and should not be counted as part of the array.  It will contain
-     * 0 in that case, and 1 otherwise.  So we could flop 0=>1, 1=>0 and
-     * subtract:
-     * SvCUR_set(invlist,
-     *           TO_INTERNAL_SIZE(len
-     *                            - (*get_invlist_zero_addr(inv_list) ^ 1)));
-     * But, this is only valid if len is not 0.  The consequences of not doing
-     * this is that the memory allocation code may think that 1 more UV is
-     * being used than actually is, and so might do an unnecessary grow.  That
-     * seems worth not bothering to make this the precise amount.
-     *
-     * Note that when inverting, SvCUR shouldn't change */
+    /* Note that when inverting, SvCUR shouldn't change */
 }
 
 PERL_STATIC_INLINE IV*
@@ -7191,10 +7182,8 @@ S_invlist_max(pTHX_ SV* const invlist)
 PERL_STATIC_INLINE UV*
 S_get_invlist_zero_addr(pTHX_ SV* invlist)
 {
-    /* Return the address of the UV that is reserved to hold 0 if the inversion
-     * list contains 0.  This has to be the last element of the heading, as the
-     * list proper starts with either it if 0, or the next element if not.
-     * (But we force it to contain either 0 or 1) */
+    /* Return the address of the UV that says whether the inversion list is
+     * offset (it contains 1) or not (contains 0) */
 
     PERL_ARGS_ASSERT_GET_INVLIST_ZERO_ADDR;
 
@@ -7211,6 +7200,7 @@ Perl__new_invlist(pTHX_ IV initial_size)
      * system default is used instead */
 
     SV* new_list;
+    UV* zero_addr;
 
     if (initial_size < 0) {
        initial_size = INVLIST_INITIAL_LEN;
@@ -7225,11 +7215,13 @@ Perl__new_invlist(pTHX_ IV initial_size)
 
     /* This should force a segfault if a method doesn't initialize this
      * properly */
-    *get_invlist_zero_addr(new_list) = UV_MAX;
+    zero_addr = get_invlist_zero_addr(new_list);
+    *zero_addr = UV_MAX;
+    *(zero_addr + 1) = 0;
 
     *get_invlist_previous_index_addr(new_list) = 0;
     *get_invlist_version_id_addr(new_list) = INVLIST_VERSION_ID;
-#if HEADER_LENGTH != 5
+#if HEADER_LENGTH != 6
 #   error Need to regenerate INVLIST_VERSION_ID by running perl -E 'say int(rand 2**31-1)', and then changing the #if to the new length
 #endif
 
@@ -7554,7 +7546,7 @@ Perl__invlist_populate_swatch(pTHX_ SV* const invlist, const UV start, const UV
 }
 
 void
-Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** output)
+Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** output)
 {
     /* Take the union of two inversion lists and point <output> to it.  *output
      * SHOULD BE DEFINED upon input, and if it points to one of the two lists,
@@ -7576,8 +7568,8 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
      * return the larger of the input lists, but then outside code might need
      * to keep track of whether to free the input list or not */
 
-    UV* array_a;    /* a's array */
-    UV* array_b;
+    const UV* array_a;    /* a's array */
+    const UV* array_b;
     UV len_a;      /* length of a's array */
     UV len_b;
 
@@ -7645,23 +7637,17 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
     if (complement_b) {
 
        /* To complement, we invert: if the first element is 0, remove it.  To
-        * do this, we just pretend the array starts one later, and clear the
-        * flag as we don't have to do anything else later */
+        * do this, we just pretend the array starts one later */
         if (array_b[0] == 0) {
             array_b++;
             len_b--;
-            complement_b = FALSE;
         }
         else {
 
-            /* But if the first element is not zero, we unshift a 0 before the
-             * array.  The data structure reserves a space for that 0 (which
-             * should be a '1' right now), so physical shifting is unneeded,
-             * but temporarily change that element to 0.  Before exiting the
-             * routine, we must restore the element to '1' */
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
             array_b--;
             len_b++;
-            array_b[0] = 0;
         }
     }
 
@@ -7778,11 +7764,6 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
        }
     }
 
-    /* If we've changed b, restore it */
-    if (complement_b) {
-        array_b[0] = 1;
-    }
-
     /*  We may be removing a reference to one of the inputs */
     if (a == *output || b == *output) {
         assert(! invlist_is_iterating(*output));
@@ -7794,7 +7775,7 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
 }
 
 void
-Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** i)
+Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** i)
 {
     /* Take the intersection of two inversion lists and point <i> to it.  *i
      * SHOULD BE DEFINED upon input, and if it points to one of the two lists,
@@ -7811,8 +7792,8 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
      * union above
      */
 
-    UV* array_a;               /* a's array */
-    UV* array_b;
+    const UV* array_a;         /* a's array */
+    const UV* array_b;
     UV len_a;  /* length of a's array */
     UV len_b;
 
@@ -7877,23 +7858,17 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
     if (complement_b) {
 
        /* To complement, we invert: if the first element is 0, remove it.  To
-        * do this, we just pretend the array starts one later, and clear the
-        * flag as we don't have to do anything else later */
+        * do this, we just pretend the array starts one later */
         if (array_b[0] == 0) {
             array_b++;
             len_b--;
-            complement_b = FALSE;
         }
         else {
 
-            /* But if the first element is not zero, we unshift a 0 before the
-             * array.  The data structure reserves a space for that 0 (which
-             * should be a '1' right now), so physical shifting is unneeded,
-             * but temporarily change that element to 0.  Before exiting the
-             * routine, we must restore the element to '1' */
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
             array_b--;
             len_b++;
-            array_b[0] = 0;
         }
     }
 
@@ -8000,11 +7975,6 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
        }
     }
 
-    /* If we've changed b, restore it */
-    if (complement_b) {
-        array_b[0] = 1;
-    }
-
     /*  We may be removing a reference to one of the inputs */
     if (a == *i || b == *i) {
         assert(! invlist_is_iterating(*i));
@@ -8343,14 +8313,14 @@ Perl__invlist_dump(pTHX_ SV* const invlist, const char * const header)
 
 #if 0
 bool
-S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
+S__invlistEQ(pTHX_ SV* const a, SV* const b, const bool complement_b)
 {
     /* Return a boolean as to if the two passed in inversion lists are
      * identical.  The final argument, if TRUE, says to take the complement of
      * the second inversion list before doing the comparison */
 
-    UV* array_a = invlist_array(a);
-    UV* array_b = invlist_array(b);
+    const UV* array_a = invlist_array(a);
+    const UV* array_b = invlist_array(b);
     UV len_a = _invlist_len(a);
     UV len_b = _invlist_len(b);
 
@@ -8372,20 +8342,15 @@ S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
 
             /* Otherwise, to complement, we invert.  Here, the first element is
              * 0, just remove it.  To do this, we just pretend the array starts
-             * one later, and clear the flag as we don't have to do anything
-             * else later */
+             * one later */
 
             array_b++;
             len_b--;
-            complement_b = FALSE;
         }
         else {
 
-            /* But if the first element is not zero, we unshift a 0 before the
-             * array.  The data structure reserves a space for that 0 (which
-             * should be a '1' right now), so physical shifting is unneeded,
-             * but temporarily change that element to 0.  Before exiting the
-             * routine, we must restore the element to '1' */
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
             array_b--;
             len_b++;
             array_b[0] = 0;
@@ -8405,9 +8370,6 @@ S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
         }
     }
 
-    if (complement_b) {
-        array_b[0] = 1;
-    }
     return retval;
 }
 #endif

diff --git a/regen/mk_invlists.pl b/regen/mk_invlists.pl
index 67b6e41..27c0802 100644 (file)
--- a/regen/mk_invlists.pl
+++ b/regen/mk_invlists.pl
@@ -15,7 +15,7 @@ require 'regen/regen_lib.pl';
 # in the headers is used to minimize the possibility of things getting
 # out-of-sync, or the wrong data structure being passed.  Currently that
 # random number is:
-my $VERSION_DATA_STRUCTURE_TYPE = 290655244;
+my $VERSION_DATA_STRUCTURE_TYPE = 1039476070;
 
 my $out_fh = open_new('charclass_invlists.h', '>',
                      {style => '*', by => $0,
@@ -36,27 +36,18 @@ sub output_invlist ($$) {
     # Output the inversion list $invlist using the name $name for it.
     # It is output in the exact internal form for inversion lists.
 
-    my $zero_or_one;    # Is the last element of the header 0, or 1 ?
-
-    # If the first element is 0, it goes in the header, instead of the body
-    if ($invlist->[0] == 0) {
-        shift @$invlist;
-
-        $zero_or_one = 0;
-
-        # Add a dummy 0 at the end so that the length is constant.  inversion
-        # lists are always stored with enough room so that if they change from
-        # beginning with 0, they don't have to grow.
-        push @$invlist, 0;
-    }
-    else {
+    # Is the last element of the header 0, or 1 ?
+    my $zero_or_one = 0;
+    my $count = @$invlist;
+    if ($invlist->[0] != 0) {
+        unshift @$invlist, 0;
         $zero_or_one = 1;
     }
 
     print $out_fh "\n#ifndef PERL_IN_XSUB_RE\n" unless exists $include_in_ext_re{$name};
     print $out_fh "\nstatic UV ${name}_invlist[] = {\n";
 
-    print $out_fh "\t", scalar @$invlist, ",\t/* Number of elements */\n";
+    print $out_fh "\t$count,\t/* Number of elements */\n";
 
     # This should be UV_MAX, but I (khw) am not confident that the suffixes
     # for specifying the constant are portable, e.g.  'ull' on a 32 bit
@@ -65,8 +56,8 @@ sub output_invlist ($$) {
     print $out_fh "\t0,\t/* Cache of previous search index result */\n";
     print $out_fh "\t$VERSION_DATA_STRUCTURE_TYPE, /* Version and data structure type */\n";
     print $out_fh "\t", $zero_or_one,
-                  ",\t/* 0 if this is the first element of the list proper;",
-                  "\n\t\t   1 if the next element is the first */\n";
+                  ",\t/* 0 if the list starts at 0;",
+                  "\n\t\t   1 if it starts at the element beyond 0 */\n";
 
     # The main body are the UVs passed in to this routine.  Do the final
     # element separately