/*
* The length is cached in PERL_UTF8_magic, in the mg_len field. Also the
- * mg_ptr is used, by sv_pos_u2b(), see the comments of S_utf8_mg_pos_init().
- * (Note that the mg_len is not the length of the mg_ptr field.)
+ * mg_ptr is used, by sv_pos_u2b() and sv_pos_b2u() - see the comments below.
+ * (Note that the mg_len is not the length of the mg_ptr field.
+ * This allows the cache to store the character length of the string without
+ * needing to malloc() extra storage to attach to the mg_ptr.)
*
*/
}
}
-/*
-=for apidoc sv_pos_u2b
-
-Converts the value pointed to by offsetp from a count of UTF-8 chars from
-the start of the string, to a count of the equivalent number of bytes; if
-lenp is non-zero, it does the same to lenp, but this time starting from
-the offset, rather than from the start of the string. Handles magic and
-type coercion.
-
-=cut
-*/
-
-/*
- * sv_pos_u2b() uses, like sv_pos_b2u(), the mg_ptr of the potential
- * PERL_UTF8_magic of the sv to store the mapping between UTF-8 and
- * byte offsets. See also the comments of S_utf8_mg_pos().
- *
- */
-
+/* Walk forwards to find the byte corresponding to the passed in UTF-8
+ offset. */
static STRLEN
S_sv_pos_u2b_forwards(pTHX_ const U8 *const start, const U8 *const send,
STRLEN uoffset)
return s - start;
}
-
+/* Given the length of the string in both bytes and UTF-8 characters, decide
+ whether to walk forwards or backwards to find the byte corresponding to
+ the passed in UTF-8 offset. */
static STRLEN
S_sv_pos_u2b_midway(pTHX_ const U8 *const start, const U8 *send,
STRLEN uoffset, STRLEN uend)
return send - start;
}
+/* For the string representation of the given scalar, find the byte
+ corresponding to the passed in UTF-8 offset. uoffset0 and boffset0
+ give another position in the string, *before* the sought offset, which
+ (which is always true, as 0, 0 is a valid pair of positions), which should
+ help reduce the amount of linear searching.
+ If *mgp is non-NULL, it should point to the UTF-8 cache magic, which
+ will be used to reduce the amount of linear searching. The cache will be
+ created if necessary, and the found value offered to it for update. */
static STRLEN
S_sv_pos_u2b_cached(pTHX_ SV *sv, MAGIC **mgp, const U8 *const start,
const U8 *const send, STRLEN uoffset,
+ S_sv_pos_u2b_forwards(aTHX_ start + boffset0,
send, uoffset - uoffset0);
}
- } else {
+ }
+ else if (cache[2] < uoffset) {
+ /* We're between the two cache entries. */
+ if (cache[2] > uoffset0) {
+ /* and the cache knows more than the passed in pair */
+ uoffset0 = cache[2];
+ boffset0 = cache[3];
+ }
+
boffset = boffset0
+ S_sv_pos_u2b_midway(aTHX_ start + boffset0,
start + cache[1],
uoffset - uoffset0,
cache[0] - uoffset0);
+ } else {
+ boffset = boffset0
+ + S_sv_pos_u2b_midway(aTHX_ start + boffset0,
+ start + cache[3],
+ uoffset - uoffset0,
+ cache[2] - uoffset0);
}
found = TRUE;
}
return boffset;
}
+
+/*
+=for apidoc sv_pos_u2b
+
+Converts the value pointed to by offsetp from a count of UTF-8 chars from
+the start of the string, to a count of the equivalent number of bytes; if
+lenp is non-zero, it does the same to lenp, but this time starting from
+the offset, rather than from the start of the string. Handles magic and
+type coercion.
+
+=cut
+*/
+
+/*
+ * sv_pos_u2b() uses, like sv_pos_b2u(), the mg_ptr of the potential
+ * PERL_UTF8_magic of the sv to store the mapping between UTF-8 and
+ * byte offsets. See also the comments of S_utf8_mg_pos_cache_update().
+ *
+ */
+
void
Perl_sv_pos_u2b(pTHX_ register SV *sv, I32* offsetp, I32* lenp)
{
return;
}
-/*
-=for apidoc sv_pos_b2u
-
-Converts the value pointed to by offsetp from a count of bytes from the
-start of the string, to a count of the equivalent number of UTF-8 chars.
-Handles magic and type coercion.
-
-=cut
+/* Create and update the UTF8 magic offset cache, with the proffered utf8/
+ byte length pairing. The (byte) length of the total SV is passed in too,
+ as blen, because for some (more esoteric) SVs, the call to SvPV_const()
+ may not have updated SvCUR, so we can't rely on reading it directly.
+
+ The proffered utf8/byte length pairing isn't used if the cache already has
+ two pairs, and swapping either for the proffered pair would increase the
+ RMS of the intervals between known byte offsets.
+
+ The cache itself consists of 4 STRLEN values
+ 0: larger UTF-8 offset
+ 1: corresponding byte offset
+ 2: smaller UTF-8 offset
+ 3: corresponding byte offset
+
+ Unused cache pairs have the value 0, 0.
+ Keeping the cache "backwards" means that the invariant of
+ cache[0] >= cache[2] is maintained even with empty slots, which means that
+ the code that uses it doesn't need to worry if only 1 entry has actually
+ been set to non-zero. It also makes the "position beyond the end of the
+ cache" logic much simpler, as the first slot is always the one to start
+ from.
*/
-
-/*
- * sv_pos_b2u() uses, like sv_pos_u2b(), the mg_ptr of the potential
- * PERL_UTF8_magic of the sv to store the mapping between UTF-8 and
- * byte offsets.
- *
- */
-
static void
S_utf8_mg_pos_cache_update(pTHX_ SV *sv, MAGIC **mgp, STRLEN byte, STRLEN utf8,
STRLEN blen)
return endu;
}
+/*
+=for apidoc sv_pos_b2u
+
+Converts the value pointed to by offsetp from a count of bytes from the
+start of the string, to a count of the equivalent number of UTF-8 chars.
+Handles magic and type coercion.
+
+=cut
+*/
+
+/*
+ * sv_pos_b2u() uses, like sv_pos_u2b(), the mg_ptr of the potential
+ * PERL_UTF8_magic of the sv to store the mapping between UTF-8 and
+ * byte offsets.
+ *
+ */
void
Perl_sv_pos_b2u(pTHX_ register SV* sv, I32* offsetp)
{
STRLEN blen;
MAGIC* mg = NULL;
const U8* send;
+ bool found = FALSE;
if (!sv)
return;
}
ASSERT_UTF8_CACHE(cache);
- if (PL_utf8cache < 0) {
- const STRLEN reallen = S_sv_pos_b2u_forwards(aTHX_ s, send);
-
- if (len != reallen) {
- /* Need to turn the assertions off otherwise we may recurse
- infinitely while printing error messages. */
- SAVEI8(PL_utf8cache);
- PL_utf8cache = 0;
- Perl_croak(aTHX_ "panic: sv_pos_b2u cache %"UVf
- " real %"UVf" for %"SVf,
- (UV) len, (UV) reallen, sv);
- }
- }
+ found = TRUE;
} else if (mg->mg_len != -1) {
len = S_sv_pos_b2u_midway(aTHX_ s, send, s + blen, mg->mg_len);
- } else {
- len = S_sv_pos_b2u_forwards(aTHX_ s, send);
+ found = TRUE;
}
}
- else {
- len = S_sv_pos_b2u_forwards(aTHX_ s, send);
+ if (!found || PL_utf8cache < 0) {
+ const STRLEN real_len = S_sv_pos_b2u_forwards(aTHX_ s, send);
+
+ if (found && PL_utf8cache < 0) {
+ if (len != real_len) {
+ /* Need to turn the assertions off otherwise we may recurse
+ infinitely while printing error messages. */
+ SAVEI8(PL_utf8cache);
+ PL_utf8cache = 0;
+ Perl_croak(aTHX_ "panic: sv_pos_b2u cache %"UVf
+ " real %"UVf" for %"SVf,
+ (UV) len, (UV) real_len, sv);
+ }
+ }
+ len = real_len;
}
*offsetp = len;
projects / p5sagit/p5-mst-13.2.git / blobdiff