else
PL_numeric_radix_sv = NULL;
- DEBUG_L(PerlIO_printf(Perl_debug_log, "Locale radix is %s, ?UTF-8=%d\n",
+ DEBUG_L(PerlIO_printf(Perl_debug_log, "Locale radix is '%s', ?UTF-8=%d\n",
(PL_numeric_radix_sv)
? SvPVX(PL_numeric_radix_sv)
: "NULL",
#ifdef MB_CUR_MAX
/* We only handle single-byte locales (outside of UTF-8 ones; so if
- * this locale requires than one byte, there are going to be
+ * this locale requires more than one byte, there are going to be
* problems. */
if (check_for_problems && MB_CUR_MAX > 1
* Any code changing the locale (outside this file) should use
* POSIX::setlocale, which calls this function. Therefore this function
* should be called directly only from this file and from
- * POSIX::setlocale() */
+ * POSIX::setlocale().
+ *
+ * The design of locale collation is that every locale change is given an
+ * index 'PL_collation_ix'. The first time a string particpates in an
+ * operation that requires collation while locale collation is active, it
+ * is given PERL_MAGIC_collxfrm magic (via sv_collxfrm_flags()). That
+ * magic includes the collation index, and the transformation of the string
+ * by strxfrm(), q.v. That transformation is used when doing comparisons,
+ * instead of the string itself. If a string changes, the magic is
+ * cleared. The next time the locale changes, the index is incremented,
+ * and so we know during a comparison that the transformation is not
+ * necessarily still valid, and so is recomputed. Note that if the locale
+ * changes enough times, the index could wrap (a U32), and it is possible
+ * that a transformation would improperly be considered valid, leading to
+ * an unlikely bug */
if (! newcoll) {
if (PL_collation_name) {
return;
}
+ /* If this is not the same locale as currently, set the new one up */
if (! PL_collation_name || strNE(PL_collation_name, newcoll)) {
++PL_collation_ix;
Safefree(PL_collation_name);
PL_collation_standard = isNAME_C_OR_POSIX(newcoll);
{
+ /* A locale collation definition includes primary, secondary,
+ * tertiary, etc. weights for each character. To sort, the primary
+ * weights are used, and only if they compare equal, then the
+ * secondary weights are used, and only if they compare equal, then
+ * the tertiary, etc. strxfrm() works by taking the input string,
+ * say ABC, and creating an output string consisting of first the
+ * primary weights, A¹B¹C¹ followed by the secondary ones, A²B²C²;
+ * and then the tertiary, etc, yielding A¹B¹C¹A²B²C²A³B³C³....
+ * Some characters may not have weights at every level. In our
+ * example, let's say B doesn't have a tertiary weight, and A
+ * doesn't have a secondary weight. The constructed string is then
+ * going to be A¹B¹C¹B²C²A³C³.... This has the desired
+ * characteristics that strcmp() will look at the secondary or
+ * tertiary weights only if the strings compare equal at all higher
+ * priority weights. The length of the transformed string is
+ * roughly a linear function of the input string. It's not exactly
+ * linear because some characters don't have weights at all levels,
+ * and there are some complications, so there is often per-string
+ * overhead. When we call strxfrm() we have to allocate some
+ * memory to hold the transformed string. The calculations below
+ * try to find constants for this locale 'm' and 'b' so that m*x +
+ * b equals how much space we need given the size of the input
+ * string in 'x'. If we calculate too small, we increase the size
+ * as needed, and call strxfrm() again, but it is better to get it
+ * right the first time to avoid wasted expensive string
+ * transformations. */
/* 2: at most so many chars ('a', 'b'). */
/* 50: surely no system expands a char more. */
#define XFRMBUFSIZE (2 * 50)
* differences. First, it handles embedded NULs. Second, it allocates
* a bit more memory than needed for the transformed data itself.
* The real transformed data begins at offset sizeof(collationix).
+ * *xlen is set to the length of that, and doesn't include the collation index
+ * size.
* Please see sv_collxfrm() to see how this is used.
*/
xAlloc = sizeof(PL_collation_ix) + PL_collxfrm_base + (PL_collxfrm_mult * len) + 1;
Newx(xbuf, xAlloc, char);
- if (! xbuf)
+ if (UNLIKELY(! xbuf))
goto bad;
+ /* Store the collation id */
*(U32*)xbuf = PL_collation_ix;
xout = sizeof(PL_collation_ix);
+
+ /* Then the transformation of the input. We loop until successful, or we
+ * give up */
for (xin = 0; xin < len; ) {
Size_t xused;
for (;;) {
xused = strxfrm(xbuf + xout, s + xin, xAlloc - xout);
- if (xused >= PERL_INT_MAX)
- goto bad;
+
+ /* If the transformed string occupies less space than we told
+ * strxfrm() was available, it means it successfully transformed
+ * the whole string. */
if ((STRLEN)xused < xAlloc - xout)
break;
+
+ if (UNLIKELY(xused >= PERL_INT_MAX))
+ goto bad;
+
+ /* Otherwise it should be that the transformation stopped in the
+ * middle because it ran out of space. Malloc more, and try again.
+ * */
xAlloc = (2 * xAlloc) + 1;
Renew(xbuf, xAlloc, char);
- if (! xbuf)
+ if (UNLIKELY(! xbuf))
goto bad;
}
https://perl5.git.perl.org / perl5.git / blobdiff