Add Perl_bytes_cmp_utf8() to compare character sequences in different encodings

Convert sv_eq_flags() and sv_cmp_flags() to use it.

Previously, to compare two strings of characters, where was was in UTF-8, and
one was not, you had to either:

1: Upgrade the second to UTF-8
2: Compare the resulting octet sequence
3: Free the temporary UTF-8 string

or:

1: Attempt to downgrade the first to bytes. If it can't be, they aren't equal
2: Else compare the resulting octet sequence
3: Free the temporary byte string

Which for the general case involves a malloc()/free() and at least two O(n)
scans per comparison.

Whereas this approach has no allocation, a single O(n) scan, which terminates
as early as the best case for the second approach.

1 files changed, 1 insertions, 0 deletions

diff --git a/embed.h b/embed.h
index b743761f7a..0d70e87f9c 100644
--- a/embed.h
+++ b/embed.h
@@ -47,6 +47,7 @@
 #define av_undef(a)		Perl_av_undef(aTHX_ a)
 #define av_unshift(a,b)		Perl_av_unshift(aTHX_ a,b)
 #define block_gimme()		Perl_block_gimme(aTHX)
+#define bytes_cmp_utf8(a,b,c,d)	Perl_bytes_cmp_utf8(aTHX_ a,b,c,d)
 #define bytes_from_utf8(a,b,c)	Perl_bytes_from_utf8(aTHX_ a,b,c)
 #define bytes_to_utf8(a,b)	Perl_bytes_to_utf8(aTHX_ a,b)
 #define call_argv(a,b,c)	Perl_call_argv(aTHX_ a,b,c)