Improve strstr performance for the common case of short needles. For a single
character strchr is best, for 2-4 characters a small loop is fastest. For these
the speedup over the Two-Way algorithm is ~10 times on large strings.
Newlib builds, the new code passes GLIBC testsuite. OK for commit?
* libc/string/str-two-way.h: New file.
* libc/string/memmem.c (memmem): New file.
* libc/include/string.h (memmem): Declare for all platforms.
* libc/string/strstr.c (strstr): Provide O(n) implementation when
not optimizing for space.
* libc/string/strcasestr.c (strcasestr): Likewise.
* libc/string/Makefile.am (ELIX_SOURCES): Rename to...
(ELIX_2_SOURCES): ...this.
(ELIX_4_SOURCES): New category, for memmem.
(lib_a_SOURCES, libstring_la_SOURCES): Build new file.
(CHEWOUT_FILES): Build documentation for memmem.
* libc/string/strings.tex: Include new docs.
Wilco Dijkstra
Yaakov Selkowitz
Eric Blake
Christopher Faylor