user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/posix/generic/strings.cpp

@@ -0,0 +1,113 @@
+
+#include <strings.h>
+#include <string.h>
+
+#include <ctype.h>
+#include <bits/ensure.h>
+#include <mlibc/strings.hpp>
+
+char *index (const char *s, int c) {
+	return strchr(s, c);
+}
+
+char *rindex(const char *s, int c) {
+	return strrchr(s, c);
+}
+
+namespace {
+
+	template<typename T>
+	int ffs_generic(T i) {
+		//Non-portably assume a byte has 8 bits; fine in all plausible cases.
+		for(size_t b = 0; b < sizeof(T) * 8;)
+			if(i & (static_cast<T>(0x1) << b++))
+				return b;
+
+		return 0;
+	}
+
+} // namespace
+
+// On RISC-V, __builtin_ffs just calls into ffs, so we can't use it here.
+#if defined(__has_builtin) && !defined(__riscv)
+#	if __has_builtin(__builtin_ffs)
+#		define __mlibc_ffs __builtin_ffs
+#	endif
+#	if __has_builtin(__builtin_ffsl)
+#		define __mlibc_ffsl __builtin_ffsl
+#	endif
+#	if __has_builtin(__builtin_ffsll)
+#		define __mlibc_ffsll __builtin_ffsll
+#	endif
+#endif
+
+int ffs(int i) {
+#ifdef __mlibc_ffs
+	return __mlibc_ffs(i);
+#else
+	return ffs_generic<int>(i);
+#endif
+}
+
+/*
+	Both ffsl() and ffsll() are glibc extensions
+	defined in string.h. They are however implemented
+	here because of similarity in logic and
+	shared code.
+*/
+
+int ffsl(long i) {
+#ifdef __mlibc_ffsl
+	return __mlibc_ffsl(i);
+#else
+	return ffs_generic<long>(i);
+#endif
+}
+
+int ffsll(long long i) {
+#ifdef __mlibc_ffsll
+	return __mlibc_ffsll(i);
+#else
+	return ffs_generic<long long>(i);
+#endif
+}
+
+int strcasecmp(const char *a, const char *b) {
+	size_t i = 0;
+	while(true) {
+		unsigned char a_byte = tolower(a[i]);
+		unsigned char b_byte = tolower(b[i]);
+		if(!a_byte && !b_byte)
+			return 0;
+		// If only one char is null, one of the following cases applies.
+		if(a_byte < b_byte)
+			return -1;
+		if(a_byte > b_byte)
+			return 1;
+		i++;
+	}
+}
+
+int strncasecmp(const char *a, const char *b, size_t size) {
+	return mlibc::strncasecmp(a, b, size);
+}
+
+// Marked as obsolete in posix 2008 but used by at least tracker
+int bcmp(const void *s1, const void *s2, size_t n) {
+	return memcmp(s1, s2, n);
+}
+
+void bcopy(const void *s1, void *s2, size_t n) {
+	memmove(s2, s1, n);
+}
+
+void bzero(void *s, size_t n) {
+	memset(s, 0, n);
+}
+
+void explicit_bzero(void *s, size_t len) {
+  memset (s, 0, len);
+  // Compiler barrier to prevent optimizing away the memset
+  asm volatile ("" ::: "memory");
+}
+