user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/options/internal/generic/search.cpp

@@ -0,0 +1,98 @@
+#include <mlibc/search.hpp>
+#include <frg/string.hpp>
+#include <stdlib.h>
+#include <stdint.h>
+#include <errno.h>
+
+struct _ENTRY {
+	ENTRY entry;
+	bool used;
+};
+
+namespace mlibc {
+
+int hcreate_r(size_t num_entries, struct hsearch_data *htab) {
+	if(!htab) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	htab->table = static_cast<_ENTRY*>(calloc(num_entries, sizeof(_ENTRY)));
+	if(!htab->table) {
+		errno = ENOMEM;
+		return 0;
+	}
+	htab->filled = 0;
+	htab->size = num_entries;
+	return 1;
+}
+
+void hdestroy_r(struct hsearch_data *htab) {
+	if(!htab) {
+		errno = EINVAL;
+		return;
+	}
+	free(htab->table);
+	htab->table = nullptr;
+	htab->size = 0;
+	htab->filled = 0;
+}
+
+
+int hsearch_r(ENTRY item, ACTION action, ENTRY **ret, struct hsearch_data *htab) {
+	auto key = frg::string_view{item.key};
+	auto hash = frg::hash<frg::string_view>{}(key);
+
+	size_t bucket_index = hash % htab->size;
+	size_t start = bucket_index;
+	while(true) {
+		auto &bucket = htab->table[bucket_index];
+
+		if(bucket.used) {
+			if(bucket.entry.key == key) {
+				*ret = &bucket.entry;
+				return 1;
+			}
+		} else if(action == FIND) {
+			errno = ESRCH;
+			*ret = nullptr;
+			return 0;
+		}
+
+		bucket_index = (bucket_index + 1) % htab->size;
+
+		if(bucket_index == start) {
+			if(action == FIND) {
+				errno = ESRCH;
+				*ret = nullptr;
+				return 0;
+			} else {
+				break;
+			}
+		}
+	}
+
+	// insert a new entry.
+	if(htab->size == htab->filled) {
+		errno = ENOMEM;
+		return 0;
+	}
+	++htab->filled;
+
+	bucket_index = start;
+	while(true) {
+		auto &bucket = htab->table[bucket_index];
+		if(!bucket.used) {
+			bucket.used = true;
+			bucket.entry = item;
+			*ret = &bucket.entry;
+			break;
+		}
+
+		bucket_index = (bucket_index + 1) % htab->size;
+	}
+
+	return 1;
+}
+
+} // namespace mlibc