BuildSystem: Move all userpace libraries under the userspace directory

As the number of libraries is increasing, root directory starts to
expand. This adds better organization for libraries

userspace/libraries/LibC/pwd.cpp

@@ -0,0 +1,140 @@
+#include <BAN/Assert.h>
+
+#include <ctype.h>
+#include <errno.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static FILE* s_pwent_fp = nullptr;
+static passwd s_pwent_struct;
+
+static bool open_pwent()
+{
+	if (s_pwent_fp)
+		return true;
+	s_pwent_fp = fopen("/etc/passwd", "r");
+	return s_pwent_fp;
+}
+
+static void clear_pwent(passwd& passwd)
+{
+	if (passwd.pw_name)
+		free(passwd.pw_name);
+	passwd.pw_name = nullptr;
+	if (passwd.pw_dir)
+		free(passwd.pw_dir);
+	passwd.pw_dir = nullptr;
+	if (passwd.pw_shell)
+		free(passwd.pw_shell);
+	passwd.pw_shell = nullptr;
+}
+
+void endpwent(void)
+{
+	if (!s_pwent_fp)
+		return;
+	fclose(s_pwent_fp);
+	s_pwent_fp = nullptr;
+	clear_pwent(s_pwent_struct);
+}
+
+struct passwd* getpwent(void)
+{
+	if (!s_pwent_fp)
+		if (!open_pwent())
+			return nullptr;
+	clear_pwent(s_pwent_struct);
+
+	static char buffer[4096];
+	if (!fgets(buffer, sizeof(buffer), s_pwent_fp))
+		return nullptr;
+
+	size_t buffer_len = strlen(buffer);
+
+	ASSERT(buffer[buffer_len - 1] == '\n');
+	buffer[buffer_len - 1] = '\0';
+	buffer_len--;
+
+	const char* ptr = buffer;
+	for (int i = 0; i < 7; i++)
+	{
+		char* end = strchr(ptr, ':');
+		ASSERT((i < 6) ? end != nullptr : end == nullptr);
+		if (!end)
+			end = buffer + buffer_len;
+		*end = '\0';
+
+		const size_t field_len = end - ptr;
+
+		switch (i)
+		{
+			case 0:
+				s_pwent_struct.pw_name = (char*)malloc(field_len + 1);
+				if (!s_pwent_struct.pw_name)
+					return nullptr;
+				strcpy(s_pwent_struct.pw_name, ptr);
+				break;
+			case 1:
+				break;
+			case 2:
+				ASSERT(1 <= field_len && field_len <= 9);
+				for (size_t j = 0; j < field_len; j++)
+					ASSERT(isdigit(ptr[j]));
+				s_pwent_struct.pw_uid = atoi(ptr);
+				break;
+			case 3:
+				ASSERT(1 <= field_len && field_len <= 9);
+				for (size_t j = 0; j < field_len; j++)
+					ASSERT(isdigit(ptr[j]));
+				s_pwent_struct.pw_uid = atoi(ptr);
+				break;
+			case 4:
+				break;
+			case 5:
+				s_pwent_struct.pw_dir = (char*)malloc(field_len + 1);
+				if (!s_pwent_struct.pw_dir)
+					return nullptr;
+				strcpy(s_pwent_struct.pw_dir, ptr);
+				break;
+			case 6:
+				s_pwent_struct.pw_shell = (char*)malloc(field_len + 1);
+				if (!s_pwent_struct.pw_shell)
+					return nullptr;
+				strcpy(s_pwent_struct.pw_shell, ptr);
+				break;
+		}
+
+		ptr = end + 1;
+	}
+
+	return &s_pwent_struct;
+}
+
+struct passwd* getpwnam(const char* name)
+{
+	passwd* pwd;
+	setpwent();
+	while ((pwd = getpwent()))
+		if (strcmp(pwd->pw_name, name) == 0)
+			return pwd;
+	return nullptr;
+}
+
+struct passwd* getpwuid(uid_t uid)
+{
+	passwd* pwd;
+	setpwent();
+	while ((pwd = getpwent()))
+		if (pwd->pw_uid == uid)
+			return pwd;
+	return nullptr;
+}
+
+void setpwent(void)
+{
+	if (!s_pwent_fp)
+		return;
+	fseek(s_pwent_fp, 0, SEEK_SET);
+}