genode/repos/base/include/util/arg_string.h

/*
 * \brief  Argument list string handling
 * \author Norman Feske
 * \date   2006-05-22
 *
 * Each argument has the form:
 *
 * ! <key>=<value>
 *
 * Key is an identifier that begins with a letter or underline
 * and may also contain digits.
 *
 * A list of arguments is specified by using comma as separator,
 * whereas the first argument is considered as the weakest. If
 * we replace an argument value of an existing argument, the
 * existing argument is removed and we append a new argument at
 * the end of the string.
 */

/*
 * Copyright (C) 2006-2013 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _INCLUDE__UTIL__ARG_STRING_H_
#define _INCLUDE__UTIL__ARG_STRING_H_

#include <util/token.h>
#include <util/string.h>
#include <base/snprintf.h>

namespace Genode {

	class Arg_string;

	class Arg
	{
		/**
		 * Define tokenizer used for argument-string parsing
		 *
		 * Argument-string tokens accept C-style identifiers.
		 */
		typedef ::Genode::Token<Scanner_policy_identifier_with_underline> Token;

		friend class Arg_string;

		private:

			Token _key;
			Token _value;

			/**
			 * Return long value of argument
			 *
			 * \param  out_value    argument converted to unsigned long value
			 * \param  out_sign     1 if positive; -1 if negative
			 * \return              true if no syntactic anomaly occured
			 *
			 * This function handles the numberic modifiers G (2^30),
			 * M (2^20), and K (2^10).
			 */
			bool read_ulong(unsigned long *out_value, int *out_sign) const
			{
				Token t = _value;

				/* check for sign; default is positive */
				*out_sign = 1;
				if (t[0] == '+')
					t = t.next();
				else if (t[0] == '-') {
					*out_sign = -1;
					t = t.next();
				}

				/* stop if token after sign is no number */
				if (t.type() != Token::NUMBER)
					return false;

				/* read numeric value and skip the corresponding tokens */
				Number_of_bytes value;
				size_t n = ascii_to(t.start(), &value);

				if (n == 0)
					return false;

				t = Token(t.start() + n);
				*out_value = value;

				/* check for strange characters at the end of the number */
				t = t.eat_whitespace();
				if (t && (t[0] != ',')) return false;

				return true;
			}

		public:

			/**
			 * Construct argument from Token(s)
			 */
			Arg(Token t = Token()) : _key(t), _value(0)
			{
				for (; t && (t[0] != ','); t = t.next().eat_whitespace())
					if (t[0] == '=') {
						_value = t.next().eat_whitespace();
						break;
					}
			}

			inline bool valid() const { return _key; }

			unsigned long ulong_value(unsigned long default_value) const
			{
				unsigned long value = 0;
				int sign = 1;

				bool valid = read_ulong(&value, &sign);
				if (sign < 0)
					return default_value;

				return valid ? value : default_value;
			}

			long long_value(long default_value) const
			{
				unsigned long value = 0;
				int sign = 1;

				bool valid = read_ulong(&value, &sign);

				/* FIXME we should check for overflows here! */
				return valid ? sign*value : default_value;
			}

			bool bool_value(bool default_value) const
			{
				/* check for known idents */
				if (_value.type() == Token::IDENT) {
					char   *p = _value.start();
					size_t  l = _value.len();

					if (!strcmp(p, "yes",  l)) return true;
					if (!strcmp(p, "true", l)) return true;
					if (!strcmp(p, "on",   l)) return true;

					if (!strcmp(p, "no",    l)) return false;
					if (!strcmp(p, "false", l)) return false;
					if (!strcmp(p, "off",   l)) return false;

					/* saxony mode ;) */
					if (!strcmp(p, "nu",  l)) return true;
					if (!strcmp(p, "nee", l)) return false;

					return default_value;
				}

				/* read values 0 (false) / !0 (true) */
				unsigned long value;
				int sign;
				bool valid = read_ulong(&value, &sign);

				return valid ? value : default_value;
			}

			void key(char *dst, size_t dst_len) const
			{
				_key.string(dst, dst_len);
			}

			void string(char *dst, size_t dst_len, const char *default_string) const
			{
				/* check for one-word string w/o quotes */
				if (_value.type() == Token::IDENT) {
					size_t  len = min(dst_len - 1, _value.len());
					memcpy(dst, _value.start(), len);
					dst[len] = 0;
					return;
				}

				/* stop here if _value is not a string */
				if (_value.type() != Token::STRING) {
					strncpy(dst, default_string, dst_len);
					return;
				}

				/* unpack string to dst */
				size_t num_chars = min(dst_len - 1, _value.len());
				unpack_string(_value.start(), dst, num_chars);
			}
	};


	class Arg_string
	{
		typedef Arg::Token Token;

		private:

			static Token _next_key(Token t)
			{
				for (; t; t = t.next().eat_whitespace())

					/* if we find a comma, return token after comma */
					if (t[0] == ',') return t.next().eat_whitespace();

				return Token();
			}

			/**
			 * Find key token in argument string
			 */
			static Token _find_key(const char *args, const char *key)
			{
				for (Token t(args); t; t = _next_key(t))

					/* check if key matches */
					if ((t.type() == Token::IDENT) && !strcmp(key, t.start(), t.len()))
						return t;

				return Token();
			}

			/**
			 * Append source string to destination string
			 *
			 * NOTE: check string length before calling this function!
			 *
			 * \return  last character of result string
			 */
			static char *_append(char *dst, const char *src)
			{
				unsigned src_len = strlen(src);
				while (*dst) dst++;
				memcpy(dst, src, src_len + 1);
				return dst + src_len;
			}

		public:

			/**
			 * Find argument by its key
			 */
			static Arg find_arg(const char *args, const char *key) {
				return (args && key) ? Arg(_find_key(args, key)) : Arg(); }

			static Arg first_arg(const char *args) {
				return Arg(Token(args)); }

			/**
			 * Remove argument with the specified key
			 */
			static bool remove_arg(char *args, const char *key)
			{
				if (!args || !key) return false;

				Token beg  = _find_key(args, key);
				Token next = _next_key(beg);

				/* no such key to remove - we are done */
				if (!beg) return true;

				/* if argument is the last one, null-terminate string right here */
				if (!next) {

					/* eat all pending whitespaces at the end of the string */
					char *s = max(beg.start() - 1, args);
					while (s > args && (*s == ' ')) s--;

					/* write string-terminating zero */
					*s = 0;
				} else
					memcpy(beg.start(), next.start(), strlen(next.start()) + 1);

				return true;
			}

			/**
			 * Add new argument
			 */
			static bool add_arg(char *args, unsigned args_len,
			                    const char *key, const char *value)
			{
				if (!args || !key || !value) return false;

				unsigned old_len = strlen(args);

				/* check if args string has enough capacity */
				if (old_len + strlen(key) + strlen(value) + 2 > args_len)
					return false;

				args += old_len;

				if (old_len)
					args = _append(args, ", ");

				_append(_append(_append(args, key), "="), value);
				return true;
			}

			/**
			 * Assign new value to argument
			 */
			static bool set_arg(char *args, unsigned args_len,
			                    const char *key, const char *value)
			{
				return remove_arg(args, key) && add_arg(args, args_len, key, value);
			}

			/**
			 * Assign new integer argument
			 */
			static bool set_arg(char *args, unsigned args_len,
			                    const char *key, int value)
			{
				enum { STRING_LONG_MAX = 32 };
				char buf[STRING_LONG_MAX];
				snprintf(buf, sizeof(buf), "%d", value);
				return remove_arg(args, key) && add_arg(args, args_len, key, buf);
			}
	};
}

#endif /* _INCLUDE__UTIL__ARG_STRING_H_ */