asterisk/include/asterisk/strings.h

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 * \brief String manipulation functions
 */

#ifndef _ASTERISK_STRINGS_H
#define _ASTERISK_STRINGS_H

#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

#include "asterisk/inline_api.h"
#include "asterisk/compiler.h"
#include "asterisk/compat.h"

static force_inline int ast_strlen_zero(const char *s)
{
	return (!s || (*s == '\0'));
}

/*! \brief returns the equivalent of logic or for strings:
 * first one if not empty, otherwise second one.
 */
#define S_OR(a, b)	(!ast_strlen_zero(a) ? (a) : (b))

/*!
  \brief Gets a pointer to the first non-whitespace character in a string.
  \param ast_skip_blanks function being used
  \param str the input string
  \return a pointer to the first non-whitespace character
 */
AST_INLINE_API(
char *ast_skip_blanks(const char *str),
{
	while (*str && *str < 33)
		str++;
	return (char *)str;
}
)

/*!
  \brief Trims trailing whitespace characters from a string.
  \param ast_trim_blanks function being used
  \param str the input string
  \return a pointer to the modified string
 */
AST_INLINE_API(
char *ast_trim_blanks(char *str),
{
	char *work = str;

	if (work) {
		work += strlen(work) - 1;
		/* It's tempting to only want to erase after we exit this loop, 
		   but since ast_trim_blanks *could* receive a constant string
		   (which we presumably wouldn't have to touch), we shouldn't
		   actually set anything unless we must, and it's easier just
		   to set each position to \0 than to keep track of a variable
		   for it */
		while ((work >= str) && *work < 33)
			*(work--) = '\0';
	}
	return str;
}
)

/*!
  \brief Gets a pointer to first whitespace character in a string.
  \param ast_skip_noblanks function being used
  \param str the input string
  \return a pointer to the first whitespace character
 */
AST_INLINE_API(
char *ast_skip_nonblanks(char *str),
{
	while (*str && *str > 32)
		str++;
	return str;
}
)
  
/*!
  \brief Strip leading/trailing whitespace from a string.
  \param s The string to be stripped (will be modified).
  \return The stripped string.

  This functions strips all leading and trailing whitespace
  characters from the input string, and returns a pointer to
  the resulting string. The string is modified in place.
*/
AST_INLINE_API(
char *ast_strip(char *s),
{
	s = ast_skip_blanks(s);
	if (s)
		ast_trim_blanks(s);
	return s;
} 
)

/*!
  \brief Strip leading/trailing whitespace and quotes from a string.
  \param s The string to be stripped (will be modified).
  \param beg_quotes The list of possible beginning quote characters.
  \param end_quotes The list of matching ending quote characters.
  \return The stripped string.

  This functions strips all leading and trailing whitespace
  characters from the input string, and returns a pointer to
  the resulting string. The string is modified in place.

  It can also remove beginning and ending quote (or quote-like)
  characters, in matching pairs. If the first character of the
  string matches any character in beg_quotes, and the last
  character of the string is the matching character in
  end_quotes, then they are removed from the string.

  Examples:
  \code
  ast_strip_quoted(buf, "\"", "\"");
  ast_strip_quoted(buf, "'", "'");
  ast_strip_quoted(buf, "[{(", "]})");
  \endcode
 */
char *ast_strip_quoted(char *s, const char *beg_quotes, const char *end_quotes);

/*!
  \brief Strip backslash for "escaped" semicolons.
  \brief s The string to be stripped (will be modified).
  \return The stripped string.
 */
char *ast_unescape_semicolon(char *s);

/*!
  \brief Size-limited null-terminating string copy.
  \param ast_copy_string function being used
  \param dst The destination buffer.
  \param src The source string
  \param size The size of the destination buffer
  \return Nothing.

  This is similar to \a strncpy, with two important differences:
    - the destination buffer will \b always be null-terminated
    - the destination buffer is not filled with zeros past the copied string length
  These differences make it slightly more efficient, and safer to use since it will
  not leave the destination buffer unterminated. There is no need to pass an artificially
  reduced buffer size to this function (unlike \a strncpy), and the buffer does not need
  to be initialized to zeroes prior to calling this function.
*/
AST_INLINE_API(
void ast_copy_string(char *dst, const char *src, size_t size),
{
	while (*src && size) {
		*dst++ = *src++;
		size--;
	}
	if (__builtin_expect(!size, 0))
		dst--;
	*dst = '\0';
}
)


/*!
  \brief Build a string in a buffer, designed to be called repeatedly
  
  This is a wrapper for snprintf, that properly handles the buffer pointer
  and buffer space available.

  \param buffer current position in buffer to place string into (will be updated on return)
  \param space remaining space in buffer (will be updated on return)
  \param fmt printf-style format string
  \return 0 on success, non-zero on failure.
*/
int ast_build_string(char **buffer, size_t *space, const char *fmt, ...) __attribute__ ((format (printf, 3, 4)));

/*!
  \brief Build a string in a buffer, designed to be called repeatedly
  
  This is a wrapper for snprintf, that properly handles the buffer pointer
  and buffer space available.

  \return 0 on success, non-zero on failure.
  \param buffer current position in buffer to place string into (will be updated on return)
  \param space remaining space in buffer (will be updated on return)
  \param fmt printf-style format string
  \param ap varargs list of arguments for format
*/
int ast_build_string_va(char **buffer, size_t *space, const char *fmt, va_list ap);

/*! Make sure something is true */
/*!
 * Determine if a string containing a boolean value is "true".
 * This function checks to see whether a string passed to it is an indication of an "true" value.  It checks to see if the string is "yes", "true", "y", "t", "on" or "1".  
 *
 * Returns 0 if val is a NULL pointer, -1 if "true", and 0 otherwise.
 */
int ast_true(const char *val);

/*! Make sure something is false */
/*!
 * Determine if a string containing a boolean value is "false".
 * This function checks to see whether a string passed to it is an indication of an "false" value.  It checks to see if the string is "no", "false", "n", "f", "off" or "0".  
 *
 * Returns 0 if val is a NULL pointer, -1 if "false", and 0 otherwise.
 */
int ast_false(const char *val);

/*
  \brief Join an array of strings into a single string.
  \param s the resulting string buffer
  \param len the length of the result buffer, s
  \param w an array of strings to join

  This function will join all of the strings in the array 'w' into a single
  string.  It will also place a space in the result buffer in between each
  string from 'w'.
*/
void ast_join(char *s, size_t len, char * const w[]);

/*
  \brief Parse a time (integer) string.
  \param src String to parse
  \param dst Destination
  \param _default Value to use if the string does not contain a valid time
  \param consumed The number of characters 'consumed' in the string by the parse (see 'man sscanf' for details)
  \return zero on success, non-zero on failure
*/
int ast_get_time_t(const char *src, time_t *dst, time_t _default, int *consumed);

/* The realloca lets us ast_restrdupa(), but you can't mix any other ast_strdup calls! */

struct ast_realloca {
	char *ptr;
	int alloclen;
};

#define ast_restrdupa(ra, s) \
	({ \
		if ((ra)->ptr && strlen(s) + 1 < (ra)->alloclen) { \
			strcpy((ra)->ptr, s); \
		} else { \
			(ra)->ptr = alloca(strlen(s) + 1 - (ra)->alloclen); \
			if ((ra)->ptr) (ra)->alloclen = strlen(s) + 1; \
		} \
		(ra)->ptr; \
	})

/*!
 * \brief Compute a hash value on a string
 *
 * This famous hash algorithm was written by Dan Bernstein and is
 * commonly used.
 *
 * http://www.cse.yorku.ca/~oz/hash.html
 */
static force_inline int ast_str_hash(const char *str)
{
	int hash = 5381;

	while (*str)
		hash = hash * 33 ^ *str++;

	return abs(hash);
}

#endif /* _ASTERISK_STRINGS_H */