buffer.h

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/*
 * Copyright (C) 2004, 2005  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1998-2002  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: buffer.h,v 1.43.18.2 2005/04/29 00:16:53 marka Exp $ */

#ifndef ISC_BUFFER_H
#define ISC_BUFFER_H 1

/*****
 ***** Module Info
 *****/

/*! \file buffer.h
 *
 * \brief A buffer is a region of memory, together with a set of related subregions.
 * Buffers are used for parsing and I/O operations.
 *
 * The 'used region' and the 'available' region are disjoint, and their
 * union is the buffer's region.  The used region extends from the beginning
 * of the buffer region to the last used byte.  The available region
 * extends from one byte greater than the last used byte to the end of the
 * buffer's region.  The size of the used region can be changed using various
 * buffer commands.  Initially, the used region is empty.
 *
 * The used region is further subdivided into two disjoint regions: the
 * 'consumed region' and the 'remaining region'.  The union of these two
 * regions is the used region.  The consumed region extends from the beginning
 * of the used region to the byte before the 'current' offset (if any).  The
 * 'remaining' region the current pointer to the end of the used
 * region.  The size of the consumed region can be changed using various
 * buffer commands.  Initially, the consumed region is empty.
 *
 * The 'active region' is an (optional) subregion of the remaining region.
 * It extends from the current offset to an offset in the remaining region
 * that is selected with isc_buffer_setactive().  Initially, the active region
 * is empty.  If the current offset advances beyond the chosen offset, the
 * active region will also be empty.
 *
 * \verbatim
 *  /------------entire length---------------\
 *  /----- used region -----\/-- available --\
 *  +----------------------------------------+
 *  | consumed  | remaining |                |
 *  +----------------------------------------+
 *  a           b     c     d                e
 *
 * a == base of buffer.
 * b == current pointer.  Can be anywhere between a and d.
 * c == active pointer.  Meaningful between b and d.
 * d == used pointer.
 * e == length of buffer.
 *
 * a-e == entire length of buffer.
 * a-d == used region.
 * a-b == consumed region.
 * b-d == remaining region.
 * b-c == optional active region.
 *\endverbatim
 *
 * The following invariants are maintained by all routines:
 *
 *\code
 *	length > 0
 *
 *	base is a valid pointer to length bytes of memory
 *
 *	0 <= used <= length
 *
 *	0 <= current <= used
 *
 *	0 <= active <= used
 *	(although active < current implies empty active region)
 *\endcode
 *
 * \li MP:
 *	Buffers have no synchronization.  Clients must ensure exclusive
 *	access.
 *
 * \li Reliability:
 *	No anticipated impact.
 *
 * \li Resources:
 *	Memory: 1 pointer + 6 unsigned integers per buffer.
 *
 * \li Security:
 *	No anticipated impact.
 *
 * \li Standards:
 *	None.
 */

/***
 *** Imports
 ***/

#include <isc/lang.h>
#include <isc/magic.h>
#include <isc/types.h>

/*!
 * To make many functions be inline macros (via #define) define this.
 * If it is undefined, a function will be used.
 */
/* #define ISC_BUFFER_USEINLINE */

ISC_LANG_BEGINDECLS

/*@{*/
/*!
 *** Magic numbers
 ***/
#define ISC_BUFFER_MAGIC		0x42756621U	/* Buf!. */
#define ISC_BUFFER_VALID(b)		ISC_MAGIC_VALID(b, ISC_BUFFER_MAGIC)
/*@}*/

/*
 * The following macros MUST be used only on valid buffers.  It is the
 * caller's responsibility to ensure this by using the ISC_BUFFER_VALID
 * check above, or by calling another isc_buffer_*() function (rather than
 * another macro.)
 */

/*@{*/
/*!
 * Fundamental buffer elements.  (A through E in the introductory comment.)
 */
#define isc_buffer_base(b)    ((void *)(b)->base)			  /*a*/
#define isc_buffer_current(b) \
		((void *)((unsigned char *)(b)->base + (b)->current))     /*b*/
#define isc_buffer_active(b)  \
		((void *)((unsigned char *)(b)->base + (b)->active))      /*c*/
#define isc_buffer_used(b)    \
		((void *)((unsigned char *)(b)->base + (b)->used))        /*d*/
#define isc_buffer_length(b)  ((b)->length)				  /*e*/
/*@}*/

/*@{*/
/*!
 * Derived lengths.  (Described in the introductory comment.)
 */
#define isc_buffer_usedlength(b)	((b)->used)		      /* d-a */
#define isc_buffer_consumedlength(b)	((b)->current)		      /* b-a */
#define isc_buffer_remaininglength(b)	((b)->used - (b)->current)    /* d-b */
#define isc_buffer_activelength(b)	((b)->active - (b)->current)  /* c-b */
#define isc_buffer_availablelength(b)	((b)->length - (b)->used)     /* e-d */
/*@}*/

/*!
 * Note that the buffer structure is public.  This is principally so buffer
 * operations can be implemented using macros.  Applications are strongly
 * discouraged from directly manipulating the structure.
 */

struct isc_buffer {
	unsigned int		magic;
	void		       *base;
        /*@{*/
	/*! The following integers are byte offsets from 'base'. */
	unsigned int		length;
	unsigned int		used;
	unsigned int 		current;
	unsigned int 		active;
        /*@}*/
	/*! linkable */
	ISC_LINK(isc_buffer_t)	link;
	/*! private internal elements */
	isc_mem_t	       *mctx;
};

/***
 *** Functions
 ***/

isc_result_t
isc_buffer_allocate(isc_mem_t *mctx, isc_buffer_t **dynbuffer,
		    unsigned int length);
/*!<
 * \brief Allocate a dynamic linkable buffer which has "length" bytes in the
 * data region.
 *
 * Requires:
 *\li	"mctx" is valid.
 *
 *\li	"dynbuffer" is non-NULL, and "*dynbuffer" is NULL.
 *
 * Returns:
 *\li	ISC_R_SUCCESS		- success
 *\li	ISC_R_NOMEMORY		- no memory available
 *
 * Note:
 *\li	Changing the buffer's length field is not permitted.
 */

void
isc_buffer_free(isc_buffer_t **dynbuffer);
/*!<
 * \brief Release resources allocated for a dynamic buffer.
 *
 * Requires:
 *\li	"dynbuffer" is not NULL.
 *
 *\li	"*dynbuffer" is a valid dynamic buffer.
 *
 * Ensures:
 *\li	"*dynbuffer" will be NULL on return, and all memory associated with
 *	the dynamic buffer is returned to the memory context used in
 *	isc_buffer_allocate().
 */

void
isc__buffer_init(isc_buffer_t *b, const void *base, unsigned int length);
/*!<
 * \brief Make 'b' refer to the 'length'-byte region starting at base.
 *
 * Requires:
 *
 *\li	'length' > 0
 *
 *\li	'base' is a pointer to a sequence of 'length' bytes.
 *
 */

void
isc__buffer_invalidate(isc_buffer_t *b);
/*!<
 * \brief Make 'b' an invalid buffer.
 *
 * Requires:
 *\li	'b' is a valid buffer.
 *
 * Ensures:
 *\li	If assertion checking is enabled, future attempts to use 'b' without
 *	calling isc_buffer_init() on it will cause an assertion failure.
 */

void
isc__buffer_region(isc_buffer_t *b, isc_region_t *r);
/*!<
 * \brief Make 'r' refer to the region of 'b'.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	'r' points to a region structure.
 */

void
isc__buffer_usedregion(isc_buffer_t *b, isc_region_t *r);
/*!<
 * \brief Make 'r' refer to the used region of 'b'.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	'r' points to a region structure.
 */

void
isc__buffer_availableregion(isc_buffer_t *b, isc_region_t *r);
/*!<
 * \brief Make 'r' refer to the available region of 'b'.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	'r' points to a region structure.
 */

void
isc__buffer_add(isc_buffer_t *b, unsigned int n);
/*!<
 * \brief Increase the 'used' region of 'b' by 'n' bytes.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer
 *
 *\li	used + n <= length
 *
 */

void
isc__buffer_subtract(isc_buffer_t *b, unsigned int n);
/*!<
 * \brief Decrease the 'used' region of 'b' by 'n' bytes.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer
 *
 *\li	used >= n
 *
 */

void
isc__buffer_clear(isc_buffer_t *b);
/*!<
 * \brief Make the used region empty.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer
 *
 * Ensures:
 *
 *\li	used = 0
 *
 */

void
isc__buffer_consumedregion(isc_buffer_t *b, isc_region_t *r);
/*!<
 * \brief Make 'r' refer to the consumed region of 'b'.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	'r' points to a region structure.
 */

void
isc__buffer_remainingregion(isc_buffer_t *b, isc_region_t *r);
/*!<
 * \brief Make 'r' refer to the remaining region of 'b'.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	'r' points to a region structure.
 */

void
isc__buffer_activeregion(isc_buffer_t *b, isc_region_t *r);
/*!<
 * \brief Make 'r' refer to the active region of 'b'.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	'r' points to a region structure.
 */

void
isc__buffer_setactive(isc_buffer_t *b, unsigned int n);
/*!<
 * \brief Sets the end of the active region 'n' bytes after current.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer.
 *
 *\li	current + n <= used
 */

void
isc__buffer_first(isc_buffer_t *b);
/*!<
 * \brief Make the consumed region empty.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer
 *
 * Ensures:
 *
 *\li	current == 0
 *
 */

void
isc__buffer_forward(isc_buffer_t *b, unsigned int n);
/*!<
 * \brief Increase the 'consumed' region of 'b' by 'n' bytes.
 *
 * Requires:
 *
 *\li	'b' is a valid buffer
 *
 *\li	current + n <= used
 *
 */

void
isc__buffer_back(isc_buffer_t *b, unsigned int n);
/*!<
 * \brief Decrease the 'consumed' region of 'b' by 'n' bytes.