path: root/epan/tvbuff.h

/* tvbuff.h
 *
 * Testy, Virtual(-izable) Buffer of guint8*'s
 *
 * "Testy" -- the buffer gets mad when an attempt is made to access data
 * 		beyond the bounds of the buffer. An exception is thrown.
 *
 * "Virtual" -- the buffer can have its own data, can use a subset of
 * 		the data of a backing tvbuff, or can be a composite of
 * 		other tvbuffs.
 *
 * $Id$
 *
 * Copyright (c) 2000 by Gilbert Ramirez <gram@alumni.rice.edu>
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifndef __TVBUFF_H__
#define __TVBUFF_H__

#include <glib.h>
#include <epan/ipv6-utils.h>
#include "exceptions.h"

/** @file
 * "testy, virtual(-izable) buffer".  They are testy in that they get mad when
 * an attempt is made to access data beyond the bounds of their array. In that
 * case, they throw an exception.
 * 
 * They are virtualizable in that new tvbuff's can be made from other tvbuffs, 
 * while only the original tvbuff may have data. That is, the new tvbuff has 
 * virtual data.
 */


/** The different types of tvbuff's */
typedef enum {
	TVBUFF_REAL_DATA,
	TVBUFF_SUBSET,
	TVBUFF_COMPOSITE
} tvbuff_type;

typedef struct {
	/* The backing tvbuff_t */
	struct tvbuff	*tvb;

	/* The offset/length of 'tvb' to which I'm privy */
	guint		offset;
	guint		length;

} tvb_backing_t;

typedef struct {
	GSList		*tvbs;

	/* Used for quick testing to see if this
	 * is the tvbuff that a COMPOSITE is
	 * interested in. */
	guint		*start_offsets;
	guint		*end_offsets;

} tvb_comp_t;

typedef void (*tvbuff_free_cb_t)(void*);

typedef struct tvbuff {
	/* Record-keeping */
	tvbuff_type		type;
	gboolean		initialized;
	guint			usage_count;
	struct tvbuff		*ds_tvb;  /* data source top-level tvbuff */

	/* The tvbuffs in which this tvbuff is a member
	 * (that is, a backing tvbuff for a TVBUFF_SUBSET
	 * or a member for a TVB_COMPOSITE) */
	GSList			*used_in;

	/* TVBUFF_SUBSET and TVBUFF_COMPOSITE keep track
	 * of the other tvbuff's they use */
	union {
		tvb_backing_t	subset;
		tvb_comp_t	composite;
	} tvbuffs;

	/* We're either a TVBUFF_REAL_DATA or a
	 * TVBUFF_SUBSET that has a backing buffer that
	 * has real_data != NULL, or a TVBUFF_COMPOSITE
	 * which has flattened its data due to a call
	 * to tvb_get_ptr().
	 */
	const guint8		*real_data;

	/* Length of virtual buffer (and/or real_data). */
	guint			length;

	/* Reported length. */
	guint			reported_length;

	/* Offset from beginning of first TVBUFF_REAL. */
	gint			raw_offset;

	/* Func to call when actually freed */
	tvbuff_free_cb_t	free_cb;
} tvbuff_t;



/** TVBUFF_REAL_DATA contains a guint8* that points to real data.
 * The data is allocated and contiguous.
 *
 * TVBUFF_SUBSET has a backing tvbuff. The TVBUFF_SUBSET is a "window"
 * through which the program sees only a portion of the backing tvbuff.
 *
 * TVBUFF_COMPOSITE combines multiple tvbuffs sequentually to produce
 * a larger byte array.
 *
 * tvbuff's of any type can be used as the backing-tvbuff of a
 * TVBUFF_SUBSET or as the member of a TVBUFF_COMPOSITE.
 * TVBUFF_COMPOSITEs can have member-tvbuffs of different types.
 *
 * Once a tvbuff is create/initialized/finalized, the tvbuff is read-only.
 * That is, it cannot point to any other data. A new tvbuff must be created if
 * you want a tvbuff that points to other data.
 */


/** "class" initialization. Called once during execution of program
 * so that tvbuff.c can initialize its data. */
extern void tvbuff_init(void);

/** "class" cleanup. Called once during execution of program
 * so that tvbuff.c can clean up its data. */
extern void tvbuff_cleanup(void);


/** Returns a pointer to a newly initialized tvbuff. Note that
 * tvbuff's of types TVBUFF_SUBSET and TVBUFF_COMPOSITE
 * require further initialization via the appropriate functions */
extern tvbuff_t* tvb_new(tvbuff_type);

/** Marks a tvbuff for freeing. The guint8* data of a TVBUFF_REAL_DATA
 * is *never* freed by the tvbuff routines. The tvbuff itself is actually freed
 * once its usage count drops to 0.
 *
 * Usage counts increment for any time the tvbuff is
 * used as a member of another tvbuff, i.e., as the backing buffer for
 * a TVBUFF_SUBSET or as a member of a TVBUFF_COMPOSITE.
 *
 * Although you may call tvb_free(), the tvbuff may still be in use
 * by other tvbuff's (TVBUFF_SUBSET or TVBUFF_COMPOSITE), so it is not
 * safe, unless you know otherwise, to free your guint8* data. If you
 * cannot be sure that your TVBUFF_REAL_DATA is not in use by another
 * tvbuff, register a callback with tvb_set_free_cb(); when your tvbuff
 * is _really_ freed, then your callback will be called, and at that time
 * you can free your original data.
 *
 * The caller can artificially increment/decrement the usage count
 * with tvbuff_increment_usage_count()/tvbuff_decrement_usage_count().
 */
extern void tvb_free(tvbuff_t*);

/** Free the tvbuff_t and all tvbuff's created from it. */
extern void tvb_free_chain(tvbuff_t*);

/** Both return the new usage count, after the increment or decrement */
extern guint tvb_increment_usage_count(tvbuff_t*, guint count);

/** If a decrement causes the usage count to drop to 0, a the tvbuff
 * is immediately freed. Be sure you know exactly what you're doing
 * if you decide to use this function, as another tvbuff could
 * still have a pointer to the just-freed tvbuff, causing corrupted data
 * or a segfault in the future */
extern guint tvb_decrement_usage_count(tvbuff_t*, guint count);

/** Set a callback function to call when a tvbuff is actually freed
 * (once the usage count drops to 0). One argument is passed to
 * that callback --- a void* that points to the real data.
 * Obviously, this only applies to a TVBUFF_REAL_DATA tvbuff. */
extern void tvb_set_free_cb(tvbuff_t*, tvbuff_free_cb_t);


/** Attach a TVBUFF_REAL_DATA tvbuff to a parent tvbuff. This connection
 * is used during a tvb_free_chain()... the "child" TVBUFF_REAL_DATA acts
 * as if is part of the chain-of-creation of the parent tvbuff, although it
 * isn't. This is useful if you need to take the data from some tvbuff,
 * run some operation on it, like decryption or decompression, and make a new
 * tvbuff from it, yet want the new tvbuff to be part of the chain. The reality
 * is that the new tvbuff *is* part of the "chain of creation", but in a way
 * that these tvbuff routines is ignorant of. Use this function to make
 * the tvbuff routines knowledgable of this fact. */
extern void tvb_set_child_real_data_tvbuff(tvbuff_t* parent, tvbuff_t* child);

/**Sets parameters for TVBUFF_REAL_DATA. Can throw ReportedBoundsError. */
extern void tvb_set_real_data(tvbuff_t*, const guint8* data, guint length,
    gint reported_length);

/** Combination of tvb_new() and tvb_set_real_data(). Can throw ReportedBoundsError. */
extern tvbuff_t* tvb_new_real_data(const guint8* data, guint length,
    gint reported_length);


/** Define the subset of the backing buffer to use.
 *
 * 'backing_offset' can be negative, to indicate bytes from
 * the end of the backing buffer.
 *
 * 'backing_length' can be 0, although the usefulness of the buffer would
 * be rather limited.
 *
 * 'backing_length' of -1 means "to the end of the backing buffer"
 *
 * Will throw BoundsError if 'backing_offset'/'length'
 * is beyond the bounds of the backing tvbuff.
 * Can throw ReportedBoundsError. */
extern void tvb_set_subset(tvbuff_t* tvb, tvbuff_t* backing,
		gint backing_offset, gint backing_length, gint reported_length);

/** Combination of tvb_new() and tvb_set_subset()
 * Can throw ReportedBoundsError. */
extern tvbuff_t* tvb_new_subset(tvbuff_t* backing,
		gint backing_offset, gint backing_length, gint reported_length);


/** Both tvb_composite_append and tvb_composite_prepend can throw
 * BoundsError if member_offset/member_length goes beyond bounds of
 * the 'member' tvbuff. */

/** Append to the list of tvbuffs that make up this composite tvbuff */
extern void tvb_composite_append(tvbuff_t* tvb, tvbuff_t* member);

/** Prepend to the list of tvbuffs that make up this composite tvbuff */
extern void tvb_composite_prepend(tvbuff_t* tvb, tvbuff_t* member);

/** Helper function that calls tvb_new(TVBUFF_COMPOSITE).
 * Provided only to maintain symmetry with other constructors */
extern tvbuff_t* tvb_new_composite(void);

/** Mark a composite tvbuff as initialized. No further appends or prepends
 * occur, data access can finally happen after this finalization. */
extern void tvb_composite_finalize(tvbuff_t* tvb);


/* Get total length of buffer */
extern guint tvb_length(tvbuff_t*);

/** Computes bytes to end of buffer, from offset (which can be negative,
 * to indicate bytes from end of buffer). Function returns -1 to
 * indicate that offset is out of bounds. No exception is thrown. */
extern gint tvb_length_remaining(tvbuff_t*, gint offset);

/** Same as above, but throws an exception if the offset is out of bounds. */
extern guint tvb_ensure_length_remaining(tvbuff_t*, gint offset);

/* Checks (w/o throwing exception) that the bytes referred to by
 * 'offset'/'length' actually exist in the buffer */
extern gboolean tvb_bytes_exist(tvbuff_t*, gint offset, gint length);

/** Checks that the bytes referred to by 'offset'/'length' actually exist
 * in the buffer, and throws an exception if they aren't. */
extern void tvb_ensure_bytes_exist(tvbuff_t *tvb, gint offset, gint length);

/* Checks (w/o throwing exception) that offset exists in buffer */
extern gboolean tvb_offset_exists(tvbuff_t*, gint offset);

/* Get reported length of buffer */
extern guint tvb_reported_length(tvbuff_t*);

/** Computes bytes of reported packet data to end of buffer, from offset
 * (which can be negative, to indicate bytes from end of buffer). Function
 * returns -1 to indicate that offset is out of bounds. No exception is
 * thrown. */
extern gint tvb_reported_length_remaining(tvbuff_t *tvb, gint offset);

/** Set the reported length of a tvbuff to a given value; used for protocols
   whose headers contain an explicit length and where the calling
   dissector's payload may include padding as well as the packet for
   this protocol.

   Also adjusts the data length. */
extern void tvb_set_reported_length(tvbuff_t*, guint);

extern int offset_from_real_beginning(tvbuff_t *tvb, int counter);

/* Returns the offset from the first byte of real data. */
#define TVB_RAW_OFFSET(tvb)			\
	((tvb->raw_offset==-1)?(tvb->raw_offset = offset_from_real_beginning(tvb, 0)):tvb->raw_offset)

/************** START OF ACCESSORS ****************/
/* All accessors will throw an exception if appropriate */

extern guint8  tvb_get_guint8(tvbuff_t*, gint offset);

extern guint16 tvb_get_ntohs(tvbuff_t*, gint offset);
extern guint32 tvb_get_ntoh24(tvbuff_t*, gint offset);
extern guint32 tvb_get_ntohl(tvbuff_t*, gint offset);
extern guint64 tvb_get_ntoh64(tvbuff_t*, gint offset);
extern gfloat tvb_get_ntohieee_float(tvbuff_t*, gint offset);
extern gdouble tvb_get_ntohieee_double(tvbuff_t*, gint offset);

extern guint16 tvb_get_letohs(tvbuff_t*, gint offset);
extern guint32 tvb_get_letoh24(tvbuff_t*, gint offset);
extern guint32 tvb_get_letohl(tvbuff_t*, gint offset);
extern guint64 tvb_get_letoh64(tvbuff_t*, gint offset);
extern gfloat tvb_get_letohieee_float(tvbuff_t*, gint offset);
extern gdouble tvb_get_letohieee_double(tvbuff_t*, gint offset);

/**
 * Fetch an IPv4 address, in network byte order.
 * We do *not* convert it to host byte order; we leave it in
 * network byte order, as that's what its callers expect. */
extern guint32 tvb_get_ipv4(tvbuff_t*, gint offset);

/* Fetch an IPv6 address. */
extern void tvb_get_ipv6(tvbuff_t*, gint offset, struct e_in6_addr *addr);

/** Returns target for convenience. Does not suffer from possible
 * expense of tvb_get_ptr(), since this routine is smart enough
 * to copy data in chunks if the request range actually exists in
 * different TVBUFF_REAL_DATA tvbuffs. This function assumes that the
 * target memory is already allocated; it does not allocate or free the
 * target memory. */
extern guint8* tvb_memcpy(tvbuff_t*, guint8* target, gint offset, gint length);

/** It is the user's responsibility to g_free() the memory allocated by
 * tvb_memdup(). Calls tvb_memcpy() */
extern guint8* tvb_memdup(tvbuff_t*, gint offset, gint length);

/* Same as above but the buffer returned from this function does not have to
* be freed. It will be automatically freed after the packet is dissected.
* Buffers allocated by this function are NOT persistent.
*/
extern guint8* ep_tvb_memdup(tvbuff_t *tvb, gint offset, gint length);

/** WARNING! This function is possibly expensive, temporarily allocating
 * another copy of the packet data. Furthermore, it's dangerous because once
 * this pointer is given to the user, there's no guarantee that the user will
 * honor the 'length' and not overstep the boundaries of the buffer.
 *
 * The returned pointer is data that is internal to the tvbuff, so do not
 * attempt to free it. Don't modify the data, either, because another tvbuff
 * that might be using this tvbuff may have already copied that portion of
 * the data (sometimes tvbuff's need to make copies of data, but that's the
 * internal implementation that you need not worry about). Assume that the
 * guint8* points to read-only data that the tvbuff manages.
 *
 * Return a pointer into our buffer if the data asked for via 'offset'/'length'
 * is contiguous (which might not be the case for TVBUFF_COMPOSITE). If the
 * data is not contiguous, a tvb_memdup() is called for the entire buffer
 * and the pointer to the newly-contiguous data is returned. This dynamically-
 * allocated memory will be freed when the tvbuff is freed, after the
 * tvbuff_free_cb_t() is called, if any. */
extern const guint8* tvb_get_ptr(tvbuff_t*, gint offset, gint length);

/** Find first occurence of any of the needles in tvbuff, starting at offset.
 * Searches at most maxlength number of bytes; if maxlength is -1, searches
 * to end of tvbuff.
 * Returns the offset of the found needle, or -1 if not found.
 * Will not throw an exception, even if maxlength exceeds boundary of tvbuff;
 * in that case, -1 will be returned if the boundary is reached before
 * finding needle. */
extern gint tvb_find_guint8(tvbuff_t*, gint offset, gint maxlength,
    guint8 needle);

/** Find first occurence of any of the needles in tvbuff, starting at offset.
 * Searches at most maxlength number of bytes. Returns the offset of the
 * found needle, or -1 if not found. Will not throw an exception, even if
 * maxlength exceeds boundary of tvbuff; in that case, -1 will be returned if
 * the boundary is reached before finding needle. */
extern gint tvb_pbrk_guint8(tvbuff_t *, gint offset, gint maxlength,
    guint8 *needles);

/** Find size of stringz (NUL-terminated string) by looking for terminating
 * NUL.  The size of the string includes the terminating NUL.
 *
 * If the NUL isn't found, it throws the appropriate exception.
 */
extern guint tvb_strsize(tvbuff_t *tvb, gint offset);

/** Find length of string by looking for end of string ('\0'), up to
 * 'maxlength' characters'; if 'maxlength' is -1, searches to end
 * of tvbuff.
 * Returns -1 if 'maxlength' reached before finding EOS. */
extern gint tvb_strnlen(tvbuff_t*, gint offset, guint maxlength);

/** Convert a string from Unicode to ASCII.  At the moment we fake it by
 * assuming all characters are ASCII  )-:  The len parameter is the number 
 * of guint16's to convert from Unicode. 
 *
 * tvb_fake_unicode() returns a buffer allocated by g_malloc() and must
 *                    be g_free() by the caller.
 * tvb_get_ephemeral_faked_unicode() returns a buffer that does not need
 *                    to be explicitely freed. Instead this buffer is
 *                    automatically freed when ethereal starts dissecting
 *                    the next packet.
 */
extern char *tvb_fake_unicode(tvbuff_t *tvb, int offset, int len,
                              gboolean little_endian);
extern char *tvb_get_ephemeral_faked_unicode(tvbuff_t *tvb, int offset, int len,
                              gboolean little_endian);

/**
 * Format the data in the tvb from offset for size ...
 */
extern gchar * tvb_format_text(tvbuff_t *tvb, gint offset, gint size);

/**
 * Like "tvb_format_text()", but for null-padded strings; don't show
 * the null padding characters as "\000".
 */
extern gchar *tvb_format_stringzpad(tvbuff_t *tvb, gint offset, gint size);


/**
 * Given a tvbuff, an offset, and a length, allocate a buffer big enough
 * to hold a non-null-terminated string of that length at that offset,
 * plus a trailing '\0', copy the string into it, and return a pointer
 * to the string.
 *
 * Throws an exception if the tvbuff ends before the string does.
 *
 * tvb_get_string()  returns a string allocated by g_malloc() and therefore
 *                   MUST be g_free() by the caller in order not to leak
 *                   memory.
 *
 * tvb_get_ephemeral_string() returns a string that does not need to be freed,
 *                   instead it will automatically be freed once the next
 *                   packet is dissected.
 */
extern guint8 *tvb_get_string(tvbuff_t *tvb, gint offset, gint length);
extern guint8 *tvb_get_ephemeral_string(tvbuff_t *tvb, gint offset, gint length);


/**
 * Given a tvbuff and an offset, with the offset assumed to refer to
 * a null-terminated string, find the length of that string (and throw
 * an exception if the tvbuff ends before we find the null), allocate
 * a buffer big enough to hold the string, copy the string into it,
 * and return a pointer to the string.  Also return the length of the
 * string (including the terminating null) through a pointer.
 *
 * tvb_get_stringz() returns a string allocated by g_malloc() and therefore
 *                   MUST be g_free() by the caller in order not to leak
 *                   memory.
 *
 * tvb_get_ephemeral_stringz() returns a string that does not need to be freed,
 *                   instead it will automatically be freed once the next
 *                   packet is dissected.
 */
extern guint8 *tvb_get_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
extern guint8 *tvb_get_ephemeral_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);

/** Looks for a stringz (NUL-terminated string) in tvbuff and copies
 * no more than bufsize number of bytes, including terminating NUL, to buffer.
 * Returns length of string (not including terminating NUL), or -1 if the string was
 * truncated in the buffer due to not having reached the terminating NUL.
 * In this way, it acts like g_snprintf().
 *
 * When processing a packet where the remaining number of bytes is less
 * than bufsize, an exception is not thrown if the end of the packet
 * is reached before the NUL is found. If no NUL is found before reaching
 * the end of the short packet, -1 is still returned, and the string
 * is truncated with a NUL, albeit not at buffer[bufsize - 1], but
 * at the correct spot, terminating the string.
 */
extern gint tvb_get_nstringz(tvbuff_t *tvb, gint offset, guint bufsize,
    guint8* buffer);

/** Like tvb_get_nstringz(), but never returns -1. The string is guaranteed to
 * have a terminating NUL. If the string was truncated when copied into buffer,
 * a NUL is placed at the end of buffer to terminate it.
 *
 * bufsize MUST be greater than 0.
 */
extern gint tvb_get_nstringz0(tvbuff_t *tvb, gint offset, guint bufsize,
    guint8* buffer);

/**
 * Given a tvbuff, an offset into the tvbuff, and a length that starts
 * at that offset (which may be -1 for "all the way to the end of the
 * tvbuff"), find the end of the (putative) line that starts at the
 * specified offset in the tvbuff, going no further than the specified
 * length.
 *
 * Return the length of the line (not counting the line terminator at
 * the end), or, if we don't find a line terminator:
 *
 *	if "deseg" is true, return -1;
 *
 *	if "deseg" is false, return the amount of data remaining in
 *	the buffer.
 *
 * Set "*next_offset" to the offset of the character past the line
 * terminator, or past the end of the buffer if we don't find a line
 * terminator.  (It's not set if we return -1.)
 */
extern gint tvb_find_line_end(tvbuff_t *tvb, gint offset, int len,
    gint *next_offset, gboolean desegment);

/**
 * Given a tvbuff, an offset into the tvbuff, and a length that starts
 * at that offset (which may be -1 for "all the way to the end of the
 * tvbuff"), find the end of the (putative) line that starts at the
 * specified offset in the tvbuff, going no further than the specified
 * length.
 *
 * However, treat quoted strings inside the buffer specially - don't
 * treat newlines in quoted strings as line terminators.
 *
 * Return the length of the line (not counting the line terminator at
 * the end), or the amount of data remaining in the buffer if we don't
 * find a line terminator.
 *
 * Set "*next_offset" to the offset of the character past the line
 * terminator, or past the end of the buffer if we don't find a line
 * terminator.
 */
extern gint tvb_find_line_end_unquoted(tvbuff_t *tvb, gint offset, int len,
    gint *next_offset);

/**
 * Call strncmp after checking if enough chars left, returning 0 if
 * it returns 0 (meaning "equal") and -1 otherwise, otherwise return -1.
 */
extern gint tvb_strneql(tvbuff_t *tvb, gint offset, const gchar *str,
    gint size);

/**
 * Call strncasecmp after checking if enough chars left, returning 0 if
 * it returns 0 (meaning "equal") and -1 otherwise, otherwise return -1.
 */
extern gint tvb_strncaseeql(tvbuff_t *tvb, gint offset, const gchar *str,
    gint size);

/**
 * Call memcmp after checking if enough chars left, returning 0 if
 * it returns 0 (meaning "equal") and -1 otherwise, otherwise return -1.
 */
extern gint tvb_memeql(tvbuff_t *tvb, gint offset, const guint8 *str,
    gint size);

/**
 * Format a bunch of data from a tvbuff as bytes, returning a pointer
 * to the string with the formatted data, with "punct" as a byte
 * separator.
 */
extern gchar *tvb_bytes_to_str_punct(tvbuff_t *tvb, gint offset, gint len,
    gchar punct);

/*
 * Format a bunch of data from a tvbuff as bytes, returning a pointer
 * to the string with the formatted data.
 */
extern gchar *tvb_bytes_to_str(tvbuff_t *tvb, gint offset, gint len);

#define TVB_GET_DS_TVB(tvb)		\
	(tvb->ds_tvb)

/** Locate a sub-tvbuff within another tvbuff, starting at position
 * 'haystack_offset'. Returns the index of the beginning of 'needle' within
 * 'haystack', or -1 if 'needle' is not found. The index is relative
 * to the start of 'haystack', not 'haystack_offset'. */
extern gint tvb_find_tvb(tvbuff_t *haystack_tvb, tvbuff_t *needle_tvb,
	gint haystack_offset);

/**
 * Uncompresses a zlib compressed packet inside a tvbuff at offset with
 * length comprlen.  Returns an uncompressed tvbuffer if uncompression
 * succeeded or NULL if uncompression failed.
 */
extern tvbuff_t* tvb_uncompress(tvbuff_t *tvb, int offset, int comprlen);

/************** END OF ACCESSORS ****************/

#endif /* __TVBUFF_H__ */