diff options
Diffstat (limited to 'epan/tvbuff_subset.c')
| -rw-r--r-- | epan/tvbuff_subset.c | 289 |
1 files changed, 289 insertions, 0 deletions
diff --git a/epan/tvbuff_subset.c b/epan/tvbuff_subset.c new file mode 100644 index 00000000..839facc3 --- /dev/null +++ b/epan/tvbuff_subset.c @@ -0,0 +1,289 @@ +/* tvbuff_subset.c + * + * Copyright (c) 2000 by Gilbert Ramirez <gram@alumni.rice.edu> + * + * Wireshark - Network traffic analyzer + * By Gerald Combs <gerald@wireshark.org> + * Copyright 1998 Gerald Combs + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#include "config.h" + +#include "tvbuff.h" +#include "tvbuff-int.h" +#include "proto.h" /* XXX - only used for DISSECTOR_ASSERT, probably a new header file? */ +#include "exceptions.h" + +typedef struct { + /** The backing tvbuff_t */ + struct tvbuff *tvb; + + /** The offset of 'tvb' to which I'm privy */ + guint offset; + /** The length of 'tvb' to which I'm privy */ + guint length; + +} tvb_backing_t; + +struct tvb_subset { + struct tvbuff tvb; + + tvb_backing_t subset; +}; + +static guint +subset_offset(const tvbuff_t *tvb, const guint counter) +{ + const struct tvb_subset *subset_tvb = (const struct tvb_subset *) tvb; + const tvbuff_t *member = subset_tvb->subset.tvb; + + return tvb_offset_from_real_beginning_counter(member, counter + subset_tvb->subset.offset); +} + +static void * +subset_memcpy(tvbuff_t *tvb, void *target, guint abs_offset, guint abs_length) +{ + struct tvb_subset *subset_tvb = (struct tvb_subset *) tvb; + + return tvb_memcpy(subset_tvb->subset.tvb, target, subset_tvb->subset.offset + abs_offset, abs_length); +} + +static const guint8 * +subset_get_ptr(tvbuff_t *tvb, guint abs_offset, guint abs_length) +{ + struct tvb_subset *subset_tvb = (struct tvb_subset *) tvb; + + return tvb_get_ptr(subset_tvb->subset.tvb, subset_tvb->subset.offset + abs_offset, abs_length); +} + +static gint +subset_find_guint8(tvbuff_t *tvb, guint abs_offset, guint limit, guint8 needle) +{ + struct tvb_subset *subset_tvb = (struct tvb_subset *) tvb; + gint result; + + result = tvb_find_guint8(subset_tvb->subset.tvb, subset_tvb->subset.offset + abs_offset, limit, needle); + if (result == -1) + return result; + + /* + * Make the result relative to the beginning of the tvbuff we + * were handed, *not* relative to the beginning of its parent + * tvbuff. + */ + return result - subset_tvb->subset.offset; +} + +static gint +subset_pbrk_guint8(tvbuff_t *tvb, guint abs_offset, guint limit, const ws_mempbrk_pattern* pattern, guchar *found_needle) +{ + struct tvb_subset *subset_tvb = (struct tvb_subset *) tvb; + gint result; + + result = tvb_ws_mempbrk_pattern_guint8(subset_tvb->subset.tvb, subset_tvb->subset.offset + abs_offset, limit, pattern, found_needle); + if (result == -1) + return result; + + /* + * Make the result relative to the beginning of the tvbuff we + * were handed, *not* relative to the beginning of its parent + * tvbuff. + */ + return result - subset_tvb->subset.offset; +} + +static tvbuff_t * +subset_clone(tvbuff_t *tvb, guint abs_offset, guint abs_length) +{ + struct tvb_subset *subset_tvb = (struct tvb_subset *) tvb; + + return tvb_clone_offset_len(subset_tvb->subset.tvb, subset_tvb->subset.offset + abs_offset, abs_length); +} + +static const struct tvb_ops tvb_subset_ops = { + sizeof(struct tvb_subset), /* size */ + + NULL, /* free */ + subset_offset, /* offset */ + subset_get_ptr, /* get_ptr */ + subset_memcpy, /* memcpy */ + subset_find_guint8, /* find_guint8 */ + subset_pbrk_guint8, /* pbrk_guint8 */ + subset_clone, /* clone */ +}; + +static tvbuff_t * +tvb_new_with_subset(tvbuff_t *backing, const guint reported_length, + const guint subset_tvb_offset, const guint subset_tvb_length) +{ + tvbuff_t *tvb = tvb_new(&tvb_subset_ops); + struct tvb_subset *subset_tvb = (struct tvb_subset *) tvb; + + subset_tvb->subset.offset = subset_tvb_offset; + subset_tvb->subset.length = subset_tvb_length; + + subset_tvb->subset.tvb = backing; + tvb->length = subset_tvb_length; + /* + * The contained length must not exceed what remains in the + * backing tvbuff. + */ + tvb->contained_length = MIN(reported_length, backing->contained_length - subset_tvb_offset); + tvb->flags = backing->flags; + + tvb->reported_length = reported_length; + tvb->initialized = TRUE; + + /* Optimization. If the backing buffer has a pointer to contiguous, real data, + * then we can point directly to our starting offset in that buffer */ + if (backing->real_data != NULL) { + tvb->real_data = backing->real_data + subset_tvb_offset; + } + + /* + * The top-level data source of this tvbuff is the top-level + * data source of its parent. + */ + tvb->ds_tvb = backing->ds_tvb; + + return tvb; +} + +tvbuff_t * +tvb_new_subset_length_caplen(tvbuff_t *backing, const gint backing_offset, const gint backing_length, const gint reported_length) +{ + tvbuff_t *tvb; + guint subset_tvb_offset; + guint subset_tvb_length; + guint actual_reported_length; + + DISSECTOR_ASSERT(backing && backing->initialized); + + THROW_ON(reported_length < -1, ReportedBoundsError); + + tvb_check_offset_length(backing, backing_offset, backing_length, + &subset_tvb_offset, + &subset_tvb_length); + + if (reported_length == -1) + actual_reported_length = backing->reported_length - subset_tvb_offset; + else + actual_reported_length = (guint)reported_length; + + /* + * Cut the captured length short, so it doesn't go past the subset's + * reported length. + */ + if (subset_tvb_length > actual_reported_length) + subset_tvb_length = actual_reported_length; + + tvb = tvb_new_with_subset(backing, actual_reported_length, + subset_tvb_offset, subset_tvb_length); + + tvb_add_to_chain(backing, tvb); + + return tvb; +} + +tvbuff_t * +tvb_new_subset_length(tvbuff_t *backing, const gint backing_offset, const gint reported_length) +{ + gint captured_length; + gint actual_reported_length; + tvbuff_t *tvb; + guint subset_tvb_offset; + guint subset_tvb_length; + + DISSECTOR_ASSERT(backing && backing->initialized); + + THROW_ON(reported_length < -1, ReportedBoundsError); + + if (reported_length == -1) + actual_reported_length = backing->reported_length; + else + actual_reported_length = reported_length; + + /* + * Cut the captured length short, so it doesn't go past the subset's + * reported length. + */ + captured_length = tvb_captured_length_remaining(backing, backing_offset); + THROW_ON(captured_length < 0, BoundsError); + if (captured_length > actual_reported_length) + captured_length = actual_reported_length; + + tvb_check_offset_length(backing, backing_offset, captured_length, + &subset_tvb_offset, + &subset_tvb_length); + + /* + * If the requested reported length is "to the end of the buffer", + * subtract the offset from the total length. We do this now, because + * the user might have passed in a negative offset. + */ + if (reported_length == -1) { + THROW_ON(backing->reported_length < subset_tvb_offset, ReportedBoundsError); + actual_reported_length -= subset_tvb_offset; + } + + tvb = tvb_new_with_subset(backing, (guint)actual_reported_length, + subset_tvb_offset, subset_tvb_length); + + tvb_add_to_chain(backing, tvb); + + return tvb; +} + +tvbuff_t * +tvb_new_subset_remaining(tvbuff_t *backing, const gint backing_offset) +{ + tvbuff_t *tvb; + guint subset_tvb_offset; + guint subset_tvb_length; + guint reported_length; + + tvb_check_offset_length(backing, backing_offset, -1 /* backing_length */, + &subset_tvb_offset, + &subset_tvb_length); + + THROW_ON(backing->reported_length < subset_tvb_offset, ReportedBoundsError); + reported_length = backing->reported_length - subset_tvb_offset; + + tvb = tvb_new_with_subset(backing, reported_length, + subset_tvb_offset, subset_tvb_length); + + tvb_add_to_chain(backing, tvb); + + return tvb; +} + +tvbuff_t * +tvb_new_proxy(tvbuff_t *backing) +{ + tvbuff_t *tvb; + + if (backing) + tvb = tvb_new_with_subset(backing, backing->reported_length, 0, backing->length); + else + tvb = tvb_new_real_data(NULL, 0, 0); + + tvb->ds_tvb = tvb; + + return tvb; +} + + +/* + * Editor modelines - https://www.wireshark.org/tools/modelines.html + * + * Local variables: + * c-basic-offset: 8 + * tab-width: 8 + * indent-tabs-mode: t + * End: + * + * vi: set shiftwidth=8 tabstop=8 noexpandtab: + * :indentSize=8:tabSize=8:noTabs=false: + */ |