runlist.c

上一个上传的有问题,这个是好的。visopsys包括系统内核和GUI的全部SOURCE code ,还包括一些基本的docs文档。里面src子目录对应所有SOURCE code.对于想研究操作系统的朋

 * On success, return a pointer to the new, combined, runlist. Note, both
 * runlists @dst and @src are deallocated before returning so you cannot use
 * the pointers for anything any more. (Strictly speaking the returned runlist
 * may be the same as @dst but this is irrelevant.)
 *
 * On error, return NULL, with errno set to the error code. Both runlists are
 * left unmodified.
 */
static __inline__ runlist_element *ntfs_rl_split(runlist_element *dst,
		int dsize, runlist_element *src, int ssize, int loc)
{
	if (!dst || !src) {
		ntfs_log_debug("Eeek. ntfs_rl_split() invoked with NULL pointer!\n");
		errno = EINVAL;
		return NULL;
	}

	/* Space required: @dst size + @src size + one new hole. */
	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize + 1);
	if (!dst)
		return dst;
	/*
	 * We are guaranteed to succeed from here so can start modifying the
	 * original runlists.
	 */

	/* Move the tail of @dst out of the way, then copy in @src. */
	ntfs_rl_mm(dst, loc + 1 + ssize, loc, dsize - loc);
	ntfs_rl_mc(dst, loc + 1, src, 0, ssize);

	/* Adjust the size of the holes either size of @src. */
	dst[loc].length		= dst[loc+1].vcn       - dst[loc].vcn;
	dst[loc+ssize+1].vcn	= dst[loc+ssize].vcn   + dst[loc+ssize].length;
	dst[loc+ssize+1].length	= dst[loc+ssize+2].vcn - dst[loc+ssize+1].vcn;

	return dst;
}


/**
 * ntfs_runlists_merge - merge two runlists into one
 * @drl:	original runlist to be worked on
 * @srl:	new runlist to be merged into @drl
 *
 * First we sanity check the two runlists @srl and @drl to make sure that they
 * are sensible and can be merged. The runlist @srl must be either after the
 * runlist @drl or completely within a hole (or unmapped region) in @drl.
 *
 * Merging of runlists is necessary in two cases:
 *   1. When attribute lists are used and a further extent is being mapped.
 *   2. When new clusters are allocated to fill a hole or extend a file.
 *
 * There are four possible ways @srl can be merged. It can:
 *	- be inserted at the beginning of a hole,
 *	- split the hole in two and be inserted between the two fragments,
 *	- be appended at the end of a hole, or it can
 *	- replace the whole hole.
 * It can also be appended to the end of the runlist, which is just a variant
 * of the insert case.
 *
 * On success, return a pointer to the new, combined, runlist. Note, both
 * runlists @drl and @srl are deallocated before returning so you cannot use
 * the pointers for anything any more. (Strictly speaking the returned runlist
 * may be the same as @dst but this is irrelevant.)
 *
 * On error, return NULL, with errno set to the error code. Both runlists are
 * left unmodified. The following error codes are defined:
 *	ENOMEM		Not enough memory to allocate runlist array.
 *	EINVAL		Invalid parameters were passed in.
 *	ERANGE		The runlists overlap and cannot be merged.
 */
runlist_element *ntfs_runlists_merge(runlist_element *drl,
		runlist_element *srl)
{
	int di, si;		/* Current index into @[ds]rl. */
	int sstart;		/* First index with lcn > LCN_RL_NOT_MAPPED. */
	int dins;		/* Index into @drl at which to insert @srl. */
	int dend, send;		/* Last index into @[ds]rl. */
	int dfinal, sfinal;	/* The last index into @[ds]rl with
				   lcn >= LCN_HOLE. */
	int marker = 0;
	VCN marker_vcn = 0;

	ntfs_log_debug("dst:\n");
	ntfs_debug_runlist_dump(drl);
	ntfs_log_debug("src:\n");
	ntfs_debug_runlist_dump(srl);

	/* Check for silly calling... */
	if (!srl)
		return drl;

	/* Check for the case where the first mapping is being done now. */
	if (!drl) {
		drl = srl;
		/* Complete the source runlist if necessary. */
		if (drl[0].vcn) {
			/* Scan to the end of the source runlist. */
			for (dend = 0; drl[dend].length; dend++)
				;
			dend++;
			drl = ntfs_rl_realloc(drl, dend, dend + 1);
			if (!drl)
				return drl;
			/* Insert start element at the front of the runlist. */
			ntfs_rl_mm(drl, 1, 0, dend);
			drl[0].vcn = 0;
			drl[0].lcn = LCN_RL_NOT_MAPPED;
			drl[0].length = drl[1].vcn;
		}
		goto finished;
	}

	si = di = 0;

	/* Skip any unmapped start element(s) in the source runlist. */
	while (srl[si].length && srl[si].lcn < (LCN)LCN_HOLE)
		si++;

	/* Can't have an entirely unmapped source runlist. */
	if (!srl[si].length) {
		ntfs_log_debug("Eeek! ntfs_runlists_merge() received entirely "
				"unmapped source runlist.\n");
		errno = EINVAL;
		return NULL;
	}

	/* Record the starting points. */
	sstart = si;

	/*
	 * Skip forward in @drl until we reach the position where @srl needs to
	 * be inserted. If we reach the end of @drl, @srl just needs to be
	 * appended to @drl.
	 */
	for (; drl[di].length; di++) {
		if (drl[di].vcn + drl[di].length > srl[sstart].vcn)
			break;
	}
	dins = di;

	/* Sanity check for illegal overlaps. */
	if ((drl[di].vcn == srl[si].vcn) && (drl[di].lcn >= 0) &&
			(srl[si].lcn >= 0)) {
		ntfs_log_debug("Run lists overlap. Cannot merge!\n");
		errno = ERANGE;
		return NULL;
	}

	/* Scan to the end of both runlists in order to know their sizes. */
	for (send = si; srl[send].length; send++)
		;
	for (dend = di; drl[dend].length; dend++)
		;

	if (srl[send].lcn == (LCN)LCN_ENOENT)
		marker_vcn = srl[marker = send].vcn;

	/* Scan to the last element with lcn >= LCN_HOLE. */
	for (sfinal = send; sfinal >= 0 && srl[sfinal].lcn < LCN_HOLE; sfinal--)
		;
	for (dfinal = dend; dfinal >= 0 && drl[dfinal].lcn < LCN_HOLE; dfinal--)
		;

	{
	BOOL start;
	BOOL finish;
	int ds = dend + 1;		/* Number of elements in drl & srl */
	int ss = sfinal - sstart + 1;

	start  = ((drl[dins].lcn <  LCN_RL_NOT_MAPPED) ||    /* End of file   */
		  (drl[dins].vcn == srl[sstart].vcn));	     /* Start of hole */
	finish = ((drl[dins].lcn >= LCN_RL_NOT_MAPPED) &&    /* End of file   */
		 ((drl[dins].vcn + drl[dins].length) <=      /* End of hole   */
		  (srl[send - 1].vcn + srl[send - 1].length)));

	/* Or we'll lose an end marker */
	if (finish && !drl[dins].length)
		ss++;
	if (marker && (drl[dins].vcn + drl[dins].length > srl[send - 1].vcn))
		finish = FALSE;

	ntfs_log_debug("dfinal = %i, dend = %i\n", dfinal, dend);
	ntfs_log_debug("sstart = %i, sfinal = %i, send = %i\n", sstart, sfinal, send);
	ntfs_log_debug("start = %i, finish = %i\n", start, finish);
	ntfs_log_debug("ds = %i, ss = %i, dins = %i\n", ds, ss, dins);

	if (start) {
		if (finish)
			drl = ntfs_rl_replace(drl, ds, srl + sstart, ss, dins);
		else
			drl = ntfs_rl_insert(drl, ds, srl + sstart, ss, dins);
	} else {
		if (finish)
			drl = ntfs_rl_append(drl, ds, srl + sstart, ss, dins);
		else
			drl = ntfs_rl_split(drl, ds, srl + sstart, ss, dins);
	}
	if (!drl) {
		ntfs_log_perror("Merge failed");
		return drl;
	}
	free(srl);
	if (marker) {
		ntfs_log_debug("Triggering marker code.\n");
		for (ds = dend; drl[ds].length; ds++)
			;
		/* We only need to care if @srl ended after @drl. */
		if (drl[ds].vcn <= marker_vcn) {
			int slots = 0;

			if (drl[ds].vcn == marker_vcn) {
				ntfs_log_debug("Old marker = %lli, replacing with "
						"LCN_ENOENT.\n",
						(long long)drl[ds].lcn);
				drl[ds].lcn = (LCN)LCN_ENOENT;
				goto finished;
			}
			/*
			 * We need to create an unmapped runlist element in
			 * @drl or extend an existing one before adding the
			 * ENOENT terminator.
			 */
			if (drl[ds].lcn == (LCN)LCN_ENOENT) {
				ds--;
				slots = 1;
			}
			if (drl[ds].lcn != (LCN)LCN_RL_NOT_MAPPED) {
				/* Add an unmapped runlist element. */
				if (!slots) {
					/* FIXME/TODO: We need to have the
					 * extra memory already! (AIA)
					 */
					drl = ntfs_rl_realloc(drl, ds, ds + 2);
					if (!drl)
						goto critical_error;
					slots = 2;
				}
				ds++;
				/* Need to set vcn if it isn't set already. */
				if (slots != 1)
					drl[ds].vcn = drl[ds - 1].vcn +
							drl[ds - 1].length;
				drl[ds].lcn = (LCN)LCN_RL_NOT_MAPPED;
				/* We now used up a slot. */
				slots--;
			}
			drl[ds].length = marker_vcn - drl[ds].vcn;
			/* Finally add the ENOENT terminator. */
			ds++;
			if (!slots) {
				/* FIXME/TODO: We need to have the extra
				 * memory already! (AIA)
				 */
				drl = ntfs_rl_realloc(drl, ds, ds + 1);
				if (!drl)
					goto critical_error;
			}
			drl[ds].vcn = marker_vcn;
			drl[ds].lcn = (LCN)LCN_ENOENT;
			drl[ds].length = (s64)0;
		}
	}
	}

finished:
	/* The merge was completed successfully. */
	ntfs_log_debug("Merged runlist:\n");
	ntfs_debug_runlist_dump(drl);
	return drl;

critical_error:
	/* Critical error! We cannot afford to fail here. */
	ntfs_log_perror("libntfs: Critical error");
	ntfs_log_debug("Forcing segmentation fault!\n");
	marker_vcn = ((runlist*)NULL)->lcn;
	return drl;
}

/**
 * ntfs_mapping_pairs_decompress - convert mapping pairs array to runlist
 * @vol:	ntfs volume on which the attribute resides
 * @attr:	attribute record whose mapping pairs array to decompress
 * @old_rl:	optional runlist in which to insert @attr's runlist
 *
 * Decompress the attribute @attr's mapping pairs array into a runlist. On
 * success, return the decompressed runlist.
 *
 * If @old_rl is not NULL, decompressed runlist is inserted into the
 * appropriate place in @old_rl and the resultant, combined runlist is
 * returned. The original @old_rl is deallocated.
 *
 * On error, return NULL with errno set to the error code. @old_rl is left
 * unmodified in that case.
 *
 * The following error codes are defined:
 *	ENOMEM		Not enough memory to allocate runlist array.
 *	EIO		Corrupt runlist.
 *	EINVAL		Invalid parameters were passed in.
 *	ERANGE		The two runlists overlap.
 *
 * FIXME: For now we take the conceptionally simplest approach of creating the
 * new runlist disregarding the already existing one and then splicing the
 * two into one, if that is possible (we check for overlap and discard the new
 * runlist if overlap present before returning NULL, with errno = ERANGE).
 */
runlist_element *ntfs_mapping_pairs_decompress(const ntfs_volume *vol,
		const ATTR_RECORD *attr, runlist_element *old_rl)
{
	VCN vcn;		/* Current vcn. */
	LCN lcn;		/* Current lcn. */
	s64 deltaxcn;		/* Change in [vl]cn. */
	runlist_element *rl;	/* The output runlist. */
	const u8 *buf;		/* Current position in mapping pairs array. */
	const u8 *attr_end;	/* End of attribute. */
	int err, rlsize;	/* Size of runlist buffer. */
	u16 rlpos;		/* Current runlist position in units of
				   runlist_elements. */
	u8 b;			/* Current byte offset in buf. */

	ntfs_log_trace("Entering for attr 0x%x.\n",
			(unsigned)le32_to_cpu(attr->type));
	/* Make sure attr exists and is non-resident. */
	if (!attr || !attr->non_resident ||
			sle64_to_cpu(attr->lowest_vcn) < (VCN)0) {
		errno = EINVAL;
		return NULL;
	}
	/* Start at vcn = lowest_vcn and lcn 0. */
	vcn = sle64_to_cpu(attr->lowest_vcn);
	lcn = 0;
	/* Get start of the mapping pairs array. */
	buf = (const u8*)attr + le16_to_cpu(attr->mapping_pairs_offset);
	attr_end = (const u8*)attr + le32_to_cpu(attr->length);
	if (buf < (const u8*)attr || buf > attr_end) {
		ntfs_log_debug("Corrupt attribute.\n");
		errno = EIO;
		return NULL;
	}
	/* Current position in runlist array. */
	rlpos = 0;
	/* Allocate first 4kiB block and set current runlist size to 4kiB. */
	rl = malloc(rlsize = 0x1000);
	if (!rl)
		return NULL;
	/* Insert unmapped starting element if necessary. */
	if (vcn) {
		rl->vcn = (VCN)0;
		rl->lcn = (LCN)LCN_RL_NOT_MAPPED;
		rl->length = vcn;
		rlpos++;
	}
	while (buf < attr_end && *buf) {
		/*
		 * Allocate more memory if needed, including space for the
		 * not-mapped and terminator elements.
		 */
		if ((int)((rlpos + 3) * sizeof(*old_rl)) > rlsize) {
			runlist_element *rl2;

			rlsize += 0x1000;
			rl2 = realloc(rl, rlsize);
			if (!rl2) {
				int eo = errno;
				free(rl);
				errno = eo;
				return NULL;
			}
			rl = rl2;
		}
		/* Enter the current vcn into the current runlist element. */
		rl[rlpos].vcn = vcn;
		/*
		 * Get the change in vcn, i.e. the run length in clusters.
		 * Doing it this way ensures that we signextend negative values.
		 * A negative run length doesn't make any sense, but hey, I
		 * didn't make up the NTFS specs and Windows NT4 treats the run
		 * length as a signed value so that's how it is...
		 */
		b = *buf & 0xf;
		if (b) {
			if (buf + b > attr_end)
				goto io_error;
			for (deltaxcn = (s8)buf[b--]; b; b--)
				deltaxcn = (deltaxcn << 8) + buf[b];
		} else { /* The length entry is compulsory. */
			ntfs_log_debug("Missing length entry in mapping pairs "
					"array.\n");
			deltaxcn = (s64)-1;
		}
		/*
		 * Assume a negative length to indicate data corruption and
		 * hence clean-up and return NULL.
		 */
		if (deltaxcn < 0) {
			ntfs_log_debug("Invalid length in mapping pairs array.\n");
			goto err_out;
		}
		/*
		 * Enter the current run length into the current runlist
		 * element.
		 */
		rl[rlpos].length = deltaxcn;
		/* Increment the current vcn by the current run length. */
		vcn += deltaxcn;
		/*
		 * There might be no lcn change at all, as is the case for
		 * sparse clusters on NTFS 3.0+, in which case we set the lcn
		 * to LCN_HOLE.
		 */
		if (!(*buf & 0xf0))
			rl[rlpos].lcn = (LCN)LCN_HOLE;
		else {
			/* Get the lcn change which really can be negative. */
			u8 b2 = *buf & 0xf;
			b = b2 + ((*buf >> 4) & 0xf);
			if (buf + b > attr_end)
				goto io_error;
			for (deltaxcn = (s8)buf[b--]; b > b2; b--)
				deltaxcn = (deltaxcn << 8) + buf[b];
			/* Change the current lcn to it's new value. */
			lcn += deltaxcn;
#ifdef DEBUG
			/*
			 * On NTFS 1.2-, apparently can have lcn == -1 to
			 * indicate a hole. But we haven't verified ourselves
			 * whether it is really the lcn or the deltaxcn that is