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rbtnode struct adapted with more bitfields to represent color,

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name attributes, name length, offset length, and number of bytes
of "padding" that are left over when a node is split.

adjusted node splitting algorithm to preserve the original location
of the lower portion of the split node (eg, when a node has "a.b" as
its name and is split into "a" and "b", "a" retains the same address
space as "a.b".)
This commit is contained in:
David Lawrence
1999-03-11 18:54:31 +00:00
parent 7cb9c09a7b
commit f036af2c71
2 changed files with 118 additions and 92 deletions
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23
lib/dns/include/dns/rbt.h
View File

@@ -32,7 +32,7 @@ ISC_LANG_BEGINDECLS
* tree of trees. NOTE WELL: the implementation manages this as a variable * tree of trees. NOTE WELL: the implementation manages this as a variable
* length structure, with the actual wire-format name and other data appended * length structure, with the actual wire-format name and other data appended
* appended to this structure. Allocating a contiguous block of memory for * appended to this structure. Allocating a contiguous block of memory for
* multiple dns_rbt_node structures will not work. * multiple dns_rbtnode structures will not work.
*/ */
typedef struct dns_rbt dns_rbt_t; typedef struct dns_rbt dns_rbt_t;
@@ -46,20 +46,25 @@ typedef struct dns_rbtnode {
struct dns_rbtnode *left; struct dns_rbtnode *left;
struct dns_rbtnode *right; struct dns_rbtnode *right;
struct dns_rbtnode *down; struct dns_rbtnode *down;
void *data;
/* /*
* We'd like to find a better place for the single bit of color * The following bitfields add up to a total bitwidth of 32.
* information. We can't pack it into the bitfield below, however, * The range of values necessary for each item is indicated,
* because it's not covered by the node lock, and changing a single * but in the case of "attributes" the field is wider to accomodate
* bit in a bitfield is going to require a read-modify-write of a * possible future expansion. "offsetlen" could be one bit
* word. This read-modify-write would include bits covered by a * narrower by always adjusting its value by 1 to find the real
* lock we don't hold, and thus violate locking. * offsetlen, but doing so does not gain anything (except perhaps
* another bit for "attributes", which doesn't yet need any more).
*/ */
unsigned int color; unsigned int color:1; /* range is 0..1 */
unsigned int attributes:6; /* range is 0..2 */
unsigned int namelen:8; /* range is 1..255 */
unsigned int offsetlen:8; /* range is 1..128 */
unsigned int padbytes:9; /* range is 0..380 */
/* /*
* These values are used in the RBT DB implementation. The appropriate * These values are used in the RBT DB implementation. The appropriate
* node lock must be held before accessing them. * node lock must be held before accessing them.
*/ */
void *data;
unsigned int dirty:1; unsigned int dirty:1;
unsigned int locknum:DNS_RBT_LOCKLENGTH; unsigned int locknum:DNS_RBT_LOCKLENGTH;
unsigned int references:DNS_RBT_REFLENGTH; unsigned int references:DNS_RBT_REFLENGTH;

187
lib/dns/rbt.c
View File

@@ -57,24 +57,48 @@ struct dns_rbtnodechain {
#define RED 0 #define RED 0
#define BLACK 1 #define BLACK 1
/*
* Elements of the rbtnode structure.
*/
#define LEFT(node) ((node)->left) #define LEFT(node) ((node)->left)
#define RIGHT(node) ((node)->right) #define RIGHT(node) ((node)->right)
#define DOWN(node) ((node)->down) #define DOWN(node) ((node)->down)
#define NAMELEN(node) (((unsigned char *)((node) + 1))[0])
#define OFFSETLEN(node) (((unsigned char *)((node) + 1))[1])
#define NAME(node) (&((unsigned char *)((node) + 1))[3])
#define DATA(node) ((node)->data) #define DATA(node) ((node)->data)
#define COLOR(node) ((node)->color) #define COLOR(node) ((node)->color)
#define NAMELEN(node) ((node)->namelen)
#define OFFSETLEN(node) ((node)->offsetlen)
#define ATTRS(node) ((node)->attributes)
#define PADBYTES(node) ((node)->padbytes)
/*
* Structure elements from the rbtdb.c, not
* used as part of the rbt.c algorithms.
*/
#define DIRTY(node) ((node)->dirty) #define DIRTY(node) ((node)->dirty)
#define LOCK(node) ((node)->locknum) #define LOCK(node) ((node)->locknum)
#define REFS(node) ((node)->references) #define REFS(node) ((node)->references)
/*
* The variable length stuff stored after the node.
*/
#define NAME(node) ((unsigned char *)((node) + 1))
#define OFFSETS(node) (NAME(node) + NAMELEN(node))
#define NODE_SIZE(node) (sizeof(*node) + \
NAMELEN(node) + OFFSETLEN(node) + PADBYTES(node))
/*
* Color management.
*/
#define IS_RED(node) ((node) != NULL && (node)->color == RED) #define IS_RED(node) ((node) != NULL && (node)->color == RED)
#define IS_BLACK(node) ((node) == NULL || (node)->color == BLACK) #define IS_BLACK(node) ((node) == NULL || (node)->color == BLACK)
#define MAKE_RED(node) ((node)->color = RED) #define MAKE_RED(node) ((node)->color = RED)
#define MAKE_BLACK(node) ((node)->color = BLACK) #define MAKE_BLACK(node) ((node)->color = BLACK)
#define NODE_SIZE(node) (sizeof(*node) + 3 + NAMELEN(node) + OFFSETLEN(node)) #define ADD_ANCESTOR(chain, node) \
(chain)->ancestors[(chain)->ancestor_count++] = (node)
#define ADD_LEVEL(chain, node) \
(chain)->levels[(chain)->level_count++] = (node)
/* /*
* The following macros directly access normally private name variables. * The following macros directly access normally private name variables.
@@ -82,23 +106,14 @@ struct dns_rbtnodechain {
* path of the tree traversal code. * path of the tree traversal code.
*/ */
#define ADD_ANCESTOR(chain, node) \
(chain)->ancestors[(chain)->ancestor_count++] = (node)
#define ADD_LEVEL(chain, node) \
(chain)->levels[(chain)->level_count++] = (node)
#define NODENAME(node, name) \ #define NODENAME(node, name) \
do { \ do { \
unsigned char *__current; \ (name)->length = NAMELEN(node); \
(name)->attributes = DNS_NAMEATTR_READONLY; \ (name)->labels = OFFSETLEN(node); \
__current = (unsigned char *)&(node)[1]; \ (name)->ndata = NAME(node); \
(name)->length = *__current++; \ (name)->offsets = OFFSETS(node); \
(name)->labels = *__current++; \ (name)->attributes = ATTRS(node); \
if (*__current++ == 1) \ (name)->attributes |= DNS_NAMEATTR_READONLY; \
(name)->attributes |= DNS_NAMEATTR_ABSOLUTE; \
(name)->ndata = __current; \
__current += (name)->length; \
(name)->offsets = __current; \
} while (0) } while (0)
#define FAST_ISABSOLUTE(name) \ #define FAST_ISABSOLUTE(name) \
@@ -232,8 +247,7 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
/* /*
* Does this thing have too many variables or what? * Does this thing have too many variables or what?
*/ */
dns_rbtnode_t **root, *current, *parent, *child; dns_rbtnode_t **root, *parent, *child, *current, *new_current;
dns_rbtnode_t *new_node, *new_current;
dns_name_t add_name, current_name, new_name, tmp_name; dns_name_t add_name, current_name, new_name, tmp_name;
dns_offsets_t add_offsets, current_offsets, new_offsets, tmp_offsets; dns_offsets_t add_offsets, current_offsets, new_offsets, tmp_offsets;
dns_namereln_t compared; dns_namereln_t compared;
@@ -257,10 +271,10 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
dns_name_fromregion(&add_name, &r); dns_name_fromregion(&add_name, &r);
if (rbt->root == NULL) { if (rbt->root == NULL) {
result = create_node(rbt->mctx, &add_name, &new_node); result = create_node(rbt->mctx, &add_name, &new_current);
if (result == DNS_R_SUCCESS) { if (result == DNS_R_SUCCESS) {
rbt->root = new_node; rbt->root = new_current;
*nodep = new_node; *nodep = new_current;
} }
return (result); return (result);
} }
@@ -316,8 +330,6 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
} }
} else { } else {
/* @@@ handle bitstrings */
/* /*
* This name has some suffix in common with the * This name has some suffix in common with the
* name at the current node. If the name at * name at the current node. If the name at
@@ -369,8 +381,22 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
* pointer made to a new tree. * pointer made to a new tree.
*/ */
INSIST(compared == dns_namereln_contains || INSIST(compared == dns_namereln_commonancestor
compared == dns_namereln_commonancestor); || compared == dns_namereln_contains);
/* @@@ handle bitstrings.
* When common_bits is non-zero, the last label
* in common (eg, vix in a.vix.com vs
* b.vix.com) is a bit label and common_bits is
* how many are in common. To split the node,
* the node in question will have to split into
* two bitstrings. A comment in name.h says,
* "Some provision still needs to be made for
* splitting bitstring labels," and Bob has
* pushed this down on the priority list,
* so for now splitting on bitstrings does not
* work.
*/
/* /*
* Get the common labels of the current name. * Get the common labels of the current name.
@@ -414,10 +440,12 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
/* /*
* Now create the new root of the subtree * Now create the new root of the subtree
* as the not-in-common labels of the current * as the not-in-common labels of the current
* node. Its down pointer and name data * node, keeping the same memory location so
* should be preserved, while left, right * as not to break any external references to
* and parent pointers are nullified (when * the node. The down pointer and name data
* the node is created in create_node()). * are preserved, while left and right
* pointers are nullified when the node is
* established as the start of the next level.
*/ */
start_label = 0; start_label = 0;
@@ -429,36 +457,37 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
keep_labels, keep_labels,
&new_name); &new_name);
result = create_node(rbt->mctx,
&new_name, &new_node);
if (result != DNS_R_SUCCESS) {
put_ancestor_mem(rbt->mctx, &chain);
return (result);
}
DATA(new_node) = DATA(current);
DOWN(new_node) = DOWN(current);
REFS(new_node) = REFS(current); /* @@@ ? */
DIRTY(new_node) = DIRTY(current); /* @@@ ? */
/* @@@ ? locknum */
/* /*
* Now that the old name in the existing * The name stored at the node is effectively
* node has been dissected into two new * truncated in place by setting the shorter
* nodes, the old node can be freed. * name length, moving the offsets to the
* end of the truncated name, and then
* updating PADBYTES to reflect the truncation.
*/ */
isc_mem_put(rbt->mctx, current,
NODE_SIZE(current)); NAMELEN(current) = new_name.length;
current = new_current; OFFSETLEN(current) = keep_labels;
memcpy(OFFSETS(current), new_name.offsets,
keep_labels);
PADBYTES(current) =
(current_name.length - new_name.length)
+ (current_labels - keep_labels);
/* /*
* Set up the new root of the next level. * Set up the new root of the next level.
* By definition it will not be the top
* level tree, so clear DNS_NAMEATTR_ABSOLUTE.
*/ */
DOWN(current) = new_node; DOWN(new_current) = current;
root = &DOWN(current); root = &DOWN(new_current);
ADD_ANCESTOR(&chain, NULL); ADD_ANCESTOR(&chain, NULL);
ADD_LEVEL(&chain, current); ADD_LEVEL(&chain, new_current);
LEFT(current) = NULL;
RIGHT(current) = NULL;
MAKE_BLACK(current);
ATTRS(current) &= ~DNS_NAMEATTR_ABSOLUTE;
if (common_labels == add_labels) { if (common_labels == add_labels) {
/* /*
@@ -466,7 +495,7 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
* the not-in-common parts down to * the not-in-common parts down to
* a new level. * a new level.
*/ */
*nodep = current; *nodep = new_current;
put_ancestor_mem(rbt->mctx, &chain); put_ancestor_mem(rbt->mctx, &chain);
return (DNS_R_SUCCESS); return (DNS_R_SUCCESS);
@@ -491,7 +520,6 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
keep_labels, keep_labels,
&add_name); &add_name);
current = new_node;
child = NULL; child = NULL;
ADD_ANCESTOR(&chain, current); ADD_ANCESTOR(&chain, current);
} }
@@ -502,10 +530,10 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
} while (child != NULL); } while (child != NULL);
result = create_node(rbt->mctx, &add_name, &new_node); result = create_node(rbt->mctx, &add_name, &new_current);
if (result == DNS_R_SUCCESS) if (result == DNS_R_SUCCESS)
result = dns_rbt_addonlevel(new_node, current, order, result = dns_rbt_addonlevel(new_current, current, order,
root, &chain); root, &chain);
/* @@@ XXXRTH Free node if add fails? */ /* @@@ XXXRTH Free node if add fails? */
/* @@@ XXXRTH Is it true that result should never be DNS_R_EXISTS? */ /* @@@ XXXRTH Is it true that result should never be DNS_R_EXISTS? */
@@ -514,7 +542,7 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
put_ancestor_mem(rbt->mctx, &chain); put_ancestor_mem(rbt->mctx, &chain);
if (result == DNS_R_SUCCESS) if (result == DNS_R_SUCCESS)
*nodep = new_node; *nodep = new_current;
return (result); return (result);
} }
@@ -876,25 +904,19 @@ create_node(isc_mem_t *mctx, dns_name_t *name, dns_rbtnode_t **nodep) {
dns_rbtnode_t *node; dns_rbtnode_t *node;
isc_region_t region; isc_region_t region;
unsigned int labels; unsigned int labels;
unsigned char *current;
unsigned char absolute;
REQUIRE(name->offsets != NULL); /* @@@ XXX direct access to name. */ REQUIRE(name->offsets != NULL); /* @@@ XXX direct access to name. */
dns_name_toregion(name, &region); dns_name_toregion(name, &region);
labels = FAST_COUNTLABELS(name); labels = FAST_COUNTLABELS(name);
if (FAST_ISABSOLUTE(name)) ENSURE(labels > 0);
absolute = 1;
else
absolute = 0;
/* /*
* Allocate space for the node structure, plus the length byte, the * Allocate space for the node structure, the namelen byte,
* offset length byte, the attributes byte (one byte for each is * the namepad byte, the offsetlen/attrs byte, length of the name
* 3 bytes), and plus the length of the name and the number of offsets. * and the number of offsets. @@@
*/ */
node = (dns_rbtnode_t *)isc_mem_get(mctx, node = (dns_rbtnode_t *)isc_mem_get(mctx, sizeof(*node) +
sizeof(*node) + 3 +
region.length + labels); region.length + labels);
if (node == NULL) if (node == NULL)
@@ -918,19 +940,18 @@ create_node(isc_mem_t *mctx, dns_name_t *name, dns_rbtnode_t **nodep) {
* and the name's offsets table. * and the name's offsets table.
* *
* @@@ * @@@
* XXX Finding a way not to waste a byte on "absolute" would be * XXX The offsets table could be made smaller by eliminating the
* a good thing, though it may be that we'll have to store * first offset, which is always 0. This requires changes to
* other attributes someday. The offsets table could be made * lib/dns/name.c.
* smaller by eliminating the first offset, which is always 0.
* This requires changes to lib/dns/name.c.
*/ */
current = (unsigned char *)&node[1]; NAMELEN(node) = region.length;
*current++ = region.length; PADBYTES(node) = 0;
*current++ = labels; OFFSETLEN(node) = labels;
*current++ = absolute; if (FAST_ISABSOLUTE(name))
memcpy(current, region.base, region.length); ATTRS(node) |= DNS_NAMEATTR_ABSOLUTE;
current += region.length;
memcpy(current, name->offsets, labels); memcpy(NAME(node), region.base, region.length);
memcpy(OFFSETS(node), name->offsets, labels);
*nodep = node; *nodep = node;