diff options
Diffstat (limited to 'include/import/ebtree.h')
| -rw-r--r-- | include/import/ebtree.h | 857 |
1 files changed, 857 insertions, 0 deletions
diff --git a/include/import/ebtree.h b/include/import/ebtree.h new file mode 100644 index 0000000..d6e51d5 --- /dev/null +++ b/include/import/ebtree.h @@ -0,0 +1,857 @@ +/* + * Elastic Binary Trees - generic macros and structures. + * Version 6.0.6 + * (C) 2002-2011 - Willy Tarreau <w@1wt.eu> + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation, version 2.1 + * exclusively. + * + * This library 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + + + +/* + General idea: + ------------- + In a radix binary tree, we may have up to 2N-1 nodes for N keys if all of + them are leaves. If we find a way to differentiate intermediate nodes (later + called "nodes") and final nodes (later called "leaves"), and we associate + them by two, it is possible to build sort of a self-contained radix tree with + intermediate nodes always present. It will not be as cheap as the ultree for + optimal cases as shown below, but the optimal case almost never happens : + + Eg, to store 8, 10, 12, 13, 14 : + + ultree this theoretical tree + + 8 8 + / \ / \ + 10 12 10 12 + / \ / \ + 13 14 12 14 + / \ + 12 13 + + Note that on real-world tests (with a scheduler), is was verified that the + case with data on an intermediate node never happens. This is because the + data spectrum is too large for such coincidences to happen. It would require + for instance that a task has its expiration time at an exact second, with + other tasks sharing that second. This is too rare to try to optimize for it. + + What is interesting is that the node will only be added above the leaf when + necessary, which implies that it will always remain somewhere above it. So + both the leaf and the node can share the exact value of the leaf, because + when going down the node, the bit mask will be applied to comparisons. So we + are tempted to have one single key shared between the node and the leaf. + + The bit only serves the nodes, and the dups only serve the leaves. So we can + put a lot of information in common. This results in one single entity with + two branch pointers and two parent pointers, one for the node part, and one + for the leaf part : + + node's leaf's + parent parent + | | + [node] [leaf] + / \ + left right + branch branch + + The node may very well refer to its leaf counterpart in one of its branches, + indicating that its own leaf is just below it : + + node's + parent + | + [node] + / \ + left [leaf] + branch + + Adding keys in such a tree simply consists in inserting nodes between + other nodes and/or leaves : + + [root] + | + [node2] + / \ + [leaf1] [node3] + / \ + [leaf2] [leaf3] + + On this diagram, we notice that [node2] and [leaf2] have been pulled away + from each other due to the insertion of [node3], just as if there would be + an elastic between both parts. This elastic-like behaviour gave its name to + the tree : "Elastic Binary Tree", or "EBtree". The entity which associates a + node part and a leaf part will be called an "EB node". + + We also notice on the diagram that there is a root entity required to attach + the tree. It only contains two branches and there is nothing above it. This + is an "EB root". Some will note that [leaf1] has no [node1]. One property of + the EBtree is that all nodes have their branches filled, and that if a node + has only one branch, it does not need to exist. Here, [leaf1] was added + below [root] and did not need any node. + + An EB node contains : + - a pointer to the node's parent (node_p) + - a pointer to the leaf's parent (leaf_p) + - two branches pointing to lower nodes or leaves (branches) + - a bit position (bit) + - an optional key. + + The key here is optional because it's used only during insertion, in order + to classify the nodes. Nothing else in the tree structure requires knowledge + of the key. This makes it possible to write type-agnostic primitives for + everything, and type-specific insertion primitives. This has led to consider + two types of EB nodes. The type-agnostic ones will serve as a header for the + other ones, and will simply be called "struct eb_node". The other ones will + have their type indicated in the structure name. Eg: "struct eb32_node" for + nodes carrying 32 bit keys. + + We will also node that the two branches in a node serve exactly the same + purpose as an EB root. For this reason, a "struct eb_root" will be used as + well inside the struct eb_node. In order to ease pointer manipulation and + ROOT detection when walking upwards, all the pointers inside an eb_node will + point to the eb_root part of the referenced EB nodes, relying on the same + principle as the linked lists in Linux. + + Another important point to note, is that when walking inside a tree, it is + very convenient to know where a node is attached in its parent, and what + type of branch it has below it (leaf or node). In order to simplify the + operations and to speed up the processing, it was decided in this specific + implementation to use the lowest bit from the pointer to designate the side + of the upper pointers (left/right) and the type of a branch (leaf/node). + This practise is not mandatory by design, but an implementation-specific + optimisation permitted on all platforms on which data must be aligned. All + known 32 bit platforms align their integers and pointers to 32 bits, leaving + the two lower bits unused. So, we say that the pointers are "tagged". And + since they designate pointers to root parts, we simply call them + "tagged root pointers", or "eb_troot" in the code. + + Duplicate keys are stored in a special manner. When inserting a key, if + the same one is found, then an incremental binary tree is built at this + place from these keys. This ensures that no special case has to be written + to handle duplicates when walking through the tree or when deleting entries. + It also guarantees that duplicates will be walked in the exact same order + they were inserted. This is very important when trying to achieve fair + processing distribution for instance. + + Algorithmic complexity can be derived from 3 variables : + - the number of possible different keys in the tree : P + - the number of entries in the tree : N + - the number of duplicates for one key : D + + Note that this tree is deliberately NOT balanced. For this reason, the worst + case may happen with a small tree (eg: 32 distinct keys of one bit). BUT, + the operations required to manage such data are so much cheap that they make + it worth using it even under such conditions. For instance, a balanced tree + may require only 6 levels to store those 32 keys when this tree will + require 32. But if per-level operations are 5 times cheaper, it wins. + + Minimal, Maximal and Average times are specified in number of operations. + Minimal is given for best condition, Maximal for worst condition, and the + average is reported for a tree containing random keys. An operation + generally consists in jumping from one node to the other. + + Complexity : + - lookup : min=1, max=log(P), avg=log(N) + - insertion from root : min=1, max=log(P), avg=log(N) + - insertion of dups : min=1, max=log(D), avg=log(D)/2 after lookup + - deletion : min=1, max=1, avg=1 + - prev/next : min=1, max=log(P), avg=2 : + N/2 nodes need 1 hop => 1*N/2 + N/4 nodes need 2 hops => 2*N/4 + N/8 nodes need 3 hops => 3*N/8 + ... + N/x nodes need log(x) hops => log2(x)*N/x + Total cost for all N nodes : sum[i=1..N](log2(i)*N/i) = N*sum[i=1..N](log2(i)/i) + Average cost across N nodes = total / N = sum[i=1..N](log2(i)/i) = 2 + + This design is currently limited to only two branches per node. Most of the + tree descent algorithm would be compatible with more branches (eg: 4, to cut + the height in half), but this would probably require more complex operations + and the deletion algorithm would be problematic. + + Useful properties : + - a node is always added above the leaf it is tied to, and never can get + below nor in another branch. This implies that leaves directly attached + to the root do not use their node part, which is indicated by a NULL + value in node_p. This also enhances the cache efficiency when walking + down the tree, because when the leaf is reached, its node part will + already have been visited (unless it's the first leaf in the tree). + + - pointers to lower nodes or leaves are stored in "branch" pointers. Only + the root node may have a NULL in either branch, it is not possible for + other branches. Since the nodes are attached to the left branch of the + root, it is not possible to see a NULL left branch when walking up a + tree. Thus, an empty tree is immediately identified by a NULL left + branch at the root. Conversely, the one and only way to identify the + root node is to check that it right branch is NULL. Note that the + NULL pointer may have a few low-order bits set. + + - a node connected to its own leaf will have branch[0|1] pointing to + itself, and leaf_p pointing to itself. + + - a node can never have node_p pointing to itself. + + - a node is linked in a tree if and only if it has a non-null leaf_p. + + - a node can never have both branches equal, except for the root which can + have them both NULL. + + - deletion only applies to leaves. When a leaf is deleted, its parent must + be released too (unless it's the root), and its sibling must attach to + the grand-parent, replacing the parent. Also, when a leaf is deleted, + the node tied to this leaf will be removed and must be released too. If + this node is different from the leaf's parent, the freshly released + leaf's parent will be used to replace the node which must go. A released + node will never be used anymore, so there's no point in tracking it. + + - the bit index in a node indicates the bit position in the key which is + represented by the branches. That means that a node with (bit == 0) is + just above two leaves. Negative bit values are used to build a duplicate + tree. The first node above two identical leaves gets (bit == -1). This + value logarithmically decreases as the duplicate tree grows. During + duplicate insertion, a node is inserted above the highest bit value (the + lowest absolute value) in the tree during the right-sided walk. If bit + -1 is not encountered (highest < -1), we insert above last leaf. + Otherwise, we insert above the node with the highest value which was not + equal to the one of its parent + 1. + + - the "eb_next" primitive walks from left to right, which means from lower + to higher keys. It returns duplicates in the order they were inserted. + The "eb_first" primitive returns the left-most entry. + + - the "eb_prev" primitive walks from right to left, which means from + higher to lower keys. It returns duplicates in the opposite order they + were inserted. The "eb_last" primitive returns the right-most entry. + + - a tree which has 1 in the lower bit of its root's right branch is a + tree with unique nodes. This means that when a node is inserted with + a key which already exists will not be inserted, and the previous + entry will be returned. + + */ + +#ifndef _EBTREE_H +#define _EBTREE_H + +#include <stdlib.h> +#include <import/ebtree-t.h> +#include <haproxy/api.h> + +static inline int flsnz8_generic(unsigned int x) +{ + int ret = 0; + if (x >> 4) { x >>= 4; ret += 4; } + return ret + ((0xFFFFAA50U >> (x << 1)) & 3) + 1; +} + +/* Note: we never need to run fls on null keys, so we can optimize the fls + * function by removing a conditional jump. + */ +#if defined(__i386__) || defined(__x86_64__) +/* this code is similar on 32 and 64 bit */ +static inline int flsnz(int x) +{ + int r; + __asm__("bsrl %1,%0\n" + : "=r" (r) : "rm" (x)); + return r+1; +} + +static inline int flsnz8(unsigned char x) +{ + int r; + __asm__("movzbl %%al, %%eax\n" + "bsrl %%eax,%0\n" + : "=r" (r) : "a" (x)); + return r+1; +} + +#else +// returns 1 to 32 for 1<<0 to 1<<31. Undefined for 0. +#define flsnz(___a) ({ \ + register int ___x, ___bits = 0; \ + ___x = (___a); \ + if (___x & 0xffff0000) { ___x &= 0xffff0000; ___bits += 16;} \ + if (___x & 0xff00ff00) { ___x &= 0xff00ff00; ___bits += 8;} \ + if (___x & 0xf0f0f0f0) { ___x &= 0xf0f0f0f0; ___bits += 4;} \ + if (___x & 0xcccccccc) { ___x &= 0xcccccccc; ___bits += 2;} \ + if (___x & 0xaaaaaaaa) { ___x &= 0xaaaaaaaa; ___bits += 1;} \ + ___bits + 1; \ + }) + +static inline int flsnz8(unsigned int x) +{ + return flsnz8_generic(x); +} + + +#endif + +static inline int fls64(unsigned long long x) +{ + unsigned int h; + unsigned int bits = 32; + + h = x >> 32; + if (!h) { + h = x; + bits = 0; + } + return flsnz(h) + bits; +} + +#define fls_auto(x) ((sizeof(x) > 4) ? fls64(x) : flsnz(x)) + +/* Linux-like "container_of". It returns a pointer to the structure of type + * <type> which has its member <name> stored at address <ptr>. + */ +#ifndef container_of +#define container_of(ptr, type, name) ((type *)(((void *)(ptr)) - ((long)&((type *)0)->name))) +#endif + +/* returns a pointer to the structure of type <type> which has its member <name> + * stored at address <ptr>, unless <ptr> is 0, in which case 0 is returned. + */ +#ifndef container_of_safe +#define container_of_safe(ptr, type, name) \ + ({ void *__p = (ptr); \ + __p ? (type *)(__p - ((long)&((type *)0)->name)) : (type *)0; \ + }) +#endif + +/* Return the structure of type <type> whose member <member> points to <ptr> */ +#define eb_entry(ptr, type, member) container_of(ptr, type, member) + +/***************************************\ + * Private functions. Not for end-user * +\***************************************/ + +/* Converts a root pointer to its equivalent eb_troot_t pointer, + * ready to be stored in ->branch[], leaf_p or node_p. NULL is not + * conserved. To be used with EB_LEAF, EB_NODE, EB_LEFT or EB_RGHT in <tag>. + */ +static inline eb_troot_t *eb_dotag(const struct eb_root *root, const int tag) +{ + return (eb_troot_t *)((void *)root + tag); +} + +/* Converts an eb_troot_t pointer pointer to its equivalent eb_root pointer, + * for use with pointers from ->branch[], leaf_p or node_p. NULL is conserved + * as long as the tree is not corrupted. To be used with EB_LEAF, EB_NODE, + * EB_LEFT or EB_RGHT in <tag>. + */ +static inline struct eb_root *eb_untag(const eb_troot_t *troot, const int tag) +{ + return (struct eb_root *)((void *)troot - tag); +} + +/* returns the tag associated with an eb_troot_t pointer */ +static inline int eb_gettag(eb_troot_t *troot) +{ + return (unsigned long)troot & 1; +} + +/* Converts a root pointer to its equivalent eb_troot_t pointer and clears the + * tag, no matter what its value was. + */ +static inline struct eb_root *eb_clrtag(const eb_troot_t *troot) +{ + return (struct eb_root *)((unsigned long)troot & ~1UL); +} + +/* Returns a pointer to the eb_node holding <root> */ +static inline struct eb_node *eb_root_to_node(struct eb_root *root) +{ + return container_of(root, struct eb_node, branches); +} + +/* Walks down starting at root pointer <start>, and always walking on side + * <side>. It either returns the node hosting the first leaf on that side, + * or NULL if no leaf is found. <start> may either be NULL or a branch pointer. + * The pointer to the leaf (or NULL) is returned. + */ +static inline struct eb_node *eb_walk_down(eb_troot_t *start, unsigned int side) +{ + /* A NULL pointer on an empty tree root will be returned as-is */ + while (eb_gettag(start) == EB_NODE) + start = (eb_untag(start, EB_NODE))->b[side]; + /* NULL is left untouched (root==eb_node, EB_LEAF==0) */ + return eb_root_to_node(eb_untag(start, EB_LEAF)); +} + +/* This function is used to build a tree of duplicates by adding a new node to + * a subtree of at least 2 entries. It will probably never be needed inlined, + * and it is not for end-user. + */ +static forceinline struct eb_node * +__eb_insert_dup(struct eb_node *sub, struct eb_node *new) +{ + struct eb_node *head = sub; + + eb_troot_t *new_left = eb_dotag(&new->branches, EB_LEFT); + eb_troot_t *new_rght = eb_dotag(&new->branches, EB_RGHT); + eb_troot_t *new_leaf = eb_dotag(&new->branches, EB_LEAF); + + /* first, identify the deepest hole on the right branch */ + while (eb_gettag(head->branches.b[EB_RGHT]) != EB_LEAF) { + struct eb_node *last = head; + head = container_of(eb_untag(head->branches.b[EB_RGHT], EB_NODE), + struct eb_node, branches); + if (head->bit > last->bit + 1) + sub = head; /* there's a hole here */ + } + + /* Here we have a leaf attached to (head)->b[EB_RGHT] */ + if (head->bit < -1) { + /* A hole exists just before the leaf, we insert there */ + new->bit = -1; + sub = container_of(eb_untag(head->branches.b[EB_RGHT], EB_LEAF), + struct eb_node, branches); + head->branches.b[EB_RGHT] = eb_dotag(&new->branches, EB_NODE); + + new->node_p = sub->leaf_p; + new->leaf_p = new_rght; + sub->leaf_p = new_left; + new->branches.b[EB_LEFT] = eb_dotag(&sub->branches, EB_LEAF); + new->branches.b[EB_RGHT] = new_leaf; + return new; + } else { + int side; + /* No hole was found before a leaf. We have to insert above + * <sub>. Note that we cannot be certain that <sub> is attached + * to the right of its parent, as this is only true if <sub> + * is inside the dup tree, not at the head. + */ + new->bit = sub->bit - 1; /* install at the lowest level */ + side = eb_gettag(sub->node_p); + head = container_of(eb_untag(sub->node_p, side), struct eb_node, branches); + head->branches.b[side] = eb_dotag(&new->branches, EB_NODE); + + new->node_p = sub->node_p; + new->leaf_p = new_rght; + sub->node_p = new_left; + new->branches.b[EB_LEFT] = eb_dotag(&sub->branches, EB_NODE); + new->branches.b[EB_RGHT] = new_leaf; + return new; + } +} + + +/**************************************\ + * Public functions, for the end-user * +\**************************************/ + +/* Return non-zero if the tree is empty, otherwise zero */ +static inline int eb_is_empty(const struct eb_root *root) +{ + return !root->b[EB_LEFT]; +} + +/* Return non-zero if the node is a duplicate, otherwise zero */ +static inline int eb_is_dup(const struct eb_node *node) +{ + return node->bit < 0; +} + +/* Return the first leaf in the tree starting at <root>, or NULL if none */ +static inline struct eb_node *eb_first(struct eb_root *root) +{ + return eb_walk_down(root->b[0], EB_LEFT); +} + +/* Return the last leaf in the tree starting at <root>, or NULL if none */ +static inline struct eb_node *eb_last(struct eb_root *root) +{ + return eb_walk_down(root->b[0], EB_RGHT); +} + +/* Return previous leaf node before an existing leaf node, or NULL if none. */ +static inline struct eb_node *eb_prev(struct eb_node *node) +{ + eb_troot_t *t = node->leaf_p; + + while (eb_gettag(t) == EB_LEFT) { + /* Walking up from left branch. We must ensure that we never + * walk beyond root. + */ + if (unlikely(eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL)) + return NULL; + t = (eb_root_to_node(eb_untag(t, EB_LEFT)))->node_p; + } + /* Note that <t> cannot be NULL at this stage */ + t = (eb_untag(t, EB_RGHT))->b[EB_LEFT]; + return eb_walk_down(t, EB_RGHT); +} + +/* Return next leaf node after an existing leaf node, or NULL if none. */ +static inline struct eb_node *eb_next(struct eb_node *node) +{ + eb_troot_t *t = node->leaf_p; + + while (eb_gettag(t) != EB_LEFT) + /* Walking up from right branch, so we cannot be below root */ + t = (eb_root_to_node(eb_untag(t, EB_RGHT)))->node_p; + + /* Note that <t> cannot be NULL at this stage */ + t = (eb_untag(t, EB_LEFT))->b[EB_RGHT]; + if (eb_clrtag(t) == NULL) + return NULL; + return eb_walk_down(t, EB_LEFT); +} + +/* Return previous leaf node within a duplicate sub-tree, or NULL if none. */ +static inline struct eb_node *eb_prev_dup(struct eb_node *node) +{ + eb_troot_t *t = node->leaf_p; + + while (eb_gettag(t) == EB_LEFT) { + /* Walking up from left branch. We must ensure that we never + * walk beyond root. + */ + if (unlikely(eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL)) + return NULL; + /* if the current node leaves a dup tree, quit */ + if ((eb_root_to_node(eb_untag(t, EB_LEFT)))->bit >= 0) + return NULL; + t = (eb_root_to_node(eb_untag(t, EB_LEFT)))->node_p; + } + /* Note that <t> cannot be NULL at this stage */ + if ((eb_root_to_node(eb_untag(t, EB_RGHT)))->bit >= 0) + return NULL; + t = (eb_untag(t, EB_RGHT))->b[EB_LEFT]; + return eb_walk_down(t, EB_RGHT); +} + +/* Return next leaf node within a duplicate sub-tree, or NULL if none. */ +static inline struct eb_node *eb_next_dup(struct eb_node *node) +{ + eb_troot_t *t = node->leaf_p; + + while (eb_gettag(t) != EB_LEFT) { + /* Walking up from right branch, so we cannot be below root */ + /* if the current node leaves a dup tree, quit */ + if ((eb_root_to_node(eb_untag(t, EB_RGHT)))->bit >= 0) + return NULL; + t = (eb_root_to_node(eb_untag(t, EB_RGHT)))->node_p; + } + + /* Note that <t> cannot be NULL at this stage. If our leaf is directly + * under the root, we must not try to cast the leaf_p into a eb_node* + * since it is a pointer to an eb_root. + */ + if (eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL) + return NULL; + + if ((eb_root_to_node(eb_untag(t, EB_LEFT)))->bit >= 0) + return NULL; + t = (eb_untag(t, EB_LEFT))->b[EB_RGHT]; + return eb_walk_down(t, EB_LEFT); +} + +/* Return previous leaf node before an existing leaf node, skipping duplicates, + * or NULL if none. */ +static inline struct eb_node *eb_prev_unique(struct eb_node *node) +{ + eb_troot_t *t = node->leaf_p; + + while (1) { + if (eb_gettag(t) != EB_LEFT) { + node = eb_root_to_node(eb_untag(t, EB_RGHT)); + /* if we're right and not in duplicates, stop here */ + if (node->bit >= 0) + break; + t = node->node_p; + } + else { + /* Walking up from left branch. We must ensure that we never + * walk beyond root. + */ + if (unlikely(eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL)) + return NULL; + t = (eb_root_to_node(eb_untag(t, EB_LEFT)))->node_p; + } + } + /* Note that <t> cannot be NULL at this stage */ + t = (eb_untag(t, EB_RGHT))->b[EB_LEFT]; + return eb_walk_down(t, EB_RGHT); +} + +/* Return next leaf node after an existing leaf node, skipping duplicates, or + * NULL if none. + */ +static inline struct eb_node *eb_next_unique(struct eb_node *node) +{ + eb_troot_t *t = node->leaf_p; + + while (1) { + if (eb_gettag(t) == EB_LEFT) { + if (unlikely(eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL)) + return NULL; /* we reached root */ + node = eb_root_to_node(eb_untag(t, EB_LEFT)); + /* if we're left and not in duplicates, stop here */ + if (node->bit >= 0) + break; + t = node->node_p; + } + else { + /* Walking up from right branch, so we cannot be below root */ + t = (eb_root_to_node(eb_untag(t, EB_RGHT)))->node_p; + } + } + + /* Note that <t> cannot be NULL at this stage */ + t = (eb_untag(t, EB_LEFT))->b[EB_RGHT]; + if (eb_clrtag(t) == NULL) + return NULL; + return eb_walk_down(t, EB_LEFT); +} + + +/* Removes a leaf node from the tree if it was still in it. Marks the node + * as unlinked. + */ +static forceinline void __eb_delete(struct eb_node *node) +{ + __label__ delete_unlink; + unsigned int pside, gpside, sibtype; + struct eb_node *parent; + struct eb_root *gparent; + + if (!node->leaf_p) + return; + + /* we need the parent, our side, and the grand parent */ + pside = eb_gettag(node->leaf_p); + parent = eb_root_to_node(eb_untag(node->leaf_p, pside)); + + /* We likely have to release the parent link, unless it's the root, + * in which case we only set our branch to NULL. Note that we can + * only be attached to the root by its left branch. + */ + + if (eb_clrtag(parent->branches.b[EB_RGHT]) == NULL) { + /* we're just below the root, it's trivial. */ + parent->branches.b[EB_LEFT] = NULL; + goto delete_unlink; + } + + /* To release our parent, we have to identify our sibling, and reparent + * it directly to/from the grand parent. Note that the sibling can + * either be a link or a leaf. + */ + + gpside = eb_gettag(parent->node_p); + gparent = eb_untag(parent->node_p, gpside); + + gparent->b[gpside] = parent->branches.b[!pside]; + sibtype = eb_gettag(gparent->b[gpside]); + + if (sibtype == EB_LEAF) { + eb_root_to_node(eb_untag(gparent->b[gpside], EB_LEAF))->leaf_p = + eb_dotag(gparent, gpside); + } else { + eb_root_to_node(eb_untag(gparent->b[gpside], EB_NODE))->node_p = + eb_dotag(gparent, gpside); + } + /* Mark the parent unused. Note that we do not check if the parent is + * our own node, but that's not a problem because if it is, it will be + * marked unused at the same time, which we'll use below to know we can + * safely remove it. + */ + parent->node_p = NULL; + + /* The parent node has been detached, and is currently unused. It may + * belong to another node, so we cannot remove it that way. Also, our + * own node part might still be used. so we can use this spare node + * to replace ours if needed. + */ + + /* If our link part is unused, we can safely exit now */ + if (!node->node_p) + goto delete_unlink; + + /* From now on, <node> and <parent> are necessarily different, and the + * <node>'s node part is in use. By definition, <parent> is at least + * below <node>, so keeping its key for the bit string is OK. + */ + + parent->node_p = node->node_p; + parent->branches = node->branches; + parent->bit = node->bit; + + /* We must now update the new node's parent... */ + gpside = eb_gettag(parent->node_p); + gparent = eb_untag(parent->node_p, gpside); + gparent->b[gpside] = eb_dotag(&parent->branches, EB_NODE); + + /* ... and its branches */ + for (pside = 0; pside <= 1; pside++) { + if (eb_gettag(parent->branches.b[pside]) == EB_NODE) { + eb_root_to_node(eb_untag(parent->branches.b[pside], EB_NODE))->node_p = + eb_dotag(&parent->branches, pside); + } else { + eb_root_to_node(eb_untag(parent->branches.b[pside], EB_LEAF))->leaf_p = + eb_dotag(&parent->branches, pside); + } + } + delete_unlink: + /* Now the node has been completely unlinked */ + node->leaf_p = NULL; + return; /* tree is not empty yet */ +} + +/* Compare blocks <a> and <b> byte-to-byte, from bit <ignore> to bit <len-1>. + * Return the number of equal bits between strings, assuming that the first + * <ignore> bits are already identical. It is possible to return slightly more + * than <len> bits if <len> does not stop on a byte boundary and we find exact + * bytes. Note that parts or all of <ignore> bits may be rechecked. It is only + * passed here as a hint to speed up the check. + */ +static forceinline int equal_bits(const unsigned char *a, + const unsigned char *b, + int ignore, int len) +{ + for (ignore >>= 3, a += ignore, b += ignore, ignore <<= 3; + ignore < len; ) { + unsigned char c; + + a++; b++; + ignore += 8; + c = b[-1] ^ a[-1]; + + if (c) { + /* OK now we know that old and new differ at byte <ptr> and that <c> holds + * the bit differences. We have to find what bit is differing and report + * it as the number of identical bits. Note that low bit numbers are + * assigned to high positions in the byte, as we compare them as strings. + */ + ignore -= flsnz8(c); + break; + } + } + return ignore; +} + +/* check that the two blocks <a> and <b> are equal on <len> bits. If it is known + * they already are on some bytes, this number of equal bytes to be skipped may + * be passed in <skip>. It returns 0 if they match, otherwise non-zero. + */ +static forceinline int check_bits(const unsigned char *a, + const unsigned char *b, + int skip, + int len) +{ + int bit, ret; + + /* This uncommon construction gives the best performance on x86 because + * it makes heavy use multiple-index addressing and parallel instructions, + * and it prevents gcc from reordering the loop since it is already + * properly oriented. Tested to be fine with 2.95 to 4.2. + */ + bit = ~len + (skip << 3) + 9; // = (skip << 3) + (8 - len) + ret = a[skip] ^ b[skip]; + if (unlikely(bit >= 0)) + return ret >> bit; + while (1) { + skip++; + if (ret) + return ret; + ret = a[skip] ^ b[skip]; + bit += 8; + if (bit >= 0) + return ret >> bit; + } +} + + +/* Compare strings <a> and <b> byte-to-byte, from bit <ignore> to the last 0. + * Return the number of equal bits between strings, assuming that the first + * <ignore> bits are already identical. Note that parts or all of <ignore> bits + * may be rechecked. It is only passed here as a hint to speed up the check. + * The caller is responsible for not passing an <ignore> value larger than any + * of the two strings. However, referencing any bit from the trailing zero is + * permitted. Equal strings are reported as a negative number of bits, which + * indicates the end was reached. + */ +static forceinline int string_equal_bits(const unsigned char *a, + const unsigned char *b, + int ignore) +{ + int beg; + unsigned char c; + + beg = ignore >> 3; + + /* skip known and identical bits. We stop at the first different byte + * or at the first zero we encounter on either side. + */ + while (1) { + unsigned char d; + + c = a[beg]; + d = b[beg]; + beg++; + + c ^= d; + if (c) + break; + if (!d) + return -1; + } + /* OK now we know that a and b differ at byte <beg>, or that both are zero. + * We have to find what bit is differing and report it as the number of + * identical bits. Note that low bit numbers are assigned to high positions + * in the byte, as we compare them as strings. + */ + return (beg << 3) - flsnz8(c); +} + +static forceinline int cmp_bits(const unsigned char *a, const unsigned char *b, unsigned int pos) +{ + unsigned int ofs; + unsigned char bit_a, bit_b; + + ofs = pos >> 3; + pos = ~pos & 7; + + bit_a = (a[ofs] >> pos) & 1; + bit_b = (b[ofs] >> pos) & 1; + + return bit_a - bit_b; /* -1: a<b; 0: a=b; 1: a>b */ +} + +static forceinline int get_bit(const unsigned char *a, unsigned int pos) +{ + unsigned int ofs; + + ofs = pos >> 3; + pos = ~pos & 7; + return (a[ofs] >> pos) & 1; +} + +/* These functions are declared in ebtree.c */ +void eb_delete(struct eb_node *node); +struct eb_node *eb_insert_dup(struct eb_node *sub, struct eb_node *new); +int eb_memcmp(const void *m1, const void *m2, size_t len); + +#endif /* _EB_TREE_H */ + +/* + * Local variables: + * c-indent-level: 8 + * c-basic-offset: 8 + * End: + */ |