/************************************************* * Exim - an Internet mail transport agent * *************************************************/ /* Copyright (c) University of Cambridge 1995 - 2015 */ /* See the file NOTICE for conditions of use and distribution. */ /* Functions for maintaining binary balanced trees and some associated functions as well. */ #include "exim.h" #ifndef MACRO_PREDEF /************************************************* * Add entry to non-recipients tree * *************************************************/ /* Duplicates are just discarded. Arguments: s string to add Returns: nothing */ void tree_add_nonrecipient(uschar *s) { tree_node *node = store_get(sizeof(tree_node) + Ustrlen(s)); Ustrcpy(node->name, s); node->data.ptr = NULL; if (!tree_insertnode(&tree_nonrecipients, node)) store_reset(node); } /************************************************* * Add entry to duplicates tree * *************************************************/ /* Duplicates are just discarded. Argument: s string to add addr the address is is a duplicate of Returns: nothing */ void tree_add_duplicate(uschar *s, address_item *addr) { tree_node *node = store_get(sizeof(tree_node) + Ustrlen(s)); Ustrcpy(node->name, s); node->data.ptr = addr; if (!tree_insertnode(&tree_duplicates, node)) store_reset(node); } /************************************************* * Add entry to unusable addresses tree * *************************************************/ /* Duplicates are simply discarded. Argument: the host item Returns: nothing */ void tree_add_unusable(host_item *h) { tree_node *node; uschar s[256]; sprintf(CS s, "T:%.200s:%s", h->name, h->address); node = store_get(sizeof(tree_node) + Ustrlen(s)); Ustrcpy(node->name, s); node->data.val = h->why; if (h->status == hstatus_unusable_expired) node->data.val += 256; if (!tree_insertnode(&tree_unusable, node)) store_reset(node); } /************************************************* * Write a tree in re-readable form * *************************************************/ /* This function writes out a tree in a form in which it can easily be re-read. It is used for writing out the non-recipients tree onto the spool, for retrieval at the next retry time. The format is as follows: . If the tree is empty, write one line containing XX. . Otherwise, each node is written, preceded by two letters (Y/N) indicating whether it has left or right children. . The left subtree (if any) then follows, then the right subtree. First, there's an internal recursive subroutine. Arguments: p current node f FILE to write to Returns: nothing */ static void write_tree(tree_node *p, FILE *f) { fprintf(f, "%c%c %s\n", p->left ? 'Y':'N', p->right ? 'Y':'N', p->name); if (p->left) write_tree(p->left, f); if (p->right) write_tree(p->right, f); } /* This is the top-level function, with the same arguments. */ void tree_write(tree_node *p, FILE *f) { if (!p) { fprintf(f, "XX\n"); return; } write_tree(p, f); } #endif /*********************************************************** * Binary Balanced Tree Management Routines * ***********************************************************/ /* This set of routines maintains a balanced binary tree using the algorithm given in Knuth Vol 3 page 455. The routines make use of uschar * pointers as byte pointers, so as to be able to do arithmetic on them, since ANSI Standard C does not permit additions and subtractions on void pointers. */ /************************************************* * Flags and Parameters * *************************************************/ #define tree_lbal 1 /* left subtree is longer */ #define tree_rbal 2 /* right subtree is longer */ #define tree_bmask 3 /* mask for flipping bits */ /************************************************* * Insert a new node into a tree * *************************************************/ /* The node->name field must (obviously) be set, but the other fields need not be initialized. Arguments: treebase pointer to the root of the tree node the note to insert, with name field set Returns: TRUE if node inserted; FALSE if not (duplicate) */ int tree_insertnode(tree_node **treebase, tree_node *node) { tree_node *p = *treebase; tree_node **q, *r, *s, **t; int a; node->left = node->right = NULL; node->balance = 0; /* Deal with an empty tree */ if (!p) { *treebase = node; return TRUE; } /* The tree is not empty. While finding the insertion point, q points to the pointer to p, and t points to the pointer to the potential re-balancing point. */ q = treebase; t = q; /* Loop to search tree for place to insert new node */ for (;;) { int c = Ustrcmp(node->name, p->name); if (c == 0) return FALSE; /* Duplicate node encountered */ /* Deal with climbing down the tree, exiting from the loop when we reach a leaf. */ q = c > 0 ? &p->right : &p->left; p = *q; if (!p) break; /* Save the address of the pointer to the last node en route which has a non-zero balance factor. */ if (p->balance != 0) t = q; } /* When the above loop completes, q points to the pointer to NULL; that is the place at which the new node must be inserted. */ *q = node; /* Set up s as the potential re-balancing point, and r as the next node after it along the route. */ s = *t; r = Ustrcmp(node->name, s->name) > 0 ? s->right : s->left; /* Adjust balance factors along the route from s to node. */ p = r; while (p != node) if (Ustrcmp(node->name, p->name) < 0) { p->balance = tree_lbal; p = p->left; } else { p->balance = tree_rbal; p = p->right; } /* Now the World-Famous Balancing Act */ a = Ustrcmp(node->name, s->name) < 0 ? tree_lbal : tree_rbal; if (s->balance == 0) s->balance = (uschar)a; /* The tree has grown higher */ else if (s->balance != (uschar)a) s->balance = 0; /* It's become more balanced */ else /* It's got out of balance */ { /* Perform a single rotation */ if (r->balance == (uschar)a) { p = r; if (a == tree_rbal) { s->right = r->left; r->left = s; } else { s->left = r->right; r->right = s; } s->balance = 0; r->balance = 0; } /* Perform a double rotation There was an occasion when the balancing factors were screwed up by a bug in the code that reads a tree from the spool. In case this ever happens again, check for changing p to NULL and don't do it. It is better to have an unbalanced tree than a crash. */ else { if (a == tree_rbal) { if (!r->left) return TRUE; /* Bail out if tree corrupt */ p = r->left; r->left = p->right; p->right = r; s->right = p->left; p->left = s; } else { if (!r->right) return TRUE; /* Bail out if tree corrupt */ p = r->right; r->right = p->left; p->left = r; s->left = p->right; p->right = s; } s->balance = p->balance == (uschar)a ? (uschar)(a^tree_bmask) : 0; r->balance = p->balance == (uschar)(a^tree_bmask) ? (uschar)a : 0; p->balance = 0; } /* Finishing touch */ *t = p; } return TRUE; /* Successful insertion */ } /************************************************* * Search tree for node by name * *************************************************/ /* Arguments: p root of tree name key to search for Returns: pointer to node, or NULL if not found */ tree_node * tree_search(tree_node *p, const uschar *name) { int c; for ( ; p; p = c < 0 ? p->left : p->right) if ((c = Ustrcmp(name, p->name)) == 0) return p; return NULL; } #ifndef MACRO_PREDEF /************************************************* * Walk tree recursively and execute function * *************************************************/ /* Arguments: p root of the tree f function to execute for each name-value-pair ctx context data for f */ void tree_walk(tree_node *p, void (*f)(uschar*, uschar*, void*), void *ctx) { if (!p) return; f(p->name, p->data.ptr, ctx); tree_walk(p->left, f, ctx); tree_walk(p->right, f, ctx); } #endif /* End of tree.c */