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Diffstat (limited to '')
| -rw-r--r-- | lib/generic/trie.c | 912 |
1 files changed, 912 insertions, 0 deletions
diff --git a/lib/generic/trie.c b/lib/generic/trie.c new file mode 100644 index 0000000..0009eef --- /dev/null +++ b/lib/generic/trie.c @@ -0,0 +1,912 @@ +/* Copyright (C) 2016-2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz> + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. + + The code originated from https://github.com/fanf2/qp/blob/master/qp.c + at revision 5f6d93753. + */ + +#include <assert.h> +#include <stdlib.h> +#include <string.h> + +#include "lib/generic/trie.h" +#include "lib/utils.h" +#include "contrib/ucw/lib.h" + +#if defined(__i386) || defined(__x86_64) || defined(_M_IX86) \ + || (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN) \ + && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) + + /*! + * \brief Use a pointer alignment hack to save memory. + * + * When on, isbranch() relies on the fact that in leaf_t the first pointer + * is aligned on multiple of 4 bytes and that the flags bitfield is + * overlaid over the lowest two bits of that pointer. + * Neither is really guaranteed by the C standards; the second part should + * be OK with x86_64 ABI and most likely any other little-endian platform. + * It would be possible to manipulate the right bits portably, but it would + * complicate the code nontrivially. C++ doesn't even guarantee type-punning. + * In debug mode we check this works OK when creating a new trie instance. + */ + #define FLAGS_HACK 1 +#else + #define FLAGS_HACK 0 +#endif + +typedef unsigned char byte; +#ifndef uint +typedef unsigned int uint; +#define uint uint +#endif +typedef uint bitmap_t; /*! Bit-maps, using the range of 1<<0 to 1<<16 (inclusive). */ + +typedef struct { + uint32_t len; // 32 bits are enough for key lengths; probably even 16 bits would be. + char chars[]; +} tkey_t; + +/*! \brief Leaf of trie. */ +typedef struct { + #if !FLAGS_HACK + byte flags; + #endif + tkey_t *key; /*!< The pointer must be aligned to 4-byte multiples! */ + trie_val_t val; +} leaf_t; + +/*! \brief A trie node is either leaf_t or branch_t. */ +typedef union node node_t; + +/*! + * \brief Branch node of trie. + * + * - The flags distinguish whether the node is a leaf_t (0), or a branch + * testing the more-important nibble (1) or the less-important one (2). + * - It stores the index of the byte that the node tests. The combined + * value (index*4 + flags) increases in branch nodes as you go deeper + * into the trie. All the keys below a branch are identical up to the + * nibble identified by the branch. Indices have to be stored because + * we skip any branch nodes that would have a single child. + * (Consequently, the skipped parts of key have to be validated in a leaf.) + * - The bitmap indicates which subtries are present. The present child nodes + * are stored in the twigs array (with no holes between them). + * - To simplify storing keys that are prefixes of each other, the end-of-string + * position is treated as another nibble value, ordered before all others. + * That affects the bitmap and twigs fields. + * + * \note The branch nodes are never allocated individually, but they are + * always part of either the root node or the twigs array of the parent. + */ +typedef struct { + #if FLAGS_HACK + uint32_t flags : 2, + bitmap : 17; /*!< The first bitmap bit is for end-of-string child. */ + #else + byte flags; + uint32_t bitmap; + #endif + uint32_t index; + node_t *twigs; +} branch_t; + +union node { + leaf_t leaf; + branch_t branch; +}; + +struct trie { + node_t root; // undefined when weight == 0, see empty_root() + size_t weight; + knot_mm_t mm; +}; + +/*! \brief Make the root node empty (debug-only). */ +static inline void empty_root(node_t *root) { +#ifndef NDEBUG + *root = (node_t){ .branch = { + .flags = 3, // invalid value that fits + .bitmap = 0, + .index = -1, + .twigs = NULL + } }; +#endif +} + +/*! \brief Check that unportable code works OK (debug-only). */ +static void assert_portability(void) { +#if FLAGS_HACK + assert(((union node){ .leaf = { + .key = (tkey_t *)(((uint8_t *)NULL) + 1), + .val = NULL + } }).branch.flags == 1); +#endif +} + +/*! \brief Propagate error codes. */ +#define ERR_RETURN(x) \ + do { \ + int err_code_ = x; \ + if (unlikely(err_code_ != KNOT_EOK)) \ + return err_code_; \ + } while (false) + +/*! + * \brief Count the number of set bits. + * + * \TODO This implementation may be relatively slow on some HW. + */ +static uint bitmap_weight(bitmap_t w) +{ + assert((w & ~((1 << 17) - 1)) == 0); // using the least-important 17 bits + return __builtin_popcount(w); +} + +/*! \brief Only keep the lowest bit in the bitmap (least significant -> twigs[0]). */ +static bitmap_t bitmap_lowest_bit(bitmap_t w) +{ + assert((w & ~((1 << 17) - 1)) == 0); // using the least-important 17 bits + return 1 << __builtin_ctz(w); +} + +/*! \brief Test flags to determine type of this node. */ +static bool isbranch(const node_t *t) +{ + uint f = t->branch.flags; + assert(f <= 2); + return f != 0; +} + +/*! \brief Make a bitmask for testing a branch bitmap. */ +static bitmap_t nibbit(byte k, uint flags) +{ + uint shift = (2 - flags) << 2; + uint nibble = (k >> shift) & 0xf; + return 1 << (nibble + 1/*because of prefix keys*/); +} + +/*! \brief Extract a nibble from a key and turn it into a bitmask. */ +static bitmap_t twigbit(const node_t *t, const char *key, uint32_t len) +{ + assert(isbranch(t)); + uint i = t->branch.index; + + if (i >= len) + return 1 << 0; // leaf position + + return nibbit((byte)key[i], t->branch.flags); +} + +/*! \brief Test if a branch node has a child indicated by a bitmask. */ +static bool hastwig(const node_t *t, bitmap_t bit) +{ + assert(isbranch(t)); + return t->branch.bitmap & bit; +} + +/*! \brief Compute offset of an existing child in a branch node. */ +static uint twigoff(const node_t *t, bitmap_t b) +{ + assert(isbranch(t)); + return bitmap_weight(t->branch.bitmap & (b - 1)); +} + +/*! \brief Get pointer to a particular child of a branch node. */ +static node_t* twig(node_t *t, uint i) +{ + assert(isbranch(t)); + return &t->branch.twigs[i]; +} + +/*! + * \brief For a branch nod, compute offset of a child and child count. + * + * Having this separate might be meaningful for performance optimization. + */ +#define TWIGOFFMAX(off, max, t, b) do { \ + off = twigoff(t, b); \ + max = bitmap_weight(t->branch.bitmap); \ + } while(0) + +/*! \brief Simple string comparator. */ +static int key_cmp(const char *k1, uint32_t k1_len, const char *k2, uint32_t k2_len) +{ + int ret = memcmp(k1, k2, MIN(k1_len, k2_len)); + if (ret != 0) { + return ret; + } + + /* Key string is equal, compare lengths. */ + if (k1_len == k2_len) { + return 0; + } else if (k1_len < k2_len) { + return -1; + } else { + return 1; + } +} + +trie_t* trie_create(knot_mm_t *mm) +{ + assert_portability(); + trie_t *trie = mm_alloc(mm, sizeof(trie_t)); + if (trie != NULL) { + empty_root(&trie->root); + trie->weight = 0; + if (mm != NULL) + trie->mm = *mm; + else + mm_ctx_init(&trie->mm); + } + return trie; +} + +/*! \brief Free anything under the trie node, except for the passed pointer itself. */ +static void clear_trie(node_t *trie, knot_mm_t *mm) +{ + if (!isbranch(trie)) { + mm_free(mm, trie->leaf.key); + } else { + branch_t *b = &trie->branch; + int len = bitmap_weight(b->bitmap); + for (int i = 0; i < len; ++i) + clear_trie(b->twigs + i, mm); + mm_free(mm, b->twigs); + } +} + +void trie_free(trie_t *tbl) +{ + if (tbl == NULL) + return; + if (tbl->weight) + clear_trie(&tbl->root, &tbl->mm); + mm_free(&tbl->mm, tbl); +} + +void trie_clear(trie_t *tbl) +{ + assert(tbl); + if (!tbl->weight) + return; + clear_trie(&tbl->root, &tbl->mm); + empty_root(&tbl->root); + tbl->weight = 0; +} + +size_t trie_weight(const trie_t *tbl) +{ + assert(tbl); + return tbl->weight; +} + +struct found { + leaf_t *l; /**< the found leaf (NULL if not found) */ + branch_t *p; /**< the leaf's parent (if exists) */ + bitmap_t b; /**< bit-mask with a single bit marking l under p */ +}; +/** Search trie for an item with the given key (equality only). */ +static struct found find_equal(trie_t *tbl, const char *key, uint32_t len) +{ + assert(tbl); + struct found ret0; + memset(&ret0, 0, sizeof(ret0)); + if (!tbl->weight) + return ret0; + /* Current node and parent while descending (returned values basically). */ + node_t *t = &tbl->root; + branch_t *p = NULL; + bitmap_t b = 0; + while (isbranch(t)) { + __builtin_prefetch(t->branch.twigs); + b = twigbit(t, key, len); + if (!hastwig(t, b)) + return ret0; + p = &t->branch; + t = twig(t, twigoff(t, b)); + } + if (key_cmp(key, len, t->leaf.key->chars, t->leaf.key->len) != 0) + return ret0; + return (struct found) { + .l = &t->leaf, + .p = p, + .b = b, + }; +} +/** Find item with the first key (lexicographical order). */ +static struct found find_first(trie_t *tbl) +{ + assert(tbl); + if (!tbl->weight) { + struct found ret0; + memset(&ret0, 0, sizeof(ret0)); + return ret0; + } + /* Current node and parent while descending (returned values basically). */ + node_t *t = &tbl->root; + branch_t *p = NULL; + while (isbranch(t)) { + p = &t->branch; + t = &p->twigs[0]; + } + return (struct found) { + .l = &t->leaf, + .p = p, + .b = p ? bitmap_lowest_bit(p->bitmap) : 0, + }; +} + +trie_val_t* trie_get_try(trie_t *tbl, const char *key, uint32_t len) +{ + struct found found = find_equal(tbl, key, len); + return found.l ? &found.l->val : NULL; +} + +trie_val_t* trie_get_first(trie_t *tbl, char **key, uint32_t *len) +{ + struct found found = find_first(tbl); + if (!found.l) + return NULL; + if (key) + *key = found.l->key->chars; + if (len) + *len = found.l->key->len; + return &found.l->val; +} + +/** Delete the found element (if any) and return value (unless NULL is passed) */ +static int del_found(trie_t *tbl, struct found found, trie_val_t *val) +{ + if (!found.l) + return KNOT_ENOENT; + mm_free(&tbl->mm, found.l->key); + if (val != NULL) + *val = found.l->val; // we return trie_val_t directly when deleting + --tbl->weight; + branch_t * const p = found.p; // short-hand + if (unlikely(!p)) { // whole trie was a single leaf + assert(tbl->weight == 0); + empty_root(&tbl->root); + return KNOT_EOK; + } + // remove leaf t as child of p; get child index via pointer arithmetic + int ci = ((union node *)found.l) - p->twigs, + cc = bitmap_weight(p->bitmap); // child count + assert(ci >= 0 && ci < cc); + + if (cc == 2) { // collapse binary node p: move the other child to this node + node_t *twigs = p->twigs; + (*(union node *)p) = twigs[1 - ci]; // it might be a leaf or branch + mm_free(&tbl->mm, twigs); + return KNOT_EOK; + } + memmove(p->twigs + ci, p->twigs + ci + 1, sizeof(node_t) * (cc - ci - 1)); + p->bitmap &= ~found.b; + node_t *twigs = mm_realloc(&tbl->mm, p->twigs, sizeof(node_t) * (cc - 1), + sizeof(node_t) * cc); + if (likely(twigs != NULL)) + p->twigs = twigs; + /* We can ignore mm_realloc failure, only beware that next time + * the prev_size passed to it wouldn't be correct; TODO? */ + return KNOT_EOK; +} + +int trie_del(trie_t *tbl, const char *key, uint32_t len, trie_val_t *val) +{ + struct found found = find_equal(tbl, key, len); + return del_found(tbl, found, val); +} + +int trie_del_first(trie_t *tbl, char *key, uint32_t *len, trie_val_t *val) +{ + struct found found = find_first(tbl); + if (!found.l) + return KNOT_ENOENT; + if (key) { + if (!len) + return KNOT_EINVAL; + if (*len < found.l->key->len) + return kr_error(ENOSPC); + memcpy(key, found.l->key->chars, found.l->key->len); + } + if (len) { // makes sense even with key == NULL + *len = found.l->key->len; + } + return del_found(tbl, found, val); +} + +/*! + * \brief Stack of nodes, storing a path down a trie. + * + * The structure also serves directly as the public trie_it_t type, + * in which case it always points to the current leaf, unless we've finished + * (i.e. it->len == 0). + */ +typedef struct trie_it { + node_t* *stack; /*!< The stack; malloc is used directly instead of mm. */ + uint32_t len; /*!< Current length of the stack. */ + uint32_t alen; /*!< Allocated/available length of the stack. */ + /*! \brief Initial storage for \a stack; it should fit in many use cases. */ + node_t* stack_init[60]; +} nstack_t; + +/*! \brief Create a node stack containing just the root (or empty). */ +static void ns_init(nstack_t *ns, trie_t *tbl) +{ + assert(tbl); + ns->stack = ns->stack_init; + ns->alen = sizeof(ns->stack_init) / sizeof(ns->stack_init[0]); + if (tbl->weight) { + ns->len = 1; + ns->stack[0] = &tbl->root; + } else { + ns->len = 0; + } +} + +/*! \brief Free inside of the stack, i.e. not the passed pointer itself. */ +static void ns_cleanup(nstack_t *ns) +{ + assert(ns && ns->stack); + if (likely(ns->stack == ns->stack_init)) + return; + free(ns->stack); + #ifndef NDEBUG + ns->stack = NULL; + ns->alen = 0; + #endif +} + +/*! \brief Allocate more space for the stack. */ +static int ns_longer_alloc(nstack_t *ns) +{ + ns->alen *= 2; + size_t new_size = sizeof(nstack_t) + ns->alen * sizeof(node_t *); + node_t **st; + if (ns->stack == ns->stack_init) { + st = malloc(new_size); + if (st != NULL) + memcpy(st, ns->stack, ns->len * sizeof(node_t *)); + } else { + st = realloc(ns->stack, new_size); + } + if (st == NULL) + return KNOT_ENOMEM; + ns->stack = st; + return KNOT_EOK; +} + +/*! \brief Ensure the node stack can be extended by one. */ +static inline int ns_longer(nstack_t *ns) +{ + // get a longer stack if needed + if (likely(ns->len < ns->alen)) + return KNOT_EOK; + return ns_longer_alloc(ns); // hand-split the part suitable for inlining +} + +/*! + * \brief Find the "branching point" as if searching for a key. + * + * The whole path to the point is kept on the passed stack; + * always at least the root will remain on the top of it. + * Beware: the precise semantics of this function is rather tricky. + * The top of the stack will contain: the corresponding leaf if exact match is found; + * or the immediate node below a branching-point-on-edge or the branching-point itself. + * + * \param info Set position of the point of first mismatch (in index and flags). + * \param first Set the value of the first non-matching character (from trie), + * optionally; end-of-string character has value -256 (that's why it's int). + * Note: the character is converted to *unsigned* char (i.e. 0..255), + * as that's the ordering used in the trie. + * + * \return KNOT_EOK or KNOT_ENOMEM. + */ +static int ns_find_branch(nstack_t *ns, const char *key, uint32_t len, + branch_t *info, int *first) +{ + assert(ns && ns->len && info); + // First find some leaf with longest matching prefix. + while (isbranch(ns->stack[ns->len - 1])) { + ERR_RETURN(ns_longer(ns)); + node_t *t = ns->stack[ns->len - 1]; + __builtin_prefetch(t->branch.twigs); + bitmap_t b = twigbit(t, key, len); + // Even if our key is missing from this branch we need to + // keep iterating down to a leaf. It doesn't matter which + // twig we choose since the keys are all the same up to this + // index. Note that blindly using twigoff(t, b) can cause + // an out-of-bounds index if it equals twigmax(t). + uint i = hastwig(t, b) ? twigoff(t, b) : 0; + ns->stack[ns->len++] = twig(t, i); + } + tkey_t *lkey = ns->stack[ns->len-1]->leaf.key; + // Find index of the first char that differs. + uint32_t index = 0; + while (index < MIN(len,lkey->len)) { + if (key[index] != lkey->chars[index]) + break; + else + ++index; + } + info->index = index; + if (first) + *first = lkey->len > index ? (unsigned char)lkey->chars[index] : -256; + // Find flags: which half-byte has matched. + uint flags; + if (index == len && len == lkey->len) { // found equivalent key + info->flags = flags = 0; + goto success; + } + if (likely(index < MIN(len,lkey->len))) { + byte k2 = (byte)lkey->chars[index]; + byte k1 = (byte)key[index]; + flags = ((k1 ^ k2) & 0xf0) ? 1 : 2; + } else { // one is prefix of another + flags = 1; + } + info->flags = flags; + // now go up the trie from the current leaf + branch_t *t; + do { + if (unlikely(ns->len == 1)) + goto success; // only the root stays on the stack + t = (branch_t*)ns->stack[ns->len - 2]; + if (t->index < index || (t->index == index && t->flags < flags)) + goto success; + --ns->len; + } while (true); +success: + #ifndef NDEBUG // invariants on successful return + assert(ns->len); + if (isbranch(ns->stack[ns->len - 1])) { + t = &ns->stack[ns->len - 1]->branch; + assert(t->index > index || (t->index == index && t->flags >= flags)); + } + if (ns->len > 1) { + t = &ns->stack[ns->len - 2]->branch; + assert(t->index < index || (t->index == index + && (t->flags < flags || (t->flags == 1 && flags == 0)))); + } + #endif + return KNOT_EOK; +} + +/*! + * \brief Advance the node stack to the last leaf in the subtree. + * + * \return KNOT_EOK or KNOT_ENOMEM. + */ +static int ns_last_leaf(nstack_t *ns) +{ + assert(ns); + do { + ERR_RETURN(ns_longer(ns)); + node_t *t = ns->stack[ns->len - 1]; + if (!isbranch(t)) + return KNOT_EOK; + int lasti = bitmap_weight(t->branch.bitmap) - 1; + assert(lasti >= 0); + ns->stack[ns->len++] = twig(t, lasti); + } while (true); +} + +/*! + * \brief Advance the node stack to the first leaf in the subtree. + * + * \return KNOT_EOK or KNOT_ENOMEM. + */ +static int ns_first_leaf(nstack_t *ns) +{ + assert(ns && ns->len); + do { + ERR_RETURN(ns_longer(ns)); + node_t *t = ns->stack[ns->len - 1]; + if (!isbranch(t)) + return KNOT_EOK; + ns->stack[ns->len++] = twig(t, 0); + } while (true); +} + +/*! + * \brief Advance the node stack to the leaf that is previous to the current node. + * + * \note Prefix leaf under the current node DOES count (if present; perhaps questionable). + * \return KNOT_EOK on success, KNOT_ENOENT on not-found, or possibly KNOT_ENOMEM. + */ +static int ns_prev_leaf(nstack_t *ns) +{ + assert(ns && ns->len > 0); + + node_t *t = ns->stack[ns->len - 1]; + if (hastwig(t, 1 << 0)) { // the prefix leaf + t = twig(t, 0); + ERR_RETURN(ns_longer(ns)); + ns->stack[ns->len++] = t; + return KNOT_EOK; + } + + do { + if (ns->len < 2) + return KNOT_ENOENT; // root without empty key has no previous leaf + t = ns->stack[ns->len - 1]; + node_t *p = ns->stack[ns->len - 2]; + int pindex = t - p->branch.twigs; // index in parent via pointer arithmetic + assert(pindex >= 0 && pindex <= 16); + if (pindex > 0) { // t isn't the first child -> go down the previous one + ns->stack[ns->len - 1] = twig(p, pindex - 1); + return ns_last_leaf(ns); + } + // we've got to go up again + --ns->len; + } while (true); +} + +/*! + * \brief Advance the node stack to the leaf that is successor to the current node. + * + * \note Prefix leaf or anything else under the current node DOES count. + * \return KNOT_EOK on success, KNOT_ENOENT on not-found, or possibly KNOT_ENOMEM. + */ +static int ns_next_leaf(nstack_t *ns) +{ + assert(ns && ns->len > 0); + + node_t *t = ns->stack[ns->len - 1]; + if (isbranch(t)) + return ns_first_leaf(ns); + do { + if (ns->len < 2) + return KNOT_ENOENT; // not found, as no more parent is available + t = ns->stack[ns->len - 1]; + node_t *p = ns->stack[ns->len - 2]; + int pindex = t - p->branch.twigs; // index in parent via pointer arithmetic + assert(pindex >= 0 && pindex <= 16); + int pcount = bitmap_weight(p->branch.bitmap); + if (pindex + 1 < pcount) { // t isn't the last child -> go down the next one + ns->stack[ns->len - 1] = twig(p, pindex + 1); + return ns_first_leaf(ns); + } + // we've got to go up again + --ns->len; + } while (true); +} + +int trie_get_leq(trie_t *tbl, const char *key, uint32_t len, trie_val_t **val) +{ + assert(tbl && val); + *val = NULL; // so on failure we can just return; + if (tbl->weight == 0) + return KNOT_ENOENT; + { // Intentionally un-indented; until end of function, to bound cleanup attr. + // First find a key with longest-matching prefix + __attribute__((cleanup(ns_cleanup))) + nstack_t ns_local; + ns_init(&ns_local, tbl); + nstack_t *ns = &ns_local; + branch_t bp; + int un_leaf; // first unmatched character in the leaf + ERR_RETURN(ns_find_branch(ns, key, len, &bp, &un_leaf)); + int un_key = bp.index < len ? (unsigned char)key[bp.index] : -256; + node_t *t = ns->stack[ns->len - 1]; + if (bp.flags == 0) { // found exact match + *val = &t->leaf.val; + return KNOT_EOK; + } + // Get t: the last node on matching path + if (isbranch(t) && t->branch.index == bp.index && t->branch.flags == bp.flags) { + // t is OK + } else { + // the top of the stack was the first unmatched node -> step up + if (ns->len == 1) { + // root was unmatched already + if (un_key < un_leaf) + return KNOT_ENOENT; + ERR_RETURN(ns_last_leaf(ns)); + goto success; + } + --ns->len; + t = ns->stack[ns->len - 1]; + } + // Now we re-do the first "non-matching" step in the trie + // but try the previous child if key was less (it may not exist) + bitmap_t b = twigbit(t, key, len); + int i = hastwig(t, b) + ? twigoff(t, b) - (un_key < un_leaf) + : twigoff(t, b) - 1 /*twigoff returns successor when !hastwig*/; + if (i >= 0) { + ERR_RETURN(ns_longer(ns)); + ns->stack[ns->len++] = twig(t, i); + ERR_RETURN(ns_last_leaf(ns)); + } else { + ERR_RETURN(ns_prev_leaf(ns)); + } +success: + assert(!isbranch(ns->stack[ns->len - 1])); + *val = &ns->stack[ns->len - 1]->leaf.val; + return 1; + } +} + +/*! \brief Initialize a new leaf, copying the key, and returning failure code. */ +static int mk_leaf(node_t *leaf, const char *key, uint32_t len, knot_mm_t *mm) +{ + tkey_t *k = mm_alloc(mm, sizeof(tkey_t) + len); + #if FLAGS_HACK + assert(((uintptr_t)k) % 4 == 0); // we need an aligned pointer + #endif + if (unlikely(!k)) + return KNOT_ENOMEM; + k->len = len; + memcpy(k->chars, key, len); + leaf->leaf = (leaf_t){ + #if !FLAGS_HACK + .flags = 0, + #endif + .val = NULL, + .key = k + }; + return KNOT_EOK; +} + +trie_val_t* trie_get_ins(trie_t *tbl, const char *key, uint32_t len) +{ + assert(tbl); + // First leaf in an empty tbl? + if (unlikely(!tbl->weight)) { + if (unlikely(mk_leaf(&tbl->root, key, len, &tbl->mm))) + return NULL; + ++tbl->weight; + return &tbl->root.leaf.val; + } + { // Intentionally un-indented; until end of function, to bound cleanup attr. + // Find the branching-point + __attribute__((cleanup(ns_cleanup))) + nstack_t ns_local; + ns_init(&ns_local, tbl); + nstack_t *ns = &ns_local; + branch_t bp; // branch-point: index and flags signifying the longest common prefix + int k2; // the first unmatched character in the leaf + if (unlikely(ns_find_branch(ns, key, len, &bp, &k2))) + return NULL; + node_t *t = ns->stack[ns->len - 1]; + if (bp.flags == 0) // the same key was already present + return &t->leaf.val; + node_t leaf; + if (unlikely(mk_leaf(&leaf, key, len, &tbl->mm))) + return NULL; + + if (isbranch(t) && bp.index == t->branch.index && bp.flags == t->branch.flags) { + // The node t needs a new leaf child. + bitmap_t b1 = twigbit(t, key, len); + assert(!hastwig(t, b1)); + uint s, m; TWIGOFFMAX(s, m, t, b1); // new child position and original child count + node_t *twigs = mm_realloc(&tbl->mm, t->branch.twigs, + sizeof(node_t) * (m + 1), sizeof(node_t) * m); + if (unlikely(!twigs)) + goto err_leaf; + memmove(twigs + s + 1, twigs + s, sizeof(node_t) * (m - s)); + twigs[s] = leaf; + t->branch.twigs = twigs; + t->branch.bitmap |= b1; + ++tbl->weight; + return &twigs[s].leaf.val; + } else { + // We need to insert a new binary branch with leaf at *t. + // Note: it works the same for the case where we insert above root t. + #ifndef NDEBUG + if (ns->len > 1) { + node_t *pt = ns->stack[ns->len - 2]; + assert(hastwig(pt, twigbit(pt, key, len))); + } + #endif + node_t *twigs = mm_alloc(&tbl->mm, sizeof(node_t) * 2); + if (unlikely(!twigs)) + goto err_leaf; + node_t t2 = *t; // Save before overwriting t. + t->branch.flags = bp.flags; + t->branch.index = bp.index; + t->branch.twigs = twigs; + bitmap_t b1 = twigbit(t, key, len); + bitmap_t b2 = unlikely(k2 == -256) ? (1 << 0) : nibbit(k2, bp.flags); + t->branch.bitmap = b1 | b2; + *twig(t, twigoff(t, b1)) = leaf; + *twig(t, twigoff(t, b2)) = t2; + ++tbl->weight; + return &twig(t, twigoff(t, b1))->leaf.val; + }; +err_leaf: + mm_free(&tbl->mm, leaf.leaf.key); + return NULL; + } +} + +/*! \brief Apply a function to every trie_val_t*, in order; a recursive solution. */ +static int apply_trie(node_t *t, int (*f)(trie_val_t *, void *), void *d) +{ + assert(t); + if (!isbranch(t)) + return f(&t->leaf.val, d); + int child_count = bitmap_weight(t->branch.bitmap); + for (int i = 0; i < child_count; ++i) + ERR_RETURN(apply_trie(twig(t, i), f, d)); + return KNOT_EOK; +} + +int trie_apply(trie_t *tbl, int (*f)(trie_val_t *, void *), void *d) +{ + assert(tbl && f); + if (!tbl->weight) + return KNOT_EOK; + return apply_trie(&tbl->root, f, d); +} + +/* These are all thin wrappers around static Tns* functions. */ +trie_it_t* trie_it_begin(trie_t *tbl) +{ + assert(tbl); + trie_it_t *it = malloc(sizeof(nstack_t)); + if (!it) + return NULL; + ns_init(it, tbl); + if (it->len == 0) // empty tbl + return it; + if (ns_first_leaf(it)) { + ns_cleanup(it); + free(it); + return NULL; + } + return it; +} + +void trie_it_next(trie_it_t *it) +{ + assert(it && it->len); + if (ns_next_leaf(it) != KNOT_EOK) + it->len = 0; +} + +bool trie_it_finished(trie_it_t *it) +{ + assert(it); + return it->len == 0; +} + +void trie_it_free(trie_it_t *it) +{ + if (!it) + return; + ns_cleanup(it); + free(it); +} + +const char* trie_it_key(trie_it_t *it, size_t *len) +{ + assert(it && it->len); + node_t *t = it->stack[it->len - 1]; + assert(!isbranch(t)); + tkey_t *key = t->leaf.key; + if (len) + *len = key->len; + return key->chars; +} + +trie_val_t* trie_it_val(trie_it_t *it) +{ + assert(it && it->len); + node_t *t = it->stack[it->len - 1]; + assert(!isbranch(t)); + return &t->leaf.val; +} |