diff options
Diffstat (limited to 'src/libbasic/strbuf.c')
| -rw-r--r-- | src/libbasic/strbuf.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/src/libbasic/strbuf.c b/src/libbasic/strbuf.c new file mode 100644 index 0000000000..77220c0251 --- /dev/null +++ b/src/libbasic/strbuf.c @@ -0,0 +1,200 @@ +/*** + This file is part of systemd. + + Copyright 2012 Kay Sievers <kay@vrfy.org> + + systemd 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; either version 2.1 of the License, or + (at your option) any later version. + + systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>. +***/ + +#include <errno.h> +#include <stdlib.h> +#include <string.h> + +#include "alloc-util.h" +#include "strbuf.h" + +/* + * Strbuf stores given strings in a single continuous allocated memory + * area. Identical strings are de-duplicated and return the same offset + * as the first string stored. If the tail of a string already exists + * in the buffer, the tail is returned. + * + * A trie (http://en.wikipedia.org/wiki/Trie) is used to maintain the + * information about the stored strings. + * + * Example of udev rules: + * $ ./udevadm test . + * ... + * read rules file: /usr/lib/udev/rules.d/99-systemd.rules + * rules contain 196608 bytes tokens (16384 * 12 bytes), 39742 bytes strings + * 23939 strings (207859 bytes), 20404 de-duplicated (171653 bytes), 3536 trie nodes used + * ... + */ + +struct strbuf *strbuf_new(void) { + struct strbuf *str; + + str = new0(struct strbuf, 1); + if (!str) + return NULL; + + str->buf = new0(char, 1); + if (!str->buf) + goto err; + str->len = 1; + + str->root = new0(struct strbuf_node, 1); + if (!str->root) + goto err; + str->nodes_count = 1; + return str; +err: + free(str->buf); + free(str->root); + free(str); + return NULL; +} + +static void strbuf_node_cleanup(struct strbuf_node *node) { + size_t i; + + for (i = 0; i < node->children_count; i++) + strbuf_node_cleanup(node->children[i].child); + free(node->children); + free(node); +} + +/* clean up trie data, leave only the string buffer */ +void strbuf_complete(struct strbuf *str) { + if (!str) + return; + if (str->root) + strbuf_node_cleanup(str->root); + str->root = NULL; +} + +/* clean up everything */ +void strbuf_cleanup(struct strbuf *str) { + if (!str) + return; + if (str->root) + strbuf_node_cleanup(str->root); + free(str->buf); + free(str); +} + +static int strbuf_children_cmp(const struct strbuf_child_entry *n1, + const struct strbuf_child_entry *n2) { + return n1->c - n2->c; +} + +static void bubbleinsert(struct strbuf_node *node, + uint8_t c, + struct strbuf_node *node_child) { + + struct strbuf_child_entry new = { + .c = c, + .child = node_child, + }; + int left = 0, right = node->children_count; + + while (right > left) { + int middle = (right + left) / 2 ; + if (strbuf_children_cmp(&node->children[middle], &new) <= 0) + left = middle + 1; + else + right = middle; + } + + memmove(node->children + left + 1, node->children + left, + sizeof(struct strbuf_child_entry) * (node->children_count - left)); + node->children[left] = new; + + node->children_count ++; +} + +/* add string, return the index/offset into the buffer */ +ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len) { + uint8_t c; + struct strbuf_node *node; + size_t depth; + char *buf_new; + struct strbuf_child_entry *child; + struct strbuf_node *node_child; + ssize_t off; + + if (!str->root) + return -EINVAL; + + /* search string; start from last character to find possibly matching tails */ + if (len == 0) + return 0; + str->in_count++; + str->in_len += len; + + node = str->root; + c = s[len-1]; + for (depth = 0; depth <= len; depth++) { + struct strbuf_child_entry search; + + /* match against current node */ + off = node->value_off + node->value_len - len; + if (depth == len || (node->value_len >= len && memcmp(str->buf + off, s, len) == 0)) { + str->dedup_len += len; + str->dedup_count++; + return off; + } + + /* lookup child node */ + c = s[len - 1 - depth]; + search.c = c; + child = bsearch(&search, node->children, node->children_count, + sizeof(struct strbuf_child_entry), + (__compar_fn_t) strbuf_children_cmp); + if (!child) + break; + node = child->child; + } + + /* add new string */ + buf_new = realloc(str->buf, str->len + len+1); + if (!buf_new) + return -ENOMEM; + str->buf = buf_new; + off = str->len; + memcpy(str->buf + off, s, len); + str->len += len; + str->buf[str->len++] = '\0'; + + /* new node */ + node_child = new0(struct strbuf_node, 1); + if (!node_child) + return -ENOMEM; + node_child->value_off = off; + node_child->value_len = len; + + /* extend array, add new entry, sort for bisection */ + child = realloc(node->children, (node->children_count + 1) * sizeof(struct strbuf_child_entry)); + if (!child) { + free(node_child); + return -ENOMEM; + } + + str->nodes_count++; + + node->children = child; + bubbleinsert(node, c, node_child); + + return off; +} |