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shared: strbuf - add string de-duplication facility

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This commit is contained in:
Kay Sievers 2012-10-22 16:27:00 +02:00
parent b87377fca3
commit 955bd501c2
3 changed files with 213 additions and 0 deletions
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2
Makefile.am
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@ -758,6 +758,8 @@ libsystemd_shared_la_SOURCES = \
src/shared/set.h \
src/shared/strv.c \
src/shared/strv.h \
src/shared/strbuf.c \
src/shared/strbuf.h \
src/shared/conf-parser.c \
src/shared/conf-parser.h \
src/shared/log.c \

155
src/shared/strbuf.c Normal file
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@ -0,0 +1,155 @@
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2012 Kay Sievers <kay.sievers@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 <stdlib.h>
#include <string.h>
#include "util.h"
#include "strbuf.h"
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);
}
void strbuf_complete(struct strbuf *str) {
if (!str)
return;
if (str->root)
strbuf_node_cleanup(str->root);
str->root = NULL;
}
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 void *v1, const void *v2) {
const struct strbuf_child_entry *n1 = v1;
const struct strbuf_child_entry *n2 = v2;
return n1->c - n2->c;
}
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),
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;
str->nodes_count++;
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)
return -ENOMEM;
node->children = child;
node->children[node->children_count].c = c;
node->children[node->children_count].child = node_child;
node->children_count++;
qsort(node->children, node->children_count, sizeof(struct strbuf_child_entry), strbuf_children_cmp);
return off;
}

56
src/shared/strbuf.h Normal file
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@ -0,0 +1,56 @@
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
#pragma once
/***
This file is part of systemd.
Copyright 2012 Kay Sievers <kay.sievers@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 <stdarg.h>
#include <stdint.h>
#include <stdbool.h>
struct strbuf {
char *buf;
size_t len;
struct strbuf_node *root;
size_t nodes_count;
size_t in_count;
size_t in_len;
size_t dedup_len;
size_t dedup_count;
};
struct strbuf_node {
size_t value_off;
size_t value_len;
struct strbuf_child_entry *children;
uint8_t children_count;
};
struct strbuf_child_entry {
uint8_t c;
struct strbuf_node *child;
};
struct strbuf *strbuf_new(void);
ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len);
void strbuf_complete(struct strbuf *str);
void strbuf_cleanup(struct strbuf *str);