Implement Aho-Corasick algorithm

src/trie.c

@@ -0,0 +1,183 @@
+/*
+  youtubeUnblock - https://github.com/Waujito/youtubeUnblock
+
+  Copyright (C) 2024-2025 Vadim Vetrov <vetrovvd@gmail.com>
+
+  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 <https://www.gnu.org/licenses/>.
+*/
+
+/**
+ * This is slightly optimized Aho-Corasick implementation 
+ *
+ * Big thanks to e-maxx http://e-maxx.ru/algo/aho_corasick
+ * for the best description and reference code samples
+ */
+
+#include "trie.h"
+
+int trie_init(struct trie_container *trie) {
+	void *vx = malloc(sizeof(struct trie_vertex) * TRIE_STARTSZ);
+	if (vx == NULL) {
+		return -ENOMEM;
+	}
+	trie->vx = vx;
+	trie->arrsz = TRIE_STARTSZ;
+	trie->sz = 1;
+
+	struct trie_vertex *trx = trie->vx;
+	trx->p = trx->link = -1;
+	trx->leaf = 0;
+	trx->depth = 0;
+	trx->pch = 0;
+	memset(trx->go, 0xff, sizeof(trie->vx[0].go));
+
+	return 0;
+}
+
+void trie_destroy(struct trie_container *trie) {
+	trie->arrsz = 0;
+	trie->sz = 0;
+	free(trie->vx);
+	trie->vx = NULL;
+}
+
+int trie_push_vertex(struct trie_container *trie) {
+	if (trie->sz == NMAX - 1) {
+		return -EINVAL;
+	}
+
+	if (trie->arrsz == trie->sz) { // realloc
+		void *pt = realloc(trie->vx, 
+		     sizeof(struct trie_vertex) * trie->arrsz * 2);
+		if (pt == NULL) {
+			return -ENOMEM;
+		}
+
+		trie->arrsz *= 2;
+		trie->vx = pt;
+	}
+
+	return trie->sz++;
+}
+
+
+int trie_add_string(struct trie_container *trie, 
+	       const uint8_t *str, size_t strlen) {
+	int v = 0;
+	int nv;
+
+	for (size_t i = 0; i < strlen; ++i) {
+		uint8_t c = str[i];
+		if (c >= TRIE_ALPHABET) {
+			return -EINVAL;
+		}
+
+		if (trie->vx[v].go[c] == -1) {
+			nv = trie_push_vertex(trie);
+			if (nv < 0) {
+				return nv;
+			}
+			struct trie_vertex *tvx = trie->vx + nv;
+
+			memset(tvx->go, 0xff, sizeof(tvx->go));
+			tvx->link = -1;
+			tvx->p = v;
+			tvx->depth = trie->vx[v].depth + 1;
+			tvx->leaf = 0;
+			tvx->pch = c;
+			trie->vx[v].go[c] = nv;
+		}
+		v = trie->vx[v].go[c];
+	}
+	
+	if (v != 0) {
+		trie->vx[v].leaf = 1;
+	}
+
+	return 0;
+}
+
+static int trie_go(struct trie_container *trie,
+	int v, uint8_t c);
+
+static int trie_get_link(struct trie_container *trie,
+	     int v) {
+	struct trie_vertex *tvx = trie->vx + v;
+
+	if (tvx->link == -1) {
+		if (v == 0 || tvx->p == 0) {
+			tvx->link = 0;
+		} else {
+			tvx->link = trie_go(trie, 
+				trie_get_link(trie, tvx->p), tvx->pch);
+		}
+	}
+
+	return tvx->link;
+}
+
+static int trie_go(struct trie_container *trie, int v, uint8_t c) {
+	struct trie_vertex *tvx = trie->vx + v;
+
+	if (tvx->go[c] == -1) {
+		tvx->go[c] = v == 0 ? 0 : 
+		trie_go(trie, trie_get_link(trie, v), c);
+	}
+
+	return tvx->go[c];
+}
+
+
+int trie_process_str(
+	struct trie_container *trie,
+	const uint8_t *str, size_t strlen,
+	int flags,
+	size_t *offset, size_t *offlen
+) {
+	int v = 0;
+	size_t i = 0;
+	uint8_t c;
+	int len;
+
+	for (; i < strlen; ++i) {
+		c = str[i];
+		if (c >= TRIE_ALPHABET) {
+			v = 0;
+			continue;
+		}
+
+		v = trie->vx[v].go[c] != -1 ? trie->vx[v].go[c] : 
+			trie_go(trie, v, str[i]);
+
+		if (trie->vx[v].leaf && 
+			((flags & TRIE_OPT_MAP_TO_END) != TRIE_OPT_MAP_TO_END ||
+			i == strlen - 1)
+		) {
+			++i;
+			break;
+		}
+	}
+
+	len = trie->vx[v].depth;
+	if (	trie->vx[v].leaf &&
+		i >= len
+	) {
+		size_t sp = i - len;
+		*offset = sp;
+		*offlen = len;
+		return 1;
+	}
+
+	return 0;
+}

src/trie.h

@@ -0,0 +1,99 @@
+/*
+  youtubeUnblock - https://github.com/Waujito/youtubeUnblock
+
+  Copyright (C) 2024-2025 Vadim Vetrov <vetrovvd@gmail.com>
+
+  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 <https://www.gnu.org/licenses/>.
+*/
+
+/**
+ * This is slightly optimized Aho-Corasick implementation 
+ *
+ * Big thanks to e-maxx http://e-maxx.ru/algo/aho_corasick
+ * for the best description and reference code samples
+ *
+ */
+
+/**
+ *
+ * This algorithm allows us to search inside the string
+ * for a list of patterns in the linear time.
+ *
+ * The algorithm will lazily initialize itself while 
+ * youtubeUnblock works. Lazy initializations considered 
+ * safe for multithreading and operate without atomicity 
+ * or synchronization primitives.
+ *
+ */
+
+#ifndef TRIE_H
+#define TRIE_H
+
+#include "types.h"
+
+// ASCII alphabet
+#define TRIE_ALPHABET 128
+// Maximum of vertexes in the trie
+#define NMAX ((1 << 15) - 1)
+
+struct trie_vertex {
+	int leaf; // boolean flag
+	int depth; // depth of tree (length of substring)
+	int p; // parent
+	uint8_t pch; // vertex char
+	int link; // sufflink
+	int16_t go[TRIE_ALPHABET]; // dynamically filled pushes
+};
+ 
+struct trie_container {
+	struct trie_vertex *vx;
+	size_t arrsz;
+	size_t sz;
+};
+
+#define TRIE_STARTSZ 32
+int trie_init(struct trie_container *trie);
+void trie_destroy(struct trie_container *trie);
+
+/**
+ *
+ * Increases trie vertex container size.
+ * Returns new vertex index or ret < 0 on error
+ *
+ */
+int trie_push_vertex(struct trie_container *trie);
+int trie_add_string(struct trie_container *trie, 
+	       const uint8_t *str, size_t strlen);
+
+/**
+ * Aligns the pattern to the end 
+ */
+#define TRIE_OPT_MAP_TO_END (1 << 1)
+
+/**
+ * Searches the string for the patterns.
+ * flags is TRIE_OPT binary mask with options for search.
+ * offset, offlen are destination variables with 
+ * offset of the given string and length of target.
+ *
+ * returns 1 if target found, 0 otherwise
+ */
+int trie_process_str(
+	struct trie_container *trie,
+	const uint8_t *str, size_t strlen,
+	int flags,
+	size_t *offset, size_t *offlen
+);
+
+#endif

src/types.h

@@ -68,6 +68,7 @@ typedef __s16 int_least16_t;	/* integer of >= 16 bits */
 
 #define free kfree
 #define malloc(size) kmalloc((size), GFP_KERNEL)
+#define realloc(pt, size) krealloc((pt), (size), GFP_KERNEL)
 #define calloc(n, size) kcalloc((n), (size), GFP_KERNEL)
 
 #define ip6_hdr ipv6hdr