345 lines
10 KiB
C
345 lines
10 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <ctype.h>
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#include "similarity_search.h"
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// Case insensitive string comparison
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int str_case_cmp(const char *s1, const char *s2) {
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while (*s1 && *s2) {
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int c1 = tolower((unsigned char)*s1);
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int c2 = tolower((unsigned char)*s2);
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if (c1 != c2) {
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return c1 - c2;
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}
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s1++;
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s2++;
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}
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return tolower((unsigned char)*s1) - tolower((unsigned char)*s2);
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}
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// Split a string into words
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int split_into_words(const char *string, char *words[MAX_WORDS]) {
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if (!string || strlen(string) >= MAX_STRING_LEN) {
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return 0;
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}
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char temp[MAX_STRING_LEN];
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strncpy(temp, string, MAX_STRING_LEN - 1);
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temp[MAX_STRING_LEN - 1] = '\0';
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int word_count = 0;
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char *token = strtok(temp, " \t\n");
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while (token != NULL && word_count < MAX_WORDS) {
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words[word_count] = strdup(token);
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if (!words[word_count]) {
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// Free any already allocated words on error
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for (int i = 0; i < word_count; i++) {
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free(words[i]);
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}
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return 0;
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}
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word_count++;
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token = strtok(NULL, " \t\n");
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}
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return word_count;
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}
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// Free memory allocated for words
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void free_words(char *words[], int word_count) {
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for (int i = 0; i < word_count; i++) {
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free(words[i]);
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}
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}
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// Calculate similarity between two words based on character matching
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float word_similarity(const char *word1, const char *word2) {
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int len1 = strlen(word1);
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int len2 = strlen(word2);
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// For very short words (3 chars or less), require exact match
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if (len1 <= 3 || len2 <= 3) {
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return str_case_cmp(word1, word2) == 0 ? 1.0f : 0.0f;
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}
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int max_len = len1 > len2 ? len1 : len2;
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if (max_len == 0) return 0.0f;
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// Count matching characters (case insensitive)
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int matches = 0;
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int i = 0, j = 0;
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while (i < len1 && j < len2) {
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if (tolower((unsigned char)word1[i]) == tolower((unsigned char)word2[j])) {
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matches++;
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i++;
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j++;
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} else if (tolower((unsigned char)word1[i]) < tolower((unsigned char)word2[j])) {
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i++;
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} else {
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j++;
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}
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}
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// Calculate similarity based on matching characters
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float char_similarity = (float)matches / max_len;
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// Require higher similarity for shorter words
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float min_similarity = 0.7f; // Default minimum
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if (len1 <= 5 || len2 <= 5) {
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min_similarity = 0.9f; // Higher requirement for short words
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}
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// If similarity is below minimum, return 0
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if (char_similarity < min_similarity) {
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return 0.0f;
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}
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// If words are the same length, give a small boost
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if (len1 == len2) {
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char_similarity = char_similarity * 1.1f; // 10% boost for same length
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if (char_similarity > 1.0f) char_similarity = 1.0f;
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}
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return char_similarity;
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}
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// Calculate similarity between query and target string
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float calculate_similarity(const char *query, const char *target, float cutoff) {
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// Split strings into words
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char *query_words[MAX_WORDS] = {0};
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char *target_words[MAX_WORDS] = {0};
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int query_word_count = split_into_words(query, query_words);
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int target_word_count = split_into_words(target, target_words);
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if (query_word_count == 0 || target_word_count == 0) {
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free_words(query_words, query_word_count);
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free_words(target_words, target_word_count);
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return 0.0;
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}
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// Track best matches for each query word
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float best_word_similarities[MAX_WORDS] = {0.0f};
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int query_words_found = 0;
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// For each query word, find its best match in target words
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for (int i = 0; i < query_word_count; i++) {
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float best_similarity = 0.0f;
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for (int j = 0; j < target_word_count; j++) {
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float similarity = word_similarity(query_words[i], target_words[j]);
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if (similarity > best_similarity) {
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best_similarity = similarity;
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}
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}
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best_word_similarities[i] = best_similarity;
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if (best_similarity >= 0.8f) { // Consider it a match if similarity is high enough
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query_words_found++;
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}
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}
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// Calculate overall similarity
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float word_match_score = (float)query_words_found / query_word_count;
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// Calculate average of best word similarities
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float avg_word_similarity = 0.0f;
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for (int i = 0; i < query_word_count; i++) {
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avg_word_similarity += best_word_similarities[i];
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}
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avg_word_similarity /= query_word_count;
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// Combine scores: 70% weight on word matches, 30% on character similarity
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float similarity = (word_match_score * 0.7f) + (avg_word_similarity * 0.3f);
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// If all query words were found with high similarity, ensure high overall score
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if (query_words_found == query_word_count && avg_word_similarity >= 0.8f) {
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similarity = 1.0f; // Perfect match
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}
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free_words(query_words, query_word_count);
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free_words(target_words, target_word_count);
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return similarity;
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}
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// Compare function for qsort to sort results by similarity (descending)
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int compare_results(const void *a, const void *b) {
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const SearchResult *result_a = (const SearchResult *)a;
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const SearchResult *result_b = (const SearchResult *)b;
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if (result_b->similarity > result_a->similarity) return 1;
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if (result_b->similarity < result_a->similarity) return -1;
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return 0;
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}
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// Generate a random word
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void generate_random_word(char *word, int max_len) {
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int len = 3 + rand() % 8; // Random length between 3 and 10
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for (int i = 0; i < len; i++) {
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word[i] = 'a' + (rand() % 26);
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}
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word[len] = '\0';
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}
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// Generate a random string consisting of multiple words
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void generate_random_string(char *string, int max_len) {
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if (!string || max_len <= 0) {
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return;
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}
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int num_words = 2 + rand() % 5; // Random number of words between 2 and 6
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string[0] = '\0';
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size_t current_len = 0;
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for (int i = 0; i < num_words; i++) {
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char word[20];
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generate_random_word(word, sizeof(word) - 1);
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size_t word_len = strlen(word);
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size_t space_needed = word_len + (i > 0 ? 1 : 0); // +1 for space if not first word
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if (current_len + space_needed < (size_t)max_len - 1) {
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if (i > 0) {
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strncat(string, " ", max_len - current_len - 1);
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current_len++;
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}
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strncat(string, word, max_len - current_len - 1);
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current_len += word_len;
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} else {
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break;
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}
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}
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}
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// Create a new search index
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SearchIndex* create_search_index(int capacity) {
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if (capacity <= 0) return NULL;
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SearchIndex* index = (SearchIndex*)malloc(sizeof(SearchIndex));
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if (!index) return NULL;
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index->strings = (char**)malloc(capacity * sizeof(char*));
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if (!index->strings) {
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free(index);
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return NULL;
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}
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index->num_strings = 0;
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index->capacity = capacity;
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return index;
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}
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// Add a string to the index
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int add_string_to_index(SearchIndex* index, const char* string) {
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if (!index || !string) return -1;
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// Check if we've reached capacity
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if (index->num_strings >= index->capacity) {
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return -1;
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}
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// Check if string is too long
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if (strlen(string) >= MAX_STRING_LEN) {
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return -1;
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}
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index->strings[index->num_strings] = strdup(string);
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if (!index->strings[index->num_strings]) return -1;
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index->num_strings++;
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return 0;
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}
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// Free the search index and all associated memory
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void free_search_index(SearchIndex* index) {
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if (!index) return;
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for (int i = 0; i < index->num_strings; i++) {
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free(index->strings[i]);
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}
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free(index->strings);
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free(index);
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}
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// Search the index with the given query and similarity cutoff
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SearchResult* search_index(SearchIndex* index, const char* query, float cutoff, int* num_results) {
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if (!index || !query || !num_results) return NULL;
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// Validate input string length
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if (strlen(query) >= MAX_STRING_LEN) {
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*num_results = 0;
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return NULL;
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}
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// Validate cutoff
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if (cutoff < 0.0f || cutoff > 1.0f) {
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*num_results = 0;
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return NULL;
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}
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// Allocate temporary array for results
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SearchResult* temp_results = (SearchResult*)malloc(index->num_strings * sizeof(SearchResult));
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if (!temp_results) return NULL;
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*num_results = 0;
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// Search through all strings in the index
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for (int i = 0; i < index->num_strings; i++) {
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float similarity = calculate_similarity(query, index->strings[i], cutoff);
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if (similarity >= cutoff) {
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// Store a copy of the string in the result
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temp_results[*num_results].string = strdup(index->strings[i]);
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if (!temp_results[*num_results].string) {
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// Free any already allocated strings on error
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for (int j = 0; j < *num_results; j++) {
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free(temp_results[j].string);
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}
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free(temp_results);
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return NULL;
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}
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temp_results[*num_results].similarity = similarity;
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(*num_results)++;
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}
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}
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// Sort results by similarity
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qsort(temp_results, *num_results, sizeof(SearchResult), compare_results);
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// Allocate final result array with exact size
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SearchResult* results = (SearchResult*)malloc(*num_results * sizeof(SearchResult));
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if (!results) {
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// Free all strings in temp_results
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for (int i = 0; i < *num_results; i++) {
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free(temp_results[i].string);
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}
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free(temp_results);
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return NULL;
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}
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// Copy results to final array
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for (int i = 0; i < *num_results; i++) {
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results[i].string = temp_results[i].string;
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results[i].similarity = temp_results[i].similarity;
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}
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free(temp_results);
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return results;
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}
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// Free the search results
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void free_search_results(SearchResult* results, int num_results) {
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if (!results) return;
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// Free all strings in the results
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for (int i = 0; i < num_results; i++) {
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free(results[i].string);
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}
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free(results);
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}
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