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d3a156caf5
A common complain with libSQL is how to run extensions. The main mechanism, with a .so, has a lot of issues around how those .so are distributed. The most common extensions are the ones in the sqlean package. We can improve this experience by bundling them in our sqlite build. Not all SQLean extensions are kosher: some of them, like fileio, use the vfs. Others, are deemed too complex. The extensions included here are a subset that we deem important enough, and low risk enough, to just be a part of the main bundle.
85 lines
2.5 KiB
C
85 lines
2.5 KiB
C
// Copyright (c) 2014 Ross Bayer, MIT License
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// https://github.com/Rostepher/libstrcmp
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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#include "fuzzy/common.h"
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/// Computes and returns the Optimal String Alignment distance for two non NULL
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/// strings. More information about the algorithm can be found here:
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/// https://en.wikipedia.org/wiki/Damerau-Levenshtein_distance
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///
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/// @param str1 first non NULL string
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/// @param str2 second non NULL string
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///
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/// @returns optimal string alignment distance for str1 and str2
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unsigned optimal_string_alignment(const char* str1, const char* str2) {
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// strings cannot be NULL
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assert(str1 != NULL);
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assert(str2 != NULL);
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size_t str1_len = strlen(str1);
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size_t str2_len = strlen(str2);
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// handle cases where one or both strings are empty
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if (str1_len == 0) {
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return str2_len;
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}
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if (str2_len == 0) {
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return str1_len;
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}
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// remove common substring
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while (str1_len > 0 && str2_len > 0 && EQ(str1[0], str2[0])) {
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str1++, str2++;
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str1_len--, str2_len--;
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}
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unsigned row, col, cost, result;
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// initialize matrix to hold distance values
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unsigned** matrix = malloc((str1_len + 1) * sizeof(unsigned*));
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for (unsigned i = 0; i <= str1_len; i++) {
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matrix[i] = calloc((str2_len + 1), sizeof(unsigned));
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}
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// set all the starting values
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matrix[0][0] = 0;
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for (row = 1; row <= str1_len; row++) {
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matrix[row][0] = row;
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}
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for (col = 1; col <= str2_len; col++) {
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matrix[0][col] = col;
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}
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// itterate through and fill in the matrix
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for (row = 1; row <= str1_len; row++) {
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for (col = 1; col <= str2_len; col++) {
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cost = EQ(str1[row - 1], str2[col - 1]) ? 0 : 1;
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matrix[row][col] = MIN3(matrix[row - 1][col] + 1, // deletion
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matrix[row][col - 1] + 1, // insertion
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matrix[row - 1][col - 1] + cost // substitution
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);
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// transpositions
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if (row > 1 && col > 1 && EQ(str1[row], str2[col - 1]) &&
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EQ(str1[row - 1], str2[col])) {
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matrix[row][col] = MIN(matrix[row][col], matrix[row - 2][col - 2] + cost);
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}
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}
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}
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result = matrix[str1_len][str2_len];
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// free allocated memory
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for (unsigned i = 0; i < str1_len + 1; i++) {
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free(matrix[i]);
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}
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free(matrix);
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return result;
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}
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