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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.
74 lines
2.0 KiB
C
74 lines
2.0 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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/// Calculates and returns the Levenshtein distance of two non NULL strings.
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/// More information about the algorithm can be found here:
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/// https://en.wikipedia.org/wiki/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 the levenshtein distance of str1 and str2
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unsigned levenshtein(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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// declare variables
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unsigned row, col;
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unsigned last_diag = 0, cur, cost;
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// initialize array to hold values
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unsigned* vector = calloc(str1_len + 1, sizeof(unsigned));
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for (col = 1; col <= str1_len; col++) {
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vector[col] = col;
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}
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// itterate through the imagined rows of arrays
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for (row = 1; row <= str2_len + 1; row++) {
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vector[0] = row;
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last_diag = row - 1; // remember the last first slot
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// itterate throught each member of the vector
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for (col = 1; col <= str1_len; col++) {
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// remember the diagonal before overwriting the array
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cur = vector[col];
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// calculate the cost
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cost = EQ(str1[col - 1], str2[row - 1]) ? 0 : 1;
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// determine min of the possible values
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vector[col] = MIN3(vector[col] + 1, vector[col - 1] + 1, last_diag + cost);
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// remember the new last_diag
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last_diag = cur;
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}
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}
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free(vector);
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return last_diag;
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}
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