mirror of
https://github.com/mozilla/gecko-dev.git
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407 lines
12 KiB
C++
407 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/ArrayUtils.h"
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#include "mozStorageSQLFunctions.h"
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#include "nsUnicharUtils.h"
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#include <algorithm>
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namespace mozilla {
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namespace storage {
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////////////////////////////////////////////////////////////////////////////////
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//// Local Helper Functions
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namespace {
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/**
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* Performs the LIKE comparison of a string against a pattern. For more detail
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* see http://www.sqlite.org/lang_expr.html#like.
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*
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* @param aPatternItr
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* An iterator at the start of the pattern to check for.
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* @param aPatternEnd
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* An iterator at the end of the pattern to check for.
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* @param aStringItr
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* An iterator at the start of the string to check for the pattern.
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* @param aStringEnd
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* An iterator at the end of the string to check for the pattern.
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* @param aEscapeChar
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* The character to use for escaping symbols in the pattern.
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* @return 1 if the pattern is found, 0 otherwise.
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*/
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int
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likeCompare(nsAString::const_iterator aPatternItr,
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nsAString::const_iterator aPatternEnd,
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nsAString::const_iterator aStringItr,
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nsAString::const_iterator aStringEnd,
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char16_t aEscapeChar)
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{
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const char16_t MATCH_ALL('%');
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const char16_t MATCH_ONE('_');
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bool lastWasEscape = false;
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while (aPatternItr != aPatternEnd) {
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/**
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* What we do in here is take a look at each character from the input
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* pattern, and do something with it. There are 4 possibilities:
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* 1) character is an un-escaped match-all character
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* 2) character is an un-escaped match-one character
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* 3) character is an un-escaped escape character
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* 4) character is not any of the above
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*/
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if (!lastWasEscape && *aPatternItr == MATCH_ALL) {
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// CASE 1
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/**
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* Now we need to skip any MATCH_ALL or MATCH_ONE characters that follow a
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* MATCH_ALL character. For each MATCH_ONE character, skip one character
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* in the pattern string.
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*/
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while (*aPatternItr == MATCH_ALL || *aPatternItr == MATCH_ONE) {
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if (*aPatternItr == MATCH_ONE) {
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// If we've hit the end of the string we are testing, no match
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if (aStringItr == aStringEnd)
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return 0;
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aStringItr++;
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}
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aPatternItr++;
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}
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// If we've hit the end of the pattern string, match
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if (aPatternItr == aPatternEnd)
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return 1;
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while (aStringItr != aStringEnd) {
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if (likeCompare(aPatternItr, aPatternEnd, aStringItr, aStringEnd,
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aEscapeChar)) {
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// we've hit a match, so indicate this
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return 1;
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}
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aStringItr++;
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}
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// No match
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return 0;
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}
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else if (!lastWasEscape && *aPatternItr == MATCH_ONE) {
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// CASE 2
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if (aStringItr == aStringEnd) {
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// If we've hit the end of the string we are testing, no match
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return 0;
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}
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aStringItr++;
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lastWasEscape = false;
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}
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else if (!lastWasEscape && *aPatternItr == aEscapeChar) {
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// CASE 3
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lastWasEscape = true;
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}
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else {
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// CASE 4
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if (::ToUpperCase(*aStringItr) != ::ToUpperCase(*aPatternItr)) {
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// If we've hit a point where the strings don't match, there is no match
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return 0;
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}
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aStringItr++;
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lastWasEscape = false;
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}
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aPatternItr++;
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}
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return aStringItr == aStringEnd;
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}
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/**
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* Compute the Levenshtein Edit Distance between two strings.
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*
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* @param aStringS
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* a string
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* @param aStringT
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* another string
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* @param _result
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* an outparam that will receive the edit distance between the arguments
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* @return a Sqlite result code, e.g. SQLITE_OK, SQLITE_NOMEM, etc.
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*/
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int
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levenshteinDistance(const nsAString &aStringS,
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const nsAString &aStringT,
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int *_result)
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{
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// Set the result to a non-sensical value in case we encounter an error.
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*_result = -1;
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const uint32_t sLen = aStringS.Length();
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const uint32_t tLen = aStringT.Length();
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if (sLen == 0) {
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*_result = tLen;
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return SQLITE_OK;
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}
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if (tLen == 0) {
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*_result = sLen;
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return SQLITE_OK;
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}
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// Notionally, Levenshtein Distance is computed in a matrix. If we
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// assume s = "span" and t = "spam", the matrix would look like this:
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// s -->
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// t s p a n
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// | 0 1 2 3 4
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// V s 1 * * * *
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// p 2 * * * *
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// a 3 * * * *
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// m 4 * * * *
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//
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// Note that the row width is sLen + 1 and the column height is tLen + 1,
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// where sLen is the length of the string "s" and tLen is the length of "t".
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// The first row and the first column are initialized as shown, and
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// the algorithm computes the remaining cells row-by-row, and
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// left-to-right within each row. The computation only requires that
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// we be able to see the current row and the previous one.
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// Allocate memory for two rows.
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AutoTArray<int, nsAutoString::kStorageSize> row1;
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AutoTArray<int, nsAutoString::kStorageSize> row2;
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// Declare the raw pointers that will actually be used to access the memory.
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int *prevRow = row1.AppendElements(sLen + 1);
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int *currRow = row2.AppendElements(sLen + 1);
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// Initialize the first row.
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for (uint32_t i = 0; i <= sLen; i++)
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prevRow[i] = i;
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const char16_t *s = aStringS.BeginReading();
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const char16_t *t = aStringT.BeginReading();
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// Compute the empty cells in the "matrix" row-by-row, starting with
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// the second row.
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for (uint32_t ti = 1; ti <= tLen; ti++) {
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// Initialize the first cell in this row.
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currRow[0] = ti;
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// Get the character from "t" that corresponds to this row.
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const char16_t tch = t[ti - 1];
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// Compute the remaining cells in this row, left-to-right,
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// starting at the second column (and first character of "s").
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for (uint32_t si = 1; si <= sLen; si++) {
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// Get the character from "s" that corresponds to this column,
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// compare it to the t-character, and compute the "cost".
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const char16_t sch = s[si - 1];
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int cost = (sch == tch) ? 0 : 1;
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// ............ We want to calculate the value of cell "d" from
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// ...ab....... the previously calculated (or initialized) cells
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// ...cd....... "a", "b", and "c", where d = min(a', b', c').
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// ............
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int aPrime = prevRow[si - 1] + cost;
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int bPrime = prevRow[si] + 1;
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int cPrime = currRow[si - 1] + 1;
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currRow[si] = std::min(aPrime, std::min(bPrime, cPrime));
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}
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// Advance to the next row. The current row becomes the previous
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// row and we recycle the old previous row as the new current row.
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// We don't need to re-initialize the new current row since we will
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// rewrite all of its cells anyway.
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int *oldPrevRow = prevRow;
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prevRow = currRow;
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currRow = oldPrevRow;
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}
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// The final result is the value of the last cell in the last row.
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// Note that that's now in the "previous" row, since we just swapped them.
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*_result = prevRow[sLen];
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return SQLITE_OK;
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}
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// This struct is used only by registerFunctions below, but ISO C++98 forbids
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// instantiating a template dependent on a locally-defined type. Boo-urns!
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struct Functions {
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const char *zName;
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int nArg;
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int enc;
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void *pContext;
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void (*xFunc)(::sqlite3_context*, int, sqlite3_value**);
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};
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} // namespace
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////////////////////////////////////////////////////////////////////////////////
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//// Exposed Functions
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int
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registerFunctions(sqlite3 *aDB)
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{
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Functions functions[] = {
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{"lower",
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1,
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SQLITE_UTF16,
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0,
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caseFunction},
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{"lower",
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1,
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SQLITE_UTF8,
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0,
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caseFunction},
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{"upper",
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1,
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SQLITE_UTF16,
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(void*)1,
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caseFunction},
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{"upper",
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1,
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SQLITE_UTF8,
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(void*)1,
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caseFunction},
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{"like",
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2,
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SQLITE_UTF16,
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0,
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likeFunction},
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{"like",
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2,
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SQLITE_UTF8,
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0,
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likeFunction},
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{"like",
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3,
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SQLITE_UTF16,
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0,
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likeFunction},
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{"like",
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3,
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SQLITE_UTF8,
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0,
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likeFunction},
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{"levenshteinDistance",
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2,
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SQLITE_UTF16,
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0,
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levenshteinDistanceFunction},
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{"levenshteinDistance",
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2,
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SQLITE_UTF8,
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0,
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levenshteinDistanceFunction},
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};
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int rv = SQLITE_OK;
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for (size_t i = 0; SQLITE_OK == rv && i < ArrayLength(functions); ++i) {
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struct Functions *p = &functions[i];
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rv = ::sqlite3_create_function(aDB, p->zName, p->nArg, p->enc, p->pContext,
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p->xFunc, nullptr, nullptr);
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}
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return rv;
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}
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////////////////////////////////////////////////////////////////////////////////
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//// SQL Functions
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void
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caseFunction(sqlite3_context *aCtx,
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int aArgc,
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sqlite3_value **aArgv)
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{
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NS_ASSERTION(1 == aArgc, "Invalid number of arguments!");
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nsAutoString data(static_cast<const char16_t *>(::sqlite3_value_text16(aArgv[0])));
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bool toUpper = ::sqlite3_user_data(aCtx) ? true : false;
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if (toUpper)
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::ToUpperCase(data);
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else
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::ToLowerCase(data);
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// Set the result.
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::sqlite3_result_text16(aCtx, data.get(), -1, SQLITE_TRANSIENT);
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}
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/**
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* This implements the like() SQL function. This is used by the LIKE operator.
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* The SQL statement 'A LIKE B' is implemented as 'like(B, A)', and if there is
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* an escape character, say E, it is implemented as 'like(B, A, E)'.
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*/
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void
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likeFunction(sqlite3_context *aCtx,
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int aArgc,
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sqlite3_value **aArgv)
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{
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NS_ASSERTION(2 == aArgc || 3 == aArgc, "Invalid number of arguments!");
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if (::sqlite3_value_bytes(aArgv[0]) > SQLITE_MAX_LIKE_PATTERN_LENGTH) {
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::sqlite3_result_error(aCtx, "LIKE or GLOB pattern too complex",
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SQLITE_TOOBIG);
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return;
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}
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if (!::sqlite3_value_text16(aArgv[0]) || !::sqlite3_value_text16(aArgv[1]))
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return;
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nsDependentString A(static_cast<const char16_t *>(::sqlite3_value_text16(aArgv[1])));
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nsDependentString B(static_cast<const char16_t *>(::sqlite3_value_text16(aArgv[0])));
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NS_ASSERTION(!B.IsEmpty(), "LIKE string must not be null!");
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char16_t E = 0;
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if (3 == aArgc)
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E = static_cast<const char16_t *>(::sqlite3_value_text16(aArgv[2]))[0];
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nsAString::const_iterator itrString, endString;
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A.BeginReading(itrString);
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A.EndReading(endString);
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nsAString::const_iterator itrPattern, endPattern;
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B.BeginReading(itrPattern);
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B.EndReading(endPattern);
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::sqlite3_result_int(aCtx, likeCompare(itrPattern, endPattern, itrString,
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endString, E));
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}
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void levenshteinDistanceFunction(sqlite3_context *aCtx,
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int aArgc,
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sqlite3_value **aArgv)
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{
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NS_ASSERTION(2 == aArgc, "Invalid number of arguments!");
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// If either argument is a SQL NULL, then return SQL NULL.
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if (::sqlite3_value_type(aArgv[0]) == SQLITE_NULL ||
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::sqlite3_value_type(aArgv[1]) == SQLITE_NULL) {
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::sqlite3_result_null(aCtx);
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return;
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}
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int aLen = ::sqlite3_value_bytes16(aArgv[0]) / sizeof(char16_t);
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const char16_t *a = static_cast<const char16_t *>(::sqlite3_value_text16(aArgv[0]));
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int bLen = ::sqlite3_value_bytes16(aArgv[1]) / sizeof(char16_t);
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const char16_t *b = static_cast<const char16_t *>(::sqlite3_value_text16(aArgv[1]));
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// Compute the Levenshtein Distance, and return the result (or error).
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int distance = -1;
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const nsDependentString A(a, aLen);
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const nsDependentString B(b, bLen);
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int status = levenshteinDistance(A, B, &distance);
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if (status == SQLITE_OK) {
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::sqlite3_result_int(aCtx, distance);
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}
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else if (status == SQLITE_NOMEM) {
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::sqlite3_result_error_nomem(aCtx);
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}
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else {
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::sqlite3_result_error(aCtx, "User function returned error code", -1);
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}
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}
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} // namespace storage
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} // namespace mozilla
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