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Add Levenshtein distance to string utilities.

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This commit is contained in:
Sandu Liviu Catalin 2021-08-22 22:23:25 +03:00
parent 2a06a00e3e
commit c0fc1aea75
1 changed files with 67 additions and 4 deletions
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71
module/Library/String.cpp
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@ -189,7 +189,7 @@ static LightObj SqCenterStr(SQChar f, uint32_t w, StackStrF & s)
else
{
// Calculate the insert position
const int32_t p = ((w/2) - (s.mLen/2));
const auto p = ((w/2) - (s.mLen/2));
// Insert only the fill character first
std::memset(b.Data(), f, w);
// Overwrite with the specified string
@ -287,7 +287,7 @@ static Buffer StrToLowercaseImpl(const SQChar * str, uint32_t len)
while (*str != '\0')
{
// Convert it and move to the next one
b.At(n++) = std::tolower(*(str++));
b.At(n++) = static_cast< char >(std::tolower(*(str++)));
}
// End the resulted string
b.At(n) = '\0';
@ -349,7 +349,7 @@ static Buffer StrToUppercaseImpl(const SQChar * str, uint32_t len)
while (*str != '\0')
{
// Convert it and move to the next one
b.At(n++) = std::toupper(*(str++));
b.At(n++) = static_cast< char >(std::toupper(*(str++)));
}
// End the resulted string
b.At(n) = '\0';
@ -594,7 +594,7 @@ static bool OnlyDelimiter(const SQChar * str, SQChar chr)
// ------------------------------------------------------------------------------------------------
static SQInteger SqStrExplode(HSQUIRRELVM vm)
{
const int32_t top = sq_gettop(vm);
const auto top = sq_gettop(vm);
// Was the delimiter character specified?
if (top <= 1)
{
@ -898,6 +898,68 @@ static String StrCharacterSwap(SQInteger a, SQInteger b, StackStrF & val)
return str;
}
// ------------------------------------------------------------------------------------------------
// Returns a size_t, depicting the difference between `a` and `b`. See: https://github.com/wooorm/levenshtein.c
// See <https://en.wikipedia.org/wiki/Levenshtein_distance> for more information.
SQMOD_NODISCARD static size_t Levenshtein_n(const char * a, const size_t a_length, const char * b, const size_t b_length) noexcept
{
// Shortcut optimizations / degenerate cases.
if (a == b)
{
return 0;
}
else if (a_length == 0)
{
return b_length;
}
else if (b_length == 0)
{
return a_length;
}
auto cache = reinterpret_cast< size_t * >(calloc(a_length, sizeof(size_t)));
size_t index = 0;
size_t b_index = 0;
size_t distance;
size_t b_distance;
size_t result;
char code;
// initialize the vector.
while (index < a_length)
{
cache[index] = index + 1;
index++;
}
// Loop
while (b_index < b_length)
{
code = b[b_index];
result = distance = b_index++;
index = SIZE_MAX;
while (++index < a_length)
{
b_distance = code == a[index] ? distance : distance + 1;
distance = cache[index];
cache[index] = result = distance > result
? b_distance > result
? result + 1
: b_distance
: b_distance > distance
? distance + 1
: b_distance;
}
}
free(cache);
return result;
}
// ------------------------------------------------------------------------------------------------
static SQInteger SqLevenshtein(StackStrF & a, StackStrF & b)
{
return static_cast< SQInteger >(Levenshtein_n(a.mPtr, static_cast< size_t >(a.mLen), b.mPtr, static_cast< size_t >(b.mLen)));
}
// ------------------------------------------------------------------------------------------------
static SQInteger SqStrToI(SQInteger base, StackStrF & s)
{
@ -940,6 +1002,7 @@ void Register_String(HSQUIRRELVM vm)
.FmtFunc(_SC("JustAlnum"), &SqJustAlphaNum)
.FmtFunc(_SC("ToInt"), &SqStrToI)
.FmtFunc(_SC("ToFloat"), &SqStrToF)
.FmtFunc(_SC("Levenshtein"), &SqLevenshtein)
.FmtFunc(_SC("AreAllSpace"), &SqAllChars< std::isspace >)
.FmtFunc(_SC("AreAllPrint"), &SqAllChars< std::isprint >)
.FmtFunc(_SC("AreAllCntrl"), &SqAllChars< std::iscntrl >)