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ICU-22520 Use a ByteSink append buffer instead of a local CharString.

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These functions that eventually write their output to a ByteSink need a
small temporary buffer for processing the subtag they're about to write
and currently use a local CharString object to provide this buffer,
which then gets written to the ByteSink and discarded.

This intermediate step is unnecessary as a ByteSink can provide an
append buffer which can be used instead, eliminating the need to
allocate a local temporary buffer and to copy the data around.

This approach also makes it natural to split the processing into two
steps, first calculating the length of the subtag, then processing it,
which makes it possible to return early when no output is requested.
This commit is contained in:
Fredrik Roubert 2024-02-06 13:46:08 +01:00 • committed by Fredrik Roubert
parent a210fc8351
commit 699555a5bd
1 changed files with 98 additions and 76 deletions
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174
icu4c/source/common/uloc.cpp
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@ -1172,7 +1172,7 @@ _getLanguage(const char* localeID,
const char** pEnd,
UErrorCode& status) {
U_ASSERT(pEnd != nullptr);
CharString result;
*pEnd = localeID;
if (uprv_stricmp(localeID, "root") == 0) {
localeID += 4;
@ -1184,104 +1184,128 @@ _getLanguage(const char* localeID,
localeID += 3;
}
constexpr int32_t MAXLEN = ULOC_LANG_CAPACITY - 1; // Minus NUL.
/* if it starts with i- or x- then copy that prefix */
if(_isIDPrefix(localeID)) {
result.append((char)uprv_tolower(*localeID), status);
result.append('-', status);
localeID+=2;
int32_t len = _isIDPrefix(localeID) ? 2 : 0;
while (!_isTerminator(localeID[len]) && !_isIDSeparator(localeID[len])) {
if (len == MAXLEN) {
status = U_ILLEGAL_ARGUMENT_ERROR;
return;
}
len++;
}
/* copy the language as far as possible and count its length */
while(!_isTerminator(*localeID) && !_isIDSeparator(*localeID)) {
result.append((char)uprv_tolower(*localeID), status);
localeID++;
*pEnd = localeID + len;
if (sink == nullptr || len == 0) { return; }
int32_t minCapacity = uprv_max(len, 4); // Minimum 3 letters plus NUL.
char scratch[MAXLEN];
int32_t capacity = 0;
char* buffer = sink->GetAppendBuffer(
minCapacity, minCapacity, scratch, UPRV_LENGTHOF(scratch), &capacity);
for (int32_t i = 0; i < len; ++i) {
buffer[i] = uprv_tolower(localeID[i]);
}
if (_isIDSeparator(localeID[1])) {
buffer[1] = '-';
}
if(result.length()==3) {
if (len == 3) {
/* convert 3 character code to 2 character code if possible *CWB*/
int32_t offset = _findIndex(LANGUAGES_3, result.data());
U_ASSERT(capacity >= 4);
buffer[3] = '\0';
int32_t offset = _findIndex(LANGUAGES_3, buffer);
if(offset>=0) {
result.clear();
result.append(LANGUAGES[offset], status);
const char* const alias = LANGUAGES[offset];
sink->Append(alias, (int32_t)uprv_strlen(alias));
return;
}
}
if (sink != nullptr && !result.isEmpty()) {
sink->Append(result.data(), result.length());
}
*pEnd = localeID;
sink->Append(buffer, len);
}
static void
_getScript(const char* localeID,
ByteSink* sink,
const char** pEnd,
UErrorCode& status) {
const char** pEnd) {
U_ASSERT(pEnd != nullptr);
CharString result;
int32_t idLen = 0;
*pEnd = localeID;
/* copy the second item as far as possible and count its length */
while(!_isTerminator(localeID[idLen]) && !_isIDSeparator(localeID[idLen])
&& uprv_isASCIILetter(localeID[idLen])) {
idLen++;
constexpr int32_t LENGTH = 4;
int32_t len = 0;
while (!_isTerminator(localeID[len]) && !_isIDSeparator(localeID[len]) &&
uprv_isASCIILetter(localeID[len])) {
if (len == LENGTH) { return; }
len++;
}
if (len != LENGTH) { return; }
*pEnd = localeID + LENGTH;
if (sink == nullptr) { return; }
char scratch[LENGTH];
int32_t capacity = 0;
char* buffer = sink->GetAppendBuffer(
LENGTH, LENGTH, scratch, UPRV_LENGTHOF(scratch), &capacity);
buffer[0] = uprv_toupper(localeID[0]);
for (int32_t i = 1; i < LENGTH; ++i) {
buffer[i] = uprv_tolower(localeID[i]);
}
/* If it's exactly 4 characters long, then it's a script and not a country. */
if (idLen == 4) {
int32_t i;
*pEnd = localeID + idLen;
if (idLen >= 1) {
result.append((char)uprv_toupper(*(localeID++)), status);
}
for (i = 1; i < idLen; i++) {
result.append((char)uprv_tolower(*(localeID++)), status);
}
}
if (sink != nullptr && !result.isEmpty()) {
sink->Append(result.data(), result.length());
}
sink->Append(buffer, LENGTH);
}
static void
_getRegion(const char* localeID,
ByteSink* sink,
const char** pEnd,
UErrorCode& status) {
const char** pEnd) {
U_ASSERT(pEnd != nullptr);
CharString result;
int32_t idLen=0;
/* copy the country as far as possible and count its length */
while(!_isTerminator(localeID[idLen]) && !_isIDSeparator(localeID[idLen])) {
result.append((char)uprv_toupper(localeID[idLen]), status);
idLen++;
}
/* the country should be either length 2 or 3 */
if (idLen == 2 || idLen == 3) {
/* convert 3 character code to 2 character code if possible *CWB*/
if(idLen==3) {
int32_t offset = _findIndex(COUNTRIES_3, result.data());
if(offset>=0) {
result.clear();
result.append(COUNTRIES[offset], status);
}
}
localeID+=idLen;
} else {
result.clear();
}
if (sink != nullptr && !result.isEmpty()) {
sink->Append(result.data(), result.length());
}
*pEnd = localeID;
constexpr int32_t MINLEN = 2;
constexpr int32_t MAXLEN = ULOC_COUNTRY_CAPACITY - 1; // Minus NUL.
int32_t len = 0;
while (!_isTerminator(localeID[len]) && !_isIDSeparator(localeID[len])) {
if (len == MAXLEN) { return; }
len++;
}
if (len < MINLEN) { return; }
*pEnd = localeID + len;
if (sink == nullptr) { return; }
char scratch[ULOC_COUNTRY_CAPACITY];
int32_t capacity = 0;
char* buffer = sink->GetAppendBuffer(
ULOC_COUNTRY_CAPACITY,
ULOC_COUNTRY_CAPACITY,
scratch,
UPRV_LENGTHOF(scratch),
&capacity);
for (int32_t i = 0; i < len; ++i) {
buffer[i] = uprv_toupper(localeID[i]);
}
if (len == 3) {
/* convert 3 character code to 2 character code if possible *CWB*/
U_ASSERT(capacity >= 4);
buffer[3] = '\0';
int32_t offset = _findIndex(COUNTRIES_3, buffer);
if(offset>=0) {
const char* const alias = COUNTRIES[offset];
sink->Append(alias, (int32_t)uprv_strlen(alias));
return;
}
}
sink->Append(buffer, len);
}
/**
@ -1475,8 +1499,7 @@ ulocimp_getSubtags(
if (_isIDSeparator(*localeID)) {
const char* begin = localeID + 1;
const char* end = nullptr;
_getScript(begin, script, &end, status);
if (U_FAILURE(status)) { return; }
_getScript(begin, script, &end);
U_ASSERT(end != nullptr);
if (end != begin) {
localeID = end;
@ -1489,8 +1512,7 @@ ulocimp_getSubtags(
if (_isIDSeparator(*localeID)) {
const char* begin = localeID + 1;
const char* end = nullptr;
_getRegion(begin, region, &end, status);
if (U_FAILURE(status)) { return; }
_getRegion(begin, region, &end);
U_ASSERT(end != nullptr);
if (end != begin) {
hasRegion = true;