From a53869e7226396ba2326b0740d1af83cdecf1d92 Mon Sep 17 00:00:00 2001
From: Fredrik Roubert <roubert@google.com>
Date: Tue, 11 Feb 2025 18:16:36 +0100
Subject: [PATCH] ICU-22901 Update Locale::init() to use StringPiece.

---
 icu4c/source/common/locid.cpp       | 43 +++++++++++++++++++++--------
 icu4c/source/common/ulocale.cpp     |  5 +---
 icu4c/source/common/unicode/locid.h |  9 +++++-
 3 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/icu4c/source/common/locid.cpp b/icu4c/source/common/locid.cpp
index 4a73f5592052..e7e86079ae91 100644
--- a/icu4c/source/common/locid.cpp
+++ b/icu4c/source/common/locid.cpp
@@ -1828,8 +1828,13 @@ ulocimp_isCanonicalizedLocaleForTest(const char* localeName)
 
 U_NAMESPACE_BEGIN
 
-/*This function initializes a Locale from a C locale ID*/
 Locale& Locale::init(const char* localeID, UBool canonicalize)
+{
+    return localeID == nullptr ? *this = getDefault() : init(StringPiece{localeID}, canonicalize);
+}
+
+/*This function initializes a Locale from a C locale ID*/
+Locale& Locale::init(StringPiece localeID, UBool canonicalize)
 {
     fIsBogus = false;
     /* Free our current storage */
@@ -1854,19 +1859,28 @@ Locale& Locale::init(const char* localeID, UBool canonicalize)
         int32_t length;
         UErrorCode err;
 
-        if(localeID == nullptr) {
-            // not an error, just set the default locale
-            return *this = getDefault();
-        }
-
         /* preset all fields to empty */
         language[0] = script[0] = country[0] = 0;
 
+        const auto parse = [canonicalize](std::string_view localeID,
+                                          char* name,
+                                          int32_t nameCapacity,
+                                          UErrorCode& status) {
+            return ByteSinkUtil::viaByteSinkToTerminatedChars(
+                name, nameCapacity,
+                [&](ByteSink& sink, UErrorCode& status) {
+                    if (canonicalize) {
+                        ulocimp_canonicalize(localeID, sink, status);
+                    } else {
+                        ulocimp_getName(localeID, sink, status);
+                    }
+                },
+                status);
+        };
+
         // "canonicalize" the locale ID to ICU/Java format
         err = U_ZERO_ERROR;
-        length = canonicalize ?
-            uloc_canonicalize(localeID, fullName, sizeof(fullNameBuffer), &err) :
-            uloc_getName(localeID, fullName, sizeof(fullNameBuffer), &err);
+        length = parse(localeID, fullName, sizeof fullNameBuffer, err);
 
         if (err == U_BUFFER_OVERFLOW_ERROR || length >= static_cast<int32_t>(sizeof(fullNameBuffer))) {
             U_ASSERT(baseName == nullptr);
@@ -1877,9 +1891,7 @@ Locale& Locale::init(const char* localeID, UBool canonicalize)
             }
             fullName = newFullName;
             err = U_ZERO_ERROR;
-            length = canonicalize ?
-                uloc_canonicalize(localeID, fullName, length+1, &err) :
-                uloc_getName(localeID, fullName, length+1, &err);
+            length = parse(localeID, fullName, length + 1, err);
         }
         if(U_FAILURE(err) || err == U_STRING_NOT_TERMINATED_WARNING) {
             /* should never occur */
@@ -2200,6 +2212,13 @@ Locale::createFromName (const char *name)
     }
 }
 
+Locale U_EXPORT2
+Locale::createFromName(StringPiece name) {
+    Locale loc("");
+    loc.init(name, false);
+    return loc;
+}
+
 Locale U_EXPORT2
 Locale::createCanonical(const char* name) {
     Locale loc("");
diff --git a/icu4c/source/common/ulocale.cpp b/icu4c/source/common/ulocale.cpp
index f2f81bc97109..33814713dc1b 100644
--- a/icu4c/source/common/ulocale.cpp
+++ b/icu4c/source/common/ulocale.cpp
@@ -10,7 +10,6 @@
 #include "unicode/locid.h"
 
 #include "bytesinkutil.h"
-#include "charstr.h"
 #include "cmemory.h"
 
 U_NAMESPACE_USE
@@ -24,9 +23,7 @@ ulocale_openForLocaleID(const char* localeID, int32_t length, UErrorCode* err) {
     if (length < 0) {
         return EXTERNAL(icu::Locale::createFromName(localeID).clone());
     }
-    CharString str(localeID, length, *err);  // Make a NUL terminated copy.
-    if (U_FAILURE(*err)) { return nullptr; }
-    return EXTERNAL(icu::Locale::createFromName(str.data()).clone());
+    return EXTERNAL(icu::Locale::createFromName(StringPiece{localeID, length}).clone());
 }
 
 ULocale*
diff --git a/icu4c/source/common/unicode/locid.h b/icu4c/source/common/unicode/locid.h
index e1afd598cf9b..a394cd9347db 100644
--- a/icu4c/source/common/unicode/locid.h
+++ b/icu4c/source/common/unicode/locid.h
@@ -449,6 +449,11 @@ class U_COMMON_API Locale : public UObject {
      */
     static Locale U_EXPORT2 createFromName(const char *name);
 
+#ifndef U_HIDE_INTERNAL_API
+    /** @internal */
+    static Locale U_EXPORT2 createFromName(StringPiece name);
+#endif  /* U_HIDE_INTERNAL_API */
+
     /**
      * Creates a locale from the given string after canonicalizing
      * the string according to CLDR by calling uloc_canonicalize().
@@ -1133,7 +1138,9 @@ class U_COMMON_API Locale : public UObject {
      * @param cLocaleID The new locale name.
      * @param canonicalize whether to call uloc_canonicalize on cLocaleID
      */
-    Locale& init(const char* cLocaleID, UBool canonicalize);
+    Locale& init(const char* localeID, UBool canonicalize);
+    /** @internal */
+    Locale& init(StringPiece localeID, UBool canonicalize);
 
     /*
      * Internal constructor to allow construction of a locale object with