Add a _span string literal operator for creating constexpr CharSpans

src/app/clusters/door-lock-server/door-lock-server.cpp

@@ -1827,7 +1827,7 @@ EmberAfStatus DoorLockServer::createUser(chip::EndpointId endpointId, chip::Fabr
         return static_cast<EmberAfStatus>(DlStatus::kOccupied);
     }
 
-    const auto & newUserName                = !userName.IsNull() ? userName.Value() : chip::CharSpan::fromCharString("");
+    const auto & newUserName                = !userName.IsNull() ? userName.Value() : ""_span;
     auto newUserUniqueId                    = userUniqueId.IsNull() ? 0xFFFFFFFF : userUniqueId.Value();
     auto newUserStatus                      = userStatus.IsNull() ? UserStatusEnum::kOccupiedEnabled : userStatus.Value();
     auto newUserType                        = userType.IsNull() ? UserTypeEnum::kUnrestrictedUser : userType.Value();

src/controller/CHIPDeviceController.cpp

@@ -2543,7 +2543,7 @@ void DeviceCommissioner::PerformCommissioningStep(DeviceProxy * proxy, Commissio
         else
         {
             // Default to "XX", for lack of anything better.
-            countryCode = CharSpan::fromCharString("XX");
+            countryCode = "XX"_span;
         }
 
         GeneralCommissioning::Commands::SetRegulatoryConfig::Type request;

src/credentials/tests/TestFabricTable.cpp

@@ -2261,32 +2261,32 @@ void TestFabricLabelChange(nlTestSuite * inSuite, void * inContext)
     // Second scope: set FabricLabel to "acme fabric", make sure it cannot be reverted
     {
         // Fabric label starts unset from prior scope
-        CharSpan fabricLabel = CharSpan::fromCharString("placeholder");
+        CharSpan fabricLabel = "placeholder"_span;
 
         NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.GetFabricLabel(1, fabricLabel));
         NL_TEST_ASSERT(inSuite, fabricLabel.size() == 0);
 
         // Set a valid name
-        NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.SetFabricLabel(1, CharSpan::fromCharString("acme fabric")));
+        NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.SetFabricLabel(1, "acme fabric"_span));
         NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.GetFabricLabel(1, fabricLabel));
-        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal(CharSpan::fromCharString("acme fabric")) == true);
+        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal("acme fabric"_span) == true);
 
         // Revert pending fabric data. Should not revert name since nothing pending.
         fabricTable.RevertPendingFabricData();
 
-        fabricLabel = CharSpan::fromCharString("placeholder");
+        fabricLabel = "placeholder"_span;
         NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.GetFabricLabel(1, fabricLabel));
-        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal(CharSpan::fromCharString("acme fabric")) == true);
+        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal("acme fabric"_span) == true);
 
         // Verify we fail to set too large a label (> kFabricLabelMaxLengthInBytes)
-        CharSpan fabricLabelTooBig = CharSpan::fromCharString("012345678901234567890123456789123456");
+        CharSpan fabricLabelTooBig = "012345678901234567890123456789123456"_span;
         NL_TEST_ASSERT(inSuite, fabricLabelTooBig.size() > chip::kFabricLabelMaxLengthInBytes);
 
         NL_TEST_ASSERT(inSuite, fabricTable.SetFabricLabel(1, fabricLabelTooBig) == CHIP_ERROR_INVALID_ARGUMENT);
 
-        fabricLabel = CharSpan::fromCharString("placeholder");
+        fabricLabel = "placeholder"_span;
         NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.GetFabricLabel(1, fabricLabel));
-        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal(CharSpan::fromCharString("acme fabric")) == true);
+        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal("acme fabric"_span) == true);
     }
 
     // Third scope: set fabric label after an update, it sticks, but then goes back after revert
@@ -2320,23 +2320,23 @@ void TestFabricLabelChange(nlTestSuite * inSuite, void * inContext)
             NL_TEST_ASSERT(inSuite, fabricInfo->GetVendorId() == kVendorId);
 
             CharSpan fabricLabel = fabricInfo->GetFabricLabel();
-            NL_TEST_ASSERT(inSuite, fabricLabel.data_equal(CharSpan::fromCharString("acme fabric")) == true);
+            NL_TEST_ASSERT(inSuite, fabricLabel.data_equal("acme fabric"_span) == true);
         }
 
         // Update fabric label
-        CharSpan fabricLabel = CharSpan::fromCharString("placeholder");
-        NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.SetFabricLabel(1, CharSpan::fromCharString("roboto fabric")));
+        CharSpan fabricLabel = "placeholder"_span;
+        NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.SetFabricLabel(1, "roboto fabric"_span));
 
-        fabricLabel = CharSpan::fromCharString("placeholder");
+        fabricLabel = "placeholder"_span;
         NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.GetFabricLabel(1, fabricLabel));
-        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal(CharSpan::fromCharString("roboto fabric")) == true);
+        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal("roboto fabric"_span) == true);
 
         // Revert pending fabric data. Should revert name to "acme fabric"
         fabricTable.RevertPendingFabricData();
 
-        fabricLabel = CharSpan::fromCharString("placeholder");
+        fabricLabel = "placeholder"_span;
         NL_TEST_ASSERT_SUCCESS(inSuite, fabricTable.GetFabricLabel(1, fabricLabel));
-        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal(CharSpan::fromCharString("acme fabric")) == true);
+        NL_TEST_ASSERT(inSuite, fabricLabel.data_equal("acme fabric"_span) == true);
     }
 }
 

src/crypto/tests/CHIPCryptoPALTest.cpp

@@ -2414,13 +2414,10 @@ static void TestSubject_x509Extraction(nlTestSuite * inSuite, void * inContext)
     NL_TEST_ASSERT(inSuite, CHIP_NO_ERROR == subjectDN_Node02_02.AddAttribute_MatterFabricId(0xFAB000000000001D));
     NL_TEST_ASSERT(inSuite,
                    CHIP_NO_ERROR ==
-                       subjectDN_Node02_02.AddAttribute_CommonName(
-                           chip::CharSpan::fromCharString("TEST CERT COMMON NAME Attr for Node02_02"), false));
+                       subjectDN_Node02_02.AddAttribute_CommonName("TEST CERT COMMON NAME Attr for Node02_02"_span, false));
     ChipDN subjectDN_Node02_04;
     NL_TEST_ASSERT(inSuite, CHIP_NO_ERROR == subjectDN_Node02_04.AddAttribute_MatterCASEAuthTag(0xABCE1002));
-    NL_TEST_ASSERT(inSuite,
-                   CHIP_NO_ERROR ==
-                       subjectDN_Node02_04.AddAttribute_CommonName(chip::CharSpan::fromCharString("TestCert02_04"), false));
+    NL_TEST_ASSERT(inSuite, CHIP_NO_ERROR == subjectDN_Node02_04.AddAttribute_CommonName("TestCert02_04"_span, false));
     NL_TEST_ASSERT(inSuite, CHIP_NO_ERROR == subjectDN_Node02_04.AddAttribute_MatterFabricId(0xFAB000000000001D));
     NL_TEST_ASSERT(inSuite, CHIP_NO_ERROR == subjectDN_Node02_04.AddAttribute_MatterCASEAuthTag(0xABCD0003));
     NL_TEST_ASSERT(inSuite, CHIP_NO_ERROR == subjectDN_Node02_04.AddAttribute_MatterNodeId(0xDEDEDEDE00020004));

src/lib/core/Unchecked.h

@@ -0,0 +1,36 @@
+/*
+ *
+ *    Copyright (c) 2023 Project CHIP Authors
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+/**
+ *    @file
+ *      This file defines the chip::Optional class to handle values which may
+ *      or may not be present.
+ *
+ */
+#pragma once
+
+namespace chip {
+
+/// Unchecked is a disambiguation tag that can be used to provide and select a variant of a
+/// constructor or other method that omits the runtime checks performed by the default variant.
+struct UncheckedType
+{
+    explicit UncheckedType() = default;
+};
+inline constexpr UncheckedType Unchecked{};
+
+} // namespace chip

src/lib/core/tests/TestOTAImageHeader.cpp

@@ -83,13 +83,13 @@ void TestHappyPath(nlTestSuite * inSuite, void * inContext)
     NL_TEST_ASSERT(inSuite, header.mVendorId == 0xDEAD);
     NL_TEST_ASSERT(inSuite, header.mProductId == 0xBEEF);
     NL_TEST_ASSERT(inSuite, header.mSoftwareVersion == 0xFFFFFFFF);
-    NL_TEST_ASSERT(inSuite, header.mSoftwareVersionString.data_equal(CharSpan::fromCharString("1.0")));
+    NL_TEST_ASSERT(inSuite, header.mSoftwareVersionString.data_equal("1.0"_span));
     NL_TEST_ASSERT(inSuite, header.mPayloadSize == strlen("test payload"));
     NL_TEST_ASSERT(inSuite, header.mMinApplicableVersion.HasValue());
     NL_TEST_ASSERT(inSuite, header.mMinApplicableVersion.Value() == 1);
     NL_TEST_ASSERT(inSuite, header.mMaxApplicableVersion.HasValue());
     NL_TEST_ASSERT(inSuite, header.mMaxApplicableVersion.Value() == 2);
-    NL_TEST_ASSERT(inSuite, header.mReleaseNotesURL.data_equal(CharSpan::fromCharString("https://rn")));
+    NL_TEST_ASSERT(inSuite, header.mReleaseNotesURL.data_equal("https://rn"_span));
     NL_TEST_ASSERT(inSuite, header.mImageDigestType == OTAImageDigestType::kSha256);
     NL_TEST_ASSERT(inSuite, header.mImageDigest.size() == 256 / 8);
 }
@@ -169,13 +169,13 @@ void TestSmallBlocks(nlTestSuite * inSuite, void * inContext)
         NL_TEST_ASSERT(inSuite, header.mVendorId == 0xDEAD);
         NL_TEST_ASSERT(inSuite, header.mProductId == 0xBEEF);
         NL_TEST_ASSERT(inSuite, header.mSoftwareVersion == 0xFFFFFFFF);
-        NL_TEST_ASSERT(inSuite, header.mSoftwareVersionString.data_equal(CharSpan::fromCharString("1.0")));
+        NL_TEST_ASSERT(inSuite, header.mSoftwareVersionString.data_equal("1.0"_span));
         NL_TEST_ASSERT(inSuite, header.mPayloadSize == strlen("test payload"));
         NL_TEST_ASSERT(inSuite, header.mMinApplicableVersion.HasValue());
         NL_TEST_ASSERT(inSuite, header.mMinApplicableVersion.Value() == 1);
         NL_TEST_ASSERT(inSuite, header.mMaxApplicableVersion.HasValue());
         NL_TEST_ASSERT(inSuite, header.mMaxApplicableVersion.Value() == 2);
-        NL_TEST_ASSERT(inSuite, header.mReleaseNotesURL.data_equal(CharSpan::fromCharString("https://rn")));
+        NL_TEST_ASSERT(inSuite, header.mReleaseNotesURL.data_equal("https://rn"_span));
         NL_TEST_ASSERT(inSuite, header.mImageDigestType == OTAImageDigestType::kSha256);
         NL_TEST_ASSERT(inSuite, header.mImageDigest.size() == 256 / 8);
     }

src/lib/support/Span.h

@@ -18,11 +18,13 @@
 #pragma once
 
 #include <array>
+#include <cstddef>
 #include <cstdint>
 #include <cstdlib>
-#include <string.h>
+#include <cstring>
 #include <type_traits>
 
+#include <lib/core/Unchecked.h>
 #include <lib/support/CodeUtils.h>
 
 namespace chip {
@@ -149,7 +151,10 @@ class Span
         return Span(reinterpret_cast<T *>(&bytes[1]), length);
     }
 
-    // Allow creating CharSpans from a character string.
+    // Creates a CharSpan from a null-terminated C character string.
+    //
+    // Note that for string literals, the user-defined `_span` string
+    // literal operator should be used instead, e.g. `"Hello"_span`.
     template <class U, typename = std::enable_if_t<std::is_same<T, const U>::value && std::is_same<const char, T>::value>>
     static Span fromCharString(U * chars)
     {
@@ -162,11 +167,31 @@ class Span
     template <typename U>
     bool operator==(const Span<U> & other) const = delete;
 
+    // Creates a Span without checking whether databuf is a null pointer.
+    //
+    // Note: The normal (checked) constructor should be used for general use;
+    // this overload exists for special use cases where databuf is guaranteed
+    // to be valid (not null) and a constexpr constructor is required.
+    //
+    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61648 prevents making
+    // operator""_span a friend (and this constructor private).
+
+    constexpr Span(UncheckedType tag, pointer databuf, size_t datalen) : mDataBuf(databuf), mDataLen(datalen) {}
+
 private:
     pointer mDataBuf;
     size_t mDataLen;
 };
 
+inline namespace literals {
+
+inline constexpr Span<const char> operator"" _span(const char * literal, size_t size)
+{
+    return Span<const char>(Unchecked, literal, size);
+}
+
+} // namespace literals
+
 namespace detail {
 
 // To make FixedSpan (specifically various FixedByteSpan types) default constructible

src/lib/support/tests/TestJsonToTlv.cpp

@@ -141,7 +141,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
     jsonString = "{\n"
                  "   \"1:STRING\" : \"hello\"\n"
                  "}\n";
-    ConvertJsonToTlvAndValidate(CharSpan::fromCharString("hello"), jsonString);
+    ConvertJsonToTlvAndValidate("hello"_span, jsonString);
 
     // Validated using https://base64.guru/converter/encode/hex
     const uint8_t byteBuf[] = { 0x01, 0x02, 0x03, 0x04, 0xff, 0xfe, 0x99, 0x88, 0xdd, 0xcd };
@@ -161,7 +161,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
     structVal.a = 20;
     structVal.b = true;
     structVal.d = byteBuf;
-    structVal.e = CharSpan::fromCharString("hello");
+    structVal.e = "hello"_span;
     structVal.g = static_cast<float>(1.0);
     structVal.h = static_cast<double>(1.0);
 

src/lib/support/tests/TestSpan.cpp

@@ -291,6 +291,14 @@ static void TestFromCharString(nlTestSuite * inSuite, void * inContext)
     NL_TEST_ASSERT(inSuite, s1.data_equal(CharSpan(str, 3)));
 }
 
+static void TestLiteral(nlTestSuite * inSuite, void * inContext)
+{
+    constexpr CharSpan literal = "HI!"_span;
+    NL_TEST_ASSERT(inSuite, literal.size() == 3);
+    NL_TEST_ASSERT(inSuite, literal.data_equal(CharSpan::fromCharString("HI!")));
+    NL_TEST_ASSERT(inSuite, ""_span.size() == 0);
+}
+
 static void TestConversionConstructors(nlTestSuite * inSuite, void * inContext)
 {
     struct Foo
@@ -330,6 +338,7 @@ static const nlTest sTests[] = {
     NL_TEST_DEF_FN(TestSubSpan),
     NL_TEST_DEF_FN(TestFromZclString),
     NL_TEST_DEF_FN(TestFromCharString),
+    NL_TEST_DEF_FN(TestLiteral),
     NL_TEST_DEF_FN(TestConversionConstructors),
     NL_TEST_SENTINEL(),
 };

src/lib/support/tests/TestStringSplitter.cpp

@@ -45,7 +45,7 @@ void TestStrdupSplitter(nlTestSuite * inSuite, void * inContext)
         StringSplitter splitter("single", ',');
 
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("single")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("single"_span));
 
         // next stays at nullptr also after valid data
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
@@ -59,11 +59,11 @@ void TestStrdupSplitter(nlTestSuite * inSuite, void * inContext)
         StringSplitter splitter("one,two,three", ',');
 
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("one")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("one"_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("two")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("two"_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("three")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("three"_span));
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
         NL_TEST_ASSERT(inSuite, out.data() == nullptr);
     }
@@ -73,15 +73,15 @@ void TestStrdupSplitter(nlTestSuite * inSuite, void * inContext)
         StringSplitter splitter("a**bc*d,e*f", '*');
 
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("a")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("a"_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("bc")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("bc"_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("d,e")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("d,e"_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("f")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("f"_span));
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
     }
 
@@ -90,37 +90,37 @@ void TestStrdupSplitter(nlTestSuite * inSuite, void * inContext)
         StringSplitter splitter(",", ',');
         // Note that even though "" is nullptr right away, "," becomes two empty strings
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
     }
     {
         StringSplitter splitter("log,", ',');
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("log")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("log"_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
     }
     {
         StringSplitter splitter(",log", ',');
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("log")));
+        NL_TEST_ASSERT(inSuite, out.data_equal("log"_span));
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
     }
     {
         StringSplitter splitter(",,,", ',');
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, splitter.Next(out));
-        NL_TEST_ASSERT(inSuite, out.data_equal(CharSpan::fromCharString("")));
+        NL_TEST_ASSERT(inSuite, out.data_equal(""_span));
         NL_TEST_ASSERT(inSuite, !splitter.Next(out));
     }
 }

src/lib/support/tests/TestTlvToJson.cpp

@@ -140,7 +140,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
                  "}\n";
     EncodeAndValidate(static_cast<double>(1.0), jsonString);
 
-    CharSpan charSpan = CharSpan::fromCharString("hello");
+    CharSpan charSpan = "hello"_span;
     jsonString        = "{\n"
                         "   \"1:STRING\" : \"hello\"\n"
                         "}\n";