[wpiutil C++] Add remove_prefix() and remove_suffix()

glass/src/libnt/native/cpp/NTField2D.cpp

@@ -126,7 +126,7 @@ void NTField2DModel::Update() {
   for (auto&& event : m_poller.ReadQueue()) {
     if (auto info = event.GetTopicInfo()) {
       // handle publish/unpublish
-      auto name = wpi::drop_front(info->name, m_path.size());
+      auto name = wpi::remove_prefix(info->name, m_path);
       if (name.empty() || name[0] == '.') {
         continue;
       }
@@ -198,7 +198,7 @@ void NTField2DModel::ForEachFieldObject(
         func) {
   for (auto&& obj : m_objects) {
     if (obj->Exists()) {
-      func(*obj, wpi::drop_front(obj->GetName(), m_path.size()));
+      func(*obj, wpi::remove_prefix(obj->GetName(), m_path));
     }
   }
 }

glass/src/libnt/native/cpp/NTMechanism2D.cpp

@@ -256,7 +256,7 @@ NTMechanism2DModel::~NTMechanism2DModel() = default;
 void NTMechanism2DModel::Update() {
   for (auto&& event : m_poller.ReadQueue()) {
     if (auto info = event.GetTopicInfo()) {
-      auto name = wpi::drop_front(info->name, m_path.size());
+      auto name = wpi::remove_prefix(info->name, m_path);
       if (name.empty() || name[0] == '.') {
         continue;
       }
@@ -307,7 +307,7 @@ void NTMechanism2DModel::Update() {
         }
       } else {
         auto fullName = nt::Topic{valueData->topic}.GetName();
-        auto name = wpi::drop_front(fullName, m_path.size());
+        auto name = wpi::remove_prefix(fullName, m_path);
         if (name.empty() || name[0] == '.') {
           continue;
         }

glass/src/libnt/native/cpp/NetworkTables.cpp

@@ -726,10 +726,10 @@ void NetworkTablesModel::ValueSource::UpdateFromValue(
         UpdateMsgpackValueSource(model, this, r, name, value.last_change());
         mpack_reader_destroy(&r);
       } else if (wpi::starts_with(typeStr, "struct:")) {
-        auto structName = wpi::drop_front(typeStr, 7);
+        auto structName = wpi::remove_prefix(typeStr, "struct:");
         bool isArray = structName.ends_with("[]");
         if (isArray) {
-          structName = wpi::drop_back(structName, 2);
+          structName = wpi::remove_suffix(structName, "[]");
         }
         auto desc = model.m_structDb.Find(structName);
         if (desc && desc->IsValid()) {
@@ -761,7 +761,7 @@ void NetworkTablesModel::ValueSource::UpdateFromValue(
           valueChildren.clear();
         }
       } else if (wpi::starts_with(typeStr, "proto:")) {
-        auto msg = model.m_protoDb.Find(wpi::drop_front(typeStr, 6));
+        auto msg = model.m_protoDb.Find(wpi::remove_prefix(typeStr, "proto:"));
         if (msg) {
           msg->Clear();
           auto raw = value.GetRaw();
@@ -807,12 +807,14 @@ void NetworkTablesModel::Update() {
           } else if (info->name == "$serversub") {
             m_server.subscribers.clear();
           } else if (wpi::starts_with(info->name, "$clientpub$")) {
-            auto it = m_clients.find(wpi::drop_front(info->name, 11));
+            auto it =
+                m_clients.find(wpi::remove_prefix(info->name, "$clientpub$"));
             if (it != m_clients.end()) {
               it->second.publishers.clear();
             }
           } else if (wpi::starts_with(info->name, "$clientsub$")) {
-            auto it = m_clients.find(wpi::drop_front(info->name, 11));
+            auto it =
+                m_clients.find(wpi::remove_prefix(info->name, "$clientsub$"));
             if (it != m_clients.end()) {
               it->second.subscribers.clear();
             }
@@ -853,12 +855,14 @@ void NetworkTablesModel::Update() {
           } else if (entry->info.name == "$serversub") {
             m_server.UpdateSubscribers(entry->value.GetRaw());
           } else if (wpi::starts_with(entry->info.name, "$clientpub$")) {
-            auto it = m_clients.find(wpi::drop_front(entry->info.name, 11));
+            auto it = m_clients.find(
+                wpi::remove_prefix(entry->info.name, "$clientpub$"));
             if (it != m_clients.end()) {
               it->second.UpdatePublishers(entry->value.GetRaw());
             }
           } else if (wpi::starts_with(entry->info.name, "$clientsub$")) {
-            auto it = m_clients.find(wpi::drop_front(entry->info.name, 11));
+            auto it = m_clients.find(
+                wpi::remove_prefix(entry->info.name, "$clientsub$"));
             if (it != m_clients.end()) {
               it->second.UpdateSubscribers(entry->value.GetRaw());
             }
@@ -867,7 +871,8 @@ void NetworkTablesModel::Update() {
                    wpi::starts_with(entry->info.name, "/.schema/struct:") &&
                    entry->info.type_str == "structschema") {
           // struct schema handling
-          auto typeStr = wpi::drop_front(entry->info.name, 16);
+          auto typeStr =
+              wpi::remove_prefix(entry->info.name, "/.schema/struct:");
           std::string_view schema{
               reinterpret_cast<const char*>(entry->value.GetRaw().data()),
               entry->value.GetRaw().size()};
@@ -886,9 +891,8 @@ void NetworkTablesModel::Update() {
               if (!wpi::starts_with(ts, "struct:")) {
                 continue;
               }
-              ts = wpi::drop_front(ts, 7);
-              if (ts == typeStr || (wpi::ends_with(ts, "[]") &&
-                                    wpi::drop_back(ts, 2) == typeStr)) {
+              ts = wpi::remove_prefix(ts, "struct:");
+              if (wpi::remove_suffix(ts, "[]") == typeStr) {
                 entryPair.second->UpdateFromValue(*this);
               }
             }
@@ -897,7 +901,8 @@ void NetworkTablesModel::Update() {
                    wpi::starts_with(entry->info.name, "/.schema/proto:") &&
                    entry->info.type_str == "proto:FileDescriptorProto") {
           // protobuf descriptor handling
-          auto filename = wpi::drop_front(entry->info.name, 15);
+          auto filename =
+              wpi::remove_prefix(entry->info.name, "/.schema/proto:");
           if (!m_protoDb.Add(filename, entry->value.GetRaw())) {
             fmt::print("could not decode protobuf '{}' filename '{}'\n",
                        entry->info.name, filename);
@@ -1079,17 +1084,17 @@ void NetworkTablesModel::UpdateClients(std::span<const uint8_t> data) {
 
 static bool GetHeadingTypeString(std::string_view* ts) {
   if (wpi::starts_with(*ts, "proto:")) {
-    *ts = wpi::drop_front(*ts, 6);
+    *ts = wpi::remove_prefix(*ts, "proto:");
     auto lastdot = ts->rfind('.');
     if (lastdot != std::string_view::npos) {
       *ts = wpi::substr(*ts, lastdot + 1);
     }
     if (wpi::starts_with(*ts, "Protobuf")) {
-      *ts = wpi::drop_front(*ts, 8);
+      *ts = wpi::remove_prefix(*ts, "Protobuf");
     }
     return true;
   } else if (wpi::starts_with(*ts, "struct:")) {
-    *ts = wpi::drop_front(*ts, 7);
+    *ts = wpi::remove_prefix(*ts, "struct:");
     return true;
   }
   return false;

glass/src/libnt/native/cpp/NetworkTablesProvider.cpp

@@ -157,7 +157,7 @@ void NetworkTablesProvider::Update() {
       }
 
       auto topicName = nt::GetTopicName(valueData->topic);
-      auto tableName = wpi::drop_back(topicName, 6);
+      auto tableName = wpi::remove_prefix(topicName, "/.type");
 
       GetOrCreateView(builderIt->second, nt::Topic{valueData->topic},
                       tableName);
@@ -198,7 +198,8 @@ void NetworkTablesProvider::Show(ViewEntry* entry, Window* window) {
   }
   if (wpi::starts_with(entry->name, "/SmartDashboard/")) {
     window->SetDefaultName(
-        fmt::format("{} (SmartDashboard)", wpi::drop_front(entry->name, 16)));
+        fmt::format("{} (SmartDashboard)",
+                    wpi::remove_prefix(entry->name, "/SmartDashboard/")));
   }
   entry->window = window;
 

ntcore/src/main/native/cpp/LocalStorage.cpp

@@ -53,10 +53,9 @@ int LocalStorage::DataLoggerData::Start(TopicData* topic, int64_t time) {
   } else if (typeStr == "int[]") {
     typeStr = "int64[]";
   }
-  return log.Start(fmt::format("{}{}", logPrefix,
-                               wpi::drop_front(topic->name, prefix.size())),
-                   typeStr, DataLoggerEntry::MakeMetadata(topic->propertiesStr),
-                   time);
+  return log.Start(
+      fmt::format("{}{}", logPrefix, wpi::remove_prefix(topic->name, prefix)),
+      typeStr, DataLoggerEntry::MakeMetadata(topic->propertiesStr), time);
 }
 
 void LocalStorage::DataLoggerEntry::Append(const Value& v) {

ntcore/src/main/native/cpp/NetworkServer.cpp

@@ -225,7 +225,7 @@ void NetworkServer::ServerConnection4::ProcessWsUpgrade() {
   std::string_view name;
   bool err = false;
   if (wpi::starts_with(path, "/nt/")) {
-    name = wpi::UnescapeURI(wpi::drop_front(path, 4), nameBuf, &err);
+    name = wpi::UnescapeURI(wpi::remove_prefix(path, "/nt/"), nameBuf, &err);
   }
   if (err || name.empty()) {
     INFO("invalid path '{}' (from {}), must match /nt/[clientId], closing",

ntcore/src/main/native/cpp/net/WireDecoder.cpp

@@ -567,7 +567,6 @@ bool nt::net::WireDecodeBinary(std::span<const uint8_t>* in, int64_t* outId,
   outValue->SetServerTime(time);
   outValue->SetTime(time == 0 ? 0 : time + localTimeOffset);
   // update input range
-  *in = wpi::drop_front(*in,
-                        in->size() - mpack_reader_remaining(&reader, nullptr));
+  *in = wpi::take_back(*in, mpack_reader_remaining(&reader, nullptr));
   return true;
 }

simulation/halsim_ws_server/src/main/native/cpp/HALSimHttpConnection.cpp

@@ -170,13 +170,13 @@ void HALSimHttpConnection::ProcessRequest() {
     // convert to fs native representation
     fs::path nativePath;
     if (wpi::starts_with(path, "/user/")) {
-      nativePath =
-          fs::path{m_server->GetWebrootSys()} /
-          fs::path{wpi::drop_front(path, 6), fs::path::format::generic_format};
+      nativePath = fs::path{m_server->GetWebrootSys()} /
+                   fs::path{wpi::remove_prefix(path, "/user/"),
+                            fs::path::format::generic_format};
     } else {
       nativePath =
           fs::path{m_server->GetWebrootSys()} /
-          fs::path{wpi::drop_front(path, 1), fs::path::format::generic_format};
+          fs::path{wpi::drop_front(path), fs::path::format::generic_format};
     }
 
     if (fs::is_directory(nativePath)) {

wpiutil/src/main/native/thirdparty/llvm/cpp/llvm/StringExtras.cpp

@@ -278,7 +278,7 @@ bool wpi::detail::ConsumeSignedInteger(
   }
 
   // Get the positive part of the value.
-  std::string_view str2 = wpi::drop_front(str, 1);
+  std::string_view str2 = wpi::drop_front(str);
   if (wpi::detail::ConsumeUnsignedInteger(str2, radix, ullVal) ||
       // Reject values so large they'd overflow as negative signed, but allow
       // "-0".  This negates the unsigned so that the negative isn't undefined

wpiutil/src/main/native/thirdparty/llvm/include/wpi/StringExtras.h

@@ -357,6 +357,30 @@ inline bool contains_lower(std::string_view str, const char* other) noexcept {
   return find_lower(str, other) != std::string_view::npos;
 }
 
+/**
+ * Return a string_view equal to @p str but with @p prefix removed if the string
+ * starts with the prefix. If the string does not start with the prefix, return
+ * a copy of the string.
+ */
+constexpr std::string_view remove_prefix(std::string_view str, std::string_view prefix) noexcept {
+  if (str.starts_with(prefix)) {
+    str.remove_prefix(prefix.size());
+  }
+  return str;
+}
+
+/**
+ * Return a string_view equal to @p str but with @p suffix removed if the
+ * string ends with the suffix. If the string does not end with the suffix,
+ * return a copy of the string.
+ */
+constexpr std::string_view remove_suffix(std::string_view str, std::string_view suffix) noexcept {
+  if (str.ends_with(suffix)) {
+    str.remove_suffix(suffix.size());
+  }
+  return str;
+}
+
 /**
  * Return a string_view equal to @p str but with the first @p n elements
  * dropped.

wpiutil/src/test/native/cpp/StringExtrasTest.cpp

@@ -0,0 +1,36 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <gtest/gtest.h>
+
+#include "wpi/StringExtras.h"
+
+TEST(StringExtrasTest, RemovePrefix) {
+  std::string_view original = "wpilib";
+  std::string_view modified = wpi::remove_prefix(original, "wpi");
+  EXPECT_EQ(original, "wpilib");
+  EXPECT_EQ(modified, "lib");
+}
+
+TEST(StringExtrasTest, RemoveSuffix) {
+  std::string_view original = "wpilib";
+  EXPECT_TRUE(original.ends_with("lib"));
+  std::string_view modified = wpi::remove_suffix(original, "lib");
+  EXPECT_EQ(original, "wpilib");
+  EXPECT_EQ(modified, "wpi");
+}
+
+TEST(StringExtrasTest, RemovePrefixNoMatch) {
+  std::string_view original = "wpilib";
+  std::string_view modified = wpi::remove_prefix(original, "foo");
+  EXPECT_EQ(original, "wpilib");
+  EXPECT_EQ(modified, "wpilib");
+}
+
+TEST(StringExtrasTest, RemoveSuffixNoMatch) {
+  std::string_view original = "wpilib";
+  std::string_view modified = wpi::remove_suffix(original, "foo");
+  EXPECT_EQ(original, "wpilib");
+  EXPECT_EQ(modified, "wpilib");
+}