[homeassistant] Keep the button, number, select, switch and text action strings in flash

progmem_string_table_find() returns the index of a RAM string in the table, for parsing a name
against a fixed set.

esphome/components/homeassistant/button/homeassistant_button.cpp

@@ -5,12 +5,21 @@
 #include "esphome/components/api/api_pb2.h"
 #include "esphome/components/api/api_server.h"
 #include "esphome/core/log.h"
+#include "esphome/core/progmem.h"
 #include "esphome/core/string_ref.h"
 
 namespace esphome::homeassistant {
 
 ESPHOME_LOG_TAG(TAG, "homeassistant.button");
 
+// In flash on the ESP8266; copied to the stack only while a request is built
+PROGMEM_STRING_TABLE(ButtonActionStrings, "button.press", "input_button.press", "entity_id");
+enum ButtonActionString : uint8_t {
+  BUTTON_ACTION_STRING_SERVICE,
+  BUTTON_ACTION_STRING_INPUT_SERVICE,
+  BUTTON_ACTION_STRING_ENTITY_ID,
+};
+
 void HomeassistantButton::dump_config() {
   LOG_BUTTON("", "Homeassistant Button", this);
   ESP_LOGCONFIG(TAG, "  Entity ID: '%s'", this->entity_id_);
@@ -31,21 +40,17 @@ void HomeassistantButton::press_action() {
   }
 #endif
 
-  static constexpr auto SERVICE_BUTTON = StringRef::from_lit("button.press");
-  static constexpr auto SERVICE_INPUT_BUTTON = StringRef::from_lit("input_button.press");
-  static constexpr auto ENTITY_ID_KEY = StringRef::from_lit("entity_id");
-  static constexpr char INPUT_PREFIX[] = "input_";
-
+  ProgmemStringTableCopy<ButtonActionStrings> strings;
+  // An input helper entity id starts with the "input_" its action name starts with
+  const bool input_helper =
+      strncmp(this->entity_id_, strings.get(BUTTON_ACTION_STRING_INPUT_SERVICE), sizeof("input_") - 1) == 0;
   api::HomeassistantActionRequest resp;
-  if (strncmp(this->entity_id_, INPUT_PREFIX, sizeof(INPUT_PREFIX) - 1) == 0) {
-    resp.service = SERVICE_INPUT_BUTTON;
-  } else {
-    resp.service = SERVICE_BUTTON;
-  }
+  resp.service =
+      StringRef(strings.get(input_helper ? BUTTON_ACTION_STRING_INPUT_SERVICE : BUTTON_ACTION_STRING_SERVICE));
 
   resp.data.init(1);
   auto &entity_id_kv = resp.data.emplace_back();
-  entity_id_kv.key = ENTITY_ID_KEY;
+  entity_id_kv.key = StringRef(strings.get(BUTTON_ACTION_STRING_ENTITY_ID));
   entity_id_kv.value = StringRef(this->entity_id_);
 
   api::global_api_server->send_homeassistant_action(resp);

esphome/components/homeassistant/number/homeassistant_number.cpp

@@ -5,12 +5,22 @@
 #include "esphome/components/api/api_pb2.h"
 #include "esphome/components/api/api_server.h"
 #include "esphome/core/log.h"
+#include "esphome/core/progmem.h"
 #include "esphome/core/string_ref.h"
 
 namespace esphome::homeassistant {
 
 ESPHOME_LOG_TAG(TAG, "homeassistant.number");
 
+// In flash on the ESP8266; copied to the stack only while a request is built
+PROGMEM_STRING_TABLE(NumberActionStrings, "number.set_value", "input_number.set_value", "entity_id", "value");
+enum NumberActionString : uint8_t {
+  NUMBER_ACTION_STRING_SERVICE,
+  NUMBER_ACTION_STRING_INPUT_SERVICE,
+  NUMBER_ACTION_STRING_ENTITY_ID,
+  NUMBER_ACTION_STRING_VALUE,
+};
+
 void HomeassistantNumber::state_changed_(StringRef state) {
   auto number_value = parse_number<float>(state.c_str());
   if (!number_value.has_value()) {
@@ -89,27 +99,22 @@ void HomeassistantNumber::control(float value) {
 
   this->publish_state(value);
 
-  static constexpr auto NUMBER_SERVICE_NAME = StringRef::from_lit("number.set_value");
-  static constexpr auto INPUT_NUMBER_SERVICE_NAME = StringRef::from_lit("input_number.set_value");
-  static constexpr char INPUT_PREFIX[] = "input_";
-  static constexpr auto ENTITY_ID_KEY = StringRef::from_lit("entity_id");
-  static constexpr auto VALUE_KEY = StringRef::from_lit("value");
-
+  ProgmemStringTableCopy<NumberActionStrings> strings;
+  // An input helper entity id starts with the "input_" its action name starts with
+  const bool input_helper =
+      strncmp(this->entity_id_, strings.get(NUMBER_ACTION_STRING_INPUT_SERVICE), sizeof("input_") - 1) == 0;
   api::HomeassistantActionRequest resp;
   // input_number entities have their own set_value action
-  if (strncmp(this->entity_id_, INPUT_PREFIX, sizeof(INPUT_PREFIX) - 1) == 0) {
-    resp.service = INPUT_NUMBER_SERVICE_NAME;
-  } else {
-    resp.service = NUMBER_SERVICE_NAME;
-  }
+  resp.service =
+      StringRef(strings.get(input_helper ? NUMBER_ACTION_STRING_INPUT_SERVICE : NUMBER_ACTION_STRING_SERVICE));
 
   resp.data.init(2);
   auto &entity_id = resp.data.emplace_back();
-  entity_id.key = ENTITY_ID_KEY;
+  entity_id.key = StringRef(strings.get(NUMBER_ACTION_STRING_ENTITY_ID));
   entity_id.value = StringRef(this->entity_id_);
 
   auto &entity_value = resp.data.emplace_back();
-  entity_value.key = VALUE_KEY;
+  entity_value.key = StringRef(strings.get(NUMBER_ACTION_STRING_VALUE));
   // Stack buffer - no heap allocation; %g produces shortest representation
   char value_buf[16];
   buf_append_printf(value_buf, sizeof(value_buf), 0, "%g", value);

esphome/components/homeassistant/select/homeassistant_select.cpp

@@ -6,12 +6,22 @@
 #include "esphome/components/api/api_server.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
+#include "esphome/core/progmem.h"
 #include "esphome/core/string_ref.h"
 
 namespace esphome::homeassistant {
 
 ESPHOME_LOG_TAG(TAG, "homeassistant.select");
 
+// In flash on the ESP8266; copied to the stack only while a request is built
+PROGMEM_STRING_TABLE(SelectActionStrings, "select.select_option", "input_select.select_option", "entity_id", "option");
+enum SelectActionString : uint8_t {
+  SELECT_ACTION_STRING_SERVICE,
+  SELECT_ACTION_STRING_INPUT_SERVICE,
+  SELECT_ACTION_STRING_ENTITY_ID,
+  SELECT_ACTION_STRING_OPTION,
+};
+
 namespace {
 
 /// Emit the UTF-8 encoding of a code point. Rejects NUL, which would end the option early.
@@ -237,26 +247,21 @@ void HomeassistantSelect::control(size_t index) {
   }
 #endif
 
-  static constexpr auto SERVICE_SELECT = StringRef::from_lit("select.select_option");
-  static constexpr auto SERVICE_INPUT_SELECT = StringRef::from_lit("input_select.select_option");
-  static constexpr auto ENTITY_ID_KEY = StringRef::from_lit("entity_id");
-  static constexpr auto OPTION_KEY = StringRef::from_lit("option");
-  static constexpr char INPUT_PREFIX[] = "input_";
-
+  ProgmemStringTableCopy<SelectActionStrings> strings;
+  // An input helper entity id starts with the "input_" its action name starts with
+  const bool input_helper =
+      strncmp(this->entity_id_, strings.get(SELECT_ACTION_STRING_INPUT_SERVICE), sizeof("input_") - 1) == 0;
   api::HomeassistantActionRequest resp;
-  if (strncmp(this->entity_id_, INPUT_PREFIX, sizeof(INPUT_PREFIX) - 1) == 0) {
-    resp.service = SERVICE_INPUT_SELECT;
-  } else {
-    resp.service = SERVICE_SELECT;
-  }
+  resp.service =
+      StringRef(strings.get(input_helper ? SELECT_ACTION_STRING_INPUT_SERVICE : SELECT_ACTION_STRING_SERVICE));
 
   resp.data.init(2);
   auto &entity_id = resp.data.emplace_back();
-  entity_id.key = ENTITY_ID_KEY;
+  entity_id.key = StringRef(strings.get(SELECT_ACTION_STRING_ENTITY_ID));
   entity_id.value = StringRef(this->entity_id_);
 
   auto &option = resp.data.emplace_back();
-  option.key = OPTION_KEY;
+  option.key = StringRef(strings.get(SELECT_ACTION_STRING_OPTION));
   option.value = StringRef(this->option_at(index));
 
   api::global_api_server->send_homeassistant_action(resp);

esphome/components/homeassistant/switch/homeassistant_switch.cpp

@@ -1,12 +1,21 @@
 #include "homeassistant_switch.h"
 #include "esphome/components/api/api_server.h"
 #include "esphome/core/log.h"
+#include "esphome/core/progmem.h"
 #include "esphome/core/string_ref.h"
 
 namespace esphome::homeassistant {
 
 ESPHOME_LOG_TAG(TAG, "homeassistant.switch");
 
+// In flash on the ESP8266; copied to the stack only while a request is built
+PROGMEM_STRING_TABLE(SwitchActionStrings, "homeassistant.turn_on", "homeassistant.turn_off", "entity_id");
+enum SwitchActionString : uint8_t {
+  SWITCH_ACTION_STRING_TURN_ON,
+  SWITCH_ACTION_STRING_TURN_OFF,
+  SWITCH_ACTION_STRING_ENTITY_ID,
+};
+
 using namespace esphome::switch_;
 
 void HomeassistantSwitch::setup() {
@@ -47,20 +56,13 @@ void HomeassistantSwitch::write_state(bool state) {
   }
 #endif
 
-  static constexpr auto SERVICE_ON = StringRef::from_lit("homeassistant.turn_on");
-  static constexpr auto SERVICE_OFF = StringRef::from_lit("homeassistant.turn_off");
-  static constexpr auto ENTITY_ID_KEY = StringRef::from_lit("entity_id");
-
+  ProgmemStringTableCopy<SwitchActionStrings> strings;
   api::HomeassistantActionRequest resp;
-  if (state) {
-    resp.service = SERVICE_ON;
-  } else {
-    resp.service = SERVICE_OFF;
-  }
+  resp.service = StringRef(strings.get(state ? SWITCH_ACTION_STRING_TURN_ON : SWITCH_ACTION_STRING_TURN_OFF));
 
   resp.data.init(1);
   auto &entity_id_kv = resp.data.emplace_back();
-  entity_id_kv.key = ENTITY_ID_KEY;
+  entity_id_kv.key = StringRef(strings.get(SWITCH_ACTION_STRING_ENTITY_ID));
   entity_id_kv.value = StringRef(this->entity_id_);
 
   api::global_api_server->send_homeassistant_action(resp);

esphome/components/homeassistant/text/homeassistant_text.cpp

@@ -6,12 +6,22 @@
 #include "esphome/components/api/api_server.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
+#include "esphome/core/progmem.h"
 #include "esphome/core/string_ref.h"
 
 namespace esphome::homeassistant {
 
 ESPHOME_LOG_TAG(TAG, "homeassistant.text");
 
+// In flash on the ESP8266; copied to the stack only while a request is built
+PROGMEM_STRING_TABLE(TextActionStrings, "text.set_value", "input_text.set_value", "entity_id", "value");
+enum TextActionString : uint8_t {
+  TEXT_ACTION_STRING_SERVICE,
+  TEXT_ACTION_STRING_INPUT_SERVICE,
+  TEXT_ACTION_STRING_ENTITY_ID,
+  TEXT_ACTION_STRING_VALUE,
+};
+
 void HomeassistantText::state_changed_(StringRef state) {
   if (state == this->state) {
     return;
@@ -86,26 +96,20 @@ void HomeassistantText::control(const std::string &value) {
   }
 #endif
 
-  static constexpr auto SERVICE_TEXT = StringRef::from_lit("text.set_value");
-  static constexpr auto SERVICE_INPUT_TEXT = StringRef::from_lit("input_text.set_value");
-  static constexpr auto ENTITY_ID_KEY = StringRef::from_lit("entity_id");
-  static constexpr auto VALUE_KEY = StringRef::from_lit("value");
-  static constexpr char INPUT_PREFIX[] = "input_";
-
+  ProgmemStringTableCopy<TextActionStrings> strings;
+  // An input helper entity id starts with the "input_" its action name starts with
+  const bool input_helper =
+      strncmp(this->entity_id_, strings.get(TEXT_ACTION_STRING_INPUT_SERVICE), sizeof("input_") - 1) == 0;
   api::HomeassistantActionRequest resp;
-  if (strncmp(this->entity_id_, INPUT_PREFIX, sizeof(INPUT_PREFIX) - 1) == 0) {
-    resp.service = SERVICE_INPUT_TEXT;
-  } else {
-    resp.service = SERVICE_TEXT;
-  }
+  resp.service = StringRef(strings.get(input_helper ? TEXT_ACTION_STRING_INPUT_SERVICE : TEXT_ACTION_STRING_SERVICE));
 
   resp.data.init(2);
   auto &entity_id_kv = resp.data.emplace_back();
-  entity_id_kv.key = ENTITY_ID_KEY;
+  entity_id_kv.key = StringRef(strings.get(TEXT_ACTION_STRING_ENTITY_ID));
   entity_id_kv.value = StringRef(this->entity_id_);
 
   auto &value_kv = resp.data.emplace_back();
-  value_kv.key = VALUE_KEY;
+  value_kv.key = StringRef(strings.get(TEXT_ACTION_STRING_VALUE));
   value_kv.value = StringRef(value.data(), value.size());
 
   api::global_api_server->send_homeassistant_action(resp);

esphome/core/progmem.h

@@ -153,4 +153,38 @@ struct LogString;
     } \
   }
 
+/// The index of the string value (len bytes, in RAM) in a PROGMEM_STRING_TABLE, or -1 when it is
+/// not one of its strings
+template<typename Table> int8_t progmem_string_table_find(const char *value, size_t len) {
+  for (uint8_t i = 0; i < Table::COUNT; i++) {
+    const char *entry = Table::get_(i, i);
+    if (ESPHOME_strlen_P(entry) == len && ESPHOME_strncmp_P(value, entry, len) == 0) {
+      return i;
+    }
+  }
+  return -1;
+}
+
+/// The strings of a PROGMEM_STRING_TABLE addressable as plain pointers, for code that hands them on
+/// without reading them itself, such as an API request. On the ESP8266 this is a copy of the table on
+/// the stack that lives as long as the object; elsewhere the table is read in place.
+///
+/// Example, with an enum that numbers the table's strings:
+///   ProgmemStringTableCopy<MyStrings> strings;
+///   request.service = StringRef(strings.get(MY_STRING_TURN_ON));
+template<typename Name> class ProgmemStringTableCopy {
+  static_assert(Name::Table::INDEXED, "the table needs offsets");
+
+ public:
+#ifdef USE_ESP8266
+  ProgmemStringTableCopy() { progmem_memcpy(this->blob_, Name::BLOB.data(), Name::BLOB_SIZE); }
+  const char *get(uint8_t idx) const { return this->blob_ + progmem_read_byte(&Name::OFFSETS[idx]); }
+
+ private:
+  char blob_[Name::BLOB_SIZE];
+#else
+  const char *get(uint8_t idx) const { return Name::get_(idx, idx); }
+#endif
+};
+
 }  // namespace esphome

tests/components/core/test_progmem_string_table_copy.cpp

@@ -0,0 +1,35 @@
+#include <gtest/gtest.h>
+
+#include <cstring>
+
+#include "esphome/core/progmem.h"
+
+namespace esphome::testing {
+
+PROGMEM_STRING_TABLE(Names, "light.turn_on", "entity_id", "rgb_color");
+
+TEST(ProgmemStringTableCopy, HandsOutEveryString) {
+  ProgmemStringTableCopy<Names> strings;
+  EXPECT_STREQ(strings.get(0), "light.turn_on");
+  EXPECT_STREQ(strings.get(1), "entity_id");
+  EXPECT_STREQ(strings.get(2), "rgb_color");
+}
+
+TEST(ProgmemStringTableCopy, StringsStayValidWhileTheCopyLives) {
+  ProgmemStringTableCopy<Names> strings;
+  const char *key = strings.get(1);
+  const char *other = strings.get(2);
+  EXPECT_EQ(std::strlen(key), 9U);
+  EXPECT_STREQ(key, "entity_id");
+  EXPECT_STREQ(other, "rgb_color");
+}
+
+TEST(ProgmemStringTableFind, FindsWholeStringsOnly) {
+  EXPECT_EQ(progmem_string_table_find<Names>("entity_id", 9), 1);
+  EXPECT_EQ(progmem_string_table_find<Names>("rgb_color", 9), 2);
+  EXPECT_EQ(progmem_string_table_find<Names>("entity", 6), -1);
+  EXPECT_EQ(progmem_string_table_find<Names>("entity_id_x", 11), -1);
+  EXPECT_EQ(progmem_string_table_find<Names>("", 0), -1);
+}
+
+}  // namespace esphome::testing