From 5596751c2c0a99d1c4df1d281d943007653424dd Mon Sep 17 00:00:00 2001
From: Oxan van Leeuwen <oxan@oxanvanleeuwen.nl>
Date: Mon, 27 Sep 2021 23:24:55 +0200
Subject: [PATCH] Add str_sprintf function that returns std::string (#2408)

---
 esphome/core/helpers.cpp | 15 +++++++++++++++
 esphome/core/helpers.h   |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/esphome/core/helpers.cpp b/esphome/core/helpers.cpp
index a190566bea..0092d202c4 100644
--- a/esphome/core/helpers.cpp
+++ b/esphome/core/helpers.cpp
@@ -351,6 +351,21 @@ bool str_startswith(const std::string &full, const std::string &start) { return
 bool str_endswith(const std::string &full, const std::string &ending) {
   return full.rfind(ending) == (full.size() - ending.size());
 }
+std::string str_sprintf(const char *fmt, ...) {
+  std::string str;
+  va_list args;
+
+  va_start(args, fmt);
+  size_t length = vsnprintf(nullptr, 0, fmt, args);
+  va_end(args);
+
+  str.resize(length);
+  va_start(args, fmt);
+  vsnprintf(&str[0], length + 1, fmt, args);
+  va_end(args);
+
+  return str;
+}
 
 uint16_t encode_uint16(uint8_t msb, uint8_t lsb) { return (uint16_t(msb) << 8) | uint16_t(lsb); }
 std::array<uint8_t, 2> decode_uint16(uint16_t value) {
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 8118585db5..f5a7a197ca 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -59,6 +59,9 @@ bool str_equals_case_insensitive(const std::string &a, const std::string &b);
 bool str_startswith(const std::string &full, const std::string &start);
 bool str_endswith(const std::string &full, const std::string &ending);
 
+/// sprintf-like function returning std::string instead of writing to char array.
+std::string __attribute__((format(printf, 1, 2))) str_sprintf(const char *fmt, ...);
+
 class HighFrequencyLoopRequester {
  public:
   void start();