Added base64 helper (#4866)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

esphome/core/helpers.cpp

@@ -433,6 +433,103 @@ int8_t step_to_accuracy_decimals(float step) {
   return str.length() - dot_pos - 1;
 }
 
+static inline bool is_base64(char c) { return (isalnum(c) || (c == '+') || (c == '/')); }
+
+std::string base64_encode(const std::vector<uint8_t> &buf) { return base64_encode(buf.data(), buf.size()); }
+
+std::string base64_encode(const char *buf, unsigned int buf_len) {
+  std::string ret;
+  int i = 0;
+  int j = 0;
+  char char_array_3[3];
+  char char_array_4[4];
+
+  while (buf_len--) {
+    char_array_3[i++] = *(buf++);
+    if (i == 3) {
+      char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
+      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
+      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
+      char_array_4[3] = char_array_3[2] & 0x3f;
+
+      for (i = 0; (i < 4); i++)
+        ret += BASE64_CHARS[char_array_4[i]];
+      i = 0;
+    }
+  }
+
+  if (i) {
+    for (j = i; j < 3; j++)
+      char_array_3[j] = '\0';
+
+    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
+    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
+    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
+    char_array_4[3] = char_array_3[2] & 0x3f;
+
+    for (j = 0; (j < i + 1); j++)
+      ret += BASE64_CHARS[char_array_4[j]];
+
+    while ((i++ < 3))
+      ret += '=';
+  }
+
+  return ret;
+}
+
+size_t base64_decode(const std::string &encoded_string, uint8_t *buf, size_t buf_len) {
+  std::vector<uint8_t> decoded = base64_decode(encoded_string);
+  if (decoded.size() > buf_len) {
+    ESP_LOGW(TAG, "Base64 decode: buffer too small, truncating");
+    decoded.resize(buf_len);
+  }
+  memcpy(buf, decoded.data(), decoded.size());
+  return decoded.size();
+}
+
+std::vector<uint8_t> base64_decode(const std::string &encoded_string) {
+  int in_len = encoded_string.size();
+  int i = 0;
+  int j = 0;
+  int in = 0;
+  uint8_t char_array_4[4], char_array_3[3];
+  std::vector<uint8_t> ret;
+
+  while (in_len-- && (encoded_string[in] != '=') && is_base64(encoded_string[in])) {
+    char_array_4[i++] = encoded_string[in];
+    in++;
+    if (i == 4) {
+      for (i = 0; i < 4; i++)
+        char_array_4[i] = BASE64_CHARS.find(char_array_4[i]);
+
+      char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
+      char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
+      char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
+
+      for (i = 0; (i < 3); i++)
+        ret.push_back(char_array_3[i]);
+      i = 0;
+    }
+  }
+
+  if (i) {
+    for (j = i; j < 4; j++)
+      char_array_4[j] = 0;
+
+    for (j = 0; j < 4; j++)
+      char_array_4[j] = BASE64_CHARS.find(char_array_4[j]);
+
+    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
+    char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
+    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
+
+    for (j = 0; (j < i - 1); j++)
+      ret.push_back(char_array_3[j]);
+  }
+
+  return ret;
+}
+
 // Colors
 
 float gamma_correct(float value, float gamma) {

esphome/core/helpers.h

@@ -435,6 +435,16 @@ std::string value_accuracy_to_string(float value, int8_t accuracy_decimals);
 /// Derive accuracy in decimals from an increment step.
 int8_t step_to_accuracy_decimals(float step);
 
+static const std::string BASE64_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                                        "abcdefghijklmnopqrstuvwxyz"
+                                        "0123456789+/";
+
+std::string base64_encode(const uint8_t *buf, size_t buf_len);
+std::string base64_encode(const std::vector<uint8_t> &buf);
+
+std::vector<uint8_t> base64_decode(const std::string &encoded_string);
+size_t base64_decode(std::string const &encoded_string, uint8_t *buf, size_t buf_len);
+
 ///@}
 
 /// @name Colors