[online_image] Remove stored RAMAllocator member from DownloadBuffer

RAMAllocator with default flags is stateless — it's just a dispatch
wrapper over heap_caps_malloc/realloc/free. There's no need to store
it as a class member. Use stack-local instances at each call site
instead, matching the pattern used in audio_transfer_buffer and
ring_buffer.

Co-Authored-By: J. Nick Koston <nick@koston.org>

esphome/components/camera/buffer_impl.cpp

@@ -3,22 +3,18 @@
 namespace esphome::camera {
 
 BufferImpl::BufferImpl(size_t size) {
-  RAMAllocator<uint8_t> allocator;
-  this->data_ = allocator.allocate(size);
+  this->data_ = this->allocator_.allocate(size);
   this->size_ = size;
 }
 
 BufferImpl::BufferImpl(CameraImageSpec *spec) {
-  RAMAllocator<uint8_t> allocator;
-  this->data_ = allocator.allocate(spec->bytes_per_image());
+  this->data_ = this->allocator_.allocate(spec->bytes_per_image());
   this->size_ = spec->bytes_per_image();
 }
 
 BufferImpl::~BufferImpl() {
-  if (this->data_ != nullptr) {
-    RAMAllocator<uint8_t> allocator;
-    allocator.deallocate(this->data_, this->size_);
-  }
+  if (this->data_ != nullptr)
+    this->allocator_.deallocate(this->data_, this->size_);
 }
 
 }  // namespace esphome::camera

esphome/components/camera/buffer_impl.h

@@ -18,6 +18,7 @@ class BufferImpl : public Buffer {
   ~BufferImpl() override;
 
  protected:
+  RAMAllocator<uint8_t> allocator_;
   size_t size_{};
   uint8_t *data_{};
 };

esphome/components/camera_encoder/encoder_buffer_impl.cpp

@@ -4,8 +4,7 @@ namespace esphome::camera_encoder {
 
 bool EncoderBufferImpl::set_buffer_size(size_t size) {
   if (size > this->capacity_) {
-    RAMAllocator<uint8_t> allocator;
-    uint8_t *p = allocator.reallocate(this->data_, size);
+    uint8_t *p = this->allocator_.reallocate(this->data_, size);
     if (p == nullptr)
       return false;
 
@@ -17,10 +16,8 @@ bool EncoderBufferImpl::set_buffer_size(size_t size) {
 }
 
 EncoderBufferImpl::~EncoderBufferImpl() {
-  if (this->data_ != nullptr) {
-    RAMAllocator<uint8_t> allocator;
-    allocator.deallocate(this->data_, this->capacity_);
-  }
+  if (this->data_ != nullptr)
+    this->allocator_.deallocate(this->data_, this->capacity_);
 }
 
 }  // namespace esphome::camera_encoder

esphome/components/camera_encoder/encoder_buffer_impl.h

@@ -16,6 +16,7 @@ class EncoderBufferImpl : public camera::EncoderBuffer {
   ~EncoderBufferImpl() override;
 
  protected:
+  RAMAllocator<uint8_t> allocator_;
   size_t capacity_{};
   size_t size_{};
   uint8_t *data_{};

esphome/components/online_image/download_buffer.cpp

@@ -7,7 +7,8 @@ namespace esphome::online_image {
 static const char *const TAG = "online_image.download_buffer";
 
 DownloadBuffer::DownloadBuffer(size_t size) : size_(size) {
-  this->buffer_ = this->allocator_.allocate(size);
+  RAMAllocator<uint8_t> allocator;
+  this->buffer_ = allocator.allocate(size);
   this->reset();
   if (!this->buffer_) {
     ESP_LOGE(TAG, "Initial allocation of download buffer failed!");
@@ -38,15 +39,16 @@ size_t DownloadBuffer::resize(size_t size) {
     // Avoid useless reallocations; if the buffer is big enough, don't reallocate.
     return this->size_;
   }
-  this->allocator_.deallocate(this->buffer_, this->size_);
-  this->buffer_ = this->allocator_.allocate(size);
+  RAMAllocator<uint8_t> allocator;
+  allocator.deallocate(this->buffer_, this->size_);
+  this->buffer_ = allocator.allocate(size);
   this->reset();
   if (this->buffer_) {
     this->size_ = size;
     return size;
   } else {
     ESP_LOGE(TAG, "allocation of %zu bytes failed. Biggest block in heap: %zu Bytes", size,
-             this->allocator_.get_max_free_block_size());
+             allocator.get_max_free_block_size());
     this->size_ = 0;
     return 0;
   }

esphome/components/online_image/download_buffer.h

@@ -15,7 +15,10 @@ namespace esphome::online_image {
 class DownloadBuffer {
  public:
   DownloadBuffer(size_t size);
-  ~DownloadBuffer() { this->allocator_.deallocate(this->buffer_, this->size_); }
+  ~DownloadBuffer() {
+    RAMAllocator<uint8_t> allocator;
+    allocator.deallocate(this->buffer_, this->size_);
+  }
 
   uint8_t *data(size_t offset = 0);
   uint8_t *append() { return this->data(this->unread_); }
@@ -34,7 +37,6 @@ class DownloadBuffer {
   size_t resize(size_t size);
 
  protected:
-  RAMAllocator<uint8_t> allocator_{};
   uint8_t *buffer_;
   size_t size_;
   /** Total number of downloaded bytes not yet read. */