Files
EMS-ESP32/src/core/psram_json_allocator.h
2026-05-16 16:26:04 +02:00

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3.6 KiB
C++

/*
* EMS-ESP - https://github.com/emsesp/EMS-ESP
* Copyright 2020-2025 emsesp.org
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef EMSESP_PSRAM_JSON_ALLOCATOR_H
#define EMSESP_PSRAM_JSON_ALLOCATOR_H
#include <ArduinoJson.h>
#ifndef EMSESP_STANDALONE
#include <esp_heap_caps.h>
#endif
namespace emsesp {
// PSRAM-backed ArduinoJson allocator with internal-heap fallback.
//
// Rationale: by default ArduinoJson allocates with malloc(), which on the
// ESP32 lands in internal DRAM. Large transient JsonDocuments (full MQTT
// payload, HA discovery configs, Web API responses, settings load/save)
// were eating multiple KB of the same internal heap that LwIP, mbedTLS and
// AsyncTCP also need. Routing them through SPIRAM via heap_caps_malloc
// keeps internal heap available for the network stack, at the cost of a
// small latency penalty on PSRAM reads/writes (a few cycles per access,
// negligible for JSON build-up which is dominated by string formatting).
//
// On the standalone (Linux) build, PSRAM doesn't exist; the allocator
// silently falls through to plain malloc/free/realloc.
//
// Usage:
// JsonDocument doc(emsesp::PsramJsonAllocator::instance());
// or with the convenience macro:
// JsonDocument doc(PSRAM_DOC);
class PsramJsonAllocator : public ArduinoJson::Allocator {
public:
void * allocate(size_t size) override {
#ifdef EMSESP_STANDALONE
return malloc(size);
#else
// Try SPIRAM first; fall back to internal heap so we never fail
// on boards without PSRAM or when PSRAM is full.
void * p = heap_caps_malloc(size, MALLOC_CAP_SPIRAM);
if (p == nullptr) {
p = malloc(size);
}
return p;
#endif
}
void deallocate(void * ptr) override {
#ifdef EMSESP_STANDALONE
free(ptr);
#else
// heap_caps_free handles both PSRAM- and internal-heap pointers.
heap_caps_free(ptr);
#endif
}
void * reallocate(void * ptr, size_t new_size) override {
#ifdef EMSESP_STANDALONE
return realloc(ptr, new_size);
#else
// Prefer keeping the block in PSRAM; heap_caps_realloc will move
// the data if the original region can't be grown in-place.
void * p = heap_caps_realloc(ptr, new_size, MALLOC_CAP_SPIRAM);
if (p == nullptr) {
p = realloc(ptr, new_size);
}
return p;
#endif
}
static ArduinoJson::Allocator * instance() {
static PsramJsonAllocator inst;
return &inst;
}
private:
PsramJsonAllocator() = default;
~PsramJsonAllocator() = default;
};
} // namespace emsesp
// Convenience shorthand. Use only for *large* or *transient* JsonDocuments
// (MQTT publish payloads, HA discovery, full API responses, big settings
// load/save). For small hot-path docs (single-command output, parse of a
// short HTTP body), keep the default allocator: PSRAM has higher access
// latency than internal SRAM, so tiny docs are faster on the regular heap.
#define PSRAM_DOC emsesp::PsramJsonAllocator::instance()
#endif