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Stage ESP8266 values in a stack buffer sized to the schema cap

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This commit is contained in:
J. Nick Koston
2026-10-08 11:13:08 -04:00
committed by GitHub
parent 1bd16ba14a
commit 441da02851
1 changed files with 9 additions and 13 deletions
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esphome/components/modbus_client/modbus_client.h
+9 -13
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@@ -4,8 +4,8 @@
#include "esphome/components/modbus/modbus_helpers.h"
#include "esphome/core/automation.h"
#include "esphome/core/hal.h"
#include "esphome/core/helpers.h"
#include <array>
#include <span>
#include <vector>
@@ -163,17 +163,13 @@ class ModbusClientSendAction : public ClientActionBase<Ts...>,
/// success status.) Each typed callback still checks succeeded() before firing its trigger: that branch
/// is unreachable today, and is kept so a future change to that interception cannot silently deliver an
/// exception as a successful reply.
// Static lists up to this size are staged on the stack on ESP8266; longer ones use the heap.
static constexpr size_t STATIC_REGISTERS_ON_STACK = 16;
static constexpr size_t STATIC_COIL_BYTES_ON_STACK = 16;
/// Calls fn with a RAM-readable span of a static values table. On ESP8266 the table is in PROGMEM, which the
/// PDU builders cannot read directly, so it is copied to the stack first (the heap above N elements).
template<size_t N, typename T, typename F> void with_static_values(const T *data, size_t len, F &&fn) {
/// PDU builders cannot read directly, so it is copied to the stack first; the schema caps len at MAX.
template<size_t MAX, typename T, typename F> void with_static_values(const T *data, size_t len, F &&fn) {
#ifdef USE_ESP8266
SmallBufferWithHeapFallback<N, T> buf(len);
progmem_memcpy(buf.get(), data, len * sizeof(T));
fn(std::span<const T>(buf.get(), len));
std::array<T, MAX> buf;
progmem_memcpy(buf.data(), data, len * sizeof(T));
fn(std::span<const T>(buf.data(), len));
#else
fn(std::span<const T>(data, len));
#endif
@@ -335,7 +331,7 @@ class WriteMultipleRegistersAction : public TypedClientActionBase<Ts...>, public
// An empty or over-long set rejects into an empty PDU inside the builder, which logs the reason;
// the empty PDU then resolves via on_not_sent like any refused send.
if (this->len_ >= 0) {
with_static_values<STATIC_REGISTERS_ON_STACK>(
with_static_values<modbus::MAX_NUM_OF_REGISTERS_TO_WRITE>(
this->values_.data, static_cast<size_t>(this->len_), [&](std::span<const uint16_t> values) {
this->send_or_resolve_(modbus::helpers::create_write_registers_pdu(start, values),
this->write_command_options_(x...));
@@ -387,7 +383,7 @@ class WriteMultipleCoilsAction : public TypedClientActionBase<Ts...>, public Wri
const uint16_t start = this->start_address_.value(x...);
if (this->count_ >= 0) {
const auto count = static_cast<uint16_t>(this->count_);
with_static_values<STATIC_COIL_BYTES_ON_STACK>(
with_static_values<modbus::packed_bit_bytes(modbus::MAX_NUM_OF_COILS_TO_WRITE)>(
this->values_.packed, modbus::packed_bit_bytes(count), [&](std::span<const uint8_t> packed) {
this->send_or_resolve_(modbus::helpers::create_write_coils_pdu(start, modbus::PackedBits(packed, count)),
this->write_command_options_(x...));
@@ -441,7 +437,7 @@ class ReadWriteMultipleRegistersAction : public TypedClientActionBase<Ts...>, pu
const uint16_t write_start = this->write_address_.value(x...);
// An out-of-range read/write count builds an empty PDU (the builder logs why), resolving via on_not_sent.
if (this->len_ >= 0) {
with_static_values<STATIC_REGISTERS_ON_STACK>(
with_static_values<modbus::MAX_NUM_OF_REGISTERS_TO_WRITE_RW>(
this->values_.data, static_cast<size_t>(this->len_), [&](std::span<const uint16_t> values) {
this->send_or_resolve_(
modbus::helpers::create_read_write_multiple_registers_pdu(read_start, read_count, write_start, values),