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[web_server_idf] Reduce flash by eliminating temporary string allocations in event formatting

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This commit is contained in:
J. Nick Koston
2025-11-01 12:39:01 -05:00
parent 55af818629
commit f502907c7a
2 changed files with 19 additions and 8 deletions
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25
esphome/components/web_server_idf/web_server_idf.cpp
View File

@@ -4,6 +4,7 @@
#include <memory>
#include <cstring>
#include <cctype>
#include <cinttypes>
#include "esphome/core/helpers.h"
#include "esphome/core/log.h"
@@ -348,7 +349,14 @@ void AsyncWebServerResponse::addHeader(const char *name, const char *value) {
httpd_resp_set_hdr(*this->req_, name, value);
}
void AsyncResponseStream::print(float value) { this->print(to_string(value)); }
void AsyncResponseStream::print(float value) {
// Use stack buffer to avoid temporary string allocation
// Size: sign (1) + digits (10) + decimal (1) + precision (6) + exponent (5) + null (1) = 24, use 32 for safety
constexpr size_t FLOAT_BUF_SIZE = 32;
char buf[FLOAT_BUF_SIZE];
int len = snprintf(buf, FLOAT_BUF_SIZE, "%f", value);
this->content_.append(buf, len);
}
void AsyncResponseStream::printf(const char *fmt, ...) {
va_list args;
@@ -594,16 +602,19 @@ bool AsyncEventSourceResponse::try_send_nodefer(const char *message, const char
event_buffer_.append(chunk_len_header);
// Use stack buffer for formatting numeric fields to avoid temporary string allocations
// Size: "retry: " (7) + max uint32 (10 digits) + CRLF (2) + null (1) = 20 bytes, use 32 for safety
constexpr size_t NUM_BUF_SIZE = 32;
char num_buf[NUM_BUF_SIZE];
if (reconnect) {
event_buffer_.append("retry: ", sizeof("retry: ") - 1);
event_buffer_.append(to_string(reconnect));
event_buffer_.append(CRLF_STR, CRLF_LEN);
int len = snprintf(num_buf, NUM_BUF_SIZE, "retry: %" PRIu32 CRLF_STR, reconnect);
event_buffer_.append(num_buf, len);
}
if (id) {
event_buffer_.append("id: ", sizeof("id: ") - 1);
event_buffer_.append(to_string(id));
event_buffer_.append(CRLF_STR, CRLF_LEN);
int len = snprintf(num_buf, NUM_BUF_SIZE, "id: %" PRIu32 CRLF_STR, id);
event_buffer_.append(num_buf, len);
}
if (event && *event) {

2
esphome/components/web_server_idf/web_server_idf.h
View File

@@ -77,7 +77,7 @@ class AsyncResponseStream : public AsyncWebServerResponse {
size_t get_content_size() const override { return this->content_.size(); };
void print(const char *str) { this->content_.append(str); }
void print(const std::string &str) { this->content_.append(str); }
void print(const std::string &str) { this->content_.append(str.c_str(), str.size()); }
void print(float value);
void printf(const char *fmt, ...) __attribute__((format(printf, 2, 3)));