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[api] Optimize plaintext varint encoding and devirtualize write_protobuf_packet (#14758)

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This commit is contained in:
J. Nick Koston
2026-03-16 07:32:58 -10:00
committed by GitHub
parent f86bb2bdb0
commit 2cd93daa5e
6 changed files with 26 additions and 27 deletions
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esphome/components/api/api_frame_helper.h
+9 -3
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@@ -12,6 +12,7 @@
#include "esphome/components/socket/socket.h"
#include "esphome/core/application.h"
#include "esphome/core/log.h"
#include "proto.h"
namespace esphome::api {
@@ -37,8 +38,6 @@ static constexpr uint16_t RX_BUF_NULL_TERMINATOR = 1;
// Must be >= MAX_INITIAL_PER_BATCH in api_connection.h (enforced by static_assert there)
static constexpr size_t MAX_MESSAGES_PER_BATCH = 34;
class ProtoWriteBuffer;
// Max client name length (e.g., "Home Assistant 2026.1.0.dev0" = 28 chars)
static constexpr size_t CLIENT_INFO_NAME_MAX_LEN = 32;
@@ -161,7 +160,14 @@ class APIFrameHelper {
this->nodelay_counter_ = 0;
}
}
virtual APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) = 0;
APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) {
// Resize buffer to include footer space if needed (e.g. Noise MAC)
if (frame_footer_size_)
buffer.get_buffer()->resize(buffer.get_buffer()->size() + frame_footer_size_);
MessageInfo msg{type, 0,
static_cast<uint16_t>(buffer.get_buffer()->size() - frame_header_padding_ - frame_footer_size_)};
return write_protobuf_messages(buffer, std::span<const MessageInfo>(&msg, 1));
}
// Write multiple protobuf messages in a single operation
// messages contains (message_type, offset, length) for each message in the buffer
// The buffer contains all messages with appropriate padding before each
esphome/components/api/api_frame_helper_noise.cpp
-8
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@@ -450,14 +450,6 @@ APIError APINoiseFrameHelper::read_packet(ReadPacketBuffer *buffer) {
buffer->type = type;
return APIError::OK;
}
APIError APINoiseFrameHelper::write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) {
// Resize to include MAC space (required for Noise encryption)
buffer.get_buffer()->resize(buffer.get_buffer()->size() + frame_footer_size_);
MessageInfo msg{type, 0,
static_cast<uint16_t>(buffer.get_buffer()->size() - frame_header_padding_ - frame_footer_size_)};
return write_protobuf_messages(buffer, std::span<const MessageInfo>(&msg, 1));
}
APIError APINoiseFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffer, std::span<const MessageInfo> messages) {
APIError aerr = this->check_data_state_();
if (aerr != APIError::OK)
esphome/components/api/api_frame_helper_noise.h
-1
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@@ -22,7 +22,6 @@ class APINoiseFrameHelper final : public APIFrameHelper {
APIError init() override;
APIError loop() override;
APIError read_packet(ReadPacketBuffer *buffer) override;
APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) override;
APIError write_protobuf_messages(ProtoWriteBuffer buffer, std::span<const MessageInfo> messages) override;
protected:
esphome/components/api/api_frame_helper_plaintext.cpp
+7 -10
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@@ -235,11 +235,6 @@ APIError APIPlaintextFrameHelper::read_packet(ReadPacketBuffer *buffer) {
buffer->type = this->rx_header_parsed_type_;
return APIError::OK;
}
APIError APIPlaintextFrameHelper::write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) {
MessageInfo msg{type, 0, static_cast<uint16_t>(buffer.get_buffer()->size() - frame_header_padding_)};
return write_protobuf_messages(buffer, std::span<const MessageInfo>(&msg, 1));
}
APIError APIPlaintextFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffer,
std::span<const MessageInfo> messages) {
APIError aerr = this->check_data_state_();
@@ -257,9 +252,11 @@ APIError APIPlaintextFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffe
uint16_t total_write_len = 0;
for (const auto &msg : messages) {
// Calculate varint sizes for header layout
uint8_t size_varint_len = api::ProtoSize::varint(static_cast<uint32_t>(msg.payload_size));
uint8_t type_varint_len = api::ProtoSize::varint(static_cast<uint32_t>(msg.message_type));
// Calculate varint sizes for header layout using inline ternary to avoid varint_slow call overhead
uint8_t size_varint_len = msg.payload_size < ProtoSize::VARINT_THRESHOLD_1_BYTE
? 1
: (msg.payload_size < ProtoSize::VARINT_THRESHOLD_2_BYTE ? 2 : 3);
uint8_t type_varint_len = msg.message_type < ProtoSize::VARINT_THRESHOLD_1_BYTE ? 1 : 2;
uint8_t total_header_len = 1 + size_varint_len + type_varint_len;
// Calculate where to start writing the header
@@ -281,8 +278,8 @@ APIError APIPlaintextFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffe
//
// Example 3 (large values): total_header_len = 6, header_offset = 6 - 6 = 0
// [0] - 0x00 indicator byte
// [1-3] - Payload size varint (3 bytes, for sizes 16384-2097151)
// [4-5] - Message type varint (2 bytes, for types 128-32767)
// [1-3] - Payload size varint (3 bytes, for sizes 16384-65535)
// [4-5] - Message type varint (2 bytes, for types 128-16383)
// [6...] - Actual payload data
//
// The message starts at offset + frame_header_padding_
esphome/components/api/api_frame_helper_plaintext.h
-1
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@@ -19,7 +19,6 @@ class APIPlaintextFrameHelper final : public APIFrameHelper {
APIError init() override;
APIError loop() override;
APIError read_packet(ReadPacketBuffer *buffer) override;
APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) override;
APIError write_protobuf_messages(ProtoWriteBuffer buffer, std::span<const MessageInfo> messages) override;
protected:
esphome/components/api/proto.h
+10 -4
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@@ -473,6 +473,12 @@ class ProtoDecodableMessage : public ProtoMessage {
class ProtoSize {
public:
// Varint encoding thresholds: values below each threshold fit in N bytes
static constexpr uint32_t VARINT_THRESHOLD_1_BYTE = 1 << 7; // 128
static constexpr uint32_t VARINT_THRESHOLD_2_BYTE = 1 << 14; // 16384
static constexpr uint32_t VARINT_THRESHOLD_3_BYTE = 1 << 21; // 2097152
static constexpr uint32_t VARINT_THRESHOLD_4_BYTE = 1 << 28; // 268435456
/**
* @brief Calculates the size in bytes needed to encode a uint32_t value as a varint
*
@@ -480,7 +486,7 @@ class ProtoSize {
* @return The number of bytes needed to encode the value
*/
static constexpr inline uint32_t ESPHOME_ALWAYS_INLINE varint(uint32_t value) {
if (value < 128) [[likely]]
if (value < VARINT_THRESHOLD_1_BYTE) [[likely]]
return 1; // Fast path: 7 bits, most common case
if (__builtin_is_constant_evaluated())
return varint_wide(value);
@@ -492,11 +498,11 @@ class ProtoSize {
static uint32_t varint_slow(uint32_t value) __attribute__((noinline));
// Shared cascade for values >= 128 (used by both constexpr and noinline paths)
static constexpr inline uint32_t ESPHOME_ALWAYS_INLINE varint_wide(uint32_t value) {
if (value < 16384)
if (value < VARINT_THRESHOLD_2_BYTE)
return 2;
if (value < 2097152)
if (value < VARINT_THRESHOLD_3_BYTE)
return 3;
if (value < 268435456)
if (value < VARINT_THRESHOLD_4_BYTE)
return 4;
return 5;
}