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[api] Inline varint and encode_varint_raw fast paths for hot loop performance (#14607)

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
J. Nick Koston
2026-03-07 22:09:12 -10:00
committed by GitHub
co-authored by Claude Opus 4.6
parent d9e76da806
commit a530aeec22
2 changed files with 41 additions and 22 deletions
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esphome/components/api/proto.cpp
+12
View File
@@ -8,6 +8,18 @@ namespace esphome::api {
static const char *const TAG = "api.proto";
uint32_t ProtoSize::varint_slow(uint32_t value) { return varint_wide(value); }
void ProtoWriteBuffer::encode_varint_raw_slow_(uint32_t value) {
do {
this->debug_check_bounds_(1);
*this->pos_++ = static_cast<uint8_t>(value | 0x80);
value >>= 7;
} while (value > 0x7F);
this->debug_check_bounds_(1);
*this->pos_++ = static_cast<uint8_t>(value);
}
#ifdef USE_API_VARINT64
optional<ProtoVarInt> ProtoVarInt::parse_wide(const uint8_t *buffer, uint32_t len, uint32_t *consumed,
uint32_t result32) {
esphome/components/api/proto.h
+29 -22
View File
@@ -240,14 +240,13 @@ class ProtoWriteBuffer {
ProtoWriteBuffer(std::vector<uint8_t> *buffer) : buffer_(buffer), pos_(buffer->data() + buffer->size()) {}
ProtoWriteBuffer(std::vector<uint8_t> *buffer, size_t write_pos)
: buffer_(buffer), pos_(buffer->data() + write_pos) {}
void encode_varint_raw(uint32_t value) {
while (value > 0x7F) {
inline void ESPHOME_ALWAYS_INLINE encode_varint_raw(uint32_t value) {
if (value < 128) [[likely]] {
this->debug_check_bounds_(1);
*this->pos_++ = static_cast<uint8_t>(value | 0x80);
value >>= 7;
*this->pos_++ = static_cast<uint8_t>(value);
return;
}
this->debug_check_bounds_(1);
*this->pos_++ = static_cast<uint8_t>(value);
this->encode_varint_raw_slow_(value);
}
void encode_varint_raw_64(uint64_t value) {
while (value > 0x7F) {
@@ -378,6 +377,9 @@ class ProtoWriteBuffer {
std::vector<uint8_t> *get_buffer() const { return buffer_; }
protected:
// Slow path for encode_varint_raw values >= 128, outlined to keep fast path small
void encode_varint_raw_slow_(uint32_t value) __attribute__((noinline));
#ifdef ESPHOME_DEBUG_API
void debug_check_bounds_(size_t bytes, const char *caller = __builtin_FUNCTION());
void debug_check_encode_size_(uint32_t field_id, uint32_t expected, ptrdiff_t actual);
@@ -511,24 +513,29 @@ class ProtoSize {
* @param value The uint32_t value to calculate size for
* @return The number of bytes needed to encode the value
*/
static constexpr uint32_t varint(uint32_t value) {
// Optimized varint size calculation using leading zeros
// Each 7 bits requires one byte in the varint encoding
if (value < 128)
return 1; // 7 bits, common case for small values
// For larger values, count bytes needed based on the position of the highest bit set
if (value < 16384) {
return 2; // 14 bits
} else if (value < 2097152) {
return 3; // 21 bits
} else if (value < 268435456) {
return 4; // 28 bits
} else {
return 5; // 32 bits (maximum for uint32_t)
}
static constexpr inline uint32_t ESPHOME_ALWAYS_INLINE varint(uint32_t value) {
if (value < 128) [[likely]]
return 1; // Fast path: 7 bits, most common case
if (__builtin_is_constant_evaluated())
return varint_wide(value);
return varint_slow(value);
}
private:
// Slow path for varint >= 128, outlined to keep fast path small
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)
return 2;
if (value < 2097152)
return 3;
if (value < 268435456)
return 4;
return 5;
}
public:
/**
* @brief Calculates the size in bytes needed to encode a uint64_t value as a varint
*