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pycapnp/capnp/helpers/serialize.h
teal@teallvbs.xyz 05cc505ef4
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Optimize numeric array conversion and serialize directly into Python bytes
2026-09-21 22:48:21 -05:00

35 lines
1.2 KiB
C++

// Copyright (c) 2026 IQ.Lvbs. All rights reserved.
#pragma once
#include <Python.h>
#include <capnp/message.h>
#include <capnp/serialize.h>
#include <kj/debug.h>
#include <cstring>
inline PyObject* messageToPythonBytes(capnp::MessageBuilder& builder) {
auto segments = builder.getSegmentsForOutput();
auto words = capnp::computeSerializedSizeInWords(segments);
KJ_REQUIRE(words <= static_cast<size_t>(PY_SSIZE_T_MAX) / sizeof(capnp::word));
PyObject* result = PyBytes_FromStringAndSize(nullptr, words * sizeof(capnp::word));
if (result == nullptr) return nullptr;
char* data = PyBytes_AS_STRING(result);
auto write32 = [data](size_t index, uint32_t value) {
for (unsigned int byte = 0; byte < 4; ++byte) {
data[index * 4 + byte] = static_cast<char>(value >> (byte * 8));
}
};
write32(0, segments.size() - 1);
for (size_t index = 0; index < segments.size(); ++index) {
write32(index + 1, segments[index].size());
}
if (segments.size() % 2 == 0) write32(segments.size() + 1, 0);
char* output = data + (segments.size() / 2 + 1) * sizeof(capnp::word);
for (auto segment : segments) {
auto size = segment.size() * sizeof(capnp::word);
std::memcpy(output, segment.begin(), size);
output += size;
}
return result;
}