From 1aa98f8b93abb7c67c7c65401b919b32c6c555b5 Mon Sep 17 00:00:00 2001
From: Roman-Koshelev <34384083+Roman-Koshelev@users.noreply.github.com>
Date: Thu, 9 Sep 2021 18:10:29 +0300
Subject: [PATCH] Eliminate double copying in vformat_to_n (#2489)
---
include/fmt/core.h | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/include/fmt/core.h b/include/fmt/core.h
index cba989c3..6d4196a4 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -879,6 +879,46 @@ class iterator_buffer final : public Traits, public buffer<T> {
auto count() const -> size_t { return Traits::count() + this->size(); }
};
+template <typename T>
+class iterator_buffer<T*, T, fixed_buffer_traits> final : public fixed_buffer_traits, public buffer<T> {
+ private:
+ T* out_;
+ enum { buffer_size = 256 };
+ T data_[buffer_size];
+
+ protected:
+ void grow(size_t) override {
+ if (this->size() == this->capacity()) flush();
+ }
+
+ void flush() {
+ size_t n = this->limit(this->size());
+ if (this->data() == out_) {
+ out_ += n;
+ this->set(data_, buffer_size);
+ }
+ this->clear();
+ }
+
+ public:
+ explicit iterator_buffer(T* out, size_t n = buffer_size)
+ : fixed_buffer_traits(n), buffer<T>(out, 0, n), out_(out) {}
+ iterator_buffer(iterator_buffer&& other)
+ : fixed_buffer_traits(other), buffer<T>(std::move(other)), out_(other.out_) {
+ if (this->data() != out_) {
+ this->set(data_, buffer_size);
+ this->clear();
+ }
+ }
+ ~iterator_buffer() { flush(); }
+
+ auto out() -> T* {
+ flush();
+ return out_;
+ }
+ auto count() const -> size_t { return fixed_buffer_traits::count() + this->size(); }
+};
+
template <typename T> class iterator_buffer<T*, T> final : public buffer<T> {
protected:
void grow(size_t) override {}