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Improve string view to reduce string allocation. (#6644)

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This commit is contained in:
Jiaming Yuan
2021-01-27 19:08:52 +08:00
committed by GitHub
parent bc08e0c9d1
commit 1b70a323a7
4 changed files with 33 additions and 9 deletions
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13
include/xgboost/json.h
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@@ -1,5 +1,5 @@
/*!
* Copyright (c) by XGBoost Contributors 2019-2020
* Copyright (c) by XGBoost Contributors 2019-2021
*/
#ifndef XGBOOST_JSON_H_
#define XGBOOST_JSON_H_
@@ -301,12 +301,14 @@ class JsonBoolean : public Value {
struct StringView {
private:
using CharT = char; // unsigned char
using Traits = std::char_traits<CharT>;
CharT const* str_;
size_t size_;
public:
StringView() = default;
StringView(CharT const* str, size_t size) : str_{str}, size_{size} {}
explicit StringView(CharT const* str) : str_{str}, size_{Traits::length(str)} {}
CharT const& operator[](size_t p) const { return str_[p]; }
CharT const& at(size_t p) const { // NOLINT
@@ -322,9 +324,16 @@ struct StringView {
CHECK_LE(beg, size_);
return std::string {str_ + beg, n < (size_ - beg) ? n : (size_ - beg)};
}
char const* c_str() const { return str_; } // NOLINT
CharT const* c_str() const { return str_; } // NOLINT
CharT const* cbegin() const { return str_; } // NOLINT
CharT const* cend() const { return str_ + size(); } // NOLINT
CharT const* begin() const { return str_; } // NOLINT
CharT const* end() const { return str_ + size(); } // NOLINT
};
std::ostream &operator<<(std::ostream &os, StringView const v);
/*!
* \brief Data structure representing JSON format.
*