Extract string_builder

commit_hash:1573c88f09db79bab2755c9c2c3ffd0bc219b2d2

1 files changed, 65 insertions, 15 deletions

diff --git a/library/cpp/yt/string/string_builder.h b/library/cpp/yt/string/string_builder.h
index de1c1abb1e..ac3aa26a7c 100644
--- a/library/cpp/yt/string/string_builder.h
+++ b/library/cpp/yt/string/string_builder.h
@@ -1,13 +1,68 @@
 #pragma once
 
-#include "format.h"
-
 #include <util/generic/string.h>
 
 namespace NYT {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+//! A simple helper for constructing strings by a sequence of appends.
+class TStringBuilderBase
+{
+public:
+    virtual ~TStringBuilderBase() = default;
+
+    char* Preallocate(size_t size);
+
+    void Reserve(size_t size);
+
+    size_t GetLength() const;
+
+    TStringBuf GetBuffer() const;
+
+    void Advance(size_t size);
+
+    void AppendChar(char ch);
+    void AppendChar(char ch, int n);
+
+    void AppendString(TStringBuf str);
+    void AppendString(const char* str);
+
+    template <size_t Length, class... TArgs>
+    void AppendFormat(const char (&format)[Length], TArgs&&... args);
+    template <class... TArgs>
+    void AppendFormat(TStringBuf format, TArgs&&... args);
+
+    void Reset();
+
+protected:
+    char* Begin_ = nullptr;
+    char* Current_ = nullptr;
+    char* End_ = nullptr;
+
+    virtual void DoReset() = 0;
+    virtual void DoReserve(size_t newLength) = 0;
+
+    static constexpr size_t MinBufferLength = 128;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+class TStringBuilder
+    : public TStringBuilderBase
+{
+public:
+    TString Flush();
+
+protected:
+    TString Buffer_;
+
+    void DoReset() override;
+    void DoReserve(size_t size) override;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
 //! Appends a certain delimiter starting from the second call.
 class TDelimitedStringBuilderWrapper
     : private TNonCopyable
@@ -15,19 +70,10 @@ class TDelimitedStringBuilderWrapper
 public:
     TDelimitedStringBuilderWrapper(
         TStringBuilderBase* builder,
-        TStringBuf delimiter = TStringBuf(", "))
-        : Builder_(builder)
-        , Delimiter_(delimiter)
-    { }
-
-    TStringBuilderBase* operator->()
-    {
-        if (!FirstCall_) {
-            Builder_->AppendString(Delimiter_);
-        }
-        FirstCall_ = false;
-        return Builder_;
-    }
+        TStringBuf delimiter = TStringBuf(", "));
+
+    TStringBuilderBase* operator->();
+    TStringBuilderBase* operator&();
 
 private:
     TStringBuilderBase* const Builder_;
@@ -39,3 +85,7 @@ private:
 ////////////////////////////////////////////////////////////////////////////////
 
 } // namespace NYT
+
+#define STRING_BUILDER_INL_H_
+#include "string_builder-inl.h"
+#undef STRING_BUILDER_INL_H_