Add std::string-backed stream adapters to library/cpp/yt/string

commit_hash:54a07f0d411d0ece7af812a9fdf91509f25ee5cb

1 files changed, 144 insertions, 0 deletions

diff --git a/library/cpp/yt/string/stream.cpp b/library/cpp/yt/string/stream.cpp
new file mode 100644
index 00000000000..4bf8dcd599c
--- /dev/null
+++ b/library/cpp/yt/string/stream.cpp
@@ -0,0 +1,144 @@
+#include "stream.h"
+
+#include <util/generic/bitops.h>
+#include <util/generic/string.h>
+#include <util/generic/utility.h>
+#include <util/system/yassert.h>
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+static constexpr size_t MinBufferGrowSize = 16;
+
+////////////////////////////////////////////////////////////////////////////////
+
+TStdStringOutput::TStdStringOutput(std::string& string) noexcept
+    : String_(&string)
+{ }
+
+TStdStringOutput::~TStdStringOutput() = default;
+
+void TStdStringOutput::Reserve(size_t size)
+{
+    String_->reserve(String_->size() + size);
+}
+
+void TStdStringOutput::Swap(TStdStringOutput& other) noexcept
+{
+    DoSwap(String_, other.String_);
+}
+
+size_t TStdStringOutput::DoNext(void** ptr)
+{
+    if (String_->size() == String_->capacity()) {
+        String_->reserve(FastClp2(String_->capacity() + MinBufferGrowSize));
+    }
+    size_t previousSize = String_->size();
+    ResizeUninitialized(*String_, String_->capacity());
+    *ptr = String_->data() + previousSize;
+    return String_->size() - previousSize;
+}
+
+void TStdStringOutput::DoUndo(size_t len)
+{
+    Y_ABORT_UNLESS(len <= String_->size(), "trying to undo more bytes than actually written");
+    String_->resize(String_->size() - len);
+}
+
+void TStdStringOutput::DoWrite(const void* buf, size_t len)
+{
+    String_->append(static_cast<const char*>(buf), len);
+}
+
+void TStdStringOutput::DoWriteC(char c)
+{
+    String_->push_back(c);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+TStdStringStream::TStdStringStream()
+    : TEmbeddedString()
+    , TStdStringOutput(*TEmbeddedString::Ptr())
+{ }
+
+TStdStringStream::TStdStringStream(const std::string& string)
+    : TEmbeddedString(string)
+    , TStdStringOutput(*TEmbeddedString::Ptr())
+{ }
+
+TStdStringStream::TStdStringStream(std::string&& string)
+    : TEmbeddedString(std::move(string))
+    , TStdStringOutput(*TEmbeddedString::Ptr())
+{ }
+
+TStdStringStream::TStdStringStream(const TStdStringStream& other)
+    : TEmbeddedString(other.Str())
+    , TStdStringOutput(*TEmbeddedString::Ptr())
+{ }
+
+TStdStringStream::TStdStringStream(TStdStringStream&& other) noexcept
+    : TEmbeddedString(std::move(other).Str())
+    , TStdStringOutput(*TEmbeddedString::Ptr())
+{ }
+
+TStdStringStream& TStdStringStream::operator=(const TStdStringStream& other)
+{
+    // The embedded string reference remains valid; only its contents change.
+    Str() = other.Str();
+    return *this;
+}
+
+TStdStringStream& TStdStringStream::operator=(TStdStringStream&& other) noexcept
+{
+    // The embedded string reference remains valid; only its contents change.
+    Str() = std::move(other).Str();
+    return *this;
+}
+
+TStdStringStream::~TStdStringStream() = default;
+
+TStdStringStream::operator bool() const noexcept
+{
+    return !Empty();
+}
+
+std::string& TStdStringStream::Str() & noexcept
+{
+    return *Ptr();
+}
+
+const std::string& TStdStringStream::Str() const& noexcept
+{
+    return *Ptr();
+}
+
+std::string&& TStdStringStream::Str() && noexcept
+{
+    return std::move(*Ptr());
+}
+
+const char* TStdStringStream::Data() const noexcept
+{
+    return Ptr()->data();
+}
+
+size_t TStdStringStream::Size() const noexcept
+{
+    return Ptr()->size();
+}
+
+bool TStdStringStream::Empty() const noexcept
+{
+    return Ptr()->empty();
+}
+
+void TStdStringStream::Clear()
+{
+    Str().clear();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT