Add blob utility methods

src/fb-cpp/Attachment.cpp

@@ -116,6 +116,86 @@ void Attachment::resetSession()
 		&statusWrapper, nullptr, 0, "alter session reset", SQL_DIALECT_V6, nullptr, nullptr, nullptr, nullptr);
 }
 
+std::optional<std::string> Attachment::blobIdToString(
+	Transaction& transaction, std::optional<BlobId> blobId, const BlobOptions& options)
+{
+	if (!blobId.has_value())
+		return std::nullopt;
+
+	Blob reader{*this, transaction, blobId.value(), options};
+	const auto lengthHint = reader.getLength();
+	std::string value;
+	value.reserve(lengthHint);
+	std::vector<char> buffer(std::numeric_limits<std::uint16_t>::max());
+
+	for (;;)
+	{
+		const auto read = reader.readSegment(buffer);
+
+		if (read == 0u)
+			break;
+
+		value.append(buffer.data(), read);
+	}
+
+	reader.close();
+
+	return value;
+}
+
+std::optional<std::vector<std::byte>> Attachment::blobIdToBytes(
+	Transaction& transaction, std::optional<BlobId> blobId, const BlobOptions& options)
+{
+	if (!blobId.has_value())
+		return std::nullopt;
+
+	Blob reader{*this, transaction, blobId.value(), options};
+	const auto lengthHint = reader.getLength();
+	std::vector<std::byte> value;
+	value.reserve(lengthHint);
+	std::vector<std::byte> buffer(std::numeric_limits<std::uint16_t>::max());
+
+	for (;;)
+	{
+		const auto read = reader.readSegment(buffer);
+
+		if (read == 0u)
+			break;
+
+		value.insert(value.end(), buffer.data(), buffer.data() + read);
+	}
+
+	reader.close();
+
+	return value;
+}
+
+std::optional<BlobId> Attachment::blobIdFromString(
+	Transaction& transaction, std::optional<std::string_view> value, const BlobOptions& options)
+{
+	if (!value.has_value())
+		return std::nullopt;
+
+	Blob writer{*this, transaction, options};
+	writer.write(std::span<const char>{value->data(), value->size()});
+	writer.close();
+
+	return writer.getId();
+}
+
+std::optional<BlobId> Attachment::blobIdFromBytes(
+	Transaction& transaction, std::optional<std::span<const std::byte>> value, const BlobOptions& options)
+{
+	if (!value.has_value())
+		return std::nullopt;
+
+	Blob writer{*this, transaction, options};
+	writer.write(value.value());
+	writer.close();
+
+	return writer.getId();
+}
+
 bool Attachment::execute(Transaction& transaction, std::string_view sql, const StatementOptions& options)
 {
 	Statement statement{*this, transaction, sql, options};

src/fb-cpp/Attachment.h

@@ -27,6 +27,7 @@
 
 #include "fb-cpp-export.h"
 #include "fb-api.h"
+#include "Blob.h"
 #include "RowSet.h"
 #include "SmartPtrs.h"
 #include "StatementOptions.h"
@@ -297,6 +298,30 @@ namespace fbcpp
 			return handle;
 		}
 
+		///
+		/// Reads a blob as a string, or returns nullopt for a null identifier.
+		///
+		std::optional<std::string> blobIdToString(
+			Transaction& transaction, std::optional<BlobId> blobId, const BlobOptions& options = {});
+
+		///
+		/// Reads a blob as bytes, or returns nullopt for a null identifier.
+		///
+		std::optional<std::vector<std::byte>> blobIdToBytes(
+			Transaction& transaction, std::optional<BlobId> blobId, const BlobOptions& options = {});
+
+		///
+		/// Creates a blob from a string, or returns nullopt for a null value.
+		///
+		std::optional<BlobId> blobIdFromString(
+			Transaction& transaction, std::optional<std::string_view> value, const BlobOptions& options = {});
+
+		///
+		/// Creates a blob from bytes, or returns nullopt for a null value.
+		///
+		std::optional<BlobId> blobIdFromBytes(
+			Transaction& transaction, std::optional<std::span<const std::byte>> value, const BlobOptions& options = {});
+
 		///
 		/// Disconnects from the database.
 		///

src/test/Attachment.cpp

@@ -30,6 +30,8 @@
 #include "fb-cpp/Transaction.h"
 #include <cstddef>
 #include <exception>
+#include <limits>
+#include <string>
 #include <vector>
 
 
@@ -95,6 +97,63 @@ BOOST_AUTO_TEST_CASE(createDatabaseWithForcedWritesOff)
 	transaction.commit();
 }
 
+BOOST_AUTO_TEST_CASE(blobIdConversions)
+{
+	const auto database = getTempFile("Attachment-blobIdConversions.fdb");
+
+	Attachment attachment{getClient(), database,
+		AttachmentOptions().setCreateDatabase(true).setForcedWrites(false).setConnectionCharSet("UTF8")};
+	FbDropDatabase attachmentDrop{attachment};
+
+	Transaction transaction{attachment};
+	const auto streamOptions = BlobOptions().setType(BlobType::STREAM);
+	const auto multiSegmentSize =
+		static_cast<std::size_t>(std::numeric_limits<std::uint16_t>::max()) + std::size_t{1024};
+
+	std::string text(multiSegmentSize, '\0');
+	for (std::size_t i = 0; i < text.size(); ++i)
+		text[i] = static_cast<char>(i % 251);
+
+	const auto textBlobId = attachment.blobIdFromString(transaction, text, streamOptions);
+	BOOST_REQUIRE(textBlobId.has_value());
+	BOOST_CHECK(textBlobId->isEmpty() == false);
+
+	const auto textResult = attachment.blobIdToString(transaction, textBlobId, streamOptions);
+	BOOST_REQUIRE(textResult.has_value());
+	BOOST_CHECK_EQUAL(*textResult, text);
+
+	std::vector<std::byte> bytes(multiSegmentSize);
+	for (std::size_t i = 0; i < bytes.size(); ++i)
+		bytes[i] = static_cast<std::byte>(i % 251);
+
+	const auto bytesBlobId = attachment.blobIdFromBytes(transaction, bytes, streamOptions);
+	BOOST_REQUIRE(bytesBlobId.has_value());
+	BOOST_CHECK(bytesBlobId->isEmpty() == false);
+
+	const auto bytesResult = attachment.blobIdToBytes(transaction, bytesBlobId, streamOptions);
+	BOOST_REQUIRE(bytesResult.has_value());
+	BOOST_CHECK(*bytesResult == bytes);
+
+	std::string emptyText;
+	const auto emptyTextBlobId = attachment.blobIdFromString(transaction, emptyText, streamOptions);
+	BOOST_REQUIRE(emptyTextBlobId.has_value());
+	const auto emptyTextResult = attachment.blobIdToString(transaction, emptyTextBlobId, streamOptions);
+	BOOST_REQUIRE(emptyTextResult.has_value());
+	BOOST_CHECK(emptyTextResult->empty());
+
+	std::vector<std::byte> emptyBytes;
+	const auto emptyBytesBlobId = attachment.blobIdFromBytes(transaction, emptyBytes, streamOptions);
+	BOOST_REQUIRE(emptyBytesBlobId.has_value());
+	const auto emptyBytesResult = attachment.blobIdToBytes(transaction, emptyBytesBlobId, streamOptions);
+	BOOST_REQUIRE(emptyBytesResult.has_value());
+	BOOST_CHECK(emptyBytesResult->empty());
+
+	BOOST_CHECK(!attachment.blobIdFromString(transaction, std::nullopt, streamOptions).has_value());
+	BOOST_CHECK(!attachment.blobIdFromBytes(transaction, std::nullopt, streamOptions).has_value());
+	BOOST_CHECK(!attachment.blobIdToString(transaction, std::nullopt, streamOptions).has_value());
+	BOOST_CHECK(!attachment.blobIdToBytes(transaction, std::nullopt, streamOptions).has_value());
+}
+
 BOOST_AUTO_TEST_CASE(executePreparesAndExecutesStatement)
 {
 	const auto database = getTempFile("Attachment-executePreparesAndExecutesStatement.fdb");