Seek reworking.

dbms/src/Disks/tests/gtest_disk.cpp

@@ -92,6 +92,41 @@ TYPED_TEST(DiskTest, writeFile)
 }
 
 
+TYPED_TEST(DiskTest, readFile)
+{
+	const auto & disk = this->getDisk();
+
+	{
+		std::unique_ptr<DB::WriteBuffer> out = disk->writeFile("test_file");
+		writeString("test data", *out);
+	}
+
+	// Test SEEK_SET
+	{
+		DB::String data;
+		std::unique_ptr<DB::SeekableReadBuffer> in = disk->readFile("test_file");
+		in->seek(5, SEEK_SET);
+		readString(data, *in);
+		EXPECT_EQ("data", data);
+	}
+
+	// Test SEEK_CUR
+	{
+		std::unique_ptr<DB::SeekableReadBuffer> in = disk->readFile("test_file");
+		String buf(4, '0');
+
+		in->readStrict(buf.data(), 4);
+		EXPECT_EQ("test", buf);
+
+		// Skip whitespace
+		in->seek(1, SEEK_CUR);
+
+		in->readStrict(buf.data(), 4);
+		EXPECT_EQ("data", buf);
+	}
+}
+
+
 TYPED_TEST(DiskTest, iterateDirectory)
 {
     const auto & disk = this->getDisk();

dbms/src/IO/ReadBufferFromMemory.cpp

@@ -0,0 +1,45 @@
+#include "ReadBufferFromMemory.h"
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+	extern const int CANNOT_SEEK_THROUGH_FILE;
+	extern const int SEEK_POSITION_OUT_OF_BOUND;
+}
+
+off_t ReadBufferFromMemory::seek(off_t offset, int whence)
+{
+	if (whence == SEEK_SET)
+	{
+		if (offset >= 0 && working_buffer.begin() + offset < working_buffer.end())
+		{
+			pos = working_buffer.begin() + offset;
+			return size_t(pos - working_buffer.begin());
+		}
+		else
+			throw Exception("Seek position is out of bounds. "
+				   "Offset: " + std::to_string(offset) +
+				   ", Max: " + std::to_string(size_t(working_buffer.end() - working_buffer.begin())),
+				   ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
+	}
+	else if (whence == SEEK_CUR)
+	{
+		Position new_pos = pos + offset;
+		if (new_pos >= working_buffer.begin() && new_pos < working_buffer.end())
+		{
+			pos = new_pos;
+			return size_t(pos - working_buffer.begin());
+		}
+		else
+			throw Exception("Seek position is out of bounds. "
+				  "Offset: " + std::to_string(offset) +
+				  ", Max: " + std::to_string(size_t(working_buffer.end() - working_buffer.begin())),
+				  ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
+	}
+	else
+		throw Exception("Only SEEK_SET and SEEK_CUR seek modes allowed.", ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
+}
+
+}

dbms/src/IO/ReadBufferFromMemory.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <IO/ReadBuffer.h>
 #include "SeekableReadBuffer.h"
 
 
@@ -23,7 +22,7 @@ public:
     ReadBufferFromMemory(const signed char * buf, size_t size)
         : SeekableReadBuffer(const_cast<char *>(reinterpret_cast<const char *>(buf)), size, 0) {}
 
-    off_t seek(off_t, int) override { return 0; }
+	off_t seek(off_t off, int whence) override;
 };
 
 }

dbms/src/IO/ReadBufferFromS3.cpp

@@ -17,6 +17,8 @@ namespace DB
 namespace ErrorCodes
 {
     extern const int S3_ERROR;
+    extern const int CANNOT_SEEK_THROUGH_FILE;
+    extern const int SEEK_POSITION_OUT_OF_BOUND;
 }
 
 
@@ -49,10 +51,21 @@ bool ReadBufferFromS3::nextImpl()
     return true;
 }
 
-off_t ReadBufferFromS3::seek(off_t offset_, int)
+off_t ReadBufferFromS3::seek(off_t offset_, int whence)
 {
-    if (!initialized && offset_)
-        offset = offset_;
+	if (initialized)
+		throw Exception("Seek is allowed only before first read attempt from the buffer.",
+		                ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
+
+	if (whence != SEEK_SET)
+		throw Exception("Only SEEK_SET mode is allowed.",
+		                ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
+
+	if (offset_ < 0)
+		throw Exception("Seek position is out of bounds. Offset: " + std::to_string(offset_),
+		                ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
+
+    offset = offset_;
 
     return offset;
 }

dbms/src/IO/tests/gtest_aio_seek_back_after_eof.cpp

@@ -50,7 +50,7 @@ TEST(ReadBufferAIOTest, TestReadAfterAIO)
     EXPECT_TRUE(testbuf.eof());
 
 
-    testbuf.seek(data.length() - 100);
+    testbuf.seek(data.length() - 100, SEEK_SET);
 
     std::string smalldata;
     smalldata.resize(100);
@@ -59,7 +59,7 @@ TEST(ReadBufferAIOTest, TestReadAfterAIO)
     EXPECT_TRUE(testbuf.eof());
 
 
-    testbuf.seek(0);
+    testbuf.seek(0, SEEK_SET);
     std::string repeatdata;
     repeatdata.resize(data.length());
     size_t read_after_eof_big = testbuf.read(repeatdata.data(), repeatdata.size());

dbms/src/Storages/tests/storage_log.cpp

@@ -30,7 +30,7 @@ try
     context.setPath("./");
 
     DiskPtr disk = std::make_unique<DiskLocal>("default", "./", 0);
-    StoragePtr table = StorageLog::create(disk, "./", StorageID("test", "test"), ColumnsDescription{names_and_types}, ConstraintsDescription{}, 1048576);
+    StoragePtr table = StorageLog::create(disk, "table", StorageID("test", "test"), ColumnsDescription{names_and_types}, ConstraintsDescription{}, 1048576);
 
     table->startup();
 

utils/check-marks/main.cpp

@@ -65,7 +65,7 @@ void checkCompressedHeaders(const std::string & mrk_path, const std::string & bi
 
         out << "Mark " << mark_num << ", points to " << offset_in_compressed_file << ", " << offset_in_decompressed_block << ". ";
 
-        bin_in.seek(offset_in_compressed_file);
+        bin_in.seek(offset_in_compressed_file, SEEK_SET);
         auto sizes = stat(bin_in, out);
 
         out << "Block sizes: " << sizes.first << ", " << sizes.second << '\n' << DB::flush;