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74 lines
1.5 KiB
C++
74 lines
1.5 KiB
C++
#pragma once
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#include <unistd.h>
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#include <errno.h>
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#include <Poco/NumberFormatter.h>
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#include <DB/Core/Exception.h>
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#include <DB/Core/ErrorCodes.h>
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#include <DB/IO/ReadBuffer.h>
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#include <DB/IO/BufferWithOwnMemory.h>
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namespace DB
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{
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/** Работает с готовым файловым дескриптором. Не открывает и не закрывает файл.
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*/
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class ReadBufferFromFileDescriptor : public BufferWithOwnMemory<ReadBuffer>
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{
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protected:
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int fd;
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bool nextImpl()
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{
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size_t bytes_read = 0;
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while (!bytes_read)
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{
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ssize_t res = ::read(fd, internal_buffer.begin(), internal_buffer.size());
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if (!res)
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break;
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if (-1 == res && errno != EINTR)
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throwFromErrno("Cannot read from file " + getFileName(), ErrorCodes::CANNOT_READ_FROM_FILE_DESCRIPTOR);
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if (res > 0)
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bytes_read += res;
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}
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if (bytes_read)
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working_buffer.resize(bytes_read);
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else
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return false;
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return true;
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}
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/// Имя или описание файла
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virtual std::string getFileName()
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{
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return "(fd = " + Poco::NumberFormatter::format(fd) + ")";
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}
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public:
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ReadBufferFromFileDescriptor(int fd_, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE)
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: BufferWithOwnMemory<ReadBuffer>(buf_size), fd(fd_) {}
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int getFD()
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{
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return fd;
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}
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off_t seek(off_t offset, int whence = SEEK_SET)
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{
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off_t res = lseek(fd, offset, whence);
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if (-1 == res)
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throwFromErrno("Cannot seek through file " + getFileName(), ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
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return res;
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}
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};
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}
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