59 lines
1.1 KiB
C
59 lines
1.1 KiB
C
/*-------------------------------------------------------------------------
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*
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* pread.c
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* Implementation of pread(2) for platforms that lack one.
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*
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* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/port/pread.c
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*
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* Note that this implementation changes the current file position, unlike
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* the POSIX function, so we use the name pg_pread().
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#ifdef WIN32
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#include <windows.h>
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#else
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#include <unistd.h>
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#endif
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ssize_t
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pg_pread(int fd, void *buf, size_t size, off_t offset)
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{
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#ifdef WIN32
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OVERLAPPED overlapped = {0};
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HANDLE handle;
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DWORD result;
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handle = (HANDLE) _get_osfhandle(fd);
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if (handle == INVALID_HANDLE_VALUE)
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{
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errno = EBADF;
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return -1;
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}
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overlapped.Offset = offset;
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if (!ReadFile(handle, buf, size, &result, &overlapped))
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{
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if (GetLastError() == ERROR_HANDLE_EOF)
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return 0;
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_dosmaperr(GetLastError());
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return -1;
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}
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return result;
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#else
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if (lseek(fd, offset, SEEK_SET) < 0)
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return -1;
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return read(fd, buf, size);
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#endif
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}
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