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b6d8a60aba
Commitscf112c12anda0dc8271were a little too hasty in getting rid of the pg_ prefixes where we use pread(), pwrite() and vectored variants. We dropped support for ancient Unixes where we needed to use lseek() to implement replacements for those, but it turns out that Windows also changes the current position even when you pass in an offset to ReadFile() and WriteFile() if the file handle is synchronous, despite its documentation saying otherwise. Switching to asynchronous file handles would fix that, but have other complications. For now let's just put back the pg_ prefix and add some comments to highlight the non-standard side-effect, which we can now describe as Windows-only. Reported-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Discussion: https://postgr.es/m/20220923202439.GA1156054%40nathanxps13
44 lines
812 B
C
44 lines
812 B
C
/*-------------------------------------------------------------------------
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*
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* preadv.c
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* Implementation of preadv(2) for platforms that lack one.
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*
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* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/port/preadv.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#include <unistd.h>
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#include "port/pg_iovec.h"
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ssize_t
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pg_preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset)
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{
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ssize_t sum = 0;
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ssize_t part;
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for (int i = 0; i < iovcnt; ++i)
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{
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part = pg_pread(fd, iov[i].iov_base, iov[i].iov_len, offset);
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if (part < 0)
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{
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if (i == 0)
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return -1;
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else
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return sum;
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}
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sum += part;
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offset += part;
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if (part < iov[i].iov_len)
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return sum;
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}
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return sum;
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}
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