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Commit3fd2a79

Browse files
committed
Provide pg_pread() and pg_pwrite() for random I/O.
Forward to POSIX pread() and pwrite(), or emulate them if unavailable.The emulation is not perfect as the file position is changed, sowe'll put pg_ prefixes on the names to minimize the risk of confusionin future patches that might inadvertently try to mix pread() and read()on the same file descriptor.Author: Thomas MunroReviewed-by: Tom Lane, Jesper PedersenDiscussion:https://postgr.es/m/CAEepm=02rapCpPR3ZGF2vW=SBHSdFYO_bz_f-wwWJonmA3APgw@mail.gmail.com
1 parentb43df56 commit3fd2a79

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8 files changed

+168
-0
lines changed

8 files changed

+168
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‎configure

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Original file line numberDiff line numberDiff line change
@@ -15539,6 +15539,32 @@ esac
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fi
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ac_fn_c_check_func "$LINENO" "pread" "ac_cv_func_pread"
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if test "x$ac_cv_func_pread" = xyes; then :
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$as_echo "#define HAVE_PREAD 1" >>confdefs.h
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else
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case " $LIBOBJS " in
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*" pread.$ac_objext "* ) ;;
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*) LIBOBJS="$LIBOBJS pread.$ac_objext"
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;;
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esac
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fi
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ac_fn_c_check_func "$LINENO" "pwrite" "ac_cv_func_pwrite"
15556+
if test "x$ac_cv_func_pwrite" = xyes; then :
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$as_echo "#define HAVE_PWRITE 1" >>confdefs.h
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else
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case " $LIBOBJS " in
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*" pwrite.$ac_objext "* ) ;;
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*) LIBOBJS="$LIBOBJS pwrite.$ac_objext"
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;;
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esac
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fi
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ac_fn_c_check_func "$LINENO" "random" "ac_cv_func_random"
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if test "x$ac_cv_func_random" = xyes; then :
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$as_echo "#define HAVE_RANDOM 1" >>confdefs.h

‎configure.in

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@@ -1698,6 +1698,8 @@ AC_REPLACE_FUNCS(m4_normalize([
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getrusage
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inet_aton
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mkdtemp
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pread
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pwrite
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random
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rint
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srandom

‎src/include/pg_config.h.in

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@@ -438,6 +438,9 @@
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/* Define to 1 if you have the `ppoll' function. */
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#undef HAVE_PPOLL
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/* Define to 1 if you have the `pread' function. */
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#undef HAVE_PREAD
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/* Define to 1 if you have the `pstat' function. */
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#undef HAVE_PSTAT
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@@ -453,6 +456,9 @@
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/* Have PTHREAD_PRIO_INHERIT. */
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#undef HAVE_PTHREAD_PRIO_INHERIT
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/* Define to 1 if you have the `pwrite' function. */
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#undef HAVE_PWRITE
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/* Define to 1 if you have the `random' function. */
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#undef HAVE_RANDOM
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‎src/include/pg_config.h.win32

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@@ -322,12 +322,18 @@
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/* Define to 1 if you have the `ppoll' function. */
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/* #undef HAVE_PPOLL */
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/* Define to 1 if you have the `pread' function. */
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/* #undef HAVE_PREAD */
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/* Define to 1 if you have the `pstat' function. */
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/* #undef HAVE_PSTAT */
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/* Define to 1 if the PS_STRINGS thing exists. */
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/* #undef HAVE_PS_STRINGS */
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/* Define to 1 if you have the `pwrite' function. */
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/* #undef HAVE_PWRITE */
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/* Define to 1 if you have the `random' function. */
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/* #undef HAVE_RANDOM */
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‎src/include/port.h

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Original file line numberDiff line numberDiff line change
@@ -392,6 +392,23 @@ extern double rint(double x);
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externintinet_aton(constchar*cp,structin_addr*addr);
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#endif
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/*
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* Windows and older Unix don't have pread(2) and pwrite(2). We have
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* replacement functions, but they have slightly different semantics so we'll
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* use a name with a pg_ prefix to avoid confusion.
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*/
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#ifdefHAVE_PREAD
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#definepg_pread pread
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#else
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externssize_tpg_pread(intfd,void*buf,size_tnbyte,off_toffset);
404+
#endif
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#ifdefHAVE_PWRITE
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#definepg_pwrite pwrite
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#else
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externssize_tpg_pwrite(intfd,constvoid*buf,size_tnbyte,off_toffset);
410+
#endif
411+
395412
#if !HAVE_DECL_STRLCAT
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externsize_tstrlcat(char*dst,constchar*src,size_tsiz);
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#endif

‎src/port/pread.c

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@@ -0,0 +1,55 @@
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/*-------------------------------------------------------------------------
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*
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* pread.c
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* Implementation of pread(2) for platforms that lack one.
5+
*
6+
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
7+
*
8+
* IDENTIFICATION
9+
* src/port/pread.c
10+
*
11+
* Note that this implementation changes the current file position, unlike
12+
* the POSIX function, so we use the name pg_pread().
13+
*
14+
*-------------------------------------------------------------------------
15+
*/
16+
17+
18+
#include"postgres.h"
19+
20+
#ifdefWIN32
21+
#include<windows.h>
22+
#else
23+
#include<unistd.h>
24+
#endif
25+
26+
ssize_t
27+
pg_pread(intfd,void*buf,size_tsize,off_toffset)
28+
{
29+
#ifdefWIN32
30+
OVERLAPPEDoverlapped= {0};
31+
HANDLEhandle;
32+
DWORDresult;
33+
34+
handle= (HANDLE)_get_osfhandle(fd);
35+
if (handle==INVALID_HANDLE_VALUE)
36+
{
37+
errno=EBADF;
38+
return-1;
39+
}
40+
41+
overlapped.Offset=offset;
42+
if (!ReadFile(handle,buf,size,&result,&overlapped))
43+
{
44+
_dosmaperr(GetLastError());
45+
return-1;
46+
}
47+
48+
returnresult;
49+
#else
50+
if (lseek(fd,offset,SEEK_SET)<0)
51+
return-1;
52+
53+
returnread(fd,buf,size);
54+
#endif
55+
}

‎src/port/pwrite.c

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@@ -0,0 +1,55 @@
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/*-------------------------------------------------------------------------
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*
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* pwrite.c
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* Implementation of pwrite(2) for platforms that lack one.
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
9+
* src/port/pwrite.c
10+
*
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* Note that this implementation changes the current file position, unlike
12+
* the POSIX function, so we use the name pg_write().
13+
*
14+
*-------------------------------------------------------------------------
15+
*/
16+
17+
18+
#include"postgres.h"
19+
20+
#ifdefWIN32
21+
#include<windows.h>
22+
#else
23+
#include<unistd.h>
24+
#endif
25+
26+
ssize_t
27+
pg_pwrite(intfd,constvoid*buf,size_tsize,off_toffset)
28+
{
29+
#ifdefWIN32
30+
OVERLAPPEDoverlapped= {0};
31+
HANDLEhandle;
32+
DWORDresult;
33+
34+
handle= (HANDLE)_get_osfhandle(fd);
35+
if (handle==INVALID_HANDLE_VALUE)
36+
{
37+
errno=EBADF;
38+
return-1;
39+
}
40+
41+
overlapped.Offset=offset;
42+
if (!WriteFile(handle,buf,size,&result,&overlapped))
43+
{
44+
_dosmaperr(GetLastError());
45+
return-1;
46+
}
47+
48+
returnresult;
49+
#else
50+
if (lseek(fd,offset,SEEK_SET)<0)
51+
return-1;
52+
53+
returnwrite(fd,buf,size);
54+
#endif
55+
}

‎src/tools/msvc/Mkvcbuild.pm

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Original file line numberDiff line numberDiff line change
@@ -97,6 +97,7 @@ sub mkvcbuild
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srandom.c getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
9898
erand48.c snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c
9999
dirent.c dlopen.c getopt.c getopt_long.c
100+
pread.c pwrite.c
100101
pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
101102
pqsignal.c mkdtemp.c qsort.c qsort_arg.c quotes.c system.c
102103
sprompt.c strerror.c tar.c thread.c

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