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Commit2fd4e77

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committed
Modify libpq's pqexpbuffer to eliminate length restriction on how much
data can be formatted per call. This requires relying on vsnprintf().On machines that haven't got vsnprintf, link in the version frombackend/port/.
1 parent6759f43 commit2fd4e77

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3 files changed

+92
-55
lines changed

3 files changed

+92
-55
lines changed

‎src/interfaces/libpq/Makefile.in‎

Lines changed: 13 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
# Copyright (c) 1994, Regents of the University of California
77
#
88
# IDENTIFICATION
9-
# $Header: /cvsroot/pgsql/src/interfaces/libpq/Attic/Makefile.in,v 1.51 2000/01/10 15:41:30 momjian Exp $
9+
# $Header: /cvsroot/pgsql/src/interfaces/libpq/Attic/Makefile.in,v 1.52 2000/01/17 02:59:46 tgl Exp $
1010
#
1111
#-------------------------------------------------------------------------
1212

@@ -28,7 +28,7 @@ CFLAGS+= $(MBFLAGS)
2828
endif
2929

3030
OBJS= fe-auth.o fe-connect.o fe-exec.o fe-misc.o fe-print.o fe-lobj.o\
31-
pqexpbuffer.o dllist.o pqsignal.o
31+
pqexpbuffer.o dllist.o pqsignal.o @SNPRINTF@
3232

3333
ifdefMULTIBYTE
3434
OBJS+= common.o wchar.o conv.o big5.o
@@ -42,14 +42,19 @@ SHLIB_LINK+= $(findstring -lcrypt,$(LIBS))
4242
include$(SRCDIR)/Makefile.shlib
4343

4444

45-
# We need to compile this with special options for shared libs,
46-
# so we can't use the object in $(SRCDIR)/backend
45+
# We use several backend modules verbatim, but since we need to compile
46+
# with appropriate options to build a shared lib, we can't necessarily
47+
# use the same object files as the backend uses. Instead, symlink the
48+
# source files in here and build our own object file.
49+
4750
dllist.c:$(SRCDIR)/backend/lib/dllist.c
4851
-$(LN_S)$(SRCDIR)/backend/lib/dllist.c.
4952

53+
# this only gets done if configure finds system doesn't have snprintf()
54+
snprintf.c:$(SRCDIR)/backend/port/snprintf.c
55+
-$(LN_S)$(SRCDIR)/backend/port/snprintf.c.
56+
5057
ifdefMULTIBYTE
51-
# We need to compile this with special options for shared libs,
52-
# so we can't use the object in $(SRCDIR)/backend
5358
common.c:$(SRCDIR)/backend/utils/mb/common.c
5459
-$(LN_S)$(SRCDIR)/backend/utils/mb/common.c.
5560

@@ -63,6 +68,7 @@ big5.c: $(SRCDIR)/backend/utils/mb/big5.c
6368
-$(LN_S)$(SRCDIR)/backend/utils/mb/big5.c.
6469
endif
6570

71+
6672
# The following rules cause dependencies in the backend directory to
6773
# get made if they don't exist, but don't cause them to get remade if they
6874
# are out of date.
@@ -87,7 +93,7 @@ install-headers: libpq-fe.h libpq-int.h
8793

8894
clean: clean-shlib
8995
rm -f lib$(NAME).a$(OBJS)
90-
rm -f dllist.c common.c wchar.c conv.c big5.c
96+
rm -f dllist.csnprintf.ccommon.c wchar.c conv.c big5.c
9197

9298
dependdep:
9399
$(CC) -MM$(CFLAGS)*.c>depend

‎src/interfaces/libpq/pqexpbuffer.c‎

Lines changed: 73 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -8,11 +8,15 @@
88
*
99
* This module is essentially the same as the backend's StringInfo data type,
1010
* but it is intended for use in frontend libpq and client applications.
11-
* Thus, it does not rely on palloc(), elog(), nor vsnprintf().
11+
* Thus, it does not rely on palloc() nor elog().
12+
*
13+
* It does rely on vsnprintf(); if configure finds that libc doesn't provide
14+
* a usable vsnprintf(), then a copy of our own implementation of it will
15+
* be linked into libpq.
1216
*
1317
* Copyright (c) 1994, Regents of the University of California
1418
*
15-
* $Header: /cvsroot/pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.1 1999/08/31 01:37:37 tgl Exp $
19+
* $Header: /cvsroot/pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.2 2000/01/17 02:59:46 tgl Exp $
1620
*
1721
*-------------------------------------------------------------------------
1822
*/
@@ -148,27 +152,47 @@ enlargePQExpBuffer(PQExpBuffer str, int needed)
148152
* and insert it into str. More space is allocated to str if necessary.
149153
* This is a convenience routine that does the same thing as
150154
* resetPQExpBuffer() followed by appendPQExpBuffer().
151-
*
152-
* CAUTION: the frontend version of this routine WILL FAIL if the result of
153-
* the sprintf formatting operation exceeds 1KB of data (but the size of the
154-
* pre-existing string in the buffer doesn't matter). We could make it
155-
* support larger strings, but that requires vsnprintf() which is not
156-
* universally available. Currently there is no need for long strings to be
157-
* formatted in the frontend. We could support it, if necessary, by
158-
* conditionally including a vsnprintf emulation.
159155
*/
160156
void
161157
printfPQExpBuffer(PQExpBufferstr,constchar*fmt,...)
162158
{
163159
va_listargs;
164-
charbuffer[1024];
165-
166-
va_start(args,fmt);
167-
vsprintf(buffer,fmt,args);
168-
va_end(args);
160+
intavail,
161+
nprinted;
169162

170163
resetPQExpBuffer(str);
171-
appendPQExpBufferStr(str,buffer);
164+
165+
for (;;)
166+
{
167+
/*----------
168+
* Try to format the given string into the available space;
169+
* but if there's hardly any space, don't bother trying,
170+
* just fall through to enlarge the buffer first.
171+
*----------
172+
*/
173+
avail=str->maxlen-str->len-1;
174+
if (avail>16)
175+
{
176+
va_start(args,fmt);
177+
nprinted=vsnprintf(str->data+str->len,avail,
178+
fmt,args);
179+
va_end(args);
180+
/*
181+
* Note: some versions of vsnprintf return the number of chars
182+
* actually stored, but at least one returns -1 on failure.
183+
* Be conservative about believing whether the print worked.
184+
*/
185+
if (nprinted >=0&&nprinted<avail-1)
186+
{
187+
/* Success. Note nprinted does not include trailing null. */
188+
str->len+=nprinted;
189+
break;
190+
}
191+
}
192+
/* Double the buffer size and try again. */
193+
if (!enlargePQExpBuffer(str,str->maxlen))
194+
return;/* oops, out of memory */
195+
}
172196
}
173197

174198
/*------------------------
@@ -178,26 +202,45 @@ printfPQExpBuffer(PQExpBuffer str, const char *fmt,...)
178202
* and append it to whatever is already in str. More space is allocated
179203
* to str if necessary. This is sort of like a combination of sprintf and
180204
* strcat.
181-
*
182-
* CAUTION: the frontend version of this routine WILL FAIL if the result of
183-
* the sprintf formatting operation exceeds 1KB of data (but the size of the
184-
* pre-existing string in the buffer doesn't matter). We could make it
185-
* support larger strings, but that requires vsnprintf() which is not
186-
* universally available. Currently there is no need for long strings to be
187-
* formatted in the frontend. We could support it, if necessary, by
188-
* conditionally including a vsnprintf emulation.
189205
*/
190206
void
191207
appendPQExpBuffer(PQExpBufferstr,constchar*fmt,...)
192208
{
193209
va_listargs;
194-
charbuffer[1024];
195-
196-
va_start(args,fmt);
197-
vsprintf(buffer,fmt,args);
198-
va_end(args);
210+
intavail,
211+
nprinted;
199212

200-
appendPQExpBufferStr(str,buffer);
213+
for (;;)
214+
{
215+
/*----------
216+
* Try to format the given string into the available space;
217+
* but if there's hardly any space, don't bother trying,
218+
* just fall through to enlarge the buffer first.
219+
*----------
220+
*/
221+
avail=str->maxlen-str->len-1;
222+
if (avail>16)
223+
{
224+
va_start(args,fmt);
225+
nprinted=vsnprintf(str->data+str->len,avail,
226+
fmt,args);
227+
va_end(args);
228+
/*
229+
* Note: some versions of vsnprintf return the number of chars
230+
* actually stored, but at least one returns -1 on failure.
231+
* Be conservative about believing whether the print worked.
232+
*/
233+
if (nprinted >=0&&nprinted<avail-1)
234+
{
235+
/* Success. Note nprinted does not include trailing null. */
236+
str->len+=nprinted;
237+
break;
238+
}
239+
}
240+
/* Double the buffer size and try again. */
241+
if (!enlargePQExpBuffer(str,str->maxlen))
242+
return;/* oops, out of memory */
243+
}
201244
}
202245

203246
/*------------------------

‎src/interfaces/libpq/pqexpbuffer.h‎

Lines changed: 6 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -9,11 +9,15 @@
99
*
1010
* This module is essentially the same as the backend's StringInfo data type,
1111
* but it is intended for use in frontend libpq and client applications.
12-
* Thus, it does not rely on palloc(), elog(), nor vsnprintf().
12+
* Thus, it does not rely on palloc() nor elog().
13+
*
14+
* It does rely on vsnprintf(); if configure finds that libc doesn't provide
15+
* a usable vsnprintf(), then a copy of our own implementation of it will
16+
* be linked into libpq.
1317
*
1418
* Copyright (c) 1994, Regents of the University of California
1519
*
16-
* $Id: pqexpbuffer.h,v 1.1 1999/08/31 01:37:37 tgl Exp $
20+
* $Id: pqexpbuffer.h,v 1.2 2000/01/17 02:59:46 tgl Exp $
1721
*
1822
*-------------------------------------------------------------------------
1923
*/
@@ -116,14 +120,6 @@ extern int enlargePQExpBuffer(PQExpBuffer str, int needed);
116120
* and insert it into str. More space is allocated to str if necessary.
117121
* This is a convenience routine that does the same thing as
118122
* resetPQExpBuffer() followed by appendPQExpBuffer().
119-
*
120-
* CAUTION: the frontend version of this routine WILL FAIL if the result of
121-
* the sprintf formatting operation exceeds 1KB of data (but the size of the
122-
* pre-existing string in the buffer doesn't matter). We could make it
123-
* support larger strings, but that requires vsnprintf() which is not
124-
* universally available. Currently there is no need for long strings to be
125-
* formatted in the frontend. We could support it, if necessary, by
126-
* conditionally including a vsnprintf emulation.
127123
*/
128124
externvoidprintfPQExpBuffer(PQExpBufferstr,constchar*fmt,...);
129125

@@ -133,14 +129,6 @@ extern void printfPQExpBuffer(PQExpBuffer str, const char *fmt,...);
133129
* and append it to whatever is already in str. More space is allocated
134130
* to str if necessary. This is sort of like a combination of sprintf and
135131
* strcat.
136-
*
137-
* CAUTION: the frontend version of this routine WILL FAIL if the result of
138-
* the sprintf formatting operation exceeds 1KB of data (but the size of the
139-
* pre-existing string in the buffer doesn't matter). We could make it
140-
* support larger strings, but that requires vsnprintf() which is not
141-
* universally available. Currently there is no need for long strings to be
142-
* formatted in the frontend. We could support it, if necessary, by
143-
* conditionally including a vsnprintf emulation.
144132
*/
145133
externvoidappendPQExpBuffer(PQExpBufferstr,constchar*fmt,...);
146134

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