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fe-exec.c
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fe-exec.c
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/*-------------------------------------------------------------------------
*
* fe-exec.c
* functions related to sending a query down to the backend
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.122.2.3 2006/05/21 20:20:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres_fe.h"
#include <errno.h>
#include <ctype.h>
#include <fcntl.h>
#include "libpq-fe.h"
#include "libpq-int.h"
#include "mb/pg_wchar.h"
#ifdef WIN32
#include "win32.h"
#else
#include <unistd.h>
#endif
/* keep this in same order as ExecStatusType in libpq-fe.h */
char *const pgresStatus[] = {
"PGRES_EMPTY_QUERY",
"PGRES_COMMAND_OK",
"PGRES_TUPLES_OK",
"PGRES_COPY_OUT",
"PGRES_COPY_IN",
"PGRES_BAD_RESPONSE",
"PGRES_NONFATAL_ERROR",
"PGRES_FATAL_ERROR"
};
/*
* static state needed by PQescapeString and PQescapeBytea; initialize to
* values that result in backward-compatible behavior
*/
int PQ_static_client_encoding = PG_SQL_ASCII;
static bool static_std_strings = false;
/* Note: DONOTICE macro will work if applied to either PGconn or PGresult */
#define DONOTICE(conn,message) \
((*(conn)->noticeHook) ((conn)->noticeArg, (message)))
static void pqCatenateResultError(PGresult *res, const char *msg);
static void saveErrorResult(PGconn *conn);
static PGresult *prepareAsyncResult(PGconn *conn);
static int addTuple(PGresult *res, PGresAttValue * tup);
static void parseInput(PGconn *conn);
static void handleSendFailure(PGconn *conn);
static int getRowDescriptions(PGconn *conn);
static int getAnotherTuple(PGconn *conn, int binary);
static int getNotify(PGconn *conn);
static int getNotice(PGconn *conn);
/* ---------------
* Escaping arbitrary strings to get valid SQL strings/identifiers.
*
* Replaces "'" with "''", and if not std_strings, replaces "\" with "\\".
* length is the length of the buffer pointed to by
* from. The buffer at to must be at least 2*length + 1 characters
* long. A terminating NUL character is written.
* ---------------
*/
static size_t
PQescapeStringInternal(PGconn *conn,
char *to, const char *from, size_t length,
int *error,
int encoding, bool std_strings)
{
const char *source = from;
char *target = to;
size_t remaining = length;
if (error)
*error = 0;
while (remaining > 0 && *source != '\0')
{
char c = *source;
int len;
int i;
/* Fast path for plain ASCII */
if (!IS_HIGHBIT_SET(c))
{
/* Apply quoting if needed */
if (c == '\'' ||
(c == '\\' && !std_strings))
*target++ = c;
/* Copy the character */
*target++ = c;
source++;
remaining--;
continue;
}
/* Slow path for possible multibyte characters */
len = pg_encoding_mblen(encoding, source);
/* Copy the character */
for (i = 0; i < len; i++)
{
if (remaining == 0 || *source == '\0')
break;
*target++ = *source++;
remaining--;
}
/*
* If we hit premature end of string (ie, incomplete multibyte
* character), try to pad out to the correct length with spaces.
* We may not be able to pad completely, but we will always be able
* to insert at least one pad space (since we'd not have quoted a
* multibyte character). This should be enough to make a string that
* the server will error out on.
*/
if (i < len)
{
if (error)
*error = 1;
if (conn)
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("incomplete multibyte character\n"));
for (; i < len; i++)
{
if (((size_t) (target - to)) / 2 >= length)
break;
*target++ = ' ';
}
break;
}
}
/* Write the terminating NUL character. */
*target = '\0';
return target - to;
}
size_t
PQescapeStringConn(PGconn *conn,
char *to, const char *from, size_t length,
int *error)
{
if (!conn)
{
/* force empty-string result */
*to = '\0';
if (error)
*error = 1;
return 0;
}
return PQescapeStringInternal(conn, to, from, length, error,
conn->client_encoding,
static_std_strings);
}
size_t
PQescapeString(char *to, const char *from, size_t length)
{
return PQescapeStringInternal(NULL, to, from, length, NULL,
PQ_static_client_encoding,
static_std_strings);
}
/*
* PQescapeBytea - converts from binary string to the
* minimal encoding necessary to include the string in an SQL
* INSERT statement with a bytea type column as the target.
*
* The following transformations are applied
* '\0' == ASCII 0 == \000
* '\'' == ASCII 39 == ''
* '\\' == ASCII 92 == \\
* anything < 0x20, or > 0x7e ---> \ooo
* (where ooo is an octal expression)
* If not std_strings, all backslashes sent to the output are doubled.
*/
static unsigned char *
PQescapeByteaInternal(PGconn *conn,
const unsigned char *from, size_t from_length,
size_t *to_length, bool std_strings)
{
const unsigned char *vp;
unsigned char *rp;
unsigned char *result;
size_t i;
size_t len;
size_t bslash_len = (std_strings ? 1 : 2);
/*
* empty string has 1 char ('\0')
*/
len = 1;
vp = from;
for (i = from_length; i > 0; i--, vp++)
{
if (*vp < 0x20 || *vp > 0x7e)
len += bslash_len + 3;
else if (*vp == '\'')
len += 2;
else if (*vp == '\\')
len += bslash_len + bslash_len;
else
len++;
}
*to_length = len;
rp = result = (unsigned char *) malloc(len);
if (rp == NULL)
{
if (conn)
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("out of memory\n"));
return NULL;
}
vp = from;
for (i = from_length; i > 0; i--, vp++)
{
if (*vp < 0x20 || *vp > 0x7e)
{
if (!std_strings)
*rp++ = '\\';
(void) sprintf((char *) rp, "\\%03o", *vp);
rp += 4;
}
else if (*vp == '\'')
{
*rp++ = '\'';
*rp++ = '\'';
}
else if (*vp == '\\')
{
if (!std_strings)
{
*rp++ = '\\';
*rp++ = '\\';
}
*rp++ = '\\';
*rp++ = '\\';
}
else
*rp++ = *vp;
}
*rp = '\0';
return result;
}
unsigned char *
PQescapeByteaConn(PGconn *conn,
const unsigned char *from, size_t from_length,
size_t *to_length)
{
if (!conn)
return NULL;
return PQescapeByteaInternal(conn, from, from_length, to_length,
static_std_strings);
}
unsigned char *
PQescapeBytea(unsigned char *from, size_t from_length, size_t *to_length)
{
return PQescapeByteaInternal(NULL, from, from_length, to_length,
static_std_strings);
}
/*
* PQunescapeBytea - converts the null terminated string representation
* of a bytea, strtext, into binary, filling a buffer. It returns a
* pointer to the buffer which is NULL on error, and the size of the
* buffer in retbuflen. The pointer may subsequently be used as an
* argument to the function PQfreemem.
*
* The following transformations are reversed:
* '\0' == ASCII 0 == \000
* '\'' == ASCII 39 == \'
* '\\' == ASCII 92 == \\
*
* States:
* 0 normal 0->1->2->3->4
* 1 \ 1->5
* 2 \0 1->6
* 3 \00
* 4 \000
* 5 \'
* 6 \\
*/
unsigned char *
PQunescapeBytea(unsigned char *strtext, size_t *retbuflen)
{
size_t buflen;
unsigned char *buffer,
*sp,
*bp;
unsigned int state = 0;
if (strtext == NULL)
return NULL;
buflen = strlen(strtext); /* will shrink, also we discover if
* strtext */
buffer = (unsigned char *) malloc(buflen); /* isn't NULL terminated */
if (buffer == NULL)
return NULL;
for (bp = buffer, sp = strtext; *sp != '\0'; bp++, sp++)
{
switch (state)
{
case 0:
if (*sp == '\\')
state = 1;
*bp = *sp;
break;
case 1:
if (*sp == '\'') /* state=5 */
{ /* replace \' with 39 */
bp--;
*bp = '\'';
buflen--;
state = 0;
}
else if (*sp == '\\') /* state=6 */
{ /* replace \\ with 92 */
bp--;
*bp = '\\';
buflen--;
state = 0;
}
else
{
if (isdigit(*sp))
state = 2;
else
state = 0;
*bp = *sp;
}
break;
case 2:
if (isdigit(*sp))
state = 3;
else
state = 0;
*bp = *sp;
break;
case 3:
if (isdigit(*sp)) /* state=4 */
{
int v;
bp -= 3;
sscanf(sp - 2, "%03o", &v);
*bp = v;
buflen -= 3;
state = 0;
}
else
{
*bp = *sp;
state = 0;
}
break;
}
}
buffer = realloc(buffer, buflen);
if (buffer == NULL)
return NULL;
*retbuflen = buflen;
return buffer;
}
/* ----------------
* Space management for PGresult.
*
* Formerly, libpq did a separate malloc() for each field of each tuple
* returned by a query. This was remarkably expensive --- malloc/free
* consumed a sizable part of the application's runtime. And there is
* no real need to keep track of the fields separately, since they will
* all be freed together when the PGresult is released. So now, we grab
* large blocks of storage from malloc and allocate space for query data
* within these blocks, using a trivially simple allocator. This reduces
* the number of malloc/free calls dramatically, and it also avoids
* fragmentation of the malloc storage arena.
* The PGresult structure itself is still malloc'd separately. We could
* combine it with the first allocation block, but that would waste space
* for the common case that no extra storage is actually needed (that is,
* the SQL command did not return tuples).
*
* We also malloc the top-level array of tuple pointers separately, because
* we need to be able to enlarge it via realloc, and our trivial space
* allocator doesn't handle that effectively. (Too bad the FE/BE protocol
* doesn't tell us up front how many tuples will be returned.)
* All other subsidiary storage for a PGresult is kept in PGresult_data blocks
* of size PGRESULT_DATA_BLOCKSIZE. The overhead at the start of each block
* is just a link to the next one, if any. Free-space management info is
* kept in the owning PGresult.
* A query returning a small amount of data will thus require three malloc
* calls: one for the PGresult, one for the tuples pointer array, and one
* PGresult_data block.
*
* Only the most recently allocated PGresult_data block is a candidate to
* have more stuff added to it --- any extra space left over in older blocks
* is wasted. We could be smarter and search the whole chain, but the point
* here is to be simple and fast. Typical applications do not keep a PGresult
* around very long anyway, so some wasted space within one is not a problem.
*
* Tuning constants for the space allocator are:
* PGRESULT_DATA_BLOCKSIZE: size of a standard allocation block, in bytes
* PGRESULT_ALIGN_BOUNDARY: assumed alignment requirement for binary data
* PGRESULT_SEP_ALLOC_THRESHOLD: objects bigger than this are given separate
* blocks, instead of being crammed into a regular allocation block.
* Requirements for correct function are:
* PGRESULT_ALIGN_BOUNDARY must be a multiple of the alignment requirements
* of all machine data types. (Currently this is set from configure
* tests, so it should be OK automatically.)
* PGRESULT_SEP_ALLOC_THRESHOLD + PGRESULT_BLOCK_OVERHEAD <=
* PGRESULT_DATA_BLOCKSIZE
* pqResultAlloc assumes an object smaller than the threshold will fit
* in a new block.
* The amount of space wasted at the end of a block could be as much as
* PGRESULT_SEP_ALLOC_THRESHOLD, so it doesn't pay to make that too large.
* ----------------
*/
#ifdef MAX
#undef MAX
#endif
#define MAX(a,b) ((a) > (b) ? (a) : (b))
#define PGRESULT_DATA_BLOCKSIZE 2048
#define PGRESULT_ALIGN_BOUNDARY MAXIMUM_ALIGNOF /* from configure */
#define PGRESULT_BLOCK_OVERHEAD MAX(sizeof(PGresult_data), PGRESULT_ALIGN_BOUNDARY)
#define PGRESULT_SEP_ALLOC_THRESHOLD (PGRESULT_DATA_BLOCKSIZE / 2)
/*
* PQmakeEmptyPGresult
* returns a newly allocated, initialized PGresult with given status.
* If conn is not NULL and status indicates an error, the conn's
* errorMessage is copied.
*
* Note this is exported --- you wouldn't think an application would need
* to build its own PGresults, but this has proven useful in both libpgtcl
* and the Perl5 interface, so maybe it's not so unreasonable.
*/
PGresult *
PQmakeEmptyPGresult(PGconn *conn, ExecStatusType status)
{
PGresult *result;
result = (PGresult *) malloc(sizeof(PGresult));
result->xconn = conn; /* might be NULL */
result->ntups = 0;
result->numAttributes = 0;
result->attDescs = NULL;
result->tuples = NULL;
result->tupArrSize = 0;
result->resultStatus = status;
result->cmdStatus[0] = '\0';
result->binary = 0;
result->errMsg = NULL;
result->null_field[0] = '\0';
result->curBlock = NULL;
result->curOffset = 0;
result->spaceLeft = 0;
if (conn)
{
/* copy connection data we might need for operations on PGresult */
result->noticeHook = conn->noticeHook;
result->noticeArg = conn->noticeArg;
result->client_encoding = conn->client_encoding;
/* consider copying conn's errorMessage */
switch (status)
{
case PGRES_EMPTY_QUERY:
case PGRES_COMMAND_OK:
case PGRES_TUPLES_OK:
case PGRES_COPY_OUT:
case PGRES_COPY_IN:
/* non-error cases */
break;
default:
pqSetResultError(result, conn->errorMessage.data);
break;
}
}
else
{
/* defaults... */
result->noticeHook = NULL;
result->noticeArg = NULL;
result->client_encoding = 0; /* should be SQL_ASCII */
}
return result;
}
/*
* pqResultAlloc -
* Allocate subsidiary storage for a PGresult.
*
* nBytes is the amount of space needed for the object.
* If isBinary is true, we assume that we need to align the object on
* a machine allocation boundary.
* If isBinary is false, we assume the object is a char string and can
* be allocated on any byte boundary.
*/
void *
pqResultAlloc(PGresult *res, size_t nBytes, bool isBinary)
{
char *space;
PGresult_data *block;
if (!res)
return NULL;
if (nBytes <= 0)
return res->null_field;
/*
* If alignment is needed, round up the current position to an
* alignment boundary.
*/
if (isBinary)
{
int offset = res->curOffset % PGRESULT_ALIGN_BOUNDARY;
if (offset)
{
res->curOffset += PGRESULT_ALIGN_BOUNDARY - offset;
res->spaceLeft -= PGRESULT_ALIGN_BOUNDARY - offset;
}
}
/* If there's enough space in the current block, no problem. */
if (nBytes <= (size_t) res->spaceLeft)
{
space = res->curBlock->space + res->curOffset;
res->curOffset += nBytes;
res->spaceLeft -= nBytes;
return space;
}
/*
* If the requested object is very large, give it its own block; this
* avoids wasting what might be most of the current block to start a
* new block. (We'd have to special-case requests bigger than the
* block size anyway.) The object is always given binary alignment in
* this case.
*/
if (nBytes >= PGRESULT_SEP_ALLOC_THRESHOLD)
{
block = (PGresult_data *) malloc(nBytes + PGRESULT_BLOCK_OVERHEAD);
if (!block)
return NULL;
space = block->space + PGRESULT_BLOCK_OVERHEAD;
if (res->curBlock)
{
/*
* Tuck special block below the active block, so that we don't
* have to waste the free space in the active block.
*/
block->next = res->curBlock->next;
res->curBlock->next = block;
}
else
{
/* Must set up the new block as the first active block. */
block->next = NULL;
res->curBlock = block;
res->spaceLeft = 0; /* be sure it's marked full */
}
return space;
}
/* Otherwise, start a new block. */
block = (PGresult_data *) malloc(PGRESULT_DATA_BLOCKSIZE);
if (!block)
return NULL;
block->next = res->curBlock;
res->curBlock = block;
if (isBinary)
{
/* object needs full alignment */
res->curOffset = PGRESULT_BLOCK_OVERHEAD;
res->spaceLeft = PGRESULT_DATA_BLOCKSIZE - PGRESULT_BLOCK_OVERHEAD;
}
else
{
/* we can cram it right after the overhead pointer */
res->curOffset = sizeof(PGresult_data);
res->spaceLeft = PGRESULT_DATA_BLOCKSIZE - sizeof(PGresult_data);
}
space = block->space + res->curOffset;
res->curOffset += nBytes;
res->spaceLeft -= nBytes;
return space;
}
/*
* pqResultStrdup -
* Like strdup, but the space is subsidiary PGresult space.
*/
char *
pqResultStrdup(PGresult *res, const char *str)
{
char *space = (char *) pqResultAlloc(res, strlen(str) + 1, FALSE);
if (space)
strcpy(space, str);
return space;
}
/*
* pqSetResultError -
* assign a new error message to a PGresult
*/
void
pqSetResultError(PGresult *res, const char *msg)
{
if (!res)
return;
if (msg && *msg)
res->errMsg = pqResultStrdup(res, msg);
else
res->errMsg = NULL;
}
/*
* pqCatenateResultError -
* concatenate a new error message to the one already in a PGresult
*/
static void
pqCatenateResultError(PGresult *res, const char *msg)
{
PQExpBufferData errorBuf;
if (!res || !msg)
return;
initPQExpBuffer(&errorBuf);
if (res->errMsg)
appendPQExpBufferStr(&errorBuf, res->errMsg);
appendPQExpBufferStr(&errorBuf, msg);
pqSetResultError(res, errorBuf.data);
termPQExpBuffer(&errorBuf);
}
/*
* PQclear -
* free's the memory associated with a PGresult
*/
void
PQclear(PGresult *res)
{
PGresult_data *block;
if (!res)
return;
/* Free all the subsidiary blocks */
while ((block = res->curBlock) != NULL)
{
res->curBlock = block->next;
free(block);
}
/* Free the top-level tuple pointer array */
if (res->tuples)
free(res->tuples);
/* Free the PGresult structure itself */
free(res);
}
/*
* Handy subroutine to deallocate any partially constructed async result.
*/
void
pqClearAsyncResult(PGconn *conn)
{
if (conn->result)
PQclear(conn->result);
conn->result = NULL;
conn->curTuple = NULL;
}
/*
* This subroutine deletes any existing async result, sets conn->result
* to a PGresult with status PGRES_FATAL_ERROR, and stores the current
* contents of conn->errorMessage into that result. It differs from a
* plain call on PQmakeEmptyPGresult() in that if there is already an
* async result with status PGRES_FATAL_ERROR, the current error message
* is APPENDED to the old error message instead of replacing it. This
* behavior lets us report multiple error conditions properly, if necessary.
* (An example where this is needed is when the backend sends an 'E' message
* and immediately closes the connection --- we want to report both the
* backend error and the connection closure error.)
*/
static void
saveErrorResult(PGconn *conn)
{
/*
* If no old async result, just let PQmakeEmptyPGresult make one.
* Likewise if old result is not an error message.
*/
if (conn->result == NULL ||
conn->result->resultStatus != PGRES_FATAL_ERROR ||
conn->result->errMsg == NULL)
{
pqClearAsyncResult(conn);
conn->result = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
}
else
{
/* Else, concatenate error message to existing async result. */
pqCatenateResultError(conn->result, conn->errorMessage.data);
}
}
/*
* This subroutine prepares an async result object for return to the caller.
* If there is not already an async result object, build an error object
* using whatever is in conn->errorMessage. In any case, clear the async
* result storage and make sure PQerrorMessage will agree with the result's
* error string.
*/
static PGresult *
prepareAsyncResult(PGconn *conn)
{
PGresult *res;
/*
* conn->result is the PGresult to return. If it is NULL (which
* probably shouldn't happen) we assume there is an appropriate error
* message in conn->errorMessage.
*/
res = conn->result;
conn->result = NULL; /* handing over ownership to caller */
conn->curTuple = NULL; /* just in case */
if (!res)
res = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
else
{
/*
* Make sure PQerrorMessage agrees with result; it could be
* different if we have concatenated messages.
*/
resetPQExpBuffer(&conn->errorMessage);
appendPQExpBufferStr(&conn->errorMessage,
PQresultErrorMessage(res));
}
return res;
}
/*
* addTuple
* add a row pointer to the PGresult structure, growing it if necessary
* Returns TRUE if OK, FALSE if not enough memory to add the row
*/
static int
addTuple(PGresult *res, PGresAttValue * tup)
{
if (res->ntups >= res->tupArrSize)
{
/*
* Try to grow the array.
*
* We can use realloc because shallow copying of the structure is
* okay. Note that the first time through, res->tuples is NULL.
* While ANSI says that realloc() should act like malloc() in that
* case, some old C libraries (like SunOS 4.1.x) coredump instead.
* On failure realloc is supposed to return NULL without damaging
* the existing allocation. Note that the positions beyond
* res->ntups are garbage, not necessarily NULL.
*/
int newSize = (res->tupArrSize > 0) ? res->tupArrSize * 2 : 128;
PGresAttValue **newTuples;
if (res->tuples == NULL)
newTuples = (PGresAttValue **)
malloc(newSize * sizeof(PGresAttValue *));
else
newTuples = (PGresAttValue **)
realloc(res->tuples, newSize * sizeof(PGresAttValue *));
if (!newTuples)
return FALSE; /* malloc or realloc failed */
res->tupArrSize = newSize;
res->tuples = newTuples;
}
res->tuples[res->ntups] = tup;
res->ntups++;
return TRUE;
}
/*
* PQsendQuery
* Submit a query, but don't wait for it to finish
*
* Returns: 1 if successfully submitted
* 0 if error (conn->errorMessage is set)
*/
int
PQsendQuery(PGconn *conn, const char *query)
{
if (!conn)
return 0;
/* clear the error string */
resetPQExpBuffer(&conn->errorMessage);
if (!query)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("command string is a null pointer\n"));
return 0;
}
/* Don't try to send if we know there's no live connection. */
if (conn->status != CONNECTION_OK)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("no connection to the server\n"));
return 0;
}
/* Can't send while already busy, either. */
if (conn->asyncStatus != PGASYNC_IDLE)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("another command is already in progress\n"));
return 0;
}
/* initialize async result-accumulation state */
conn->result = NULL;
conn->curTuple = NULL;
/* send the query to the backend; */
/*
* in order to guarantee that we don't send a partial query where we
* would become out of sync with the backend and/or block during a
* non-blocking connection we must first flush the send buffer before
* sending more data
*
* an alternative is to implement 'queue reservations' where we are able
* to roll up a transaction (the 'Q' along with our query) and make
* sure we have enough space for it all in the send buffer.
*/
if (pqIsnonblocking(conn))
{
/*
* the buffer must have emptied completely before we allow a new
* query to be buffered
*/
if (pqFlush(conn))
return 0;
/* 'Q' == queries */
/* XXX: if we fail here we really ought to not block */
if (pqPutc('Q', conn) != 0 || pqPuts(query, conn) != 0)
{
handleSendFailure(conn);
return 0;
}
/*
* give the data a push, ignore the return value as ConsumeInput()
* will do any aditional flushing if needed
*/
pqFlush(conn);
}
else
{
/*
* the frontend-backend protocol uses 'Q' to designate queries
*/
if (pqPutc('Q', conn) != 0 || pqPuts(query, conn) != 0 ||
pqFlush(conn) != 0)
{
handleSendFailure(conn);
return 0;
}
}
/* OK, it's launched! */
conn->asyncStatus = PGASYNC_BUSY;
return 1;
}
/*
* handleSendFailure: try to clean up after failure to send command.
*
* Primarily, what we want to accomplish here is to process an async
* WARNING message that the backend might have sent just before it died.
*
* NOTE: this routine should only be called in PGASYNC_IDLE state.
*/
static void
handleSendFailure(PGconn *conn)
{
/*
* Accept any available input data, ignoring errors. Note that if
* pqReadData decides the backend has closed the channel, it will
* close our side of the socket --- that's just what we want here.
*/
while (pqReadData(conn) > 0)
/* loop until no more data readable */ ;
/*
* Parse any available input messages. Since we are in PGASYNC_IDLE
* state, only WARNING and NOTIFY messages will be eaten.
*/
parseInput(conn);
}
/*
* Consume any available input from the backend
* 0 return: some kind of trouble
* 1 return: no problem
*/
int
PQconsumeInput(PGconn *conn)
{
if (!conn)
return 0;
/*
* Load more data, if available. We do this no matter what state we
* are in, since we are probably getting called because the
* application wants to get rid of a read-select condition. Note that
* we will NOT block waiting for more input.
*/
if (pqReadData(conn) < 0)
{
/*
* for non-blocking connections try to flush the send-queue
* otherwise we may never get a responce for something that may
* not have already been sent because it's in our write buffer!
*/
if (pqIsnonblocking(conn))
(void) pqFlush(conn);
return 0;
}
/* Parsing of the data waits till later. */
return 1;
}
/*
* parseInput: if appropriate, parse input data from backend
* until input is exhausted or a stopping state is reached.
* Note that this function will NOT attempt to read more data from the backend.
*/
static void
parseInput(PGconn *conn)
{
char id;
char noticeWorkspace[128];
/*
* Loop to parse successive complete messages available in the buffer.
*/
for (;;)
{
/*
* Quit if in COPY_OUT state: we expect raw data from the server
* until PQendcopy is called. Don't try to parse it according to
* the normal protocol. (This is bogus. The data lines ought to
* be part of the protocol and have identifying leading
* characters.)
*/
if (conn->asyncStatus == PGASYNC_COPY_OUT)
return;
/*
* OK to try to read a message type code.