-<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.209 2006/05/17 21:50:54 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.210 2006/05/21 20:19:23 tgl Exp $ -->
<chapter id="libpq">
<title><application>libpq</application> - C Library</title>
<sect2 id="libpq-exec-escape-string">
<title>Escaping Strings for Inclusion in SQL Commands</title>
+ <indexterm zone="libpq-exec-escape-string"><primary>PQescapeStringConn</></>
<indexterm zone="libpq-exec-escape-string"><primary>PQescapeString</></>
<indexterm zone="libpq-exec-escape-string"><primary>escaping strings</></>
<para>
-<function>PQescapeString</function> escapes a string for use within an SQL
+<function>PQescapeStringConn</function> escapes a string for use within an SQL
command. This is useful when inserting data values as literal constants
in SQL commands. Certain characters (such as quotes and backslashes) must
be escaped to prevent them from being interpreted specially by the SQL parser.
-<function>PQescapeString</> performs this operation.
+<function>PQescapeStringConn</> performs this operation.
</para>
<tip>
its sibling routines.
<synopsis>
-size_t PQescapeString (char *to, const char *from, size_t length);
+size_t PQescapeStringConn (PGconn *conn,
+ char *to, const char *from, size_t length,
+ int *error);
</synopsis>
</para>
<para>
+<function>PQescapeStringConn</> writes an escaped
+version of the <parameter>from</> string to the <parameter>to</>
+buffer, escaping special characters so that they cannot cause any
+harm, and adding a terminating zero byte. The single quotes that
+must surround <productname>PostgreSQL</> string literals are not
+included in the result string; they should be provided in the SQL
+command that the result is inserted into.
The parameter <parameter>from</> points to the first character of the string
that is to be escaped, and the <parameter>length</> parameter gives the
-number of characters in this string. A terminating zero byte is not
+number of bytes in this string. A terminating zero byte is not
required, and should not be counted in <parameter>length</>. (If
a terminating zero byte is found before <parameter>length</> bytes are
-processed, <function>PQescapeString</> stops at the zero; the behavior
+processed, <function>PQescapeStringConn</> stops at the zero; the behavior
is thus rather like <function>strncpy</>.)
<parameter>to</> shall point to a
-buffer that is able to hold at least one more character than twice
+buffer that is able to hold at least one more byte than twice
the value of <parameter>length</>, otherwise the behavior is
-undefined. A call to <function>PQescapeString</> writes an escaped
-version of the <parameter>from</> string to the <parameter>to</>
-buffer, replacing special characters so that they cannot cause any
-harm, and adding a terminating zero byte. The single quotes that
-must surround <productname>PostgreSQL</> string literals are not
-included in the result string; they should be provided in the SQL
-command that the result is inserted into.
+undefined.
+Behavior is likewise undefined if the <parameter>to</> and <parameter>from</>
+strings overlap.
+</para>
+<para>
+If the <parameter>error</> parameter is not NULL, then <literal>*error</>
+is set to zero on success, nonzero on error. Presently the only possible
+error conditions involve invalid multibyte encoding in the source string.
+The output string is still generated on error, but it can be expected that
+the server will reject it as malformed. On error, a suitable message is
+stored in the <parameter>conn</> object, whether or not <parameter>error</>
+is NULL.
</para>
<para>
-<function>PQescapeString</> returns the number of characters written
+<function>PQescapeStringConn</> returns the number of bytes written
to <parameter>to</>, not including the terminating zero byte.
</para>
+
<para>
-Behavior is undefined if the <parameter>to</> and <parameter>from</>
-strings overlap.
+<synopsis>
+size_t PQescapeString (char *to, const char *from, size_t length);
+</synopsis>
+</para>
+
+<para>
+<function>PQescapeString</> is an older, deprecated version of
+<function>PQescapeStringConn</>; the difference is that it does not
+take <parameter>conn</> or <parameter>error</> parameters. Because of this,
+it cannot adjust its behavior depending on the connection properties (such as
+character encoding) and therefore <emphasis>it may give the wrong results</>.
+Also, it has no way to report error conditions.
+</para>
+<para>
+<function>PQescapeString</> can be used safely in single-threaded client
+programs that work with only one <productname>PostgreSQL</> connection at
+a time (in this case it can find out what it needs to know <quote>behind the
+scenes</>). In other contexts it is a security hazard and should be avoided
+in favor of <function>PQescapeStringConn</>.
</para>
</sect2>
<variablelist>
<varlistentry>
- <term><function>PQescapeBytea</function><indexterm><primary>PQescapeBytea</></></term>
+ <term><function>PQescapeByteaConn</function><indexterm><primary>PQescapeByteaConn</></></term>
<listitem>
<para>
Escapes binary data for use within an SQL command with the type
- <type>bytea</type>. As with <function>PQescapeString</function>,
+ <type>bytea</type>. As with <function>PQescapeStringConn</function>,
this is only used when inserting data directly into an SQL command string.
<synopsis>
-unsigned char *PQescapeBytea(const unsigned char *from,
- size_t from_length,
- size_t *to_length);
+unsigned char *PQescapeByteaConn(PGconn *conn,
+ const unsigned char *from,
+ size_t from_length,
+ size_t *to_length);
</synopsis>
</para>
of a <type>bytea</type> literal in an <acronym>SQL</acronym>
statement. In general, to escape a byte, it is converted into the
three digit octal number equal to the octet value, and preceded by
- two backslashes. The single quote (<literal>'</>) and backslash
+ one or two backslashes. The single quote (<literal>'</>) and backslash
(<literal>\</>) characters have special alternative escape
sequences. See <xref linkend="datatype-binary"> for more
- information. <function>PQescapeBytea</function> performs this
+ information. <function>PQescapeByteaConn</function> performs this
operation, escaping only the minimally required bytes.
</para>
bytes in this binary string. (A terminating zero byte is
neither necessary nor counted.) The <parameter>to_length</parameter>
parameter points to a variable that will hold the resultant
- escaped string length. The result string length includes the terminating
+ escaped string length. This result string length includes the terminating
zero byte of the result.
</para>
<para>
- <function>PQescapeBytea</> returns an escaped version of the
+ <function>PQescapeByteaConn</> returns an escaped version of the
<parameter>from</parameter> parameter binary string in memory
- allocated with <function>malloc()</> (a null pointer is returned if
- memory could not be allocated). This memory must be freed using
- <function>PQfreemem</> when the result is no longer needed. The
+ allocated with <function>malloc()</>. This memory must be freed using
+ <function>PQfreemem()</> when the result is no longer needed. The
return string has all special characters replaced so that they can
be properly processed by the <productname>PostgreSQL</productname>
string literal parser, and the <type>bytea</type> input function. A
surround <productname>PostgreSQL</productname> string literals are
not part of the result string.
</para>
+
+ <para>
+ On error, a NULL pointer is returned, and a suitable error message
+ is stored in the <parameter>conn</> object. Currently, the only
+ possible error is insufficient memory for the result string.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><function>PQescapeBytea</function><indexterm><primary>PQescapeBytea</></></term>
+ <listitem>
+ <para>
+ <function>PQescapeBytea</> is an older, deprecated version of
+ <function>PQescapeByteaConn</>.
+<synopsis>
+unsigned char *PQescapeBytea(const unsigned char *from,
+ size_t from_length,
+ size_t *to_length);
+</synopsis>
+</para>
+
+<para>
+ The only difference from <function>PQescapeByteaConn</> is that
+ <function>PQescapeBytea</> does not
+ take a <structname>PGconn</> parameter. Because of this, it cannot adjust
+ its behavior depending on the connection properties (in particular,
+ whether standard-conforming strings are enabled)
+ and therefore <emphasis>it may give the wrong results</>. Also, it
+ has no way to return an error message on failure.
+ </para>
+
+ <para>
+ <function>PQescapeBytea</> can be used safely in single-threaded client
+ programs that work with only one <productname>PostgreSQL</> connection at
+ a time (in this case it can find out what it needs to know <quote>behind the
+ scenes</>). In other contexts it is a security hazard and should be
+ avoided in favor of <function>PQescapeByteaConn</>.
+ </para>
</listitem>
</varlistentry>
<term><function>PQunescapeBytea</function><indexterm><primary>PQunescapeBytea</></></term>
<listitem>
<para>
- Converts an escaped string representation of binary data into binary
+ Converts a string representation of binary data into binary
data — the reverse of <function>PQescapeBytea</function>.
This is needed when retrieving <type>bytea</type> data in text format,
but not when retrieving it in binary format.
</synopsis>
</para>
-<para>
- The <parameter>from</parameter> parameter points to an escaped string
- such as might be returned by <function>PQgetvalue</function> when applied to a
- <type>bytea</type> column. <function>PQunescapeBytea</function> converts
- this string representation into its binary representation.
+ The <parameter>from</parameter> parameter points to a string
+ such as might be returned by <function>PQgetvalue</function> when applied
+ to a <type>bytea</type> column. <function>PQunescapeBytea</function>
+ converts this string representation into its binary representation.
It returns a pointer to a buffer allocated with
<function>malloc()</function>, or null on error, and puts the size of
the buffer in <parameter>to_length</parameter>. The result must be
freed using <function>PQfreemem</> when it is no longer needed.
</para>
+
+ <para>
+ This conversion is not exactly the inverse of
+ <function>PQescapeBytea</function>, because the string is not expected
+ to be <quote>escaped</> when received from <function>PQgetvalue</function>.
+ In particular this means there is no need for string quoting considerations,
+ and so no need for a <structname>PGconn</> parameter.
+ </para>
</listitem>
</varlistentry>
<para>
Frees memory allocated by <application>libpq</>, particularly
+ <function>PQescapeByteaConn</function>,
<function>PQescapeBytea</function>,
<function>PQunescapeBytea</function>,
and <function>PQnotifies</function>.
entries first when you are using wildcards.)
If an entry needs to contain <literal>:</literal> or
<literal>\</literal>, escape this character with <literal>\</literal>.
-A hostname of <literal>localhost</> matches both TCP <literal>host</> (hostname <literal>localhost</>)
-and Unix domain socket <literal>local</> (<literal>pghost</> empty or the default socket directory)
-connections coming from the local machine.
+A hostname of <literal>localhost</> matches both TCP (hostname
+<literal>localhost</>) and Unix domain socket (<literal>pghost</> empty or the
+default socket directory) connections coming from the local machine.
</para>
<para>
-# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.7 2005/12/26 14:58:05 petere Exp $
+# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.8 2006/05/21 20:19:23 tgl Exp $
# Functions to be exported by libpq DLLs
PQconnectdb 1
PQsetdbLogin 2
lo_create 123
PQinitSSL 124
PQregisterThreadLock 125
-PQencryptPassword 126
+PQescapeStringConn 126
+PQescapeByteaConn 127
+PQencryptPassword 128
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/interfaces/libpq/fe-connect.c,v 1.331 2006/05/19 14:26:58 alvherre Exp $
+ * $PostgreSQL: pgsql/src/interfaces/libpq/fe-connect.c,v 1.332 2006/05/21 20:19:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
conn->nonblocking = false;
conn->setenv_state = SETENV_STATE_IDLE;
conn->client_encoding = PG_SQL_ASCII;
+ conn->std_strings = false; /* unless server says differently */
conn->verbosity = PQERRORS_DEFAULT;
conn->sock = -1;
#ifdef USE_SSL
status = -1;
else
{
- /* change libpq internal encoding */
- conn->client_encoding = pg_char_to_encoding(encoding);
+ /*
+ * In protocol 2 we have to assume the setting will stick, and
+ * adjust our state immediately. In protocol 3 and up we can
+ * rely on the backend to report the parameter value, and we'll
+ * change state at that time.
+ */
+ if (PG_PROTOCOL_MAJOR(conn->pversion) < 3)
+ pqSaveParameterStatus(conn, "client_encoding", encoding);
status = 0; /* everything is ok */
}
PQclear(res);
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.182 2006/03/14 22:48:23 tgl Exp $
+ * $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.183 2006/05/21 20:19:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
"PGRES_FATAL_ERROR"
};
+/*
+ * static state needed by PQescapeString and PQescapeBytea; initialize to
+ * values that result in backward-compatible behavior
+ */
+static int static_client_encoding = PG_SQL_ASCII;
+static bool static_std_strings = false;
static bool PQsendQueryStart(PGconn *conn);
}
/*
- * Special hacks: remember client_encoding as a numeric value, and convert
- * server version to a numeric form as well.
+ * Special hacks: remember client_encoding and standard_conforming_strings,
+ * and convert server version to a numeric form. We keep the first two of
+ * these in static variables as well, so that PQescapeString and
+ * PQescapeBytea can behave somewhat sanely (at least in single-
+ * connection-using programs).
*/
if (strcmp(name, "client_encoding") == 0)
+ {
conn->client_encoding = pg_char_to_encoding(value);
+ static_client_encoding = conn->client_encoding;
+ }
+ else if (strcmp(name, "standard_conforming_strings") == 0)
+ {
+ conn->std_strings = (strcmp(value, "on") == 0);
+ static_std_strings = conn->std_strings;
+ }
else if (strcmp(name, "server_version") == 0)
{
int cnt;
/*
* Escaping arbitrary strings to get valid SQL literal strings.
*
- * Replaces "\\" with "\\\\" and "'" with "''".
+ * Replaces "'" with "''", and if not std_strings, replaces "\" with "\\".
*
* length is the length of the source string. (Note: if a terminating NUL
* is encountered sooner, PQescapeString stops short of "length"; the behavior
*
* Returns the actual length of the output (not counting the terminating NUL).
*/
-size_t
-PQescapeString(char *to, const char *from, size_t length)
+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')
{
- if (SQL_STR_DOUBLE(*source))
- *target++ = *source;
- *target++ = *source++;
- remaining--;
+ 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. */
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,
+ conn->std_strings);
+}
+
+size_t
+PQescapeString(char *to, const char *from, size_t length)
+{
+ return PQescapeStringInternal(NULL, to, from, length, NULL,
+ 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
+ * '\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.
*/
-unsigned char *
-PQescapeBytea(const unsigned char *bintext, size_t binlen, size_t *bytealen)
+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 = bintext;
- for (i = binlen; i > 0; i--, vp++)
+ vp = from;
+ for (i = from_length; i > 0; i--, vp++)
{
if (*vp < 0x20 || *vp > 0x7e)
- len += 5; /* '5' is for '\\ooo' */
+ len += bslash_len + 3;
else if (*vp == '\'')
len += 2;
else if (*vp == '\\')
- len += 4;
+ 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 = bintext;
- *bytealen = len;
-
- for (i = binlen; i > 0; i--, vp++)
+ vp = from;
+ for (i = from_length; i > 0; i--, vp++)
{
if (*vp < 0x20 || *vp > 0x7e)
{
- (void) sprintf((char *) rp, "\\\\%03o", *vp);
- rp += 5;
+ if (!std_strings)
+ *rp++ = '\\';
+ (void) sprintf((char *) rp, "\\%03o", *vp);
+ rp += 4;
}
else if (*vp == '\'')
{
- rp[0] = '\'';
- rp[1] = '\'';
- rp += 2;
+ *rp++ = '\'';
+ *rp++ = '\'';
}
else if (*vp == '\\')
{
- rp[0] = '\\';
- rp[1] = '\\';
- rp[2] = '\\';
- rp[3] = '\\';
- rp += 4;
+ if (!std_strings)
+ {
+ *rp++ = '\\';
+ *rp++ = '\\';
+ }
+ *rp++ = '\\';
+ *rp++ = '\\';
}
else
*rp++ = *vp;
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,
+ conn->std_strings);
+}
+
+unsigned char *
+PQescapeBytea(const unsigned char *from, size_t from_length, size_t *to_length)
+{
+ return PQescapeByteaInternal(NULL, from, from_length, to_length,
+ static_std_strings);
+}
+
+
#define ISFIRSTOCTDIGIT(CH) ((CH) >= '0' && (CH) <= '3')
#define ISOCTDIGIT(CH) ((CH) >= '0' && (CH) <= '7')
#define OCTVAL(CH) ((CH) - '0')
* of a bytea, strtext, into binary, filling a buffer. It returns a
* pointer to the buffer (or NULL on error), and the size of the
* buffer in retbuflen. The pointer may subsequently be used as an
- * argument to the function free(3). It is the reverse of PQescapeBytea.
+ * argument to the function PQfreemem.
*
* The following transformations are made:
* \\ == ASCII 92 == \
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.127 2006/04/27 00:53:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.128 2006/05/21 20:19:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/* Quoting strings before inclusion in queries. */
-extern size_t PQescapeString(char *to, const char *from, size_t length);
-extern unsigned char *PQescapeBytea(const unsigned char *bintext, size_t binlen,
- size_t *bytealen);
+extern size_t PQescapeStringConn(PGconn *conn,
+ char *to, const char *from, size_t length,
+ int *error);
+extern unsigned char *PQescapeByteaConn(PGconn *conn,
+ const unsigned char *from, size_t from_length,
+ size_t *to_length);
extern unsigned char *PQunescapeBytea(const unsigned char *strtext,
size_t *retbuflen);
+/* These forms are deprecated! */
+extern size_t PQescapeString(char *to, const char *from, size_t length);
+extern unsigned char *PQescapeBytea(const unsigned char *from, size_t from_length,
+ size_t *to_length);
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/interfaces/libpq/libpq-int.h,v 1.112 2006/03/14 22:48:23 tgl Exp $
+ * $PostgreSQL: pgsql/src/interfaces/libpq/libpq-int.h,v 1.113 2006/05/21 20:19:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
char cryptSalt[2]; /* password salt received from backend */
pgParameterStatus *pstatus; /* ParameterStatus data */
int client_encoding; /* encoding id */
+ bool std_strings; /* standard_conforming_strings */
PGVerbosity verbosity; /* error/notice message verbosity */
PGlobjfuncs *lobjfuncs; /* private state for large-object access fns */
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