1 files changed, 430 insertions, 0 deletions
diff --git a/libpq/pqexpbuffer.c b/libpq/pqexpbuffer.c
new file mode 100644
index 0000000..8d82d5c
--- /dev/null
+++ b/libpq/pqexpbuffer.c
@@ -0,0 +1,430 @@
+/*-------------------------------------------------------------------------
+ *
+ * pqexpbuffer.c
+ *
+ * PQExpBuffer provides an indefinitely-extensible string data type.
+ * It can be used to buffer either ordinary C strings (null-terminated text)
+ * or arbitrary binary data.  All storage is allocated with malloc().
+ *
+ * This module is essentially the same as the backend's StringInfo data type,
+ * but it is intended for use in frontend libpq and client applications.
+ * Thus, it does not rely on palloc() nor elog(), nor psprintf.c which
+ * will exit() on error.
+ *
+ * It does rely on vsnprintf(); if configure finds that libc doesn't provide
+ * a usable vsnprintf(), then a copy of our own implementation of it will
+ * be linked into libpq.
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/interfaces/libpq/pqexpbuffer.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include <limits.h>
+
+#include "pqexpbuffer.h"
+
+#ifdef WIN32
+#include "win32.h"
+#endif
+
+
+/* All "broken" PQExpBuffers point to this string. */
+static const char oom_buffer[1] = "";
+
+static bool appendPQExpBufferVA(PQExpBuffer str, const char *fmt, va_list args) pg_attribute_printf(2, 0);
+
+
+/*
+ * markPQExpBufferBroken
+ *
+ * Put a PQExpBuffer in "broken" state if it isn't already.
+ */
+static void
+markPQExpBufferBroken(PQExpBuffer str)
+{
+	if (str->data != oom_buffer)
+		free(str->data);
+
+	/*
+	 * Casting away const here is a bit ugly, but it seems preferable to not
+	 * marking oom_buffer const.  We want to do that to encourage the compiler
+	 * to put oom_buffer in read-only storage, so that anyone who tries to
+	 * scribble on a broken PQExpBuffer will get a failure.
+	 */
+	str->data = (char *) oom_buffer;
+	str->len = 0;
+	str->maxlen = 0;
+}
+
+/*
+ * createPQExpBuffer
+ *
+ * Create an empty 'PQExpBufferData' & return a pointer to it.
+ */
+PQExpBuffer
+createPQExpBuffer(void)
+{
+	PQExpBuffer res;
+
+	res = (PQExpBuffer) malloc(sizeof(PQExpBufferData));
+	if (res != NULL)
+		initPQExpBuffer(res);
+
+	return res;
+}
+
+/*
+ * initPQExpBuffer
+ *
+ * Initialize a PQExpBufferData struct (with previously undefined contents)
+ * to describe an empty string.
+ */
+void
+initPQExpBuffer(PQExpBuffer str)
+{
+	str->data = (char *) malloc(INITIAL_EXPBUFFER_SIZE);
+	if (str->data == NULL)
+	{
+		str->data = (char *) oom_buffer;		/* see comment above */
+		str->maxlen = 0;
+		str->len = 0;
+	}
+	else
+	{
+		str->maxlen = INITIAL_EXPBUFFER_SIZE;
+		str->len = 0;
+		str->data[0] = '\0';
+	}
+}
+
+/*
+ * destroyPQExpBuffer(str);
+ *
+ *		free()s both the data buffer and the PQExpBufferData.
+ *		This is the inverse of createPQExpBuffer().
+ */
+void
+destroyPQExpBuffer(PQExpBuffer str)
+{
+	if (str)
+	{
+		termPQExpBuffer(str);
+		free(str);
+	}
+}
+
+/*
+ * termPQExpBuffer(str)
+ *		free()s the data buffer but not the PQExpBufferData itself.
+ *		This is the inverse of initPQExpBuffer().
+ */
+void
+termPQExpBuffer(PQExpBuffer str)
+{
+	if (str->data != oom_buffer)
+		free(str->data);
+	/* just for luck, make the buffer validly empty. */
+	str->data = (char *) oom_buffer;	/* see comment above */
+	str->maxlen = 0;
+	str->len = 0;
+}
+
+/*
+ * resetPQExpBuffer
+ *		Reset a PQExpBuffer to empty
+ *
+ * Note: if possible, a "broken" PQExpBuffer is returned to normal.
+ */
+void
+resetPQExpBuffer(PQExpBuffer str)
+{
+	if (str)
+	{
+		if (str->data != oom_buffer)
+		{
+			str->len = 0;
+			str->data[0] = '\0';
+		}
+		else
+		{
+			/* try to reinitialize to valid state */
+			initPQExpBuffer(str);
+		}
+	}
+}
+
+/*
+ * enlargePQExpBuffer
+ * Make sure there is enough space for 'needed' more bytes in the buffer
+ * ('needed' does not include the terminating null).
+ *
+ * Returns 1 if OK, 0 if failed to enlarge buffer.  (In the latter case
+ * the buffer is left in "broken" state.)
+ */
+int
+enlargePQExpBuffer(PQExpBuffer str, size_t needed)
+{
+	size_t		newlen;
+	char	   *newdata;
+
+	if (PQExpBufferBroken(str))
+		return 0;				/* already failed */
+
+	/*
+	 * Guard against ridiculous "needed" values, which can occur if we're fed
+	 * bogus data.  Without this, we can get an overflow or infinite loop in
+	 * the following.
+	 */
+	if (needed >= ((size_t) INT_MAX - str->len))
+	{
+		markPQExpBufferBroken(str);
+		return 0;
+	}
+
+	needed += str->len + 1;		/* total space required now */
+
+	/* Because of the above test, we now have needed <= INT_MAX */
+
+	if (needed <= str->maxlen)
+		return 1;				/* got enough space already */
+
+	/*
+	 * We don't want to allocate just a little more space with each append;
+	 * for efficiency, double the buffer size each time it overflows.
+	 * Actually, we might need to more than double it if 'needed' is big...
+	 */
+	newlen = (str->maxlen > 0) ? (2 * str->maxlen) : 64;
+	while (needed > newlen)
+		newlen = 2 * newlen;
+
+	/*
+	 * Clamp to INT_MAX in case we went past it.  Note we are assuming here
+	 * that INT_MAX <= UINT_MAX/2, else the above loop could overflow.  We
+	 * will still have newlen >= needed.
+	 */
+	if (newlen > (size_t) INT_MAX)
+		newlen = (size_t) INT_MAX;
+
+	newdata = (char *) realloc(str->data, newlen);
+	if (newdata != NULL)
+	{
+		str->data = newdata;
+		str->maxlen = newlen;
+		return 1;
+	}
+
+	markPQExpBufferBroken(str);
+	return 0;
+}
+
+/*
+ * printfPQExpBuffer
+ * Format text data under the control of fmt (an sprintf-like format string)
+ * and insert it into str.  More space is allocated to str if necessary.
+ * This is a convenience routine that does the same thing as
+ * resetPQExpBuffer() followed by appendPQExpBuffer().
+ */
+void
+printfPQExpBuffer(PQExpBuffer str, const char *fmt,...)
+{
+	va_list		args;
+	bool		done;
+
+	resetPQExpBuffer(str);
+
+	if (PQExpBufferBroken(str))
+		return;					/* already failed */
+
+	/* Loop in case we have to retry after enlarging the buffer. */
+	do
+	{
+		va_start(args, fmt);
+		done = appendPQExpBufferVA(str, fmt, args);
+		va_end(args);
+	} while (!done);
+}
+
+/*
+ * appendPQExpBuffer
+ *
+ * Format text data under the control of fmt (an sprintf-like format string)
+ * and append it to whatever is already in str.  More space is allocated
+ * to str if necessary.  This is sort of like a combination of sprintf and
+ * strcat.
+ */
+void
+appendPQExpBuffer(PQExpBuffer str, const char *fmt,...)
+{
+	va_list		args;
+	bool		done;
+
+	if (PQExpBufferBroken(str))
+		return;					/* already failed */
+
+	/* Loop in case we have to retry after enlarging the buffer. */
+	do
+	{
+		va_start(args, fmt);
+		done = appendPQExpBufferVA(str, fmt, args);
+		va_end(args);
+	} while (!done);
+}
+
+/*
+ * appendPQExpBufferVA
+ * Shared guts of printfPQExpBuffer/appendPQExpBuffer.
+ * Attempt to format data and append it to str.  Returns true if done
+ * (either successful or hard failure), false if need to retry.
+ */
+static bool
+appendPQExpBufferVA(PQExpBuffer str, const char *fmt, va_list args)
+{
+	size_t		avail;
+	size_t		needed;
+	int			nprinted;
+
+	/*
+	 * Try to format the given string into the available space; but if there's
+	 * hardly any space, don't bother trying, just enlarge the buffer first.
+	 */
+	if (str->maxlen > str->len + 16)
+	{
+		/*
+		 * Note: we intentionally leave one byte unused, as a guard against
+		 * old broken versions of vsnprintf.
+		 */
+		avail = str->maxlen - str->len - 1;
+
+		errno = 0;
+
+		nprinted = vsnprintf(str->data + str->len, avail, fmt, args);
+
+		/*
+		 * If vsnprintf reports an error other than ENOMEM, fail.
+		 */
+		if (nprinted < 0 && errno != 0 && errno != ENOMEM)
+		{
+			markPQExpBufferBroken(str);
+			return true;
+		}
+
+		/*
+		 * Note: some versions of vsnprintf return the number of chars
+		 * actually stored, not the total space needed as C99 specifies.  And
+		 * at least one returns -1 on failure.  Be conservative about
+		 * believing whether the print worked.
+		 */
+		if (nprinted >= 0 && (size_t) nprinted < avail - 1)
+		{
+			/* Success.  Note nprinted does not include trailing null. */
+			str->len += nprinted;
+			return true;
+		}
+
+		if (nprinted >= 0 && (size_t) nprinted > avail)
+		{
+			/*
+			 * This appears to be a C99-compliant vsnprintf, so believe its
+			 * estimate of the required space. (If it's wrong, the logic will
+			 * still work, but we may loop multiple times.)  Note that the
+			 * space needed should be only nprinted+1 bytes, but we'd better
+			 * allocate one more than that so that the test above will succeed
+			 * next time.
+			 *
+			 * In the corner case where the required space just barely
+			 * overflows, fail.
+			 */
+			if (nprinted > INT_MAX - 2)
+			{
+				markPQExpBufferBroken(str);
+				return true;
+			}
+			needed = nprinted + 2;
+		}
+		else
+		{
+			/*
+			 * Buffer overrun, and we don't know how much space is needed.
+			 * Estimate twice the previous buffer size, but not more than
+			 * INT_MAX.
+			 */
+			if (avail >= INT_MAX / 2)
+				needed = INT_MAX;
+			else
+				needed = avail * 2;
+		}
+	}
+	else
+	{
+		/*
+		 * We have to guess at how much to enlarge, since we're skipping the
+		 * formatting work.
+		 */
+		needed = 32;
+	}
+
+	/* Increase the buffer size and try again. */
+	if (!enlargePQExpBuffer(str, needed))
+		return true;			/* oops, out of memory */
+
+	return false;
+}
+
+/*
+ * appendPQExpBufferStr
+ * Append the given string to a PQExpBuffer, allocating more space
+ * if necessary.
+ */
+void
+appendPQExpBufferStr(PQExpBuffer str, const char *data)
+{
+	appendBinaryPQExpBuffer(str, data, strlen(data));
+}
+
+/*
+ * appendPQExpBufferChar
+ * Append a single byte to str.
+ * Like appendPQExpBuffer(str, "%c", ch) but much faster.
+ */
+void
+appendPQExpBufferChar(PQExpBuffer str, char ch)
+{
+	/* Make more room if needed */
+	if (!enlargePQExpBuffer(str, 1))
+		return;
+
+	/* OK, append the character */
+	str->data[str->len] = ch;
+	str->len++;
+	str->data[str->len] = '\0';
+}
+
+/*
+ * appendBinaryPQExpBuffer
+ *
+ * Append arbitrary binary data to a PQExpBuffer, allocating more space
+ * if necessary.
+ */
+void
+appendBinaryPQExpBuffer(PQExpBuffer str, const char *data, size_t datalen)
+{
+	/* Make more room if needed */
+	if (!enlargePQExpBuffer(str, datalen))
+		return;
+
+	/* OK, append the data */
+	memcpy(str->data + str->len, data, datalen);
+	str->len += datalen;
+
+	/*
+	 * Keep a trailing null in place, even though it's probably useless for
+	 * binary data...
+	 */
+	str->data[str->len] = '\0';
+}