1 files changed, 86 insertions, 0 deletions
diff --git a/src/backend/utils/adt/expandedstring.c b/src/backend/utils/adt/expandedstring.c
new file mode 100644
index 0000000000..4e279a3aa1
--- /dev/null
+++ b/src/backend/utils/adt/expandedstring.c
@@ -0,0 +1,86 @@
+/*-------------------------------------------------------------------------
+ *
+ * expandedstring.c
+ *	  Expand a varlena into a StringInfo.
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/adt/expandeddatum.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "fmgr.h"
+#include "utils/expandedstring.h"
+#include "utils/memutils.h"
+
+static Size ESI_get_flat_size(ExpandedObjectHeader *eohptr);
+static void ESI_flatten_into(ExpandedObjectHeader *eohptr,
+				 void *result, Size allocated_size);
+
+static const ExpandedObjectMethods ESI_methods =
+{
+	ESI_get_flat_size,
+	ESI_flatten_into
+};
+
+/*
+ * Construct an expanded datum consisting of an empty StringInfo.
+ *
+ * Caller must ensure that CurrentMemoryContext points to a context with
+ * a suitable lifetime.
+ */
+ExpandedStringInfoHeader *
+GetExpandedStringInfo(void)
+{
+	ExpandedStringInfoHeader *esih;
+	MemoryContext	objcxt;
+	MemoryContext	oldcxt;
+
+	objcxt = AllocSetContextCreate(CurrentMemoryContext,
+								   "stringinfo expanded object",
+								   ALLOCSET_SMALL_MINSIZE,
+								   ALLOCSET_SMALL_INITSIZE,
+								   ALLOCSET_DEFAULT_MAXSIZE);
+
+	oldcxt = MemoryContextSwitchTo(objcxt);	
+	esih = palloc(sizeof(ExpandedStringInfoHeader));
+	EOH_init_header(&esih->hdr, &ESI_methods, objcxt);
+	initStringInfo(&esih->buf);
+	MemoryContextSwitchTo(oldcxt);
+
+	return esih;
+}
+
+/*
+ * The space required to flatten a StringInfo back to a plain old varlena is
+ * just the number of bytes we have in the buffer, plus the size of a 4-byte
+ * header.  Even if the buffer is short, we can't flatten to a packed
+ * representation.
+ */
+static Size
+ESI_get_flat_size(ExpandedObjectHeader *eohptr)
+{
+	ExpandedStringInfoHeader *esih = (ExpandedStringInfoHeader *) eohptr;
+
+	return VARHDRSZ + esih->buf.len;
+}
+
+/*
+ * Flattening a StringInfo just involves copying the data into the allocated
+ * space.
+ */
+static void
+ESI_flatten_into(ExpandedObjectHeader *eohptr,
+				 void *result, Size allocated_size)
+{
+	ExpandedStringInfoHeader *esih = (ExpandedStringInfoHeader *) eohptr;
+
+	Assert(allocated_size == VARHDRSZ + esih->buf.len);
+	memcpy(VARDATA(result), esih->buf.data, esih->buf.len);
+	SET_VARSIZE(result, VARHDRSZ + esih->buf.len);
+}