1 files changed, 85 insertions, 0 deletions
diff --git a/src/common/pg_get_line.c b/src/common/pg_get_line.c
new file mode 100644
index 00000000000..38433675d43
--- /dev/null
+++ b/src/common/pg_get_line.c
@@ -0,0 +1,85 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_get_line.c
+ *	  fgets() with an expansible result buffer
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/common/pg_get_line.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+#include "common/string.h"
+#include "lib/stringinfo.h"
+
+
+/*
+ * pg_get_line()
+ *
+ * This is meant to be equivalent to fgets(), except that instead of
+ * reading into a caller-supplied, fixed-size buffer, it reads into
+ * a palloc'd (in frontend, really malloc'd) string, which is resized
+ * as needed to handle indefinitely long input lines.  The caller is
+ * responsible for pfree'ing the result string when appropriate.
+ *
+ * As with fgets(), returns NULL if there is a read error or if no
+ * characters are available before EOF.  The caller can distinguish
+ * these cases by checking ferror(stream).
+ *
+ * Since this is meant to be equivalent to fgets(), the trailing newline
+ * (if any) is not stripped.  Callers may wish to apply pg_strip_crlf().
+ *
+ * Note that while I/O errors are reflected back to the caller to be
+ * dealt with, an OOM condition for the palloc'd buffer will not be;
+ * there'll be an ereport(ERROR) or exit(1) inside stringinfo.c.
+ */
+char *
+pg_get_line(FILE *stream)
+{
+	StringInfoData buf;
+
+	initStringInfo(&buf);
+
+	/* Read some data, appending it to whatever we already have */
+	while (fgets(buf.data + buf.len, buf.maxlen - buf.len, stream) != NULL)
+	{
+		buf.len += strlen(buf.data + buf.len);
+
+		/* Done if we have collected a newline */
+		if (buf.len > 0 && buf.data[buf.len - 1] == '\n')
+			return buf.data;
+
+		/* Make some more room in the buffer, and loop to read more data */
+		enlargeStringInfo(&buf, 128);
+	}
+
+	/* Did fgets() fail because of an I/O error? */
+	if (ferror(stream))
+	{
+		/* ensure that free() doesn't mess up errno */
+		int			save_errno = errno;
+
+		pfree(buf.data);
+		errno = save_errno;
+		return NULL;
+	}
+
+	/* If we read no data before reaching EOF, we should return NULL */
+	if (buf.len == 0)
+	{
+		pfree(buf.data);
+		return NULL;
+	}
+
+	/* No newline at EOF ... so return what we have */
+	return buf.data;
+}