1 files changed, 137 insertions, 0 deletions
diff --git a/src/common/percentrepl.c b/src/common/percentrepl.c
new file mode 100644
index 0000000000..d78571fec0
--- /dev/null
+++ b/src/common/percentrepl.c
@@ -0,0 +1,137 @@
+/*-------------------------------------------------------------------------
+ *
+ * percentrepl.c
+ *	  Common routines to replace percent placeholders in strings
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/common/percentrepl.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#include "common/logging.h"
+#endif
+
+#include "common/percentrepl.h"
+#include "lib/stringinfo.h"
+
+/*
+ * replace_percent_placeholders
+ *
+ * Replace percent-letter placeholders in input string with the supplied
+ * values.  For example, to replace %f with foo and %b with bar, call
+ *
+ * replace_percent_placeholders(instr, "param_name", "bf", bar, foo);
+ *
+ * The return value is palloc'd.
+ *
+ * "%%" is replaced by a single "%".
+ *
+ * This throws an error for an unsupported placeholder or a "%" at the end of
+ * the input string.
+ *
+ * A value may be NULL.  If the corresponding placeholder is found in the
+ * input string, it will be treated as if an unsupported placeholder was used.
+ * This allows callers to share a "letters" specification but vary the
+ * actually supported placeholders at run time.
+ *
+ * This functions is meant for cases where all the values are readily
+ * available or cheap to compute and most invocations will use most values
+ * (for example for archive_command).  Also, it requires that all values are
+ * strings.  It won't be a good match for things like log prefixes or prompts
+ * that use a mix of data types and any invocation will only use a few of the
+ * possible values.
+ *
+ * param_name is the name of the underlying GUC parameter, for error
+ * reporting.  At the moment, this function is only used for GUC parameters.
+ * If other kinds of uses were added, the error reporting would need to be
+ * revised.
+ */
+char *
+replace_percent_placeholders(const char *instr, const char *param_name, const char *letters,...)
+{
+	StringInfoData result;
+
+	initStringInfo(&result);
+
+	for (const char *sp = instr; *sp; sp++)
+	{
+		if (*sp == '%')
+		{
+			if (sp[1] == '%')
+			{
+				/* Convert %% to a single % */
+				sp++;
+				appendStringInfoChar(&result, *sp);
+			}
+			else if (sp[1] == '\0')
+			{
+				/* Incomplete escape sequence, expected a character afterward */
+#ifdef FRONTEND
+				pg_log_error("invalid value for parameter \"%s\": \"%s\"", param_name, instr);
+				pg_log_error_detail("String ends unexpectedly after escape character \"%%\".");
+				exit(1);
+#else
+				ereport(ERROR,
+						errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						errmsg("invalid value for parameter \"%s\": \"%s\"", param_name, instr),
+						errdetail("String ends unexpectedly after escape character \"%%\"."));
+#endif
+			}
+			else
+			{
+				/* Look up placeholder character */
+				bool		found = false;
+				va_list		ap;
+
+				sp++;
+
+				va_start(ap, letters);
+				for (const char *lp = letters; *lp; lp++)
+				{
+					char	   *val = va_arg(ap, char *);
+
+					if (*sp == *lp)
+					{
+						if (val)
+						{
+							appendStringInfoString(&result, val);
+							found = true;
+						}
+						/* If val is NULL, we will report an error. */
+						break;
+					}
+				}
+				va_end(ap);
+				if (!found)
+				{
+					/* Unknown escape sequence */
+#ifdef FRONTEND
+					pg_log_error("invalid value for parameter \"%s\": \"%s\"", param_name, instr);
+					pg_log_error_detail("String contains unexpected escape sequence \"%c\".", *sp);
+					exit(1);
+#else
+					ereport(ERROR,
+							errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+							errmsg("invalid value for parameter \"%s\": \"%s\"", param_name, instr),
+							errdetail("String contains unexpected escape sequence \"%c\".", *sp));
+#endif
+				}
+			}
+		}
+		else
+		{
+			appendStringInfoChar(&result, *sp);
+		}
+	}
+
+	return result.data;
+}