From 9f09c5741b7644342f0165f52715cc8b0b76ef83 Mon Sep 17 00:00:00 2001
From: Sebastien GODARD <sysstat@users.noreply.github.com>
Date: Sun, 17 Sep 2017 10:12:30 +0200
Subject: [PATCH] Add function to swap bytes of the fields of a structure

This function will be used to convert from one endianness type
(little/big endian) to the other.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>
---
 sa.h        |  2 ++
 sa_common.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/sa.h b/sa.h
index f83314c..88bd38e 100644
--- a/sa.h
+++ b/sa.h
@@ -1203,5 +1203,7 @@ void set_hdr_rectime
 	(unsigned int, struct tm *, struct file_header *);
 void set_record_timestamp_string
 	(unsigned int, struct record_header *, char *, char *, int, struct tm *);
+void swap_struct
+	(int [], void *, int);
 
 #endif  /* _SA_H */
diff --git a/sa_common.c b/sa_common.c
index 82c0f41..87d16e8 100644
--- a/sa_common.c
+++ b/sa_common.c
@@ -22,6 +22,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <time.h>
 #include <errno.h>
 #include <unistd.h>	/* For STDOUT_FILENO, among others */
@@ -977,6 +978,54 @@ void select_default_activity(struct activity *act[])
 	}
 }
 
+/*
+ ***************************************************************************
+ * Swap bytes for every numerical field in structure. Used to convert from
+ * one endianness type (big-endian or little-endian) to the other.
+ *
+ * IN:
+ * @types_nr	Number of fields in structure for each following types:
+ *		unsigned long long, unsigned long and int.
+ * @ps		Pointer on structure.
+ * @is64bit	TRUE if data come from a 64-bit machine.
+ ***************************************************************************
+ */
+void swap_struct(int types_nr[], void *ps, int is64bit)
+{
+	int i;
+	uint64_t *x;
+	uint32_t *y;
+
+	x = (uint64_t *) ps;
+	/* For each field of type long long (or double) */
+	for (i = 0; i < types_nr[0]; i++) {
+		*x = __builtin_bswap64(*x);
+		x = (uint64_t *) ((char *) x + ULL_ALIGNMENT_WIDTH);
+	}
+
+	y = (uint32_t *) x;
+	/* For each field of type long */
+	for (i = 0; i < types_nr[1]; i++) {
+		if (is64bit) {
+			*x = __builtin_bswap64(*x);
+			x = (uint64_t *) ((char *) x + UL_ALIGNMENT_WIDTH);
+		}
+		else {
+			*y = __builtin_bswap32(*y);
+			y = (uint32_t *) ((char *) y + UL_ALIGNMENT_WIDTH);
+		}
+	}
+
+	if (is64bit) {
+		y = (uint32_t *) x;
+	}
+	/* For each field of type int */
+	for (i = 0; i < types_nr[2]; i++) {
+		*y = __builtin_bswap32(*y);
+		y = (uint32_t *) ((char *) y + U_ALIGNMENT_WIDTH);
+	}
+}
+
 /*
  ***************************************************************************
  * Read data from a system activity data file.
-- 
2.40.0