From 86fd58c8c6bcc24184150ce78af8b5b0f23d1eba Mon Sep 17 00:00:00 2001
From: Jef Driesen <jef@libdivecomputer.org>
Date: Mon, 27 Feb 2023 20:14:59 +0100
Subject: [PATCH] Move the sign extension function to a common place

---
 src/array.c               | 20 ++++++++++++++++++++
 src/array.h               |  3 +++
 src/uwatec_smart_parser.c | 21 +--------------------
 3 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/src/array.c b/src/array.c
index 1216d41..29f5faf 100644
--- a/src/array.c
+++ b/src/array.c
@@ -384,3 +384,23 @@ dec2bcd (unsigned char value)
 	unsigned char lo = value % 10;
 	return (hi << 4) | lo;
 }
+
+/*
+ * When turning a two's-complement number with a certain number
+ * of bits into one with more bits, the sign bit must be repeated
+ * in all the extra bits.
+ */
+unsigned int
+signextend (unsigned int value, unsigned int nbits)
+{
+	if (nbits <= 0 || nbits > 32)
+		return 0;
+
+	unsigned int signbit = 1U << (nbits - 1);
+	unsigned int mask = signbit - 1;
+
+	if ((value & signbit) == signbit)
+		return value | ~mask;
+	else
+		return value & mask;
+}
diff --git a/src/array.h b/src/array.h
index ac4c3b1..a6ef21e 100644
--- a/src/array.h
+++ b/src/array.h
@@ -123,6 +123,9 @@ bcd2dec (unsigned char value);
 unsigned char
 dec2bcd (unsigned char value);
 
+unsigned int
+signextend (unsigned int value, unsigned int nbits);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/src/uwatec_smart_parser.c b/src/uwatec_smart_parser.c
index 39a927c..bd849a8 100644
--- a/src/uwatec_smart_parser.c
+++ b/src/uwatec_smart_parser.c
@@ -893,25 +893,6 @@ uwatec_galileo_identify (unsigned char value)
 }
 
 
-static unsigned int
-uwatec_smart_fixsignbit (unsigned int x, unsigned int n)
-{
-	if (n <= 0 || n > 32)
-		return 0;
-
-	unsigned int signbit = (1 << (n - 1));
-	unsigned int mask = (signbit - 1);
-
-	// When turning a two's-complement number with a certain number
-	// of bits into one with more bits, the sign bit must be repeated
-	// in all the extra bits.
-	if ((x & signbit) == signbit)
-		return x | ~mask;
-	else
-		return x & mask;
-}
-
-
 static dc_status_t
 uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback, void *userdata)
 {
@@ -1018,7 +999,7 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 		}
 
 		// Fix the sign bit.
-		signed int svalue = uwatec_smart_fixsignbit (value, nbits);
+		signed int svalue = signextend (value, nbits);
 
 		// Parse the value.
 		unsigned int idx = 0;