From 08a7c255db7f633e69df76901230c475cd3f6b0b Mon Sep 17 00:00:00 2001
From: Intel A80486DX2-66 <larry.holst@disroot.org>
Date: Tue, 2 Jan 2024 00:19:51 +0300
Subject: [PATCH] fwrite_le.*: optimize, extract a function

---
 src/fwrite_le.c | 48 +++++++++++++++++++++++++++++++++---------------
 src/fwrite_le.h |  7 +++++++
 2 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/src/fwrite_le.c b/src/fwrite_le.c
index ee5ff12..1e6d502 100644
--- a/src/fwrite_le.c
+++ b/src/fwrite_le.c
@@ -17,6 +17,29 @@ int detect_endianness(void) {
 	return UNSUPPORTED_ENDIANNESS;
 }
 
+void reorder_le_for_be(
+#if FWRITE_LE_NO_MODIFICATION
+	uint8_t* dest, uint8_t* src,
+#else
+	uint8_t* bytes,
+#endif
+	size_t count, size_t step) {
+	for (size_t i = 0; i < count; i += step) {
+		const size_t div_size = step >> 1; // divide by 2
+		for (size_t j = 0; j < div_size; j++) {
+			const size_t old_pos = i + j, new_pos = i + step - j - 1;
+#if FWRITE_LE_NO_MODIFICATION
+			dest[old_pos] = src[new_pos];
+			dest[new_pos] = src[old_pos];
+#else
+			uint8_t temp = bytes[old_pos];
+			bytes[old_pos] = bytes[new_pos];
+			bytes[new_pos] = temp;
+#endif
+		}
+	}
+}
+
 size_t fwrite_le(void* ptr, size_t size, size_t count, FILE* stream) {
 	/*
 	 * warning: this function modifies `void* ptr` by default!
@@ -41,31 +64,26 @@ size_t fwrite_le(void* ptr, size_t size, size_t count, FILE* stream) {
 		exit(EXIT_FAILURE);
 	}
 	memcpy(bytes, ptr, bytes_count);
-#else
-	uint8_t* bytes = (uint8_t*) ptr;
 #endif
 
-	for (size_t i = 0; i < bytes_count; i += size) {
-		const size_t div_size = size >> 1; // divide by 2
-		for (size_t j = 0; j < div_size; j++) {
-			const size_t old_pos = i + j, new_pos = i + size - j - 1;
+	reorder_le_for_be(
 #if FWRITE_LE_NO_MODIFICATION
-			bytes[old_pos] = ptr[new_pos];
-			bytes[new_pos] = ptr[old_pos];
-#else
-			uint8_t temp = bytes[old_pos];
-			bytes[old_pos] = bytes[new_pos];
-			bytes[new_pos] = temp;
+		bytes,
 #endif
-		}
-	}
+		(uint8_t*) ptr, bytes_count, size);
 
 #if FWRITE_LE_NO_MODIFICATION
 	size_t res =
 #else
 	return
 #endif
-		fwrite(bytes, size, count, stream);
+		fwrite(
+#if FWRITE_LE_NO_MODIFICATION
+			bytes,
+#else
+			(uint8_t*) ptr,
+#endif
+			size, count, stream);
 #if FWRITE_LE_NO_MODIFICATION
 	free(bytes);
 	return res;
diff --git a/src/fwrite_le.h b/src/fwrite_le.h
index aa61722..cc56b02 100644
--- a/src/fwrite_le.h
+++ b/src/fwrite_le.h
@@ -14,5 +14,12 @@
 
 int detect_endianness(void);
 size_t fwrite_le(void* ptr, size_t size, size_t count, FILE* stream);
+void reorder_le_for_be(
+#if FWRITE_LE_NO_MODIFICATION
+	uint8_t* dest, uint8_t* src,
+#else
+	uint8_t* bytes,
+#endif
+	size_t count, size_t step);
 
 #endif /* _FWRITE_LE_H */