From 70279ab5a26b62e78f5e0a6815f5b64771e87758 Mon Sep 17 00:00:00 2001
From: Vas Crabb <vas@vastheman.com>
Date: Sun, 3 Sep 2017 12:51:21 +1000
Subject: [PATCH] that doesn't require an instance (nw)

---
 src/emu/rendutil.cpp |  3 +--
 src/lib/util/png.cpp | 36 ++++++++++++++++++------------------
 src/lib/util/png.h   |  3 ++-
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/emu/rendutil.cpp b/src/emu/rendutil.cpp
index d1ffecd7c7b..3511d311bdc 100644
--- a/src/emu/rendutil.cpp
+++ b/src/emu/rendutil.cpp
@@ -815,8 +815,7 @@ ru_imgformat render_detect_image(emu_file &file, const char *dirname, const char
 		return RENDUTIL_IMGFORMAT_ERROR;
 
 	// PNG: check for valid header
-	png_info png;
-	png_error const result = png.verify_header(file);
+	png_error const result = png_info::verify_header(file);
 	if (result == PNGERR_NONE)
 	{
 		file.close();
diff --git a/src/lib/util/png.cpp b/src/lib/util/png.cpp
index a62d08c8161..0a3b616b01f 100644
--- a/src/lib/util/png.cpp
+++ b/src/lib/util/png.cpp
@@ -66,7 +66,7 @@ void png_info::free_data()
 
 namespace {
 
-#define PNG_Signature       "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A"
+constexpr std::uint8_t PNG_SIGNATURE[] = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
 #define MNG_Signature       "\x8A\x4D\x4E\x47\x0D\x0A\x1A\x0A"
 
 // Chunk names
@@ -690,21 +690,6 @@ public:
 		return PNGERR_NONE;
 	}
 
-	png_error verify_header(util::core_file &fp)
-	{
-		uint8_t signature[8];
-
-		/* read 8 bytes */
-		if (fp.read(signature, 8) != 8)
-			return PNGERR_FILE_TRUNCATED;
-
-		/* return an error if we don't match */
-		if (memcmp(signature, PNG_Signature, 8) != 0)
-			return PNGERR_BAD_SIGNATURE;
-
-		return PNGERR_NONE;
-	}
-
 	png_error read_file(util::core_file &fp)
 	{
 		// initialize the data structures
@@ -741,6 +726,21 @@ public:
 
 		return error;
 	}
+
+	static png_error verify_header(util::core_file &fp)
+	{
+		EQUIVALENT_ARRAY(PNG_SIGNATURE, std::uint8_t) signature;
+
+		// read 8 bytes
+		if (fp.read(signature, sizeof(signature)) != sizeof(signature))
+			return PNGERR_FILE_TRUNCATED;
+
+		// return an error if we don't match
+		if (std::memcmp(signature, PNG_SIGNATURE, sizeof(PNG_SIGNATURE)))
+			return PNGERR_BAD_SIGNATURE;
+
+		return PNGERR_NONE;
+	}
 };
 
 constexpr unsigned png_private::ADAM7_X_BIAS[7];
@@ -762,7 +762,7 @@ constexpr unsigned png_private::ADAM7_Y_OFFS[7];
 
 png_error png_info::verify_header(util::core_file &fp)
 {
-	return png_private(*this).verify_header(fp);
+	return png_private::verify_header(fp);
 }
 
 
@@ -1230,7 +1230,7 @@ png_error png_write_bitmap(util::core_file &fp, png_info *info, bitmap_t const &
 		info = &pnginfo;
 
 	// write the PNG signature
-	if (fp.write(PNG_Signature, 8) != 8)
+	if (fp.write(PNG_SIGNATURE, sizeof(PNG_SIGNATURE)) != sizeof(PNG_SIGNATURE))
 		return PNGERR_FILE_ERROR;
 
 	/* write the rest of the PNG data */
diff --git a/src/lib/util/png.h b/src/lib/util/png.h
index 3925f6e4032..ff14ff5f674 100644
--- a/src/lib/util/png.h
+++ b/src/lib/util/png.h
@@ -57,7 +57,6 @@ public:
 
 	~png_info() { free_data(); }
 
-	png_error verify_header(util::core_file &fp);
 	png_error read_file(util::core_file &fp);
 	png_error copy_to_bitmap(bitmap_argb32 &bitmap, bool &hasalpha);
 	png_error expand_buffer_8bit();
@@ -67,6 +66,8 @@ public:
 	void free_data();
 	void reset() { free_data(); operator=(png_info()); }
 
+	static png_error verify_header(util::core_file &fp);
+
 	std::unique_ptr<std::uint8_t []>    image;
 	std::uint32_t                       width, height;
 	std::uint32_t                       xres = 0, yres = 0;