From 66639ee119b9c274c004417e206af493801153b3 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Sat, 23 Jan 2021 03:52:23 -0800
Subject: [PATCH] ircd::png: Elaborate callback surface; add logger to prevent
 libpng writes to stderr.

---
 include/ircd/png.h |   2 +
 ircd/png.cc        | 153 ++++++++++++++++++++++++++++++++++-----------
 2 files changed, 118 insertions(+), 37 deletions(-)

diff --git a/include/ircd/png.h b/include/ircd/png.h
index 4541e89b5..5b37d6d82 100644
--- a/include/ircd/png.h
+++ b/include/ircd/png.h
@@ -14,6 +14,8 @@
 /// Portable Network Graphics; wrappers a la carte
 namespace ircd::png
 {
+	IRCD_EXCEPTION(ircd::error, error)
+
 	bool is_animated(const const_buffer &);
 
 	extern const info::versions version_api, version_abi;
diff --git a/ircd/png.cc b/ircd/png.cc
index 2fe2fc288..a04da1172 100644
--- a/ircd/png.cc
+++ b/ircd/png.cc
@@ -10,6 +10,23 @@
 
 #include <RB_INC_PNG_H
 
+namespace ircd::png
+{
+	static void handle_error(png_structp, const char *) noexcept(false);
+	static void handle_warn(png_structp, const char *) noexcept;
+	static void *handle_alloc(png_structp, size_t) noexcept;
+	static void handle_free(png_structp, void *) noexcept;
+	static void handle_read(png_structp, uint8_t *, size_t) noexcept;
+
+	extern log::log log;
+}
+
+decltype(ircd::png::log)
+ircd::png::log
+{
+	"png"
+};
+
 decltype(ircd::png::version_api)
 ircd::png::version_api
 {
@@ -43,7 +60,20 @@ ircd::png::is_animated(const const_buffer &buf)
 		return false;
 
 	png_infop info {nullptr};
-	png_structp handle {nullptr};
+	png_structp handle
+	{
+		png_create_read_struct_2
+		(
+			PNG_LIBPNG_VER_STRING,
+			nullptr,
+			&handle_error,
+			&handle_warn,
+			nullptr,
+			&handle_alloc,
+			&handle_free
+		)
+	};
+
 	const unwind destroy
 	{
 		[&handle, &info]
@@ -52,52 +82,21 @@ ircd::png::is_animated(const const_buffer &buf)
 		}
 	};
 
-	if(unlikely(!(handle = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr))))
+	if(unlikely(!handle))
 		return false;
 
 	if(unlikely(!(info = png_create_info_struct(handle))))
 		return false;
 
-	const_buffer src{buf};
-	png_set_read_fn(handle, &src, []
-	(auto handle, uint8_t *const ptr, size_t sz)
-	{
-		// Destination where libpng wants data
-		const mutable_buffer dst
-		{
-			reinterpret_cast<char *>(ptr), sz
-		};
-
-		// Get source buffer from our callback user data.
-		const_buffer &src
-		{
-			*reinterpret_cast<const_buffer *>(png_get_io_ptr(handle))
-		};
-
-		// Copy from our buffer to libpng buffer.
-		const size_t copied
-		{
-			copy(dst, src)
-		};
-
-		// Advance our source pointer for the amount copied.
-		const size_t consumed
-		{
-			consume(src, copied)
-		};
-
-		assert(copied == consumed);
-	});
+	const_buffer src {buf};
+	png_set_read_fn(handle, &src, &handle_read);
 
 	// Invokes the read callback a few times to traverse the buffer.
 	png_read_info(handle, info);
 
 	// If there's a non-zero result there's acTL for animation.
-	uint32_t frames(0), plays(0);
-	if(png_get_acTL(handle, info, &frames, &plays) != 0)
-		return true;
-
-	return false;
+	uint32_t num_frames {0}, num_plays {0};
+	return png_get_acTL(handle, info, &num_frames, &num_plays) != 0;
 }
 #else
 {
@@ -107,3 +106,83 @@ ircd::png::is_animated(const const_buffer &buf)
 	return false;
 }
 #endif
+
+void
+ircd::png::handle_read(png_structp handle,
+                       uint8_t *const ptr,
+                       size_t size)
+noexcept
+{
+	// Destination where libpng wants data
+	const mutable_buffer dst
+	{
+		reinterpret_cast<char *>(ptr), size
+	};
+
+	// Get source buffer from our callback user data.
+	const_buffer &src
+	{
+		*reinterpret_cast<const_buffer *>(png_get_io_ptr(handle))
+	};
+
+	// Copy from our buffer to libpng buffer.
+	const size_t copied
+	{
+		copy(dst, src)
+	};
+
+	// Advance our source pointer for the amount copied.
+	const size_t consumed
+	{
+		consume(src, copied)
+	};
+
+	assert(copied == consumed);
+}
+
+void *
+ircd::png::handle_alloc(png_structp handle,
+                        size_t size)
+noexcept
+{
+	return std::malloc(size);
+}
+
+void
+ircd::png::handle_free(png_structp handle,
+                       void *const ptr)
+noexcept
+{
+	std::free(ptr);
+}
+
+void
+ircd::png::handle_warn(png_structp handle,
+                       const char *const msg)
+noexcept
+{
+	log::dwarning
+	{
+		log, "handle(%p) :%s",
+		static_cast<const void *>(handle),
+		msg,
+	};
+}
+
+void
+ircd::png::handle_error(png_structp handle,
+                        const char *const msg)
+noexcept(false)
+{
+	log::error
+	{
+		log, "handle(%p) :%s",
+		static_cast<const void *>(handle),
+		msg,
+	};
+
+	throw error
+	{
+		"%s", msg
+	};
+}