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From: Antony Pavlov <antonynpavlov@gmail.com>
To: barebox@lists.infradead.org
Subject: picopng does not support big-endian CPUs
Date: Sun, 25 Jan 2015 22:26:29 +0400	[thread overview]
Message-ID: <20150125222629.c52501c7d776cabf4317c82f@gmail.com> (raw)

Hi All!

Current lib/gui/picopng.c has problems on big-endian CPUs.

Here are two examples from PNG_readPngHeader():

	if (*(uint64_t *) in != PNG_SIGNATURE) {
...
	if (*(uint32_t *) &in[12] != CHUNK_IHDR) {


Using memcmp in this situation is much better, e.g.

+	uint8_t png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
...
+	if (memcmp(in, png_signature, 8)) {


+	uint8_t chunk_header[4] = {0x49, 0x48, 0x44, 0x52};
...
+	if (memcmp(&in[12], chunk_header, 4)) {


Current lodepng works fine on big-endian, but can we disable picopng
in Kconfig for big-endian CPUs?

On mips I have CPU_BIG_ENDIAN option, so I can add
'depends on !CPU_BIG_ENDIAN' to lib/gui/Kconfig, e.g.

 config PICOPNG
+	depends on !CPU_BIG_ENDIAN
 	bool "picoPNG"

-- 
Best regards,
  Antony Pavlov

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             reply	other threads:[~2015-01-25 18:24 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-25 18:26 Antony Pavlov [this message]
2015-01-26  7:58 ` Sascha Hauer
2015-01-26  9:06   ` Jean-Christophe PLAGNIOL-VILLARD

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