源码

Debug ue4 in Fedora35

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After running Setup.sh and GenerateProjectFiles.sh, we found UE4.pro created. It's like a fresh breeze coming from the roof window, we are free now, no more need to fear the once unbearable torment in Visual Studio IDE.

Qt source is not necessary to ue4, qtcreator is only a visual debugger to ue4.

Build Steps:

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make UE4Editor-Linux-Debug ShaderCompileWorker-Linux-Debug -j8

Clean Steps:

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make UE4Editor-Linux-Debug ShaderCompileWorker-Linux-Debug ARGS=-clean -j8

refer to:
https://docs.unrealengine.com/4.27/en-US/SharingAndReleasing/Linux/BeginnerLinuxDeveloper/SettingUpQtCreator/

asn.1编码的转换

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这个工具在

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strongswan/src/libstrongswan/asn1

以下是使用示例

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#include <asn1/asn1.h>
#include <asn1/asn1_parser.h>
 
#define INTEGER_SIZE 32
 
static chunk_t chunk_to_asn1(chunk_t chunk)
{
	chunk_t x;
	chunk_t y;
	chunk_t hash;
	chunk_t content;
	chunk_t asn1;
 
	x.ptr = chunk.ptr;
	x.len = INTEGER_SIZE;
	y.ptr = chunk.ptr + INTEGER_SIZE;
	y.len = INTEGER_SIZE;
	content.ptr = y.ptr + INTEGER_SIZE;
	content.len = chunk.len - INTEGER_SIZE * 3;
	hash.ptr = content.ptr + content.len;
	hash.len = INTEGER_SIZE;
 
	asn1 = asn1_wrap(ASN1_SEQUENCE, "mmmm",
		asn1_integer("c", x),
		asn1_integer("c", y),
		asn1_simple_object(ASN1_OCTET_STRING, hash),
		asn1_simple_object(ASN1_OCTET_STRING, content));
 
	chunk_free(&chunk);
	return asn1;
}
 
static const asn1Object_t patterns[] = {
	{ 0, "seq",			ASN1_SEQUENCE,		ASN1_NONE }, /*  0 */
	{ 1,   "x",			ASN1_INTEGER,		ASN1_BODY }, /*  1 */
	{ 1,   "y",			ASN1_INTEGER,		ASN1_BODY }, /*  2 */
	{ 1,   "hash",			ASN1_OCTET_STRING,	ASN1_BODY }, /*  3 */
	{ 1,   "content",		ASN1_OCTET_STRING,	ASN1_BODY }, /*  4 */
	{ 0, "exit",			ASN1_EOC,		ASN1_EXIT }
};
#define PATTERN_KEY_X			1
#define PATTERN_KEY_Y			2
#define PATTERN_KEY_HASH		3
#define PATTERN_KEY_CONTENT		4
 
static chunk_t correct_integer(chunk_t chunk)
{
	if (chunk.len == INTEGER_SIZE + 1)
		return chunk_skip(chunk, 1);
	return chunk;
}
 
static bool parse_asn1(chunk_t asn1, chunk_t* x, chunk_t* y, chunk_t* hash, chunk_t* content)
{
	chunk_t object;
	asn1_parser_t *parser;
	bool success = FALSE;
	int object_id, oid, i;
 
	parser = asn1_parser_create(patterns, asn1);
 
	while (parser->iterate(parser, &object_id, &object))
	{
		switch (object_id)
		{
			case PATTERN_KEY_X:
				*x = correct_integer(object);
				break;
			case PATTERN_KEY_Y:
				*y = correct_integer(object);
				break;
			case PATTERN_KEY_HASH:
				*hash = object;
				break;
			case PATTERN_KEY_CONTENT:
				*content = object;
				break;
		}
	}
	success = parser->success(parser);
	parser->destroy(parser);
	return success;
}
 
static bool chunk_from_asn1(chunk_t* chunk, chunk_t asn1)
{
	chunk_t x;
	chunk_t y;
	chunk_t hash;
	chunk_t content;
 
	if (!parse_asn1(asn1, &x, &y, &hash, &content))
		return false;
 
	*chunk = chunk_cat("cccc", x, y, content, hash);
	return true;
}
 
static void random_data(chunk_t chunk)
{
	int fd = open("/dev/urandom", O_RDONLY);
	read(fd, chunk.ptr, chunk.len);
	close(fd);
}
 
int test()
{
	bool is_ok;
	chunk_t result;
	chunk_t asn1;
	chunk_t total = chunk_alloc(INTEGER_SIZE * 3 + 345);
 
	random_data(total);
 
	asn1 = chunk_to_asn1(total);
	is_ok = chunk_from_asn1(&result, asn1);
 
	chunk_free(&result);
	chunk_free(&asn1);
	chunk_free(&total);
	return is_ok;
}

因为asn1模块里对ASN1_INTEGER类型有个two's complement处理，如果这个数最高位为1，则在此数前加一个0值字节，所以correct_integer函数的目地在于更正输出。

UE4 Shader源码编译过程

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在主程序里拼成一个文件WorkerInputOnly.in后启动ShaderCompileWorker.exe进程编译shader源码。以下是调试时记录下来的命令行

D:/ue/Engine/Binaries/Win64/ShaderCompileWorker.exe "C:/Users/euhat/AppData/Local/Temp/UnrealShaderWorkingDir/A1AF8D424B2A34C30CE4378EDE6A0EFB/2/" 14492 2 WorkerInputOnly.in WorkerOutputOnly.out -communicatethroughfile  -TimeToLive=20.000000 -Multiprocess