如何在程序中包含数据目标文件(图像等)并访问符号? [英] How to include data object files (images, etc.) in program and access the symbols?

问题描述

我已经使用objcopy将几个资源文件转换为.obj文件，并将它们与我的程序源代码链接在一起. 我可以使用以下代码很好地访问程序中目标文件中的符号，但只能使用GCC/G ++(Cygwin):

I've turned a couple of resource files into .obj files using objcopy and i link them with my programs source code. I can very well access the symbols inside the object file in my program with the following code, but only with GCC/G++ (Cygwin):

extern uint8_t data[]   asm("_binary_Resources_0_png_start");
extern uint8_t size[]   asm("_binary_Resources_0_png_size");
extern uint8_t end[]    asm("_binary_Resources_0_png_end");

该代码在Visual Studio中不起作用，可能是因为VS具有它自己的__asm命令. 我想通过链接将程序资源(图像，着色器等)包含在最终可执行文件的.data部分中.

The code doesn't work in Visual Studio, probably because VS has it's own __asm command. I want to include my programs resources (Images, Shaders, etc.) in my final executable's .data section through linking them.

但是我如何才能在VC ++中访问目标文件中定义的符号? 我在没有汇编命令的情况下尝试了extern uint8_t _binary_Resources_0_png_start[]或extern "C" uint8_t _binary_Resources_0_png_start[]，但是出现了未解决的符号链接错误.

But how can i access the symbols defined in the object file in VC++? I tried extern uint8_t _binary_Resources_0_png_start[] or extern "C" uint8_t _binary_Resources_0_png_start[] without the assembly command, but i get unresolved symbol link errors.

推荐答案

解决了不同的问题并进行了测试之后，我回到了原来的方法(链接)，它就像魔术一样工作，下面是详细信息:

After working around and testing different things, i came back to my original approach (linking) and it worked like magic, here is the details:

为了将数据包含在最终可执行文件的.data部分中，您需要首先将数据文件(可以是任意二进制文件(任何东西！))转换为可链接文件格式，也称为目标文件.

In order to include data in the final executable's .data section, you need to first turn that data files (which could be an arbitrary binary file (anything!)) into a linkable file format, also known as an object file.

GNU Binutils中包含的工具objcopy，可通过Cygwin或MinGW在Windows中访问，它获取一个文件并生成一个目标文件. objcopy在生成目标文件之前需要了解两件事，即输出文件格式和输出体系结构. 为了确定这两件事，我用工具objdump检查有效的可链接目标文件:

The tool objcopy which is included in GNU Binutils and is accessible in windows through Cygwin or MinGW, takes a file and produces an object file. objcopy requires two things to know before generating the object file, the output file format and the output architecture. In order to determine these two things, i check a valid linkable object file with the tool objdump:

objdump -f main.o

这给了我以下信息:

main.o:     file format pe-x86-64
architecture: i386:x86-64, flags 0x00000039:
HAS_RELOC, HAS_DEBUG, HAS_SYMS, HAS_LOCALS
start address 0x0000000000000000

现在有了这些知识，我可以创建目标文件了:

With this knowledge now i can create the object file:

objcopy -I binary -O pe-x86-64 -B i386 data_file.data data_file_data.o

为了处理大量文件，批处理文件可能会派上用场.

In order to handle large number of files, batch files could come in handy.

然后，我只需将生成的目标文件与程序源链接在一起，并通过符号轻松引用objcopy生成的指针，这些符号的名称可以轻松查询:

I then simply link the produced object file(s) together with my programs source and dereference the pointers that objcopy generated, through the symbols, whose names could easily be queried with:

objdump -t data_file_data.o

这将导致:

data_file_data.o:     file format pe-x86-64

SYMBOL TABLE:
[  0](sec  1)(fl 0x00)(ty  0)(scl  2) (nx 0) 0x0000000000000000 _binary_data_file_data_start
[  1](sec  1)(fl 0x00)(ty  0)(scl  2) (nx 0) 0x0000000000000006 _binary_data_file_data_end
[  2](sec -1)(fl 0x00)(ty  0)(scl  2) (nx 0) 0x0000000000000006 _binary_data_file_data_size

实际上，以下代码适用于GCC/G++:

Practically speaking, the following code works with GCC/G++:

extern uint8_t data[]   asm("_binary_data_file_data_start");
extern uint8_t end[]    asm("_binary_data_file_data_end");

以及以下MSVC++:

extern "C" uint8_t _binary_data_file_data_start[]; // Same name as symbol
extern "C" uint8_t _binary_data_file_data_end[];   // Same name as symbol

每个文件的大小通过以下方式计算:

The size of each each file is calculated with:

_binary_data_file_data_end - _binary_data_file_data_start

例如，您可以将数据写回到文件中

You could for example write the data back into a file:

FILE* file;

file = fopen("data_file_reproduced.data", "wb");
fwrite(_binary_data_file_data_start,                               //Pointer to data
       1,                                                          //Write block size
       _binary_data_file_data_end - _binary_data_file_data_start,  //Data size
       file);

fclose(file);

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