我目前使用 C++ 使用 boost::graph 进行一些与图相关的计算。
boost::graph 可以将其图形输出为点文件，我使用 std::stringstream 来捕获输出点文件。因此，点文件的内容驻留在内存中。
我想使用点文件来可视化图形（尽可能快）。因此我想生成点文件，生成 svg 文件并将其打印到画布上。我想避免为此使用临时文件，因为图形应该很小并且内存无论如何都是可用的。
然而，graphviz libgraph 只有函数 extern Agraph_t *agread(FILE *); 我能想象到使其工作的唯一方法是在文件句柄 struct __FILE 中进行修改实在是不便携。
在 Unix/linux 中，如何让库将内存内容作为文件读取？
我刚刚发现 GraphViz 的 libcgraph 允许在此处输入重载版本，但到目前为止，文档并未指出一些有用的地方。
I currently use C++ to do some graph related computation using boost::graph.
boost::graph can output its graph as a dot file and I use a std::stringstream to capture the output dot file. Thus the contents of the dot file resides in memory.
I want to use the dot file to visualize the graph (as fast as possible). Thus I want to generate the dot file, generate an svg file and print it onto some canvas. I want to avoid using temporary files for this, as the graphs shall be small and memory is available anyway.
However graphviz libgraph has only the function extern Agraph_t *agread(FILE *); the only way I can imagine to make this working is to hack around in the filehandle struct __FILE which is really not portable.
How would you let a library read you memory contents as a file in Unix/linux?
I just found out that libcgraph from GraphViz allows to enter a overloaded version here, but so far the documentation doesn't point me to some usefull place.
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好吧，这可以说是 API 中的一个错误，但这里有一个想法。这是假设 agread() 函数将以二进制数据的形式读取文件。
请注意，我不熟悉您正在使用的 API，但我希望这无论如何都会有用。
mmap()将文件映射到内存中。agread()时，将该文件描述符打开到FILE *结构中（fopen()或fdopen( )如果您没有关闭描述符）。FILE *结构。编辑：或者，忽略我的回答并使用
fmemopen()调用。它可能正是您所需要的。不过，我不想删除我的答案，以防有人正在写回复:-)。Well, it is arguably a bug in the API, but here's an idea. This is assuming that the
agread()function would read the file in as binary data.Note that I am not familiar with the API you're using, but I hope this may be useful anyway.
mmap().agread(), open that file descriptor into aFILE *struct (fopen()orfdopen()if you didn't close the descriptor).FILE *struct.Edit: Or, ignore my answer and use the
fmemopen()call. It probably is exactly what you need. I didn't want to delete my answer though, in case someone is currently writing a response :-).您可以使用 < 创建管道code>pipe()，将数据写入输入端，使用
fdopen()将输出文件描述符转换为适合传递给agread()的文件句柄。但是，只有当您确定数据小于
PIPE_BUF字节；否则写入可能会永远阻塞，因为另一端没有任何读取内容。一般来说，使用临时文件更容易、更可靠。只需使用
tmpfile()获取文件句柄，将数据写入其中，倒带并将其传递给agread()：（当然，您应该检查是否有错误，但我没有这样做为了简洁起见。）
You could create a pipe with
pipe(), write the data into the input end and usefdopen()to turn the output file descriptor into a filehandle suitable for passing intoagread().However, this will only work if you're sure that the data is less than
PIPE_BUFbytes; otherwise the write might block forever, since there's nothing reading from the other end.In general, using temporary files is much easier and more reliable. Just use
tmpfile()to get a file handle, write the data into it, rewind and pass it toagread():(Of course, you should check for errors, which I didn't for the sake of brevity.)
如果您愿意使用 GNU libc 扩展，您可以将 C 字符串作为
FILE*打开；该文档位于 http://www.gnu.org/s /libc/manual/html_node/String-Streams.html。If you are willing to use a GNU libc extension, you can open a C string as a
FILE*; the documentation is at http://www.gnu.org/s/libc/manual/html_node/String-Streams.html.在 Windows 上，您可以使用 fopen 打开命名管道。
因此，您可以在单独的线程中创建一个管道，在其中推送数据，agread 将从其中读取数据，而不需要临时文件。
On Windows, you can open a named pipe with fopen.
So you can create a pipe in a separate thread where you push the data on it, and agread will read from it without a need for a temporary file.