75 lines
3.2 KiB
Go
75 lines
3.2 KiB
Go
/*
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xgbgen constructs Go source files from xproto XML description files. xgbgen
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accomplishes the same task as the Python code generator for XCB and xpyb.
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Usage:
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xgbgen [flags] some-protocol.xml
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The flags are:
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--proto-path path
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The path to a directory containing xproto XML description files.
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This is only necessary when 'some-protocol.xml' imports other
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protocol files.
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--gofmt=true
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When false, the outputted Go code will not be gofmt'd. And it won't
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be very pretty at all. This is typically useful if there are syntax
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errors that need to be debugged in code generation. gofmt will hiccup;
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this will allow you to see the raw code.
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How it works
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xgbgen works by parsing the input XML file using Go's encoding/xml package.
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The majority of this work is done in xml.go and xml_fields.go, where the
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appropriate types are declared.
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Due to the nature of the XML in the protocol description files, the types
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required to parse the XML are not well suited to reasoning about code
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generation. Because of this, all data parsed in the XML types is translated
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into more reasonable types. This translation is done in translation.go,
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and is mainly grunt work. (The only interesting tidbits are the translation
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of XML names to Go source names, and connecting fields with their
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appropriate types.)
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The organization of these types is greatly
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inspired by the description of the XML found here:
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http://cgit.freedesktop.org/xcb/proto/tree/doc/xml-xcb.txt
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These types come with a lot of supporting methods to make their use in
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code generation easier. They can be found in expression.go, field.go,
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protocol.go, request_reply.go and type.go. Of particular interest are
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expression evaluation and size calculation (in bytes).
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These types also come with supporting methods that convert their
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representation into Go source code. I've quartered such methods in
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go.go, go_error.go, go_event.go, go_list.go, go_request_reply.go,
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go_single_field.go, go_struct.go and go_union.go. The idea is to keep
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as much of the Go specific code generation in one area as possible. Namely,
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while not *all* Go related code is found in the 'go*.go' files, *most*
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of it is. (If there's any interest in using xgbgen for other languages,
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I'd be happy to try and make xgbgen a little more friendly in this regard.
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I did, however, design xgbgen with this in mind, so it shouldn't involve
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anything as serious as a re-design.)
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Why
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I wrote xgbgen because I found the existing code generator that was written in
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Python to be unwieldy. In particular, static and strong typing greatly helped
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me reason better about the code generation task.
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What does not work
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The core X protocol should be completely working. As far as I know, most
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extensions should work too, although I've only tested (and not much) the
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Xinerama and RandR extensions.
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XKB does not work. I don't have any real plans of working on this unless there
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is demand and I have some test cases to work with. (i.e., even if I could get
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something generated for XKB, I don't have the inclination to understand it
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enough to verify that it works.) XKB poses several extremely difficult
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problems that XCB also has trouble with. More info on that can be found at
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http://cgit.freedesktop.org/xcb/libxcb/tree/doc/xkb_issues and
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http://cgit.freedesktop.org/xcb/libxcb/tree/doc/xkb_internals.
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*/
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package main
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