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-This package implements the go_marshal utility.
-
-# Overview
-
-`go_marshal` is a code generation utility similar to `go_stateify` for
-marshalling go data structures to and from memory.
-
-`go_marshal` attempts to improve on `binary.Write` and the sentry's
-`binary.Marshal` by moving the expensive use of reflection from runtime to
-compile-time.
-
-`go_marshal` automatically generates implementations for `marshal.Marshallable`
-interface. Data structures that require custom serialization can be accomodated
-through a manual implementation this interface.
-
-Data structures can be flagged for code generation by adding a struct-level
-comment `// +marshal`. For additional details and options, see the documentation
-for the `marshal.Marshallable` interface.
-
-# Usage
-
-See `defs.bzl`: a new rule is provided, `go_marshal`.
-
-Under the hood, the `go_marshal` rule is used to generate a file that will
-appear in a Go target; the output file should appear explicitly in a srcs list.
-For example (note that the above is the preferred method):
-
-```
-load("<PKGPATH>/gvisor/tools/go_marshal:defs.bzl", "go_marshal")
-
-go_marshal(
- name = "foo_abi",
- srcs = ["foo.go"],
- out = "foo_abi.go",
- package = "foo",
-)
-
-go_library(
- name = "foo",
- srcs = [
- "foo.go",
- "foo_abi.go",
- ],
- ...
-)
-```
-
-As part of the interface generation, `go_marshal` also generates some tests for
-sanity checking the struct definitions for potential alignment issues, and a
-simple round-trip test through Marshal/Unmarshal to verify the implementation.
-These tests use reflection to verify properties of the ABI struct, and should be
-considered part of the generated interfaces (but are too expensive to execute at
-runtime). Ensure these tests run at some point.
-
-# Restrictions
-
-Not all valid go type definitions can be used with `go_marshal`. `go_marshal` is
-intended for ABI structs, which have these additional restrictions:
-
-- At the moment, `go_marshal` only supports struct declarations.
-
-- Structs are marshalled as packed types. This means no implicit padding is
- inserted between fields shorter than the platform register size. For
- alignment, manually insert padding fields.
-
-- Structs used with `go_marshal` must have a compile-time static size. This
- means no dynamically sizes fields like slices or strings. Use statically
- sized array (byte arrays for strings) instead.
-
-- No pointers, channel, map or function pointer fields, and no fields that are
- arrays of these types. These don't make sense in an ABI data structure.
-
-- We could support opaque pointers as `uintptr`, but this is currently not
- implemented. Implementing this would require handling the architecture
- dependent native pointer size.
-
-- Fields must either be a primitive integer type (`byte`,
- `[u]int{8,16,32,64}`), or of a type that implements `marshal.Marshallable`.
-
-- `int` and `uint` fields are not allowed. Use an explicitly-sized numeric
- type.
-
-- `float*` fields are currently not supported, but could be if necessary.
-
-# Appendix
-
-## Working with Non-Packed Structs
-
-ABI structs must generally be packed types, meaning they should have no implicit
-padding between short fields. However, if a field is tagged
-`marshal:"unaligned"`, `go_marshal` will fall back to a safer but slower
-mechanism to deal with potentially unaligned fields.
-
-Note that the non-packed property is inheritted by any other struct that embeds
-this struct, since the `go_marshal` tool currently can't reason about alignments
-for embedded structs that are not aligned.
-
-Because of this, it's generally best to avoid using `marshal:"unaligned"` and
-insert explicit padding fields instead.
-
-## Modifying the `go_marshal` Tool
-
-The following are some guidelines for modifying the `go_marshal` tool:
-
-- The `go_marshal` tool currently does a single pass over all types requesting
- code generation, in arbitrary order. This means the generated code can't
- directly obtain information about embedded marshallable types at
- compile-time. One way to work around this restriction is to add a new
- Marshallable interface method providing this piece of information, and
- calling it from the generated code. Use this sparingly, as we want to rely
- on compile-time information as much as possible for performance.
-
-- No runtime reflection in the code generated for the marshallable interface.
- The entire point of the tool is to avoid runtime reflection. The generated
- tests may use reflection.
-
-## Debugging
-
-To enable debugging output from the go-marshal tool, use one of the following
-options, depending on how go-marshal is being invoked:
-
-- Pass `--define gomarshal=verbose` to the bazel command. Note that this can
- generate a lot of output depending on what's being compiled, as this will
- enable debugging for all packages built by the command.
-
-- Set `marshal_debug = True` on the top-level `go_library` BUILD rule.
-
-- Set `debug = True` on the `go_marshal` BUILD rule.
-
-- Pass `-debug` to the go-marshal tool invocation.