51 lines
2.7 KiB
Go
51 lines
2.7 KiB
Go
// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package disklayout provides Linux ext file system's disk level structures
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// which can be directly read into from the underlying device. Structs aim to
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// emulate structures `exactly` how they are layed out on disk.
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//
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// This library aims to be compatible with all ext(2/3/4) systems so it
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// provides a generic interface for all major structures and various
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// implementations (for different versions). The user code is responsible for
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// using appropriate implementations based on the underlying device.
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//
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// Interfacing all major structures here serves a few purposes:
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// - Abstracts away the complexity of the underlying structure from client
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// code. The client only has to figure out versioning on set up and then
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// can use these as black boxes and pass it higher up the stack.
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// - Having pointer receivers forces the user to use pointers to these
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// heavy structs. Hence, prevents the client code from unintentionally
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// copying these by value while passing the interface around.
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// - Version-based implementation selection is resolved on set up hence
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// avoiding per call overhead of choosing implementation.
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// - All interface methods are pretty light weight (do not take in any
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// parameters by design). Passing pointer arguments to interface methods
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// can lead to heap allocation as the compiler won't be able to perform
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// escape analysis on an unknown implementation at compile time.
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//
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// Notes:
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// - All fields in these structs are exported because binary.Read would
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// panic otherwise.
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// - All structures on disk are in little-endian order. Only jbd2 (journal)
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// structures are in big-endian order.
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// - All OS dependent fields in these structures will be interpretted using
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// the Linux version of that field.
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// - The suffix `Lo` in field names stands for lower bits of that field.
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// - The suffix `Hi` in field names stands for upper bits of that field.
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// - The suffix `Raw` has been added to indicate that the field is not split
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// into Lo and Hi fields and also to resolve name collision with the
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// respective interface.
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package disklayout
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