91 lines
2.3 KiB
Markdown
91 lines
2.3 KiB
Markdown
# FAT Filesystem Library for Go
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This library implements the ability to create, read, and write
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FAT filesystems using pure Go.
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**WARNING:** While the implementation works (to some degree, see the
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limitations section below), I highly recommend you **don't** use this
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library, since it has many limitations and is generally a terrible
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implementation of FAT. For educational purposes, however, this library
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may be interesting.
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In this library's current state, it is very good for _reading_ FAT
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filesystems, and minimally useful for _creating_ FAT filesystems. See
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the features and limitations below.
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## Features & Limitations
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Features:
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* Format a brand new FAT filesystem on a file backed device
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* Create files and directories
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* Traverse filesystem
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Limitations:
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This library has several limitations. They're easily able to be overcome,
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but because I didn't need them for my use case, I didn't bother:
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* Files/directories cannot be deleted or renamed.
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* Files never shrink in size.
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* Deleted file/directory entries are never reclaimed, so fragmentation
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grows towards infinity. Eventually, your "disk" will become full even
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if you just create and delete a single file.
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* There are some serious corruption possibilities in error cases. Cleanup
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is not good.
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* Incomplete FAT32 implementation (although FAT12 and FAT16 are complete).
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## Usage
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Here is some example usage where an existing disk image is read and
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a file is created in the root directory:
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```go
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// Assume this file was created already with a FAT filesystem
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f, err := os.OpenFile("FLOPPY.dmg", os.O_RDWR|os.O_CREATE, 0666)
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if err != nil {
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panic(err)
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}
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defer f.Close()
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// BlockDevice backed by a file
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device, err := fs.NewFileDisk(f)
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if err != nil {
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panic(err)
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}
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filesys, err := fat.New(device)
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if err != nil {
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panic(err)
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}
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rootDir, err := filesys.RootDir()
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if err != nil {
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panic(err)
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}
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subEntry, err := rootDir.AddFile("HELLO_WORLD")
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if err != nil {
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panic(err)
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}
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file, err := subEntry.File()
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if err != nil {
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panic(err)
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}
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_, err = io.WriteString(file, "I am the contents of this file.")
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if err != nil {
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panic(err)
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}
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```
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## Thanks
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Thanks to the following resources which helped in the creation of this
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library:
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* [fat32-lib](https://code.google.com/p/fat32-lib/)
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* [File Allocation Table on Wikipedia](http://en.wikipedia.org/wiki/File_Allocation_Table)
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* Microsoft FAT filesystem specification
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