54 lines
2.1 KiB
Markdown
54 lines
2.1 KiB
Markdown
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# Filesystem Git Database
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JSGit repositories need `loadAs`, `saveAs`, `loadRaw`, `saveRaw`, `readRef`, and
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`updateRef` methods.
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Depending on the backing storage, there are various ways to implement these
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methods.
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The implementation for in-memory storage is `js-git/mixins/mem-db`, and there
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are variants for using Github or IndexDB for storage.
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The `js-git/mixins/fs-db` implementation provides these methods as well, but
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depends on a file system interface providing `readFile`, `readChunk`,
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`writeFile`, and `readDir`.
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These file system methods are implemented by the `git-fs-db` and
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`git-chrome-db` packages.
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For the purpose of this document, `=>` implies that the function does not block
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and accepts a Node.js-style callback.
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The arrow points to the type of the result.
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None of these methods need to return a continuable if the nodeback is missing.
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The type `binary` stands for whatever binary representation is appropriate for
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the underlying platform.
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For browsers, binary is a `Uint8Array`.
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For Node.js, binary is a `Buffer`.
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## readFile(path) => binary | undefined
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Reads the entirety of the file at the given path and produces the binary.
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If the file does not exist, readFile provides `undefined` instead.
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## readChunk(path, start, end) => binary | undefined
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Reads a byte range of the file at the given path.
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The byte range is a half open interval, including the byte at the initial index,
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and excluding the byte at the terminal index, such that the end minus the start
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is the length of the resulting binary data.
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The end offset may be negative, in which case it should count back from the end
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of the size of the file at the path, such that the size plus the negative end is
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the positive end.
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If the file does not exist, readChunk provides `undefined` instead.
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## writeFile(path, binary) => undefined
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Writes the given bytes to the file at the given path.
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The method creates any directories leading up to the path if they do not already
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exist.
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## readDir(path) => array of names | undefined
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Reads the names of the entries in the directory at the given path.
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The names are not fully qualified paths, just the name of the entry within the
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given directory.
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