58e72a2179
Correct an age-old calco (is that a typo-like word for calc) in the documentation. * ls/packet-line-protocol-doc-fix: pack-protocol: fix maximum pkt-line size
100 lines
2.9 KiB
Plaintext
100 lines
2.9 KiB
Plaintext
Documentation Common to Pack and Http Protocols
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===============================================
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ABNF Notation
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-------------
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ABNF notation as described by RFC 5234 is used within the protocol documents,
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except the following replacement core rules are used:
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----
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HEXDIG = DIGIT / "a" / "b" / "c" / "d" / "e" / "f"
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----
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We also define the following common rules:
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----
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NUL = %x00
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zero-id = 40*"0"
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obj-id = 40*(HEXDIGIT)
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refname = "HEAD"
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refname /= "refs/" <see discussion below>
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----
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A refname is a hierarchical octet string beginning with "refs/" and
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not violating the 'git-check-ref-format' command's validation rules.
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More specifically, they:
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. They can include slash `/` for hierarchical (directory)
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grouping, but no slash-separated component can begin with a
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dot `.`.
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. They must contain at least one `/`. This enforces the presence of a
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category like `heads/`, `tags/` etc. but the actual names are not
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restricted.
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. They cannot have two consecutive dots `..` anywhere.
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. They cannot have ASCII control characters (i.e. bytes whose
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values are lower than \040, or \177 `DEL`), space, tilde `~`,
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caret `^`, colon `:`, question-mark `?`, asterisk `*`,
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or open bracket `[` anywhere.
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. They cannot end with a slash `/` or a dot `.`.
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. They cannot end with the sequence `.lock`.
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. They cannot contain a sequence `@{`.
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. They cannot contain a `\\`.
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pkt-line Format
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---------------
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Much (but not all) of the payload is described around pkt-lines.
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A pkt-line is a variable length binary string. The first four bytes
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of the line, the pkt-len, indicates the total length of the line,
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in hexadecimal. The pkt-len includes the 4 bytes used to contain
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the length's hexadecimal representation.
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A pkt-line MAY contain binary data, so implementors MUST ensure
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pkt-line parsing/formatting routines are 8-bit clean.
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A non-binary line SHOULD BE terminated by an LF, which if present
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MUST be included in the total length. Receivers MUST treat pkt-lines
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with non-binary data the same whether or not they contain the trailing
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LF (stripping the LF if present, and not complaining when it is
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missing).
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The maximum length of a pkt-line's data component is 65516 bytes.
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Implementations MUST NOT send pkt-line whose length exceeds 65520
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(65516 bytes of payload + 4 bytes of length data).
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Implementations SHOULD NOT send an empty pkt-line ("0004").
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A pkt-line with a length field of 0 ("0000"), called a flush-pkt,
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is a special case and MUST be handled differently than an empty
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pkt-line ("0004").
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----
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pkt-line = data-pkt / flush-pkt
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data-pkt = pkt-len pkt-payload
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pkt-len = 4*(HEXDIG)
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pkt-payload = (pkt-len - 4)*(OCTET)
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flush-pkt = "0000"
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----
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Examples (as C-style strings):
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----
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pkt-line actual value
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---------------------------------
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"0006a\n" "a\n"
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"0005a" "a"
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"000bfoobar\n" "foobar\n"
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"0004" ""
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----
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