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b31222cf SC |
1 | Documentation Common to Pack and Http Protocols |
2 | =============================================== | |
3 | ||
4 | ABNF Notation | |
5 | ------------- | |
6 | ||
7 | ABNF notation as described by RFC 5234 is used within the protocol documents, | |
8 | except the following replacement core rules are used: | |
9 | ---- | |
10 | HEXDIG = DIGIT / "a" / "b" / "c" / "d" / "e" / "f" | |
11 | ---- | |
12 | ||
13 | We also define the following common rules: | |
14 | ---- | |
15 | NUL = %x00 | |
16 | zero-id = 40*"0" | |
17 | obj-id = 40*(HEXDIGIT) | |
18 | ||
19 | refname = "HEAD" | |
20 | refname /= "refs/" <see discussion below> | |
21 | ---- | |
22 | ||
23 | A refname is a hierarchical octet string beginning with "refs/" and | |
24 | not violating the 'git-check-ref-format' command's validation rules. | |
25 | More specifically, they: | |
26 | ||
27 | . They can include slash `/` for hierarchical (directory) | |
28 | grouping, but no slash-separated component can begin with a | |
29 | dot `.`. | |
30 | ||
31 | . They must contain at least one `/`. This enforces the presence of a | |
32 | category like `heads/`, `tags/` etc. but the actual names are not | |
33 | restricted. | |
34 | ||
35 | . They cannot have two consecutive dots `..` anywhere. | |
36 | ||
37 | . They cannot have ASCII control characters (i.e. bytes whose | |
38 | values are lower than \040, or \177 `DEL`), space, tilde `~`, | |
39 | caret `{caret}`, colon `:`, question-mark `?`, asterisk `*`, | |
40 | or open bracket `[` anywhere. | |
41 | ||
42 | . They cannot end with a slash `/` nor a dot `.`. | |
43 | ||
44 | . They cannot end with the sequence `.lock`. | |
45 | ||
46 | . They cannot contain a sequence `@{`. | |
47 | ||
48 | . They cannot contain a `\\`. | |
49 | ||
50 | ||
51 | pkt-line Format | |
52 | --------------- | |
53 | ||
54 | Much (but not all) of the payload is described around pkt-lines. | |
55 | ||
56 | A pkt-line is a variable length binary string. The first four bytes | |
57 | of the line, the pkt-len, indicates the total length of the line, | |
58 | in hexadecimal. The pkt-len includes the 4 bytes used to contain | |
59 | the length's hexadecimal representation. | |
60 | ||
61 | A pkt-line MAY contain binary data, so implementors MUST ensure | |
62 | pkt-line parsing/formatting routines are 8-bit clean. | |
63 | ||
64 | A non-binary line SHOULD BE terminated by an LF, which if present | |
65 | MUST be included in the total length. | |
66 | ||
67 | The maximum length of a pkt-line's data component is 65520 bytes. | |
68 | Implementations MUST NOT send pkt-line whose length exceeds 65524 | |
69 | (65520 bytes of payload + 4 bytes of length data). | |
70 | ||
71 | Implementations SHOULD NOT send an empty pkt-line ("0004"). | |
72 | ||
73 | A pkt-line with a length field of 0 ("0000"), called a flush-pkt, | |
74 | is a special case and MUST be handled differently than an empty | |
75 | pkt-line ("0004"). | |
76 | ||
77 | ---- | |
78 | pkt-line = data-pkt / flush-pkt | |
79 | ||
80 | data-pkt = pkt-len pkt-payload | |
81 | pkt-len = 4*(HEXDIG) | |
82 | pkt-payload = (pkt-len - 4)*(OCTET) | |
83 | ||
84 | flush-pkt = "0000" | |
85 | ---- | |
86 | ||
87 | Examples (as C-style strings): | |
88 | ||
89 | ---- | |
90 | pkt-line actual value | |
91 | --------------------------------- | |
92 | "0006a\n" "a\n" | |
93 | "0005a" "a" | |
94 | "000bfoobar\n" "foobar\n" | |
95 | "0004" "" | |
96 | ---- |