175 lines · 4.7 KB
| 1 | /** |
| 2 | * Git pkt-line format encoding/decoding. |
| 3 | * See: https://git-scm.com/docs/protocol-common#_pkt_line_format |
| 4 | * |
| 5 | * Each pkt-line is: 4-hex-digit length prefix + payload. |
| 6 | * Length includes the 4 prefix bytes. Special lines: |
| 7 | * "0000" = flush packet |
| 8 | * "0001" = delimiter packet |
| 9 | * "0002" = response-end packet |
| 10 | */ |
| 11 | |
| 12 | const FLUSH_PKT = '0000'; |
| 13 | const DELIM_PKT = '0001'; |
| 14 | const RESPONSE_END_PKT = '0002'; |
| 15 | |
| 16 | const encoder = new TextEncoder(); |
| 17 | const decoder = new TextDecoder(); |
| 18 | |
| 19 | /** Encode a string as a pkt-line (includes trailing newline if not present). */ |
| 20 | export function pktLineEncode(data: string): Uint8Array { |
| 21 | const payload = encoder.encode(data); |
| 22 | const len = payload.length + 4; |
| 23 | const hex = len.toString(16).padStart(4, '0'); |
| 24 | const result = new Uint8Array(len); |
| 25 | result.set(encoder.encode(hex), 0); |
| 26 | result.set(payload, 4); |
| 27 | return result; |
| 28 | } |
| 29 | |
| 30 | /** Encode raw bytes as a pkt-line. */ |
| 31 | export function pktLineEncodeBytes(data: Uint8Array): Uint8Array { |
| 32 | const len = data.length + 4; |
| 33 | const hex = len.toString(16).padStart(4, '0'); |
| 34 | const result = new Uint8Array(len); |
| 35 | result.set(encoder.encode(hex), 0); |
| 36 | result.set(data, 4); |
| 37 | return result; |
| 38 | } |
| 39 | |
| 40 | /** Return a flush packet ("0000"). */ |
| 41 | export function pktFlush(): Uint8Array { |
| 42 | return encoder.encode(FLUSH_PKT); |
| 43 | } |
| 44 | |
| 45 | /** Return a delimiter packet ("0001"). */ |
| 46 | export function pktDelim(): Uint8Array { |
| 47 | return encoder.encode(DELIM_PKT); |
| 48 | } |
| 49 | |
| 50 | /** Concatenate multiple pkt-line segments into a single Uint8Array. */ |
| 51 | export function pktConcat(...parts: Uint8Array[]): Uint8Array { |
| 52 | const totalLen = parts.reduce((sum, p) => sum + p.length, 0); |
| 53 | const result = new Uint8Array(totalLen); |
| 54 | let offset = 0; |
| 55 | for (const part of parts) { |
| 56 | result.set(part, offset); |
| 57 | offset += part.length; |
| 58 | } |
| 59 | return result; |
| 60 | } |
| 61 | |
| 62 | /** Parsed pkt-line: either a data line, flush, delimiter, or response-end. */ |
| 63 | export type PktLine = |
| 64 | | { type: 'data'; data: Uint8Array } |
| 65 | | { type: 'flush' } |
| 66 | | { type: 'delim' } |
| 67 | | { type: 'response-end' }; |
| 68 | |
| 69 | /** |
| 70 | * Parse all pkt-lines from a buffer. |
| 71 | * Returns the parsed lines and any remaining bytes that weren't a complete line. |
| 72 | */ |
| 73 | export function pktLineParse(buf: Uint8Array): { lines: PktLine[]; remaining: Uint8Array } { |
| 74 | const lines: PktLine[] = []; |
| 75 | let offset = 0; |
| 76 | |
| 77 | while (offset + 4 <= buf.length) { |
| 78 | const hexStr = decoder.decode(buf.slice(offset, offset + 4)); |
| 79 | const len = parseInt(hexStr, 16); |
| 80 | |
| 81 | if (isNaN(len)) { |
| 82 | break; |
| 83 | } |
| 84 | |
| 85 | if (len === 0) { |
| 86 | lines.push({ type: 'flush' }); |
| 87 | offset += 4; |
| 88 | continue; |
| 89 | } |
| 90 | |
| 91 | if (len === 1) { |
| 92 | lines.push({ type: 'delim' }); |
| 93 | offset += 4; |
| 94 | continue; |
| 95 | } |
| 96 | |
| 97 | if (len === 2) { |
| 98 | lines.push({ type: 'response-end' }); |
| 99 | offset += 4; |
| 100 | continue; |
| 101 | } |
| 102 | |
| 103 | if (offset + len > buf.length) { |
| 104 | // Incomplete packet |
| 105 | break; |
| 106 | } |
| 107 | |
| 108 | const data = buf.slice(offset + 4, offset + len); |
| 109 | lines.push({ type: 'data', data }); |
| 110 | offset += len; |
| 111 | } |
| 112 | |
| 113 | return { lines, remaining: buf.slice(offset) }; |
| 114 | } |
| 115 | |
| 116 | /** Parse a pkt-line data payload as a UTF-8 string, trimming trailing newline. */ |
| 117 | export function pktLineDataToString(line: PktLine): string | null { |
| 118 | if (line.type !== 'data') return null; |
| 119 | let str = decoder.decode(line.data); |
| 120 | if (str.endsWith('\n')) str = str.slice(0, -1); |
| 121 | return str; |
| 122 | } |
| 123 | |
| 124 | /** |
| 125 | * Build a service advertisement response (used by info/refs). |
| 126 | * Format: pkt-line "# service={service}\n" + flush + ref lines + flush |
| 127 | */ |
| 128 | export function buildServiceAdvertisement( |
| 129 | service: string, |
| 130 | refs: Array<{ sha: string; name: string }>, |
| 131 | capabilities: string[] |
| 132 | ): Uint8Array { |
| 133 | const parts: Uint8Array[] = []; |
| 134 | |
| 135 | // Service announcement |
| 136 | parts.push(pktLineEncode(`# service=${service}\n`)); |
| 137 | parts.push(pktFlush()); |
| 138 | |
| 139 | if (refs.length === 0) { |
| 140 | // Empty repo: advertise capabilities on a zero-id line |
| 141 | const zeroSha = '0'.repeat(40); |
| 142 | const capsStr = capabilities.join(' '); |
| 143 | parts.push(pktLineEncode(`${zeroSha} capabilities^{}\0${capsStr}\n`)); |
| 144 | } else { |
| 145 | for (let i = 0; i < refs.length; i++) { |
| 146 | const ref = refs[i]; |
| 147 | if (i === 0) { |
| 148 | // First ref includes capabilities after NUL |
| 149 | const capsStr = capabilities.join(' '); |
| 150 | parts.push(pktLineEncode(`${ref.sha} ${ref.name}\0${capsStr}\n`)); |
| 151 | } else { |
| 152 | parts.push(pktLineEncode(`${ref.sha} ${ref.name}\n`)); |
| 153 | } |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | parts.push(pktFlush()); |
| 158 | return pktConcat(...parts); |
| 159 | } |
| 160 | |
| 161 | /** Side-band-64k channel IDs. */ |
| 162 | export const SIDE_BAND = { |
| 163 | DATA: 1, |
| 164 | PROGRESS: 2, |
| 165 | ERROR: 3, |
| 166 | } as const; |
| 167 | |
| 168 | /** Wrap data in a side-band-64k pkt-line. */ |
| 169 | export function pktSideBandEncode(channel: number, data: Uint8Array): Uint8Array { |
| 170 | const payload = new Uint8Array(1 + data.length); |
| 171 | payload[0] = channel; |
| 172 | payload.set(data, 1); |
| 173 | return pktLineEncodeBytes(payload); |
| 174 | } |
| 175 |