github.com/Kolosok86/http@v0.1.2/internal/chunked.go (about) 1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // The wire protocol for HTTP's "chunked" Transfer-Encoding. 6 7 // Package internal contains HTTP internals shared by net/http and 8 // net/http/httputil. 9 package internal 10 11 import ( 12 "bufio" 13 "bytes" 14 "errors" 15 "fmt" 16 "io" 17 ) 18 19 const maxLineLength = 4096 // assumed <= bufio.defaultBufSize 20 21 var ErrLineTooLong = errors.New("header line too long") 22 23 // NewChunkedReader returns a new chunkedReader that translates the data read from r 24 // out of HTTP "chunked" format before returning it. 25 // The chunkedReader returns io.EOF when the final 0-length chunk is read. 26 // 27 // NewChunkedReader is not needed by normal applications. The http package 28 // automatically decodes chunking when reading response bodies. 29 func NewChunkedReader(r io.Reader) io.Reader { 30 br, ok := r.(*bufio.Reader) 31 if !ok { 32 br = bufio.NewReader(r) 33 } 34 return &chunkedReader{r: br} 35 } 36 37 type chunkedReader struct { 38 r *bufio.Reader 39 n uint64 // unread bytes in chunk 40 err error 41 buf [2]byte 42 checkEnd bool // whether need to check for \r\n chunk footer 43 } 44 45 func (cr *chunkedReader) beginChunk() { 46 // chunk-size CRLF 47 var line []byte 48 line, cr.err = readChunkLine(cr.r) 49 if cr.err != nil { 50 return 51 } 52 cr.n, cr.err = parseHexUint(line) 53 if cr.err != nil { 54 return 55 } 56 if cr.n == 0 { 57 cr.err = io.EOF 58 } 59 } 60 61 func (cr *chunkedReader) chunkHeaderAvailable() bool { 62 n := cr.r.Buffered() 63 if n > 0 { 64 peek, _ := cr.r.Peek(n) 65 return bytes.IndexByte(peek, '\n') >= 0 66 } 67 return false 68 } 69 70 func (cr *chunkedReader) Read(b []uint8) (n int, err error) { 71 for cr.err == nil { 72 if cr.checkEnd { 73 if n > 0 && cr.r.Buffered() < 2 { 74 // We have some data. Return early (per the io.Reader 75 // contract) instead of potentially blocking while 76 // reading more. 77 break 78 } 79 if _, cr.err = io.ReadFull(cr.r, cr.buf[:2]); cr.err == nil { 80 if string(cr.buf[:]) != "\r\n" { 81 cr.err = errors.New("malformed chunked encoding") 82 break 83 } 84 } else { 85 if cr.err == io.EOF { 86 cr.err = io.ErrUnexpectedEOF 87 } 88 break 89 } 90 cr.checkEnd = false 91 } 92 if cr.n == 0 { 93 if n > 0 && !cr.chunkHeaderAvailable() { 94 // We've read enough. Don't potentially block 95 // reading a new chunk header. 96 break 97 } 98 cr.beginChunk() 99 continue 100 } 101 if len(b) == 0 { 102 break 103 } 104 rbuf := b 105 if uint64(len(rbuf)) > cr.n { 106 rbuf = rbuf[:cr.n] 107 } 108 var n0 int 109 n0, cr.err = cr.r.Read(rbuf) 110 n += n0 111 b = b[n0:] 112 cr.n -= uint64(n0) 113 // If we're at the end of a chunk, read the next two 114 // bytes to verify they are "\r\n". 115 if cr.n == 0 && cr.err == nil { 116 cr.checkEnd = true 117 } else if cr.err == io.EOF { 118 cr.err = io.ErrUnexpectedEOF 119 } 120 } 121 return n, cr.err 122 } 123 124 // Read a line of bytes (up to \n) from b. 125 // Give up if the line exceeds maxLineLength. 126 // The returned bytes are owned by the bufio.Reader 127 // so they are only valid until the next bufio read. 128 func readChunkLine(b *bufio.Reader) ([]byte, error) { 129 p, err := b.ReadSlice('\n') 130 if err != nil { 131 // We always know when EOF is coming. 132 // If the caller asked for a line, there should be a line. 133 if err == io.EOF { 134 err = io.ErrUnexpectedEOF 135 } else if err == bufio.ErrBufferFull { 136 err = ErrLineTooLong 137 } 138 return nil, err 139 } 140 if len(p) >= maxLineLength { 141 return nil, ErrLineTooLong 142 } 143 p = trimTrailingWhitespace(p) 144 p, err = removeChunkExtension(p) 145 if err != nil { 146 return nil, err 147 } 148 return p, nil 149 } 150 151 func trimTrailingWhitespace(b []byte) []byte { 152 for len(b) > 0 && isASCIISpace(b[len(b)-1]) { 153 b = b[:len(b)-1] 154 } 155 return b 156 } 157 158 func isASCIISpace(b byte) bool { 159 return b == ' ' || b == '\t' || b == '\n' || b == '\r' 160 } 161 162 var semi = []byte(";") 163 164 // removeChunkExtension removes any chunk-extension from p. 165 // For example, 166 // 167 // "0" => "0" 168 // "0;token" => "0" 169 // "0;token=val" => "0" 170 // `0;token="quoted string"` => "0" 171 func removeChunkExtension(p []byte) ([]byte, error) { 172 p, _, _ = bytes.Cut(p, semi) 173 // TODO: care about exact syntax of chunk extensions? We're 174 // ignoring and stripping them anyway. For now just never 175 // return an error. 176 return p, nil 177 } 178 179 // NewChunkedWriter returns a new chunkedWriter that translates writes into HTTP 180 // "chunked" format before writing them to w. Closing the returned chunkedWriter 181 // sends the final 0-length chunk that marks the end of the stream but does 182 // not send the final CRLF that appears after trailers; trailers and the last 183 // CRLF must be written separately. 184 // 185 // NewChunkedWriter is not needed by normal applications. The http 186 // package adds chunking automatically if handlers don't set a 187 // Content-Length header. Using newChunkedWriter inside a handler 188 // would result in double chunking or chunking with a Content-Length 189 // length, both of which are wrong. 190 func NewChunkedWriter(w io.Writer) io.WriteCloser { 191 return &chunkedWriter{w} 192 } 193 194 // Writing to chunkedWriter translates to writing in HTTP chunked Transfer 195 // Encoding wire format to the underlying Wire chunkedWriter. 196 type chunkedWriter struct { 197 Wire io.Writer 198 } 199 200 // Write the contents of data as one chunk to Wire. 201 // NOTE: Note that the corresponding chunk-writing procedure in Conn.Write has 202 // a bug since it does not check for success of io.WriteString 203 func (cw *chunkedWriter) Write(data []byte) (n int, err error) { 204 205 // Don't send 0-length data. It looks like EOF for chunked encoding. 206 if len(data) == 0 { 207 return 0, nil 208 } 209 210 if _, err = fmt.Fprintf(cw.Wire, "%x\r\n", len(data)); err != nil { 211 return 0, err 212 } 213 if n, err = cw.Wire.Write(data); err != nil { 214 return 215 } 216 if n != len(data) { 217 err = io.ErrShortWrite 218 return 219 } 220 if _, err = io.WriteString(cw.Wire, "\r\n"); err != nil { 221 return 222 } 223 if bw, ok := cw.Wire.(*FlushAfterChunkWriter); ok { 224 err = bw.Flush() 225 } 226 return 227 } 228 229 func (cw *chunkedWriter) Close() error { 230 _, err := io.WriteString(cw.Wire, "0\r\n") 231 return err 232 } 233 234 // FlushAfterChunkWriter signals from the caller of NewChunkedWriter 235 // that each chunk should be followed by a flush. It is used by the 236 // http.Transport code to keep the buffering behavior for headers and 237 // trailers, but flush out chunks aggressively in the middle for 238 // request bodies which may be generated slowly. See Issue 6574. 239 type FlushAfterChunkWriter struct { 240 *bufio.Writer 241 } 242 243 func parseHexUint(v []byte) (n uint64, err error) { 244 for i, b := range v { 245 switch { 246 case '0' <= b && b <= '9': 247 b = b - '0' 248 case 'a' <= b && b <= 'f': 249 b = b - 'a' + 10 250 case 'A' <= b && b <= 'F': 251 b = b - 'A' + 10 252 default: 253 return 0, errors.New("invalid byte in chunk length") 254 } 255 if i == 16 { 256 return 0, errors.New("http chunk length too large") 257 } 258 n <<= 4 259 n |= uint64(b) 260 } 261 return 262 }