Source file src/pkg/http/lex.go

     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	package http
     6	
     7	// This file deals with lexical matters of HTTP
     8	
     9	func isSeparator(c byte) bool {
    10		switch c {
    11		case '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}', ' ', '\t':
    12			return true
    13		}
    14		return false
    15	}
    16	
    17	func isSpace(c byte) bool {
    18		switch c {
    19		case ' ', '\t', '\r', '\n':
    20			return true
    21		}
    22		return false
    23	}
    24	
    25	func isCtl(c byte) bool { return (0 <= c && c <= 31) || c == 127 }
    26	
    27	func isChar(c byte) bool { return 0 <= c && c <= 127 }
    28	
    29	func isAnyText(c byte) bool { return !isCtl(c) }
    30	
    31	func isQdText(c byte) bool { return isAnyText(c) && c != '"' }
    32	
    33	func isToken(c byte) bool { return isChar(c) && !isCtl(c) && !isSeparator(c) }
    34	
    35	// Valid escaped sequences are not specified in RFC 2616, so for now, we assume
    36	// that they coincide with the common sense ones used by GO. Malformed
    37	// characters should probably not be treated as errors by a robust (forgiving)
    38	// parser, so we replace them with the '?' character.
    39	func httpUnquotePair(b byte) byte {
    40		// skip the first byte, which should always be '\'
    41		switch b {
    42		case 'a':
    43			return '\a'
    44		case 'b':
    45			return '\b'
    46		case 'f':
    47			return '\f'
    48		case 'n':
    49			return '\n'
    50		case 'r':
    51			return '\r'
    52		case 't':
    53			return '\t'
    54		case 'v':
    55			return '\v'
    56		case '\\':
    57			return '\\'
    58		case '\'':
    59			return '\''
    60		case '"':
    61			return '"'
    62		}
    63		return '?'
    64	}
    65	
    66	// raw must begin with a valid quoted string. Only the first quoted string is
    67	// parsed and is unquoted in result. eaten is the number of bytes parsed, or -1
    68	// upon failure.
    69	func httpUnquote(raw []byte) (eaten int, result string) {
    70		buf := make([]byte, len(raw))
    71		if raw[0] != '"' {
    72			return -1, ""
    73		}
    74		eaten = 1
    75		j := 0 // # of bytes written in buf
    76		for i := 1; i < len(raw); i++ {
    77			switch b := raw[i]; b {
    78			case '"':
    79				eaten++
    80				buf = buf[0:j]
    81				return i + 1, string(buf)
    82			case '\\':
    83				if len(raw) < i+2 {
    84					return -1, ""
    85				}
    86				buf[j] = httpUnquotePair(raw[i+1])
    87				eaten += 2
    88				j++
    89				i++
    90			default:
    91				if isQdText(b) {
    92					buf[j] = b
    93				} else {
    94					buf[j] = '?'
    95				}
    96				eaten++
    97				j++
    98			}
    99		}
   100		return -1, ""
   101	}
   102	
   103	// This is a best effort parse, so errors are not returned, instead not all of
   104	// the input string might be parsed. result is always non-nil.
   105	func httpSplitFieldValue(fv string) (eaten int, result []string) {
   106		result = make([]string, 0, len(fv))
   107		raw := []byte(fv)
   108		i := 0
   109		chunk := ""
   110		for i < len(raw) {
   111			b := raw[i]
   112			switch {
   113			case b == '"':
   114				eaten, unq := httpUnquote(raw[i:len(raw)])
   115				if eaten < 0 {
   116					return i, result
   117				} else {
   118					i += eaten
   119					chunk += unq
   120				}
   121			case isSeparator(b):
   122				if chunk != "" {
   123					result = result[0 : len(result)+1]
   124					result[len(result)-1] = chunk
   125					chunk = ""
   126				}
   127				i++
   128			case isToken(b):
   129				chunk += string(b)
   130				i++
   131			case b == '\n' || b == '\r':
   132				i++
   133			default:
   134				chunk += "?"
   135				i++
   136			}
   137		}
   138		if chunk != "" {
   139			result = result[0 : len(result)+1]
   140			result[len(result)-1] = chunk
   141			chunk = ""
   142		}
   143		return i, result
   144	}
The Go Programming Language

Source file src/pkg/http/lex.go
