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30 .\" @(#)unvis.3 8.2 (Berkeley) 12/11/93
41 .Nd decode a visual representation of characters
47 .Fn unvis "char *cp" "int c" "int *astate" "int flag"
49 .Fn strunvis "char *dst" "const char *src"
51 .Fn strnunvis "char *dst" "size_t dlen" "const char *src"
53 .Fn strunvisx "char *dst" "const char *src" "int flag"
55 .Fn strnunvisx "char *dst" "size_t dlen" "const char *src" "int flag"
63 are used to decode a visual representation of characters, as produced
71 function is called with successive characters in
73 until a valid sequence is recognized, at which time the decoded
74 character is available at the character pointed to by
79 function decodes the characters pointed to by
81 into the buffer pointed to by
85 function simply copies
89 decoding any escape sequences along the way,
90 and returns the number of characters placed into
93 invalid escape sequence was detected.
96 should be equal to the size of
98 (that is, no expansion takes place during decoding).
102 function does the same as the
105 but it allows you to add a flag that specifies the style the string
108 Currently, the supported flags are:
115 function implements a state machine that can be used to decode an
116 arbitrary stream of bytes.
117 All state associated with the bytes being decoded is stored outside the
119 function (that is, a pointer to the state is passed in), so
120 calls decoding different streams can be freely intermixed.
121 To start decoding a stream of bytes, first initialize an integer to zero.
124 with each successive byte, along with a pointer
125 to this integer, and a pointer to a destination character.
128 function has several return codes that must be handled properly.
130 .Bl -tag -width ".Dv UNVIS_VALIDPUSH"
132 Another character is necessary; nothing has been recognized yet.
134 A valid character has been recognized and is available at the location
137 .It Dv UNVIS_VALIDPUSH
138 A valid character has been recognized and is available at the location
141 however, the character currently passed in should be passed in again.
143 A valid sequence was detected, but no character was produced.
144 This return code is necessary to indicate a logical break between characters.
146 An invalid escape sequence was detected, or the decoder is in an unknown state.
147 The decoder is placed into the starting state.
150 When all bytes in the stream have been processed, call
152 one more time with flag set to
154 to extract any remaining character (the character passed in is ignored).
158 argument is also used to specify the encoding style of the source.
164 will decode URI strings as specified in RFC 1808.
168 will decode entity references and numeric character references
169 as specified in RFC 1866.
173 will decode MIME Quoted-Printable strings as specified in RFC 2045.
181 The following code fragment illustrates a proper use of
183 .Bd -literal -offset indent
187 while ((ch = getchar()) != EOF) {
189 switch(unvis(&out, ch, &state, 0)) {
196 case UNVIS_VALIDPUSH:
200 errx(EXIT_FAILURE, "Bad character sequence!");
203 if (unvis(&out, '\e0', &state, UNVIS_END) == UNVIS_VALID)
213 will return \-1 on error and set
218 An invalid escape sequence was detected, or the decoder is in an unknown state.
221 In addition the functions
230 Not enough space to perform the conversion.
238 .%T Relative Uniform Resource Locators
251 functions appeared in
259 Percent-encoding was defined in RFC 1738, the original RFC for URL.
260 RFC 1866 defines HTML 2.0, an application of SGML, from which it
261 inherits concepts of numeric character references and entity