Line data Source code
1 : /*
2 : punycode.c from RFC 3492
3 : http://www.nicemice.net/idn/
4 : Adam M. Costello
5 : http://www.nicemice.net/amc/
6 :
7 : This is ANSI C code (C89) implementing Punycode (RFC 3492).
8 :
9 :
10 : C. Disclaimer and license
11 :
12 : Regarding this entire document or any portion of it (including
13 : the pseudocode and C code), the author makes no guarantees and
14 : is not responsible for any damage resulting from its use. The
15 : author grants irrevocable permission to anyone to use, modify,
16 : and distribute it in any way that does not diminish the rights
17 : of anyone else to use, modify, and distribute it, provided that
18 : redistributed derivative works do not contain misleading author or
19 : version information. Derivative works need not be licensed under
20 : similar terms.
21 : */
22 :
23 : #include "punycode.h"
24 :
25 : /**********************************************************/
26 : /* Implementation (would normally go in its own .c file): */
27 :
28 : #include <string.h>
29 :
30 : /*** Bootstring parameters for Punycode ***/
31 :
32 : enum { base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700,
33 : initial_bias = 72, initial_n = 0x80, delimiter = 0x2D };
34 :
35 : /* basic(cp) tests whether cp is a basic code point: */
36 : #define basic(cp) ((punycode_uint)(cp) < 0x80)
37 :
38 : /* delim(cp) tests whether cp is a delimiter: */
39 : #define delim(cp) ((cp) == delimiter)
40 :
41 : /* decode_digit(cp) returns the numeric value of a basic code */
42 : /* point (for use in representing integers) in the range 0 to */
43 : /* base-1, or base if cp is does not represent a value. */
44 :
45 0 : static punycode_uint decode_digit(punycode_uint cp)
46 : {
47 0 : return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 :
48 0 : cp - 97 < 26 ? cp - 97 : base;
49 : }
50 :
51 : /* encode_digit(d,flag) returns the basic code point whose value */
52 : /* (when used for representing integers) is d, which needs to be in */
53 : /* the range 0 to base-1. The lowercase form is used unless flag is */
54 : /* nonzero, in which case the uppercase form is used. The behavior */
55 : /* is undefined if flag is nonzero and digit d has no uppercase form. */
56 :
57 0 : static char encode_digit(punycode_uint d, int flag)
58 : {
59 0 : return d + 22 + 75 * (d < 26) - ((flag != 0) << 5);
60 : /* 0..25 map to ASCII a..z or A..Z */
61 : /* 26..35 map to ASCII 0..9 */
62 : }
63 :
64 : /* flagged(bcp) tests whether a basic code point is flagged */
65 : /* (uppercase). The behavior is undefined if bcp is not a */
66 : /* basic code point. */
67 :
68 : #define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26)
69 :
70 : /* encode_basic(bcp,flag) forces a basic code point to lowercase */
71 : /* if flag is zero, uppercase if flag is nonzero, and returns */
72 : /* the resulting code point. The code point is unchanged if it */
73 : /* is caseless. The behavior is undefined if bcp is not a basic */
74 : /* code point. */
75 :
76 0 : static char encode_basic(punycode_uint bcp, int flag)
77 : {
78 0 : bcp -= (bcp - 97 < 26) << 5;
79 0 : return bcp + ((!flag && (bcp - 65 < 26)) << 5);
80 : }
81 :
82 : /*** Platform-specific constants ***/
83 :
84 : /* maxint is the maximum value of a punycode_uint variable: */
85 : static const punycode_uint maxint = (punycode_uint) -1;
86 : /* Because maxint is unsigned, -1 becomes the maximum value. */
87 :
88 : /*** Bias adaptation function ***/
89 :
90 0 : static punycode_uint adapt(
91 : punycode_uint delta, punycode_uint numpoints, int firsttime )
92 : {
93 : punycode_uint k;
94 :
95 0 : delta = firsttime ? delta / damp : delta >> 1;
96 : /* delta >> 1 is a faster way of doing delta / 2 */
97 0 : delta += delta / numpoints;
98 :
99 0 : for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base) {
100 0 : delta /= base - tmin;
101 : }
102 :
103 0 : return k + (base - tmin + 1) * delta / (delta + skew);
104 : }
105 :
106 : /*** Main encode function ***/
107 :
108 0 : enum punycode_status punycode_encode(
109 : punycode_uint input_length,
110 : const punycode_uint input[],
111 : const unsigned char case_flags[],
112 : punycode_uint *output_length,
113 : char output[] )
114 : {
115 : punycode_uint n, delta, h, b, out, max_out, bias, j, m, q, k, t;
116 :
117 : /* Initialize the state: */
118 :
119 0 : n = initial_n;
120 0 : delta = out = 0;
121 0 : max_out = *output_length;
122 0 : bias = initial_bias;
123 :
124 : /* Handle the basic code points: */
125 :
126 0 : for (j = 0; j < input_length; ++j) {
127 0 : if (basic(input[j])) {
128 0 : if (max_out - out < 2) return punycode_big_output;
129 0 : output[out++] =
130 0 : case_flags ? encode_basic(input[j], case_flags[j]) : (char)input[j];
131 : }
132 : /* else if (input[j] < n) return punycode_bad_input; */
133 : /* (not needed for Punycode with unsigned code points) */
134 : }
135 :
136 0 : h = b = out;
137 :
138 : /* h is the number of code points that have been handled, b is the */
139 : /* number of basic code points, and out is the number of characters */
140 : /* that have been output. */
141 :
142 0 : if (b > 0) output[out++] = delimiter;
143 :
144 : /* Main encoding loop: */
145 :
146 0 : while (h < input_length) {
147 : /* All non-basic code points < n have been */
148 : /* handled already. Find the next larger one: */
149 :
150 0 : for (m = maxint, j = 0; j < input_length; ++j) {
151 : /* if (basic(input[j])) continue; */
152 : /* (not needed for Punycode) */
153 0 : if (input[j] >= n && input[j] < m) m = input[j];
154 : }
155 :
156 : /* Increase delta enough to advance the decoder's */
157 : /* <n,i> state to <m,0>, but guard against overflow: */
158 :
159 0 : if (m - n > (maxint - delta) / (h + 1)) return punycode_overflow;
160 0 : delta += (m - n) * (h + 1);
161 0 : n = m;
162 :
163 0 : for (j = 0; j < input_length; ++j) {
164 : /* Punycode does not need to check whether input[j] is basic: */
165 0 : if (input[j] < n /* || basic(input[j]) */ ) {
166 0 : if (++delta == 0) return punycode_overflow;
167 : }
168 :
169 0 : if (input[j] == n) {
170 : /* Represent delta as a generalized variable-length integer: */
171 :
172 0 : for (q = delta, k = base; ; k += base) {
173 0 : if (out >= max_out) return punycode_big_output;
174 0 : t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */
175 0 : k >= bias + tmax ? tmax : k - bias;
176 0 : if (q < t) break;
177 0 : output[out++] = encode_digit(t + (q - t) % (base - t), 0);
178 0 : q = (q - t) / (base - t);
179 : }
180 :
181 0 : output[out++] = encode_digit(q, case_flags && case_flags[j]);
182 0 : bias = adapt(delta, h + 1, h == b);
183 0 : delta = 0;
184 0 : ++h;
185 : }
186 : }
187 :
188 0 : ++delta, ++n;
189 : }
190 :
191 0 : *output_length = out;
192 0 : return punycode_success;
193 : }
194 :
195 : /*** Main decode function ***/
196 :
197 0 : enum punycode_status punycode_decode(
198 : punycode_uint input_length,
199 : const char input[],
200 : punycode_uint *output_length,
201 : punycode_uint output[],
202 : unsigned char case_flags[] )
203 : {
204 : punycode_uint n, out, i, max_out, bias,
205 : b, j, in, oldi, w, k, digit, t;
206 :
207 0 : if (!input_length) {
208 0 : return punycode_bad_input;
209 : }
210 :
211 : /* Initialize the state: */
212 :
213 0 : n = initial_n;
214 0 : out = i = 0;
215 0 : max_out = *output_length;
216 0 : bias = initial_bias;
217 :
218 : /* Handle the basic code points: Let b be the number of input code */
219 : /* points before the last delimiter, or 0 if there is none, then */
220 : /* copy the first b code points to the output. */
221 :
222 0 : for (b = 0, j = input_length - 1 ; j > 0; --j) {
223 0 : if (delim(input[j])) {
224 0 : b = j;
225 0 : break;
226 : }
227 : }
228 0 : if (b > max_out) return punycode_big_output;
229 :
230 0 : for (j = 0; j < b; ++j) {
231 0 : if (case_flags) case_flags[out] = flagged(input[j]);
232 0 : if (!basic(input[j])) return punycode_bad_input;
233 0 : output[out++] = input[j];
234 : }
235 :
236 : /* Main decoding loop: Start just after the last delimiter if any */
237 : /* basic code points were copied; start at the beginning otherwise. */
238 :
239 0 : for (in = b > 0 ? b + 1 : 0; in < input_length; ++out) {
240 :
241 : /* in is the index of the next character to be consumed, and */
242 : /* out is the number of code points in the output array. */
243 :
244 : /* Decode a generalized variable-length integer into delta, */
245 : /* which gets added to i. The overflow checking is easier */
246 : /* if we increase i as we go, then subtract off its starting */
247 : /* value at the end to obtain delta. */
248 :
249 0 : for (oldi = i, w = 1, k = base; ; k += base) {
250 0 : if (in >= input_length) return punycode_bad_input;
251 0 : digit = decode_digit(input[in++]);
252 0 : if (digit >= base) return punycode_bad_input;
253 0 : if (digit > (maxint - i) / w) return punycode_overflow;
254 0 : i += digit * w;
255 0 : t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */
256 0 : k >= bias + tmax ? tmax : k - bias;
257 0 : if (digit < t) break;
258 0 : if (w > maxint / (base - t)) return punycode_overflow;
259 0 : w *= (base - t);
260 : }
261 :
262 0 : bias = adapt(i - oldi, out + 1, oldi == 0);
263 :
264 : /* i was supposed to wrap around from out+1 to 0, */
265 : /* incrementing n each time, so we'll fix that now: */
266 :
267 0 : if (i / (out + 1) > maxint - n) return punycode_overflow;
268 0 : n += i / (out + 1);
269 0 : i %= (out + 1);
270 :
271 : /* Insert n at position i of the output: */
272 :
273 : /* not needed for Punycode: */
274 : /* if (decode_digit(n) <= base) return punycode_invalid_input; */
275 0 : if (out >= max_out) return punycode_big_output;
276 :
277 0 : if (case_flags) {
278 0 : memmove(case_flags + i + 1, case_flags + i, out - i);
279 : /* Case of last character determines uppercase flag: */
280 0 : case_flags[i] = flagged(input[in - 1]);
281 : }
282 :
283 0 : memmove(output + i + 1, output + i, (out - i) * sizeof *output);
284 0 : output[i++] = n;
285 : }
286 :
287 0 : *output_length = out;
288 0 : return punycode_success;
289 : }
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