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created the repository for the thymian project
author ferencd
date Tue, 17 Aug 2021 11:19:54 +0200
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-1:000000000000 0:a4671277546c
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
11 #include <string.h>
12
13 /*** Bootstring parameters for Punycode ***/
14
15 enum { base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700,
16 initial_bias = 72, initial_n = 0x80, delimiter = 0x2D };
17
18 /* basic(cp) tests whether cp is a basic code point: */
19 #define basic(cp) ((punycode_uint)(cp) < 0x80)
20
21 /* delim(cp) tests whether cp is a delimiter: */
22 #define delim(cp) ((cp) == delimiter)
23
24 /* decode_digit(cp) returns the numeric value of a basic code */
25 /* point (for use in representing integers) in the range 0 to */
26 /* base-1, or base if cp is does not represent a value. */
27
28 static punycode_uint decode_digit(punycode_uint cp)
29 {
30 return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 :
31 cp - 97 < 26 ? cp - 97 : (punycode_uint) base;
32 }
33
34 /* encode_digit(d,flag) returns the basic code point whose value */
35 /* (when used for representing integers) is d, which needs to be in */
36 /* the range 0 to base-1. The lowercase form is used unless flag is */
37 /* nonzero, in which case the uppercase form is used. The behavior */
38 /* is undefined if flag is nonzero and digit d has no uppercase form. */
39
40 static char encode_digit(punycode_uint d, int flag)
41 {
42 return d + 22 + 75 * (d < 26) - ((flag != 0) << 5);
43 /* 0..25 map to ASCII a..z or A..Z */
44 /* 26..35 map to ASCII 0..9 */
45 }
46
47 /* flagged(bcp) tests whether a basic code point is flagged */
48 /* (uppercase). The behavior is undefined if bcp is not a */
49 /* basic code point. */
50
51 #define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26)
52
53 /* encode_basic(bcp,flag) forces a basic code point to lowercase */
54 /* if flag is zero, uppercase if flag is nonzero, and returns */
55 /* the resulting code point. The code point is unchanged if it */
56 /* is caseless. The behavior is undefined if bcp is not a basic */
57 /* code point. */
58
59 static char encode_basic(punycode_uint bcp, int flag)
60 {
61 bcp -= (bcp - 97 < 26) << 5;
62 return bcp + ((!flag && (bcp - 65 < 26)) << 5);
63 }
64
65 /*** Platform-specific constants ***/
66
67 /* maxint is the maximum value of a punycode_uint variable: */
68 static const punycode_uint maxint = -1U;
69 /* Because maxint is unsigned, -1 becomes the maximum value. */
70
71 /*** Bias adaptation function ***/
72
73 static punycode_uint adapt(
74 punycode_uint delta, punycode_uint numpoints, int firsttime )
75 {
76 punycode_uint k;
77
78 delta = firsttime ? delta / damp : delta >> 1;
79 /* delta >> 1 is a faster way of doing delta / 2 */
80 delta += delta / numpoints;
81
82 for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base) {
83 delta /= base - tmin;
84 }
85
86 return k + (base - tmin + 1) * delta / (delta + skew);
87 }
88
89 /*** Main encode function ***/
90
91 enum punycode_status punycode_encode(
92 punycode_uint input_length,
93 const punycode_uint input[],
94 const unsigned char case_flags[],
95 punycode_uint *output_length,
96 char output[] )
97 {
98 punycode_uint n, delta, h, b, out, max_out, bias, j, m, q, k, t;
99
100 /* Initialize the state: */
101
102 n = initial_n;
103 delta = out = 0;
104 max_out = *output_length;
105 bias = initial_bias;
106
107 /* Handle the basic code points: */
108
109 for (j = 0; j < input_length; ++j) {
110 if (basic(input[j])) {
111 if (max_out - out < 2) return punycode_big_output;
112 output[out++] =
113 case_flags ? encode_basic(input[j], case_flags[j]) : input[j];
114 }
115 /* else if (input[j] < n) return punycode_bad_input; */
116 /* (not needed for Punycode with unsigned code points) */
117 }
118
119 h = b = out;
120
121 /* h is the number of code points that have been handled, b is the */
122 /* number of basic code points, and out is the number of characters */
123 /* that have been output. */
124
125 if (b > 0) output[out++] = delimiter;
126
127 /* Main encoding loop: */
128
129 while (h < input_length) {
130 /* All non-basic code points < n have been */
131 /* handled already. Find the next larger one: */
132
133 for (m = maxint, j = 0; j < input_length; ++j) {
134 /* if (basic(input[j])) continue; */
135 /* (not needed for Punycode) */
136 if (input[j] >= n && input[j] < m) m = input[j];
137 }
138
139 /* Increase delta enough to advance the decoder's */
140 /* <n,i> state to <m,0>, but guard against overflow: */
141
142 if (m - n > (maxint - delta) / (h + 1)) return punycode_overflow;
143 delta += (m - n) * (h + 1);
144 n = m;
145
146 for (j = 0; j < input_length; ++j) {
147 /* Punycode does not need to check whether input[j] is basic: */
148 if (input[j] < n /* || basic(input[j]) */ ) {
149 if (++delta == 0) return punycode_overflow;
150 }
151
152 if (input[j] == n) {
153 /* Represent delta as a generalized variable-length integer: */
154
155 for (q = delta, k = base; ; k += base) {
156 if (out >= max_out) return punycode_big_output;
157 t = k <= bias /* + tmin */ ? (punycode_uint) tmin : /* +tmin not needed */
158 k >= (punycode_uint) bias + (punycode_uint) tmax ? (punycode_uint) tmax : k - (punycode_uint) bias;
159 if (q < t) break;
160 output[out++] = encode_digit(t + (q - t) % (base - t), 0);
161 q = (q - t) / (base - t);
162 }
163
164 output[out++] = encode_digit(q, case_flags && case_flags[j]);
165 bias = adapt(delta, h + 1, h == b);
166 delta = 0;
167 ++h;
168 }
169 }
170
171 ++delta, ++n;
172 }
173
174 *output_length = out;
175 return punycode_success;
176 }
177
178 /*** Main decode function ***/
179
180 enum punycode_status punycode_decode(
181 punycode_uint input_length,
182 const char input[],
183 punycode_uint *output_length,
184 punycode_uint output[],
185 unsigned char case_flags[] )
186 {
187 punycode_uint n, out, i, max_out, bias,
188 b, j, in, oldi, w, k, digit, t;
189
190 /* Initialize the state: */
191
192 n = initial_n;
193 out = i = 0;
194 max_out = *output_length;
195 bias = initial_bias;
196
197 /* Handle the basic code points: Let b be the number of input code */
198 /* points before the last delimiter, or 0 if there is none, then */
199 /* copy the first b code points to the output. */
200
201 for (b = j = 0; j < input_length; ++j) if (delim(input[j])) b = j;
202 if (b > max_out) return punycode_big_output;
203
204 for (j = 0; j < b; ++j) {
205 if (case_flags) case_flags[out] = flagged(input[j]);
206 if (!basic(input[j])) return punycode_bad_input;
207 output[out++] = input[j];
208 }
209
210 /* Main decoding loop: Start just after the last delimiter if any */
211 /* basic code points were copied; start at the beginning otherwise. */
212
213 for (in = b > 0 ? b + 1 : 0; in < input_length; ++out) {
214
215 /* in is the index of the next character to be consumed, and */
216 /* out is the number of code points in the output array. */
217
218 /* Decode a generalized variable-length integer into delta, */
219 /* which gets added to i. The overflow checking is easier */
220 /* if we increase i as we go, then subtract off its starting */
221 /* value at the end to obtain delta. */
222
223 for (oldi = i, w = 1, k = base; ; k += base) {
224 if (in >= input_length) return punycode_bad_input;
225 digit = decode_digit(input[in++]);
226 if (digit >= base) return punycode_bad_input;
227 if (digit > (maxint - i) / w) return punycode_overflow;
228 i += digit * w;
229 t = k <= (punycode_uint) bias /* + tmin */ ? (punycode_uint) tmin : /* +tmin not needed */
230 k >= (punycode_uint) bias + (punycode_uint) tmax ? (punycode_uint) tmax : k - (punycode_uint) bias;
231 if (digit < t) break;
232 if (w > maxint / (base - t)) return punycode_overflow;
233 w *= (base - t);
234 }
235
236 bias = adapt(i - oldi, out + 1, oldi == 0);
237
238 /* i was supposed to wrap around from out+1 to 0, */
239 /* incrementing n each time, so we'll fix that now: */
240
241 if (i / (out + 1) > maxint - n) return punycode_overflow;
242 n += i / (out + 1);
243 i %= (out + 1);
244
245 /* Insert n at position i of the output: */
246
247 /* not needed for Punycode: */
248 /* if (decode_digit(n) <= base) return punycode_invalid_input; */
249 if (out >= max_out) return punycode_big_output;
250
251 if (case_flags) {
252 memmove(case_flags + i + 1, case_flags + i, out - i);
253 /* Case of last character determines uppercase flag: */
254 case_flags[i] = flagged(input[in - 1]);
255 }
256
257 memmove(output + i + 1, output + i, (out - i) * sizeof *output);
258 output[i++] = n;
259 }
260
261 *output_length = out;
262 return punycode_success;
263 }