/* punycode-sample.c 2.0.0 (2004-Mar-21-Sun) http://www.nicemice.net/idn/ Adam M. Costello http://www.nicemice.net/amc/ This is ANSI C code (C89) implementing Punycode 1.0.x. */ /**********************************************************/ /* Implementation (would normally go in its own .c file): */ #include <string.h> #include "punycode.h" /*** Bootstring parameters for Punycode ***/ enum { base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700, initial_bias = 72, initial_n = 0x80, delimiter = 0x2D }; /* basic(cp) tests whether cp is a basic code point: */ #define basic(cp) ((punycode_uint)(cp) < 0x80) /* delim(cp) tests whether cp is a delimiter: */ #define delim(cp) ((cp) == delimiter) /* decode_digit(cp) returns the numeric value of a basic code */ /* point (for use in representing integers) in the range 0 to */ /* base-1, or base if cp does not represent a value. */ static punycode_uint decode_digit(punycode_uint cp) { return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 : cp - 97 < 26 ? cp - 97 : base; } /* encode_digit(d,flag) returns the basic code point whose value */ /* (when used for representing integers) is d, which needs to be in */ /* the range 0 to base-1. The lowercase form is used unless flag is */ /* nonzero, in which case the uppercase form is used. The behavior */ /* is undefined if flag is nonzero and digit d has no uppercase form. */ static char encode_digit(punycode_uint d, int flag) { return d + 22 + 75 * (d < 26) - ((flag != 0) << 5); /* 0..25 map to ASCII a..z or A..Z */ /* 26..35 map to ASCII 0..9 */ } /* flagged(bcp) tests whether a basic code point is flagged */ /* (uppercase). The behavior is undefined if bcp is not a */ /* basic code point. */ #define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26) /* encode_basic(bcp,flag) forces a basic code point to lowercase */ /* if flag is zero, uppercase if flag is nonzero, and returns */ /* the resulting code point. The code point is unchanged if it */ /* is caseless. The behavior is undefined if bcp is not a basic */ /* code point. */ static char encode_basic(punycode_uint bcp, int flag) { bcp -= (bcp - 97 < 26) << 5; return bcp + ((!flag && (bcp - 65 < 26)) << 5); } /*** Platform-specific constants ***/ /* maxint is the maximum value of a punycode_uint variable: */ static const punycode_uint maxint = -1; /* Because maxint is unsigned, -1 becomes the maximum value. */ /*** Bias adaptation function ***/ static punycode_uint adapt( punycode_uint delta, punycode_uint numpoints, int firsttime ) { punycode_uint k; delta = firsttime ? delta / damp : delta >> 1; /* delta >> 1 is a faster way of doing delta / 2 */ delta += delta / numpoints; for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base) { delta /= base - tmin; } return k + (base - tmin + 1) * delta / (delta + skew); } /*** Main encode function ***/ enum punycode_status punycode_encode( size_t input_length_orig, const punycode_uint input[], const unsigned char case_flags[], size_t *output_length, char output[] ) { punycode_uint input_length, n, delta, h, b, bias, j, m, q, k, t; size_t out, max_out; /* The Punycode spec assumes that the input length is the same type */ /* of integer as a code point, so we need to convert the size_t to */ /* a punycode_uint, which could overflow. */ if (input_length_orig > maxint) return punycode_overflow; input_length = (punycode_uint) input_length_orig; /* Initialize the state: */ n = initial_n; delta = 0; out = 0; max_out = *output_length; bias = initial_bias; /* Handle the basic code points: */ for (j = 0; j < input_length; ++j) { if (basic(input[j])) { if (max_out - out < 2) return punycode_big_output; output[out++] = case_flags ? encode_basic(input[j], case_flags[j]) : (char) input[j]; } /* else if (input[j] < n) return punycode_bad_input; */ /* (not needed for Punycode with unsigned code points) */ } h = b = (punycode_uint) out; /* cannot overflow because out <= input_length <= maxint */ /* h is the number of code points that have been handled, b is the */ /* number of basic code points, and out is the number of ASCII code */ /* points that have been output. */ if (b > 0) output[out++] = delimiter; /* Main encoding loop: */ while (h < input_length) { /* All non-basic code points < n have been */ /* handled already. Find the next larger one: */ for (m = maxint, j = 0; j < input_length; ++j) { /* if (basic(input[j])) continue; */ /* (not needed for Punycode) */ if (input[j] >= n && input[j] < m) m = input[j]; } /* Increase delta enough to advance the decoder's */ /* <n,i> state to <m,0>, but guard against overflow: */ if (m - n > (maxint - delta) / (h + 1)) return punycode_overflow; delta += (m - n) * (h + 1); n = m; for (j = 0; j < input_length; ++j) { /* Punycode does not need to check whether input[j] is basic: */ if (input[j] < n /* || basic(input[j]) */ ) { if (++delta == 0) return punycode_overflow; } if (input[j] == n) { /* Represent delta as a generalized variable-length integer: */ for (q = delta, k = base; ; k += base) { if (out >= max_out) return punycode_big_output; t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */ k >= bias + tmax ? tmax : k - bias; if (q < t) break; output[out++] = encode_digit(t + (q - t) % (base - t), 0); q = (q - t) / (base - t); } output[out++] = encode_digit(q, case_flags && case_flags[j]); bias = adapt(delta, h + 1, h == b); delta = 0; ++h; } } ++delta, ++n; } *output_length = out; return punycode_success; } /*** Main decode function ***/ enum punycode_status punycode_decode( size_t input_length, const char input[], size_t *output_length, punycode_uint output[], unsigned char case_flags[] ) { punycode_uint n, out, i, max_out, bias, oldi, w, k, digit, t; size_t b, j, in; /* Initialize the state: */ n = initial_n; out = i = 0; max_out = *output_length > maxint ? maxint : (punycode_uint) *output_length; bias = initial_bias; /* Handle the basic code points: Let b be the number of input code */ /* points before the last delimiter, or 0 if there is none, then */ /* copy the first b code points to the output. */ for (b = j = 0; j < input_length; ++j) if (delim(input[j])) b = j; if (b > max_out) return punycode_big_output; for (j = 0; j < b; ++j) { if (case_flags) case_flags[out] = flagged(input[j]); if (!basic(input[j])) return punycode_bad_input; output[out++] = input[j]; } /* Main decoding loop: Start just after the last delimiter if any */ /* basic code points were copied; start at the beginning otherwise. */ for (in = b > 0 ? b + 1 : 0; in < input_length; ++out) { /* in is the index of the next ASCII code point to be consumed, */ /* and out is the number of code points in the output array. */ /* Decode a generalized variable-length integer into delta, */ /* which gets added to i. The overflow checking is easier */ /* if we increase i as we go, then subtract off its starting */ /* value at the end to obtain delta. */ for (oldi = i, w = 1, k = base; ; k += base) { if (in >= input_length) return punycode_bad_input; digit = decode_digit(input[in++]); if (digit >= base) return punycode_bad_input; if (digit > (maxint - i) / w) return punycode_overflow; i += digit * w; t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */ k >= bias + tmax ? tmax : k - bias; if (digit < t) break; if (w > maxint / (base - t)) return punycode_overflow; w *= (base - t); } bias = adapt(i - oldi, out + 1, oldi == 0); /* i was supposed to wrap around from out+1 to 0, */ /* incrementing n each time, so we'll fix that now: */ if (i / (out + 1) > maxint - n) return punycode_overflow; n += i / (out + 1); i %= (out + 1); /* Insert n at position i of the output: */ /* not needed for Punycode: */ /* if (basic(n)) return punycode_bad_input; */ if (out >= max_out) return punycode_big_output; if (case_flags) { memmove(case_flags + i + 1, case_flags + i, out - i); /* Case of last ASCII code point determines case flag: */ case_flags[i] = flagged(input[in - 1]); } memmove(output + i + 1, output + i, (out - i) * sizeof *output); output[i++] = n; } *output_length = (size_t) out; /* cannot overflow because out <= old value of *output_length */ return punycode_success; }