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