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-rw-r--r--escape.c428
1 files changed, 428 insertions, 0 deletions
diff --git a/escape.c b/escape.c
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+++ b/escape.c
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+/*
+ * Copyright (C) 2015, 2016 "IoT.bzh"
+ * Author: José Bollo <jose.bollo@iot.bzh>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#define _GNU_SOURCE
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+/*
+ * Test if 'c' is to be escaped or not.
+ * Any character that is not in [-.0-9A-Z_a-z~]
+ * must be escaped.
+ * Note that space versus + is not managed here.
+ */
+static inline int should_escape(char c)
+{
+/* ASCII CODES OF UNESCAPED CHARS
+car hx/oct idx
+'-' 2d/055 1
+'.' 2e/056 2
+'0' 30/060 3
+... ..
+'9' 39/071 12
+'A' 41/101 13
+... ..
+'Z' 5a/132 38
+'_' 5f/137 39
+'a' 61/141 40
+... ..
+'z' 7a/172 65
+'~' 7e/176 66
+*/
+ /* [-.0-9A-Z_a-z~] */
+ if (c <= 'Z') {
+ /* [-.0-9A-Z] */
+ if (c < '0') {
+ /* [-.] */
+ return c != '-' && c != '.';
+ } else {
+ /* [0-9A-Z] */
+ return c < 'A' && c > '9';
+ }
+ } else {
+ /* [_a-z~] */
+ if (c <= 'z') {
+ /* [_a-z] */
+ return c < 'a' && c != '_';
+ } else {
+ /* [~] */
+ return c != '~';
+ }
+ }
+}
+
+/*
+ * returns the ASCII char for the hexadecimal
+ * digit of the binary value 'f'.
+ * returns 0 if f isn't in [0 ... 15].
+ */
+static inline char bin2hex(int f)
+{
+ if ((f & 15) != f)
+ f = 0;
+ else if (f < 10)
+ f += '0';
+ else
+ f += 'A' - 10;
+ return (char)f;
+}
+
+/*
+ * returns the binary value for the hexadecimal
+ * digit whose char is 'c'.
+ * returns -1 if c isn't i n[0-9A-Fa-f]
+ */
+static inline int hex2bin(char c)
+{
+ /* [0-9A-Fa-f] */
+ if (c <= 'F') {
+ /* [0-9A-F] */
+ if (c <= '9') {
+ /* [0-9] */
+ if (c >= '0') {
+ return (int)(c - '0');
+ }
+ } else if (c >= 'A') {
+ /* [A-F] */
+ return (int)(c - ('A' - 10));
+ }
+ } else {
+ /* [a-f] */
+ if (c >= 'a' && c <= 'f') {
+ return (int)(c - ('a' - 10));
+ }
+ }
+ return -1;
+}
+
+/*
+ * returns the length that will have the text 'itext' of length
+ * 'ilen' when escaped. When 'ilen' == 0, strlen is used to
+ * compute the size of 'itext'.
+ */
+static size_t escaped_length(const char *itext, size_t ilen)
+{
+ char c;
+ size_t i, r;
+
+ if (!ilen)
+ ilen = strlen(itext);
+ c = itext[i = r = 0];
+ while (i < ilen) {
+ r += c != ' ' && should_escape(c) ? 3 : 1;
+ c = itext[++i];
+ }
+ return r;
+}
+
+/*
+ * Escapes the text 'itext' of length 'ilen'.
+ * When 'ilen' == 0, strlen is used to compute the size of 'itext'.
+ * The escaped text is put in 'otext' of length 'olen'.
+ * Returns the length of the escaped text (it can be greater than 'olen').
+ * When 'olen' is greater than the needed length, an extra null terminator
+ * is appened to the escaped string.
+ */
+static size_t escape_to(const char *itext, size_t ilen, char *otext, size_t olen)
+{
+ char c;
+ size_t i, r;
+
+ if (!ilen)
+ ilen = strlen(itext);
+ c = itext[i = r = 0];
+ while (i < ilen) {
+ if (c == ' ')
+ c = '+';
+ else if (should_escape(c)) {
+ if (r < olen)
+ otext[r] = '%';
+ r++;
+ if (r < olen)
+ otext[r] = bin2hex((c >> 4) & 15);
+ r++;
+ c = bin2hex(c & 15);
+ }
+ if (r < olen)
+ otext[r] = c;
+ r++;
+ c = itext[++i];
+ }
+ if (r < olen)
+ otext[r] = 0;
+ return r;
+}
+
+/*
+ * returns the length of 'itext' of length 'ilen' that can be unescaped.
+ * compute the size of 'itext' when 'ilen' == 0.
+ */
+static size_t unescapable_length(const char *itext, size_t ilen)
+{
+ char c;
+ size_t i;
+
+ c = itext[i = 0];
+ while (i < ilen) {
+ if (c != '%')
+ i++;
+ else {
+ if (i + 3 > ilen
+ || hex2bin(itext[i + 1]) < 0
+ || hex2bin(itext[i + 2]) < 0)
+ break;
+ i += 3;
+ }
+ c = itext[i];
+ }
+ return i;
+}
+
+/*
+ * returns the length that will have the text 'itext' of length
+ * 'ilen' when escaped. When 'ilen' == 0, strlen is used to
+ * compute the size of 'itext'.
+ */
+static size_t unescaped_length(const char *itext, size_t ilen)
+{
+ char c;
+ size_t i, r;
+
+ c = itext[i = r = 0];
+ while (i < ilen) {
+ i += (size_t)(1 + ((c == '%') << 1));
+ r++;
+ c = itext[i];
+ }
+ return r;
+}
+
+static size_t unescape_to(const char *itext, size_t ilen, char *otext, size_t olen)
+{
+ char c;
+ size_t i, r;
+ int h, l;
+
+ ilen = unescapable_length(itext, ilen);
+ c = itext[i = r = 0];
+ while (i < ilen) {
+ if (c != '%') {
+ if (c == '+')
+ c = ' ';
+ i++;
+ } else {
+ if (i + 2 >= ilen)
+ break;
+ h = hex2bin(itext[i + 1]);
+ l = hex2bin(itext[i + 2]);
+ c = (char)((h << 4) | l);
+ i += 3;
+ }
+ if (r < olen)
+ otext[r] = c;
+ r++;
+ c = itext[i];
+ }
+ if (r < olen)
+ otext[r] = 0;
+ return r;
+}
+
+/* create an url */
+char *escape_url(const char *base, const char *path, const char * const *args, size_t *length)
+{
+ int i;
+ size_t lb, lp, lq, l, L;
+ const char *null;
+ char *result;
+
+ /* ensure args */
+ if (!args) {
+ null = NULL;
+ args = &null;
+ }
+
+ /* compute lengths */
+ lb = base ? strlen(base) : 0;
+ lp = path ? strlen(path) : 0;
+ lq = 0;
+ i = 0;
+ while (args[i]) {
+ lq += 1 + escaped_length(args[i], strlen(args[i]));
+ i++;
+ if (args[i])
+ lq += 1 + escaped_length(args[i], strlen(args[i]));
+ i++;
+ }
+
+ /* allocation */
+ L = lb + lp + lq + 1;
+ result = malloc(L + 1);
+ if (result) {
+ /* make the resulting url */
+ l = lb;
+ if (lb) {
+ memcpy(result, base, lb);
+ if (result[l - 1] != '/' && path && path[0] != '/')
+ result[l++] = '/';
+ }
+ if (lp) {
+ memcpy(result + l, path, lp);
+ l += lp;
+ }
+ i = 0;
+ while (args[i]) {
+ if (i) {
+ result[l++] = '&';
+ } else if (base || path) {
+ result[l] = memchr(result, '?', l) ? '&' : '?';
+ l++;
+ }
+ l += escape_to(args[i], strlen(args[i]), result + l, L - l);
+ i++;
+ if (args[i]) {
+ result[l++] = '=';
+ l += escape_to(args[i], strlen(args[i]), result + l, L - l);
+ }
+ i++;
+ }
+ result[l] = 0;
+ if (length)
+ *length = l;
+ }
+ return result;
+}
+
+char *escape_args(const char * const *args, size_t *length)
+{
+ return escape_url(NULL, NULL, args, length);
+}
+
+const char **unescape_args(const char *args)
+{
+ const char **r, **q;
+ char c, *p;
+ size_t j, z, l, n, lt;
+
+ lt = n = 0;
+ if (args[0]) {
+ z = 0;
+ do {
+ l = strcspn(&args[z], "&=");
+ j = 1 + unescaped_length(&args[z], l);
+ lt += j;
+ z += l;
+ c = args[z++];
+ if (c == '=') {
+ l = strcspn(&args[z], "&");
+ j = 1 + unescaped_length(&args[z], l);
+ lt += j;
+ z += l;
+ c = args[z++];
+ }
+ n++;
+ } while(c);
+ }
+
+ l = lt + (2 * n + 1) * sizeof(char *);
+ r = malloc(l);
+ if (!r)
+ return r;
+
+ q = r;
+ p = (void*)&r[2 * n + 1];
+ if (args[0]) {
+ z = 0;
+ do {
+ q[0] = p;
+ l = strcspn(&args[z], "&=");
+ j = 1 + unescape_to(&args[z], l, p, lt);
+ lt -= j;
+ p += j;
+ z += l;
+ c = args[z++];
+ if (c != '=')
+ q[1] = NULL;
+ else {
+ q[1] = p;
+ l = strcspn(&args[z], "&");
+ j = 1 + unescape_to(&args[z], l, p, lt);
+ lt -= j;
+ p += j;
+ z += l;
+ c = args[z++];
+ }
+ q = &q[2];
+ } while(c);
+ }
+ q[0] = NULL;
+ return r;
+}
+
+char *escape(const char *text, size_t textlen, size_t *reslength)
+{
+ size_t len;
+ char *result;
+
+ len = 1 + escaped_length(text, textlen);
+ result = malloc(len);
+ if (result)
+ escape_to(text, textlen, result, len);
+ if (reslength)
+ *reslength = len - 1;
+ return result;
+}
+
+char *unescape(const char *text, size_t textlen, size_t *reslength)
+{
+ size_t len;
+ char *result;
+
+ len = 1 + unescaped_length(text, textlen);
+ result = malloc(len);
+ if (result)
+ unescape_to(text, textlen, result, len);
+ if (reslength)
+ *reslength = len - 1;
+ return result;
+}
+
+#if 1
+#include <stdio.h>
+int main(int ac, char **av)
+{
+ int i;
+ char *x = escape_args((void*)++av, NULL);
+ char *y = escape(x, strlen(x), NULL);
+ char *z = unescape(y, strlen(y), NULL);
+ const char **v = unescape_args(x);
+
+ printf("%s\n%s\n%s\n", x, y, z);
+ free(x);
+ free(y);
+ free(z);
+ i = 0;
+ while(v[i]) {
+ printf("%s=%s / %s=%s\n", av[i], av[i+1], v[i], v[i+1]);
+ i += 2;
+ }
+ free(v);
+ return 0;
+}
+#endif
+/* vim: set colorcolumn=80: */