+static int
+hexdigit (char d)
+{
+ switch (d) {
+ case '0'...'9': return d - '0';
+ case 'a'...'f': return d - 'a' + 10;
+ case 'A'...'F': return d - 'A' + 10;
+ default: return -1;
+ }
+}
+
+/* Parse double-quoted strings, replacing backslash escape sequences
+ * with the true character. Since the string is returned in place,
+ * the escapes must make the string shorter.
+ */
+static int
+parse_quoted_string (char *p)
+{
+ char *start = p;
+
+ for (; *p && *p != '"'; p++) {
+ if (*p == '\\') {
+ int m = 1, c;
+
+ switch (p[1]) {
+ case '\\': break;
+ case 'a': *p = '\a'; break;
+ case 'b': *p = '\b'; break;
+ case 'f': *p = '\f'; break;
+ case 'n': *p = '\n'; break;
+ case 'r': *p = '\r'; break;
+ case 't': *p = '\t'; break;
+ case 'v': *p = '\v'; break;
+ case '"': *p = '"'; break;
+ case '\'': *p = '\''; break;
+ case '?': *p = '?'; break;
+
+ case '0'...'7': /* octal escape - always 3 digits */
+ m = 3;
+ if (p[2] >= '0' && p[2] <= '7' &&
+ p[3] >= '0' && p[3] <= '7') {
+ c = (p[1] - '0') * 0100 + (p[2] - '0') * 010 + (p[3] - '0');
+ if (c < 1 || c > 255)
+ goto error;
+ *p = c;
+ }
+ else
+ goto error;
+ break;
+
+ case 'x': /* hex escape - always 2 digits */
+ m = 3;
+ if (c_isxdigit (p[2]) && c_isxdigit (p[3])) {
+ c = hexdigit (p[2]) * 0x10 + hexdigit (p[3]);
+ if (c < 1 || c > 255)
+ goto error;
+ *p = c;
+ }
+ else
+ goto error;
+ break;
+
+ default:
+ error:
+ fprintf (stderr, _("%s: invalid escape sequence in string (starting at offset %d)\n"),
+ program_name, (int) (p - start));
+ return -1;
+ }
+ memmove (p+1, p+1+m, strlen (p+1+m) + 1);
+ }
+ }
+
+ if (!*p) {
+ fprintf (stderr, _("%s: unterminated double quote\n"), program_name);
+ return -1;
+ }
+
+ *p = '\0';
+ return p - start;
+}
+