[hackers] [libgrapheme] Improve parsing of hexadecimal strings || Laslo Hunhold

[git]

commit 92a5a67ed17573d9ad7d0a85ae602cb17d154f82
Author:     Laslo Hunhold <d...@frign.de>
AuthorDate: Sun Dec 12 15:51:04 2021 +0100
Commit:     Laslo Hunhold <d...@frign.de>
CommitDate: Sun Dec 12 15:51:04 2021 +0100

    Improve parsing of hexadecimal strings
    
    Trying to get strtoul()-usage right is so frustrating that it's easier
    and simpler to just roll your own. While at it, modify it in such a
    way that we don't modify the constant str in range_parse().
    
    Signed-off-by: Laslo Hunhold <d...@frign.de>

diff --git a/gen/util.c b/gen/util.c
index 2275538..9bd9985 100644
--- a/gen/util.c
+++ b/gen/util.c
@@ -20,31 +20,42 @@ struct segment_test_payload
 };
 
 static int
-valid_hexstring(const char *str)
+hextocp(const char *str, size_t len, uint_least32_t *cp)
 {
-       const char *p = str;
+       size_t i;
+       int off;
+       char relative;
 
-       while ((*p >= '0' && *p <= '9') ||
-              (*p >= 'a' && *p <= 'f') ||
-              (*p >= 'A' && *p <= 'F')) {
-               p++;
+       /* the maximum valid codepoint is 0x10FFFF */
+       if (len > 6) {
+               fprintf(stderr, "hextocp: '%.*s' is too long.\n", (int)len, 
str);
+               return 1;
        }
 
-       if (*p != '\0') {
-               fprintf(stderr, "valid_hexstring: Invalid code point range 
'%s'\n", str);
-               return 0;
-       }
+       for (i = 0, *cp = 0; i < len; i++) {
+               if (str[i] >= '0' && str[i] <= '9') {
+                       relative = '0';
+                       off = 0;
+               } else if (str[i] >= 'a' && str[i] <= 'f') {
+                       relative = 'a';
+                       off = 10;
+               } else if (str[i] >= 'A' && str[i] <= 'F') {
+                       relative = 'A';
+                       off = 10;
+               } else {
+                       fprintf(stderr, "hextocp: '%.*s' is not hexadecimal.\n",
+                               (int)len, str);
+                       return 1;
+               }
 
-       return 1;
-}
+               *cp += ((uint_least32_t)1 << (4 * (len - i - 1))) *
+                      (uint_least32_t)(str[i] - relative + off);
+       }
 
-static int
-cp_parse(const char *str, uint_least32_t *cp)
-{
-       if (!valid_hexstring(str)) {
+       if (*cp > 0x10ffff) {
+               fprintf(stderr, "hextocp: '%.*s' is too large.\n", (int)len, 
str);
                return 1;
        }
-       *cp = strtol(str, NULL, 16);
 
        return 0;
 }
@@ -56,19 +67,16 @@ range_parse(const char *str, struct range *range)
 
        if ((p = strstr(str, "..")) == NULL) {
                /* input has the form "XXXXXX" */
-               if (!valid_hexstring(str)) {
+               if (hextocp(str, strlen(str), &range->lower)) {
                        return 1;
                }
-               range->lower = range->upper = strtol(str, NULL, 16);
+               range->upper = range->lower;
        } else {
                /* input has the form "XXXXXX..XXXXXX" */
-               *p = '\0';
-               p += 2;
-               if (!valid_hexstring(str) || !valid_hexstring(p)) {
+               if (hextocp(str, (size_t)(p - str), &range->lower) ||
+                   hextocp(p + 2, strlen(p + 2), &range->upper)) {
                        return 1;
                }
-               range->lower = strtol(str, NULL, 16);
-               range->upper = strtol(p, NULL, 16);
        }
 
        return 0;
@@ -308,7 +316,7 @@ segment_test_callback(char *fname, char **field, size_t 
nfields, char *comment,
                                fprintf(stderr, "realloc: %s\n", 
strerror(errno));
                                return 1;
                        }
-                       if (cp_parse(token, &t->cp[t->cplen - 1])) {
+                       if (hextocp(token, strlen(token), &t->cp[t->cplen - 
1])) {
                                return 1;
                        }
                        if (t->lenlen > 0) {