Add a "fork" of musl as //fusl.

fusl/src/network/dn_comp.c

+#include <string.h>
+#include <resolv.h>
+#include "libc.h"
+
+/* RFC 1035 message compression */
+
+/* label start offsets of a compressed domain name s */
+static int getoffs(short *offs, const unsigned char *base, const unsigned char *s)
+{
+        int i=0;
+        for (;;) {
+                while (*s & 0xc0) {
+                        if ((*s & 0xc0) != 0xc0) return 0;
+                        s = base + ((s[0]&0x3f)<<8 | s[1]);
+                }
+                if (!*s) return i;
+                if (s-base >= 0x4000) return 0;
+                offs[i++] = s-base;
+                s += *s + 1;
+        }
+}
+
+/* label lengths of an ascii domain name s */
+static int getlens(unsigned char *lens, const char *s, int l)
+{
+        int i=0,j=0,k=0;
+        for (;;) {
+                for (; j<l && s[j]!='.'; j++);
+                if (j-k-1u > 62) return 0;
+                lens[i++] = j-k;
+                if (j==l) return i;
+                k = ++j;
+        }
+}
+
+/* longest suffix match of an ascii domain with a compressed domain name dn */
+static int match(int *offset, const unsigned char *base, const unsigned char *dn,
+        const char *end, const unsigned char *lens, int nlen)
+{
+        int l, o, m=0;
+        short offs[128];
+        int noff = getoffs(offs, base, dn);
+        if (!noff) return 0;
+        for (;;) {
+                l = lens[--nlen];
+                o = offs[--noff];
+                end -= l;
+                if (l != base[o] || memcmp(base+o+1, end, l))
+                        return m;
+                *offset = o;
+                m += l;
+                if (nlen) m++;
+                if (!nlen || !noff) return m;
+                end--;
+        }
+}
+
+int __dn_comp(const char *src, unsigned char *dst, int space, unsigned char **dnptrs, unsigned char **lastdnptr)
+{
+        int i, j, n, m=0, offset, bestlen=0, bestoff;
+        unsigned char lens[127];
+        unsigned char **p;
+        const char *end;
+        size_t l = strnlen(src, 255);
+        if (l && src[l-1] == '.') l--;
+        if (l>253 || space<=0) return -1;
+        if (!l) {
+                *dst = 0;
+                return 1;
+        }
+        end = src+l;
+        n = getlens(lens, src, l);
+        if (!n) return -1;
+
+        p = dnptrs;
+        if (p && *p) for (p++; *p; p++) {
+                m = match(&offset, *dnptrs, *p, end, lens, n);
+                if (m > bestlen) {
+                        bestlen = m;
+                        bestoff = offset;
+                        if (m == l)
+                                break;
+                }
+        }
+
+        /* encode unmatched part */
+        if (space < l-bestlen+2+(bestlen-1 < l-1)) return -1;
+        memcpy(dst+1, src, l-bestlen);
+        for (i=j=0; i<l-bestlen; i+=lens[j++]+1)
+                dst[i] = lens[j];
+
+        /* add tail */
+        if (bestlen) {
+                dst[i++] = 0xc0 | bestoff>>8;
+                dst[i++] = bestoff;
+        } else
+                dst[i++] = 0;
+
+        /* save dst pointer */
+        if (i>2 && lastdnptr && dnptrs && *dnptrs) {
+                while (*p) p++;
+                if (p+1 < lastdnptr) {
+                        *p++ = dst;
+                        *p=0;
+                }
+        }
+        return i;
+}
+
+weak_alias(__dn_comp, dn_comp);