resolved: add alignment to base64

We try to fit the lengthy key data into available space. If the other
fields take less than half of the available columns, we use align everything
in the remaining columns. Otherwise, we put everything after a newline,
indented with 8 spaces.

This is similar to dig and other tools do.

$ COLUMNS=78 ./systemd-resolve -t any .
. IN SOA   a.root-servers.net nstld.verisign-grs.com 2016012701 1800 900 604800 86400
. IN RRSIG SOA RSASHA256 0 86400 20160206170000 20160127160000 54549
        S1uhUoBAReAFi5wH/KczVDgwLb+B9Zp57dSYj9aX4XxBhKuzccIducpg0wWXhjCRAWuzY
        fQ/J2anm4+C4BLUTdlytPIemd42SUffQk2WGuuukI8e67nkrNF3WFtoeXQ4OchsyO24t2
        rxi682Zo9ViqmXZ+MSsjWKt1jdem4noaY=
. IN NS    h.root-servers.net
. IN NS    k.root-servers.net
. IN NS    e.root-servers.net
. IN NS    c.root-servers.net
. IN NS    b.root-servers.net
. IN NS    g.root-servers.net
. IN NS    d.root-servers.net
. IN NS    f.root-servers.net
. IN NS    i.root-servers.net
. IN NS    j.root-servers.net
. IN NS    m.root-servers.net
. IN NS    a.root-servers.net
. IN NS    l.root-servers.net
. IN RRSIG NS RSASHA256 0 518400 20160206170000 20160127160000 54549
        rxhmTVKUgs72G3VzL+1JRuD0nGLIrPM+ISfmUx0eYUH5wZD5XMu2X+8PfkAsEQT1dziPs
        ac+zK1YZPbNgr3yGI5H/wEbK8S7DmlvO+/I9WKTLp/Zxn3yncvnTOdjFMZxkAqHbjVOm+
        BFz7RjQuvCQlEJX4PQBFphgEnkiOnmMdI=
. IN NSEC  aaa ( NS SOA RRSIG NSEC DNSKEY )
. IN RRSIG NSEC RSASHA256 0 86400 20160206170000 20160127160000 54549
        HY49/nGkUJJP1zLmH33MIKnkNH33jQ7bsAHE9itEjvC4wfAzgq8+Oh9fjYav1R1GDeJ2Z
        HOu3Z2uDRif10R8RsmZbxyZXJs7eHui9KcAMot1U4uKCCooC/5GImf+oUDbvaraUCMQRU
        D3mUzoa0BGWfxgZEDqZ55raVFT/olEgG8=
. IN DNSKEY 257 3 RSASHA256 AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0
                            O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0
                            NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL4
                            96M/QZxkjf5/Efucp2gaDX6RS6CXpoY68LsvPVjR0ZSwzz1ap
                            AzvN9dlzEheX7ICJBBtuA6G3LQpzW5hOA2hzCTMjJPJ8LbqF6
                            dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relSQageu+ipAdTTJ2
                            5AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1
                            ihz0=
. IN DNSKEY 256 3 RSASHA256 AwEAAbr/RV0stAWYbmKOldjShp4AOQGOyY3ATI1NUpP4X1qBs
                            6lsXpc+1ABgv6zkg02IktjZrHnmD0HsElu3wqXMrT5KL1W7Sp
                            mg0Pou9WZ8QttdTKXwrVXrASsaGI2z/pLBSnK8EdzqUrTVxY4
                            TEGZtxV519isM06CCMihxTn5cfFBF
. IN RRSIG DNSKEY RSASHA256 0 172800 20160204235959 20160121000000 19036
        XYewrVdYKRDfZptAATwT+W4zng04riExV36+z04kok09W0RmOtDlQrlrwHLlD2iN/zYpg
        EqGgDF5T2xlrQdNpn+PFHhypHM7NQAgLTrwmiw6mGbV0bsZN3rhFxHwW7QVUFAvo9eNVu
        INrjm+sArwxq3DnPkmA+3K4ikKD2iiT/jT91VYr9SHFqXXURccLjI+nmaE7m31hXcirX/
        r5i3J+B4Fx4415IavSD72r7cmruocnCVjcp+ZAUKeMyW+RwigzevLz3oEcCZ4nrTpGLEj
        wFaVePYoP+rfdmfLfTdmkkm4APRJa2My3XOdGFlgNS1pW1pH4az5LapLE2vMO7p1aQ==

-- Information acquired via protocol DNS in 14.4ms.
-- Data is authenticated: no

1 files changed, 58 insertions, 3 deletions

diff --git a/src/basic/hexdecoct.c b/src/basic/hexdecoct.c
index 1e907de228..f30e028f45 100644
--- a/src/basic/hexdecoct.c
+++ b/src/basic/hexdecoct.c
@@ -514,14 +514,14 @@ int unbase64char(char c) {
         return -EINVAL;
 }
 
-char *base64mem(const void *p, size_t l) {
+ssize_t base64mem(const void *p, size_t l, char **out) {
         char *r, *z;
         const uint8_t *x;
 
         /* three input bytes makes four output bytes, padding is added so we must round up */
         z = r = malloc(4 * (l + 2) / 3 + 1);
         if (!r)
-                return NULL;
+                return -ENOMEM;
 
         for (x = p; x < (const uint8_t*) p + (l / 3) * 3; x += 3) {
                 /* x[0] == XXXXXXXX; x[1] == YYYYYYYY; x[2] == ZZZZZZZZ */
@@ -549,9 +549,64 @@ char *base64mem(const void *p, size_t l) {
         }
 
         *z = 0;
-        return r;
+        *out = r;
+        return z - r;
+}
+
+static int base64_append_width(char **prefix, int plen,
+                               const char *sep, int indent,
+                               const void *p, size_t l,
+                               int width) {
+
+        _cleanup_free_ char *x = NULL;
+        char *t, *s;
+        ssize_t slen, len, avail;
+        int line, lines;
+
+        len = base64mem(p, l, &x);
+        if (len <= 0)
+                return len;
+
+        lines = (len + width - 1) / width;
+
+        slen = sep ? strlen(sep) : 0;
+        t = realloc(*prefix, plen + 1 + slen + (indent + width + 1) * lines);
+        if (!t)
+                return -ENOMEM;
+
+        memcpy(t + plen, sep, slen);
+
+        for (line = 0, s = t + plen + slen, avail = len; line < lines; line++) {
+                int act = MIN(width, avail);
+
+                if (line > 0 || sep) {
+                        memset(s, ' ', indent);
+                        s += indent;
+                }
+
+                memcpy(s, x + width * line, act);
+                s += act;
+                *(s++) = line < lines - 1 ? '\n' : '\0';
+                avail -= act;
+        }
+        assert(avail == 0);
+
+        *prefix = t;
+        return 0;
 }
 
+int base64_append(char **prefix, int plen,
+                  const void *p, size_t l,
+                  int indent, int width) {
+        if (plen > width / 2 || plen + indent > width)
+                /* leave indent on the left, keep last column free */
+                return base64_append_width(prefix, plen, "\n", indent, p, l, width - indent - 1);
+        else
+                /* leave plen on the left, keep last column free */
+                return base64_append_width(prefix, plen, NULL, plen, p, l, width - plen - 1);
+};
+
+
 int unbase64mem(const char *p, size_t l, void **mem, size_t *_len) {
         _cleanup_free_ uint8_t *r = NULL;
         int a, b, c, d;