doh: Constify some input pointers

Closes #5306

3 files changed, 19 insertions, 17 deletions

diff --git a/lib/doh.c b/lib/doh.c
index dd2bbf125..10867cc34 100644
--- a/lib/doh.c
+++ b/lib/doh.c
@@ -174,7 +174,7 @@ UNITTEST DOHcode doh_encode(const char *host,
 }
 
 static size_t
-doh_write_cb(void *contents, size_t size, size_t nmemb, void *userp)
+doh_write_cb(const void *contents, size_t size, size_t nmemb, void *userp)
 {
   size_t realsize = size * nmemb;
   struct dohresponse *mem = (struct dohresponse *)userp;
@@ -439,7 +439,7 @@ Curl_addrinfo *Curl_doh(struct connectdata *conn,
   return NULL;
 }
 
-static DOHcode skipqname(unsigned char *doh, size_t dohlen,
+static DOHcode skipqname(const unsigned char *doh, size_t dohlen,
                          unsigned int *indexp)
 {
   unsigned char length;
@@ -463,12 +463,12 @@ static DOHcode skipqname(unsigned char *doh, size_t dohlen,
   return DOH_OK;
 }
 
-static unsigned short get16bit(unsigned char *doh, int index)
+static unsigned short get16bit(const unsigned char *doh, int index)
 {
   return (unsigned short)((doh[index] << 8) | doh[index + 1]);
 }
 
-static unsigned int get32bit(unsigned char *doh, int index)
+static unsigned int get32bit(const unsigned char *doh, int index)
 {
    /* make clang and gcc optimize this to bswap by incrementing
       the pointer first. */
@@ -480,7 +480,7 @@ static unsigned int get32bit(unsigned char *doh, int index)
   return ( (unsigned)doh[0] << 24) | (doh[1] << 16) |(doh[2] << 8) | doh[3];
 }
 
-static DOHcode store_a(unsigned char *doh, int index, struct dohentry *d)
+static DOHcode store_a(const unsigned char *doh, int index, struct dohentry *d)
 {
   /* silently ignore addresses over the limit */
   if(d->numaddr < DOH_MAX_ADDR) {
@@ -492,7 +492,9 @@ static DOHcode store_a(unsigned char *doh, int index, struct dohentry *d)
   return DOH_OK;
 }
 
-static DOHcode store_aaaa(unsigned char *doh, int index, struct dohentry *d)
+static DOHcode store_aaaa(const unsigned char *doh,
+                          int index,
+                          struct dohentry *d)
 {
   /* silently ignore addresses over the limit */
   if(d->numaddr < DOH_MAX_ADDR) {
@@ -505,7 +507,7 @@ static DOHcode store_aaaa(unsigned char *doh, int index, struct dohentry *d)
 }
 
 static DOHcode cnameappend(struct cnamestore *c,
-                           unsigned char *src,
+                           const unsigned char *src,
                            size_t len)
 {
   if(!c->alloc) {
@@ -530,7 +532,7 @@ static DOHcode cnameappend(struct cnamestore *c,
   return DOH_OK;
 }
 
-static DOHcode store_cname(unsigned char *doh,
+static DOHcode store_cname(const unsigned char *doh,
                            size_t dohlen,
                            unsigned int index,
                            struct dohentry *d)
@@ -585,7 +587,7 @@ static DOHcode store_cname(unsigned char *doh,
   return DOH_OK;
 }
 
-static DOHcode rdata(unsigned char *doh,
+static DOHcode rdata(const unsigned char *doh,
                      size_t dohlen,
                      unsigned short rdlength,
                      unsigned short type,
@@ -635,7 +637,7 @@ static void init_dohentry(struct dohentry *de)
 }
 
 
-UNITTEST DOHcode doh_decode(unsigned char *doh,
+UNITTEST DOHcode doh_decode(const unsigned char *doh,
                             size_t dohlen,
                             DNStype dnstype,
                             struct dohentry *d)
@@ -775,12 +777,12 @@ UNITTEST DOHcode doh_decode(unsigned char *doh,
 
 #ifndef CURL_DISABLE_VERBOSE_STRINGS
 static void showdoh(struct Curl_easy *data,
-                    struct dohentry *d)
+                    const struct dohentry *d)
 {
   int i;
   infof(data, "TTL: %u seconds\n", d->ttl);
   for(i = 0; i < d->numaddr; i++) {
-    struct dohaddr *a = &d->addr[i];
+    const struct dohaddr *a = &d->addr[i];
     if(a->type == DNS_TYPE_A) {
       infof(data, "DOH A: %u.%u.%u.%u\n",
             a->ip.v4[0], a->ip.v4[1],
diff --git a/lib/doh.h b/lib/doh.h
index fc053eddf..97d459f09 100644
--- a/lib/doh.h
+++ b/lib/doh.h
@@ -99,7 +99,7 @@ DOHcode doh_encode(const char *host,
                    unsigned char *dnsp, /* buffer */
                    size_t len,  /* buffer size */
                    size_t *olen); /* output length */
-DOHcode doh_decode(unsigned char *doh,
+DOHcode doh_decode(const unsigned char *doh,
                    size_t dohlen,
                    DNStype dnstype,
                    struct dohentry *d);
diff --git a/tests/unit/unit1650.c b/tests/unit/unit1650.c
index 35ac12c81..502bf9df0 100644
--- a/tests/unit/unit1650.c
+++ b/tests/unit/unit1650.c
@@ -185,7 +185,7 @@ UNITTEST_START
     size_t len;
     int u;
     memset(&d, 0, sizeof(d));
-    rc = doh_decode((unsigned char *)resp[i].packet, resp[i].size,
+    rc = doh_decode((const unsigned char *)resp[i].packet, resp[i].size,
                     resp[i].type, &d);
     if(rc != resp[i].rc) {
       fprintf(stderr, "resp %zu: Expected return code %d got %d\n", i,
@@ -241,7 +241,7 @@ UNITTEST_START
       struct dohentry d;
       int rc;
       memset(&d, 0, sizeof(d));
-      rc = doh_decode((unsigned char *)full49, i, DNS_TYPE_A, &d);
+      rc = doh_decode((const unsigned char *)full49, i, DNS_TYPE_A, &d);
       if(!rc) {
         /* none of them should work */
         fprintf(stderr, "%zu: %d\n", i, rc);
@@ -253,7 +253,7 @@ UNITTEST_START
       struct dohentry d;
       int rc;
       memset(&d, 0, sizeof(d));
-      rc = doh_decode((unsigned char *)&full49[i], sizeof(full49)-i-1,
+      rc = doh_decode((const unsigned char *)&full49[i], sizeof(full49)-i-1,
                       DNS_TYPE_A, &d);
       if(!rc) {
         /* none of them should work */
@@ -266,7 +266,7 @@ UNITTEST_START
       struct dohentry d;
       struct dohaddr *a;
       memset(&d, 0, sizeof(d));
-      rc = doh_decode((unsigned char *)full49, sizeof(full49)-1,
+      rc = doh_decode((const unsigned char *)full49, sizeof(full49)-1,
                       DNS_TYPE_A, &d);
       fail_if(d.numaddr != 1, "missing address");
       a = &d.addr[0];