dynbuf: introduce internal generic dynamic buffer functions

A common set of functions instead of many separate implementations for
creating buffers that can grow when appending data to them. Existing
functionality has been ported over.

In my early basic testing, the total number of allocations seem at
roughly the same amount as before, possibly a few less.

See docs/DYNBUF.md for a description of the API.

Closes #5300

1 files changed, 29 insertions, 63 deletions

diff --git a/lib/doh.c b/lib/doh.c
index 10867cc34..4e60af7e4 100644
--- a/lib/doh.c
+++ b/lib/doh.c
@@ -35,13 +35,13 @@
 #include "curl_base64.h"
 #include "connect.h"
 #include "strdup.h"
+#include "dynbuf.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
 #include "memdebug.h"
 
 #define DNS_CLASS_IN 0x01
-#define DOH_MAX_RESPONSE_SIZE 3000 /* bytes */
 
 #ifndef CURL_DISABLE_VERBOSE_STRINGS
 static const char * const errors[]={
@@ -177,20 +177,11 @@ static size_t
 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;
+  struct dynbuf *mem = (struct dynbuf *)userp;
 
-  if((mem->size + realsize) > DOH_MAX_RESPONSE_SIZE)
-    /* suspiciously much for us */
+  if(Curl_dyn_addn(mem, contents, realsize))
     return 0;
 
-  mem->memory = Curl_saferealloc(mem->memory, mem->size + realsize);
-  if(!mem->memory)
-    /* out of memory! */
-    return 0;
-
-  memcpy(&(mem->memory[mem->size]), contents, realsize);
-  mem->size += realsize;
-
   return realsize;
 }
 
@@ -238,10 +229,7 @@ static CURLcode dohprobe(struct Curl_easy *data,
   }
 
   p->dnstype = dnstype;
-  p->serverdoh.memory = NULL;
-  /* the memory will be grown as needed by realloc in the doh_write_cb
-     function */
-  p->serverdoh.size = 0;
+  Curl_dyn_init(&p->serverdoh, DYN_DOH_RESPONSE);
 
   /* Note: this is code for sending the DoH request with GET but there's still
      no logic that actually enables this. We should either add that ability or
@@ -272,7 +260,7 @@ static CURLcode dohprobe(struct Curl_easy *data,
   if(!result) {
     /* pass in the struct pointer via a local variable to please coverity and
        the gcc typecheck helpers */
-    struct dohresponse *resp = &p->serverdoh;
+    struct dynbuf *resp = &p->serverdoh;
     ERROR_CHECK_SETOPT(CURLOPT_URL, url);
     ERROR_CHECK_SETOPT(CURLOPT_WRITEFUNCTION, doh_write_cb);
     ERROR_CHECK_SETOPT(CURLOPT_WRITEDATA, resp);
@@ -506,38 +494,12 @@ static DOHcode store_aaaa(const unsigned char *doh,
   return DOH_OK;
 }
 
-static DOHcode cnameappend(struct cnamestore *c,
-                           const unsigned char *src,
-                           size_t len)
-{
-  if(!c->alloc) {
-    c->allocsize = len + 1;
-    c->alloc = malloc(c->allocsize);
-    if(!c->alloc)
-      return DOH_OUT_OF_MEM;
-  }
-  else if(c->allocsize < (c->allocsize + len + 1)) {
-    char *ptr;
-    c->allocsize += len + 1;
-    ptr = realloc(c->alloc, c->allocsize);
-    if(!ptr) {
-      free(c->alloc);
-      return DOH_OUT_OF_MEM;
-    }
-    c->alloc = ptr;
-  }
-  memcpy(&c->alloc[c->len], src, len);
-  c->len += len;
-  c->alloc[c->len] = 0; /* keep it zero terminated */
-  return DOH_OK;
-}
-
 static DOHcode store_cname(const unsigned char *doh,
                            size_t dohlen,
                            unsigned int index,
                            struct dohentry *d)
 {
-  struct cnamestore *c;
+  struct dynbuf *c;
   unsigned int loop = 128; /* a valid DNS name can never loop this much */
   unsigned char length;
 
@@ -566,18 +528,15 @@ static DOHcode store_cname(const unsigned char *doh,
       index++;
 
     if(length) {
-      DOHcode rc;
-      if(c->len) {
-        rc = cnameappend(c, (unsigned char *)".", 1);
-        if(rc)
-          return rc;
+      if(Curl_dyn_len(c)) {
+        if(Curl_dyn_add(c, "."))
+          return DOH_OUT_OF_MEM;
       }
       if((index + length) > dohlen)
         return DOH_DNS_BAD_LABEL;
 
-      rc = cnameappend(c, &doh[index], length);
-      if(rc)
-        return rc;
+      if(Curl_dyn_addn(c, &doh[index], length))
+        return DOH_OUT_OF_MEM;
       index += length;
     }
   } while(length && --loop);
@@ -630,10 +589,13 @@ static DOHcode rdata(const unsigned char *doh,
   return DOH_OK;
 }
 
-static void init_dohentry(struct dohentry *de)
+UNITTEST void de_init(struct dohentry *de)
 {
+  int i;
   memset(de, 0, sizeof(*de));
   de->ttl = INT_MAX;
+  for(i = 0; i < DOH_MAX_CNAME; i++)
+    Curl_dyn_init(&de->cname[i], DYN_DOH_CNAME);
 }
 
 
@@ -808,7 +770,7 @@ static void showdoh(struct Curl_easy *data,
     }
   }
   for(i = 0; i < d->numcname; i++) {
-    infof(data, "CNAME: %s\n", d->cname[i].alloc);
+    infof(data, "CNAME: %s\n", Curl_dyn_ptr(&d->cname[i]));
   }
 }
 #else
@@ -941,7 +903,7 @@ UNITTEST void de_cleanup(struct dohentry *d)
 {
   int i = 0;
   for(i = 0; i < d->numcname; i++) {
-    free(d->cname[i].alloc);
+    Curl_dyn_free(&d->cname[i]);
   }
 }
 
@@ -959,7 +921,9 @@ CURLcode Curl_doh_is_resolved(struct connectdata *conn,
       CURLE_COULDNT_RESOLVE_HOST;
   }
   else if(!data->req.doh.pending) {
-    DOHcode rc[DOH_PROBE_SLOTS];
+    DOHcode rc[DOH_PROBE_SLOTS] = {
+      DOH_OK, DOH_OK
+    };
     struct dohentry de;
     int slot;
     /* remove DOH handles from multi handle and close them */
@@ -968,17 +932,19 @@ CURLcode Curl_doh_is_resolved(struct connectdata *conn,
       Curl_close(&data->req.doh.probe[slot].easy);
     }
     /* parse the responses, create the struct and return it! */
-    init_dohentry(&de);
+    de_init(&de);
     for(slot = 0; slot < DOH_PROBE_SLOTS; slot++) {
-      rc[slot] = doh_decode(data->req.doh.probe[slot].serverdoh.memory,
-                            data->req.doh.probe[slot].serverdoh.size,
-                            data->req.doh.probe[slot].dnstype,
+      struct dnsprobe *p = &data->req.doh.probe[slot];
+      if(!p->dnstype)
+        continue;
+      rc[slot] = doh_decode(Curl_dyn_uptr(&p->serverdoh),
+                            Curl_dyn_len(&p->serverdoh),
+                            p->dnstype,
                             &de);
-      Curl_safefree(data->req.doh.probe[slot].serverdoh.memory);
+      Curl_dyn_free(&p->serverdoh);
       if(rc[slot]) {
         infof(data, "DOH: %s type %s for %s\n", doh_strerror(rc[slot]),
-              type2name(data->req.doh.probe[slot].dnstype),
-              data->req.doh.host);
+              type2name(p->dnstype), data->req.doh.host);
       }
     } /* next slot */