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, 16 insertions, 55 deletions

diff --git a/lib/mprintf.c b/lib/mprintf.c
index bc0091351..d6d836c02 100644
--- a/lib/mprintf.c
+++ b/lib/mprintf.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1999 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1999 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -36,6 +36,7 @@
  */
 
 #include "curl_setup.h"
+#include "dynbuf.h"
 #include <curl/mprintf.h>
 
 #include "curl_memory.h"
@@ -168,11 +169,9 @@ struct nsprintf {
 };
 
 struct asprintf {
-  char *buffer; /* allocated buffer */
-  size_t len;   /* length of string */
-  size_t alloc; /* length of alloc */
-  int fail;     /* (!= 0) if an alloc has failed and thus
-                   the output is not the complete data */
+  struct dynbuf b;
+  bool fail; /* if an alloc has failed and thus the output is not the complete
+                data */
 };
 
 static long dprintf_DollarString(char *input, char **end)
@@ -1031,35 +1030,10 @@ static int alloc_addbyter(int output, FILE *data)
   struct asprintf *infop = (struct asprintf *)data;
   unsigned char outc = (unsigned char)output;
 
-  if(!infop->buffer) {
-    infop->buffer = malloc(32);
-    if(!infop->buffer) {
-      infop->fail = 1;
-      return -1; /* fail */
-    }
-    infop->alloc = 32;
-    infop->len = 0;
+  if(Curl_dyn_addn(&infop->b, &outc, 1)) {
+    infop->fail = 1;
+    return -1; /* fail */
   }
-  else if(infop->len + 1 >= infop->alloc) {
-    char *newptr = NULL;
-    size_t newsize = infop->alloc*2;
-
-    /* detect wrap-around or other overflow problems */
-    if(newsize > infop->alloc)
-      newptr = realloc(infop->buffer, newsize);
-
-    if(!newptr) {
-      infop->fail = 1;
-      return -1; /* fail */
-    }
-    infop->buffer = newptr;
-    infop->alloc = newsize;
-  }
-
-  infop->buffer[ infop->len ] = outc;
-
-  infop->len++;
-
   return outc; /* fputc() returns like this on success */
 }
 
@@ -1068,24 +1042,18 @@ char *curl_maprintf(const char *format, ...)
   va_list ap_save; /* argument pointer */
   int retcode;
   struct asprintf info;
-
-  info.buffer = NULL;
-  info.len = 0;
-  info.alloc = 0;
+  Curl_dyn_init(&info.b, DYN_APRINTF);
   info.fail = 0;
 
   va_start(ap_save, format);
   retcode = dprintf_formatf(&info, alloc_addbyter, format, ap_save);
   va_end(ap_save);
   if((-1 == retcode) || info.fail) {
-    if(info.alloc)
-      free(info.buffer);
+    Curl_dyn_free(&info.b);
     return NULL;
   }
-  if(info.alloc) {
-    info.buffer[info.len] = 0; /* we terminate this with a zero byte */
-    return info.buffer;
-  }
+  if(Curl_dyn_len(&info.b))
+    return Curl_dyn_ptr(&info.b);
   return strdup("");
 }
 
@@ -1093,23 +1061,16 @@ char *curl_mvaprintf(const char *format, va_list ap_save)
 {
   int retcode;
   struct asprintf info;
-
-  info.buffer = NULL;
-  info.len = 0;
-  info.alloc = 0;
+  Curl_dyn_init(&info.b, DYN_APRINTF);
   info.fail = 0;
 
   retcode = dprintf_formatf(&info, alloc_addbyter, format, ap_save);
   if((-1 == retcode) || info.fail) {
-    if(info.alloc)
-      free(info.buffer);
+    Curl_dyn_free(&info.b);
     return NULL;
   }
-
-  if(info.alloc) {
-    info.buffer[info.len] = 0; /* we terminate this with a zero byte */
-    return info.buffer;
-  }
+  if(Curl_dyn_len(&info.b))
+    return Curl_dyn_ptr(&info.b);
   return strdup("");
 }