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, 228 insertions, 0 deletions

diff --git a/lib/dynbuf.c b/lib/dynbuf.c
new file mode 100644
index 000000000..81e30ce94
--- /dev/null
+++ b/lib/dynbuf.c
@@ -0,0 +1,228 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 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
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.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 MIN_FIRST_ALLOC 32
+
+#define DYNINIT 0xbee51da /* random pattern */
+
+/*
+ * Init a dynbuf struct.
+ */
+void Curl_dyn_init(struct dynbuf *s, size_t toobig)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(toobig);
+  s->bufr = NULL;
+  s->leng = 0;
+  s->allc = 0;
+  s->toobig = toobig;
+#ifdef DEBUGBUILD
+  s->init = DYNINIT;
+#endif
+}
+
+/*
+ * free the buffer and re-init the necessary fields. It doesn't touch the
+ * 'init' field and thus this buffer can be reused to add data to again.
+ */
+void Curl_dyn_free(struct dynbuf *s)
+{
+  DEBUGASSERT(s);
+  Curl_safefree(s->bufr);
+  s->leng = s->allc = 0;
+}
+
+/*
+ * Store/append an chunk of memory to the dynbuf.
+ */
+static CURLcode dyn_nappend(struct dynbuf *s,
+                            const unsigned char *mem, size_t len)
+{
+  size_t indx = s->leng;
+  size_t a = s->allc;
+  size_t fit = len + indx + 1; /* new string + old string + zero byte */
+
+  /* try to detect if there's rubbish in the struct */
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(s->toobig);
+  DEBUGASSERT(indx < s->toobig);
+  DEBUGASSERT(!s->leng || s->bufr);
+
+  if(fit > s->toobig) {
+    Curl_dyn_free(s);
+    return CURLE_OUT_OF_MEMORY;
+  }
+  else if(!a) {
+    DEBUGASSERT(!indx);
+    /* first invoke */
+    if(fit < MIN_FIRST_ALLOC)
+      a = MIN_FIRST_ALLOC;
+    else
+      a = fit;
+  }
+  else {
+    while(a < fit)
+      a *= 2;
+  }
+
+  if(a != s->allc) {
+    s->bufr = Curl_saferealloc(s->bufr, a);
+    if(!s->bufr) {
+      s->leng = s->allc = 0;
+      return CURLE_OUT_OF_MEMORY;
+    }
+    s->allc = a;
+  }
+
+  if(len)
+    memcpy(&s->bufr[indx], mem, len);
+  s->leng = indx + len;
+  s->bufr[s->leng] = 0;
+  return CURLE_OK;
+}
+
+/*
+ * Clears the string, keeps the allocation. This can also be called on a
+ * buffer that already was freed.
+ */
+void Curl_dyn_reset(struct dynbuf *s)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  if(s->leng)
+    s->bufr[0] = 0;
+  s->leng = 0;
+}
+
+#if 0
+/*
+ * Specify the size of the tail to keep (number of bytes from the end of the
+ * buffer). The rest will be dropped.
+ */
+CURLcode Curl_dyn_tail(struct dynbuf *s, size_t trail)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  if(trail > s->leng)
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  else if(trail == s->leng)
+    return CURLE_OK;
+  else if(!trail) {
+    Curl_dyn_reset(s);
+  }
+  else {
+    memmove(&s->bufr[0], &s->bufr[s->leng - trail], trail);
+    s->leng = trail;
+  }
+  return CURLE_OK;
+
+}
+
+#endif
+
+/*
+ * Appends a buffer with length.
+ */
+CURLcode Curl_dyn_addn(struct dynbuf *s, const void *mem, size_t len)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  return dyn_nappend(s, mem, len);
+}
+
+/*
+ * Append a zero terminated string at the end.
+ */
+CURLcode Curl_dyn_add(struct dynbuf *s, const char *str)
+{
+  size_t n = strlen(str);
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  return dyn_nappend(s, (unsigned char *)str, n);
+}
+
+/*
+ * Append a string printf()-style
+ */
+CURLcode Curl_dyn_addf(struct dynbuf *s, const char *fmt, ...)
+{
+  char *str;
+  va_list ap;
+  va_start(ap, fmt);
+  str = vaprintf(fmt, ap); /* this allocs a new string to append */
+  va_end(ap);
+
+  if(str) {
+    CURLcode result = dyn_nappend(s, (unsigned char *)str, strlen(str));
+    free(str);
+    return result;
+  }
+  /* If we failed, we cleanup the whole buffer and return error */
+  Curl_dyn_free(s);
+  return CURLE_OUT_OF_MEMORY;
+}
+
+/*
+ * Returns a pointer to the buffer.
+ */
+char *Curl_dyn_ptr(const struct dynbuf *s)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  return s->leng ? s->bufr : (char *)"";
+}
+
+/*
+ * Returns an unsigned pointer to the buffer.
+ */
+unsigned char *Curl_dyn_uptr(const struct dynbuf *s)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  return s->leng ? (unsigned char *)s->bufr : (unsigned char *)"";
+}
+
+/*
+ * Returns the length of the buffer.
+ */
+size_t Curl_dyn_len(const struct dynbuf *s)
+{
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  return s->leng;
+}