Add solv_fmemopen() function

The solv_xfopen_buf() function we have has the disadvantage
that it updates the buffer pointer/length when reading/writing.
This can easily lead to writing to locations that went out of
scope, like with our usage in testcase.c.

So solv_fmemopen() removes that indirection and directly takes
the buffer pointer and length as arguments. Only reading is
currently supported.

Author: mlschroe

ext/libsolvext.ver

@@ -55,6 +55,7 @@ SOLV_1.0 {
 		rpm_stat_database;
 		rpm_state_create;
 		rpm_state_free;
+		solv_fmemopen;
 		solv_verify_sig;
 		solv_xfopen;
 		solv_xfopen_buf;

ext/solv_xfopen.c

@@ -798,6 +798,7 @@ struct bufcookie {
   size_t *buflp;
   char *freemem;
   size_t bufl_int;
+  char *buf_int;
 };
 
 static ssize_t cookie_bufread(void *cookie, char *buf, size_t nbytes)
@@ -870,30 +871,48 @@ solv_xfopen_buf(const char *fn, char **bufp, size_t *buflp, const char *mode)
   return fp;
 }
 
+FILE *
+solv_fmemopen(const char *buf, size_t bufl, const char *mode)
+{
+  struct bufcookie *bc;
+  FILE *fp;
+  if (*mode != 'r')
+    return 0;
+  bc = solv_calloc(1, sizeof(*bc));
+  bc->buf_int = (char *)buf;
+  bc->bufl_int = bufl;
+  bc->bufp = &bc->buf_int;
+  bc->buflp = &bc->bufl_int;
+  fp = cookieopen(bc, mode, cookie_bufread, cookie_bufwrite, cookie_bufclose);
+  if (!strcmp(mode, "rf"))	/* auto-free */
+    bc->freemem = bc->buf_int;
+  if (!fp)
+    cookie_bufclose(bc);
+  return fp;
+}
+
 #else
 
 FILE *
-solv_xfopen_buf(const char *fn, char **bufp, size_t *buflp, const char *mode)
+solv_fmemopen(const char *buf, size_t bufl, const char *mode)
 {
   FILE *fp;
-  size_t l;
   if (*mode != 'r')
     return 0;
-  l = buflp ? *buflp : strlen(*bufp);
   if (!strcmp(mode, "rf"))
     {
-      if (!(fp = fmemopen(0, l, "r+")))
+      if (!(fp = fmemopen(0, bufl, "r+")))
 	return 0;
-      if (l && fwrite(*bufp, l, 1, fp) != 1)
+      if (bufl && fwrite(buf, bufl, 1, fp) != 1)
 	{
 	  fclose(fp);
 	  return 0;
 	}
-      solv_free(*bufp);
+      solv_free((char *)buf);
       rewind(fp);
     }
   else
-    fp = fmemopen(*bufp, l, "r");
+    fp = fmemopen((char *)buf, bufl, "r");
   return fp;
 }
 

ext/solv_xfopen.h

@@ -12,5 +12,6 @@ extern FILE *solv_xfopen(const char *fn, const char *mode);
 extern FILE *solv_xfopen_fd(const char *fn, int fd, const char *mode);
 extern FILE *solv_xfopen_buf(const char *fn, char **bufp, size_t *buflp, const char *mode);
 extern int   solv_xfopen_iscompressed(const char *fn);
+extern FILE *solv_fmemopen(const char *buf, size_t bufl, const char *mode);
 
 #endif

ext/testcase.c

@@ -2071,7 +2071,7 @@ testcase_read(Pool *pool, FILE *fp, const char *testcase, Queue *job, char **res
 		{
 		  char *idata = read_inline_file(fp, &buf, &bufp, &bufl);
 		  rdata = "<inline>";
-		  rfp = solv_xfopen_buf(rdata, &idata, 0, "rf");
+		  rfp = solv_fmemopen(idata, strlen(idata), "rf");
 		}
 	      else
 		{