libmds_compose_v: make it easy to exclude headers conditionally

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 32 insertions, 10 deletions

diff --git a/src/libmdsclient/proto-util.c b/src/libmdsclient/proto-util.c
index b4c580e..a2b24f6 100644
--- a/src/libmdsclient/proto-util.c
+++ b/src/libmdsclient/proto-util.c
@@ -596,11 +596,14 @@ void libmds_headers_sort(char** restrict headers, size_t header_count)
  *                          header line, that is, the header name, colon, blank space and then
  *                          the header's value. No LF should be included. The following
  *                          arguments should be the argument to format the header line.
- *                          This may be be iterated any number of this. The last argument
- *                          should be `NULL` to specify that there are no more headers.
- *                          The `Length`-header should not be included, it is added automatically.
- *                          A header may not have a length larger than 2¹⁵, otherwise
- *                          the behaviour of this function is undefined.
+ *                          If a format for a line begins with a question mark, the remainder
+ *                          of the line used, but only if the next argument is non-zero
+ *                          (it should be of type `int`,) that argument will not be used
+ *                          for the formatting. This may be be iterated any number of this.
+ *                          The last argument should be `NULL` to specify that there are no
+ *                          more headers. The `Length`-header should not be included, it is
+ *                          added automatically. A header may not have a length larger than
+ *                          2¹⁵, otherwise the behaviour of this function is undefined.
  * @return                  Zero on success, -1 on error, `errno` will have been set
  *                          accordingly on error.
  * 
@@ -649,11 +652,14 @@ int libmds_compose(char** restrict buffer, size_t* restrict buffer_size, size_t*
  *                          header line, that is, the header name, colon, blank space and then
  *                          the header's value. No LF should be included. The following
  *                          arguments should be the argument to format the header line.
- *                          This may be be iterated any number of this. The last argument
- *                          should be `NULL` to specify that there are no more headers.
- *                          The `Length`-header should not be included, it is added automatically.
- *                          A header may not have a length larger than 2¹⁵, otherwise
- *                          the behaviour of this function is undefined.
+ *                          If a format for a line begins with a question mark, the remainder
+ *                          of the line used, but only if the next argument is non-zero
+ *                          (it should be of type `int`,) that argument will not be used
+ *                          for the formatting. This may be be iterated any number of this.
+ *                          The last argument should be `NULL` to specify that there are no
+ *                          more headers. The `Length`-header should not be included, it is
+ *                          added automatically. A header may not have a length larger than
+ *                          2¹⁵, otherwise the behaviour of this function is undefined.
  * @return                  Zero on success, -1 on error, `errno` will have been set
  *                          accordingly on error.
  * 
@@ -670,6 +676,7 @@ int libmds_compose_v(char** restrict buffer, size_t* restrict buffer_size, size_
   char* part_msg;
   size_t payload_len = 0;
   const char* format;
+  int include;
   int saved_errno;
   
   *length = 0;
@@ -691,11 +698,26 @@ int libmds_compose_v(char** restrict buffer, size_t* restrict buffer_size, size_
       if (format == NULL)
 	break;
       
+      include = 1;
+      if (*format == '?')
+	{
+	  include = va_arg(args, int);
+	  format++;
+	}
+      
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Wformat-nonliteral"
 # pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
       part_len = vasprintf(&part_msg, format, args);
 # pragma GCC diagnostic pop
+      
+      if (include == 0)
+	{
+	  if (part_len >= 0)
+	    free(part_msg);
+	  continue;
+	}
+      
       if (part_len < 0)
 	return -1;