@@@ random mess

[mLib] / struct / buf.c

diff --git a/struct/buf.c b/struct/buf.c
index 4b02b28bc456ba64f6a0c3f7a73be2568bbe7f7a..10e05444b9b84051302b0ff719305063d6d69278 100644 (file)
--- a/struct/buf.c
+++ b/struct/buf.c
@@ -223,6 +223,60 @@ int buf_fill(buf *b, int ch, size_t sz)
 int (dbuf_fill)(dbuf *db, int ch, size_t sz)
   { return (dbuf_fill(db, ch, sz)); }
 
 int (dbuf_fill)(dbuf *db, int ch, size_t sz)
   { return (dbuf_fill(db, ch, sz)); }
 

+/* --- @align_step@ --- *
+ *
+ * Arguments:  @buf *b@ = pointer to a buffer block
+ *             @size_t m, a@ = alignment parameters
+ *
+ * Returns:    The number of bytes to skip or fill.
+ */
+
+static size_t align_step(buf *b, size_t m, size_t a)
+{
+  if (m < 2) return (0);
+  else if (!(m&(m - 1))) return ((a - BLEN(b))&(m - 1));
+  else return ((a + m - BLEN(b)%m)%m);
+}
+
+/* --- @{,d}buf_alignskip@ --- *
+ *
+ * Arguments:  @buf *b@ or @dbuf *db@ = pointer to a buffer block
+ *             @size_t m, a@ = alignment multiple and offset
+ *
+ * Returns:    Zero if it worked, nonzero if there wasn't enough space.
+ *
+ * Use:                Advance the buffer position as little as possible such that
+ *             it is @a@ greater than a multiple of @m@.  This doesn't write
+ *             anything to the buffer, so it's probably not suitable for
+ *             output: use @buf_alignfill@ instead.
+ */
+
+int buf_alignskip(buf *b, size_t m, size_t a)
+{
+  if (!buf_get(b, align_step(b, m, a))) return (-1);
+  else return (0);
+}
+int (dbuf_alignskip)(dbuf *db, size_t m, size_t a)
+  { return (dbuf_alignskip(db, m, a)); }
+
+/* --- @{,d}buf_alignfill@ --- *
+ *
+ * Arguments:  @buf *b@ or @dbuf *db@ = pointer to a buffer block
+ *             @int ch@ = fill character
+ *             @size_t m, a@ = alignment multiple and offset
+ *
+ * Returns:    Zero if it worked, nonzero if there wasn't enough space.
+ *
+ * Use:                Fill the buffer with as few copies of @ch@ as possible, as if
+ *             by @memset@, to advance the buffer position to a value @a@
+ *             greater than a multiple of @m@.
+ */
+
+int buf_alignfill(buf *b, int ch, size_t m, size_t a)
+  { return (buf_fill(b, ch, align_step(b, m, a))); }
+int (dbuf_alignfill)(dbuf *db, int ch, size_t m, size_t a)
+  { return (dbuf_alignfill(db, ch, m, a)); }
+

 /* --- @{,d}buf_getbyte@ --- *
  *
  * Arguments:  @buf *b@ or @dbuf *db@ = pointer to a buffer block
 /* --- @{,d}buf_getbyte@ --- *
  *
  * Arguments:  @buf *b@ or @dbuf *db@ = pointer to a buffer block