diff --git a/buffer/buffer_fromsa.3 b/buffer/buffer_fromsa.3
index 30b51dd..6d2c274 100644
--- a/buffer/buffer_fromsa.3
+++ b/buffer/buffer_fromsa.3
@@ -16,4 +16,4 @@ particular, do not call stralloc_free on it!
 
 Reading data from the buffer will not change the stralloc.
 .SH "SEE ALSO"
-buffer_init(3), buffer(3)
+buffer_tosa(3), buffer_init(3), buffer(3)
diff --git a/buffer/buffer_tosa.3 b/buffer/buffer_tosa.3
new file mode 100644
index 0000000..243e62b
--- /dev/null
+++ b/buffer/buffer_tosa.3
@@ -0,0 +1,19 @@
+.TH buffer_tosa 3
+.SH NAME
+buffer_tosa \- initialize buffer for writing to stralloc
+.SH SYNTAX
+.B #include <buffer.h>
+
+int \fBbuffer_tosa\fR(buffer* \fIb\fR,stralloc* \fIsa\fR);
+.SH DESCRIPTION
+buffer_tosa makes a virtual write buffer from a stralloc.  The buffer
+writing functions will append data to the stralloc until the stralloc
+fails to allocate more memory.  You still need to flush the buffer.
+
+Note that in the end the stralloc will have allocated more memory than
+is needed to hold the actual contents.  The waste is 1024 bytes.
+.SH "RETURN VALUE"
+buffer_tosa returns 0 if everything was fine, -1 if it failed to
+allocate space for the initial data in the stralloc.
+.SH "SEE ALSO"
+buffer_tosa(3), buffer_init(3), buffer(3)