2 files changed, 73 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index b6f4fd4..f98e393 100644
--- a/Makefile
+++ b/Makefile
@@ -19,6 +19,7 @@ MAN += deflateSetDictionary.3
 MAN += deflateSetHeader.3
 MAN += deflateTune.3
 MAN += gzbuffer.3
+MAN += gzdirect.3
 MAN += gzeof.3
 MAN += gzflush.3
 MAN += gzfread.3
diff --git a/gzdirect.3 b/gzdirect.3
new file mode 100644
index 0000000..478db6d
--- /dev/null
+++ b/gzdirect.3
@@ -0,0 +1,72 @@
+.Dd November 13, 2018
+.Dt GZDIRECT 3
+.Os
+.
+.Sh NAME
+.Nm gzdirect
+.Nd check direct copy
+.
+.Sh LIBRARY
+.Lb libz
+.
+.Sh SYNOPSIS
+.In zlib.h
+.Ft int
+.Fn gzdirect "gzFile file"
+.
+.Sh DESCRIPTION
+Returns true (1) if
+.Fa file
+is being copied directly while reading,
+or false (0) if
+.Fa file
+is a gzip stream being decompressed.
+.
+.Pp
+If the input file is empty,
+.Fn gzdirect
+will return true,
+since the input does not contain a gzip stream.
+.
+.Pp
+If
+.Fn gzdirect
+is used immediately after
+.Xr gzopen 3
+or
+.Xr gzdopen 3
+it will cause buffers to be allocated
+to allow reading the file
+to determine if it is a gzip file.
+Therefore if
+.Xr gzbuffer 3
+is used,
+it should be called before
+.Fn gzdirect .
+.
+.Pp
+When writing,
+.Fn gzdirect
+returns true (1)
+if transparent writing was requested
+.Po
+.Dq wT
+for the
+.Xr gzopen 3
+mode
+.Pc ,
+or false (0) otherwise.
+.Po
+Note:
+.Fn gzdirect
+is not needed when writing.
+Transparent writing
+must be explicitly requested,
+so the application already knows the answer.
+When linking statically,
+using
+.Fn gzdirect
+will include all of the zlib code
+for gzip file reading and decompression,
+which may not be desired.
+.Pc