cache: use sendfile() instead of a pair of read() + write()

sendfile() does the same job and avoids to copy the content into userland
and back. One has to define NO_SENDFILE in case the OS (kernel / libc)
does not supported. It is disabled by default on non-linux environemnts.
According to the glibc, sendfile64() was added in Linux 2.4 (so it has
been there for a while) but after browsing over the mapage of FreeBSD's I
noticed that the prototype is little different.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>

1 files changed, 8 insertions, 0 deletions

diff --git a/cgit.mk b/cgit.mk
index 056c3f9..3b8b79a 100644
--- a/cgit.mk
+++ b/cgit.mk
@@ -68,6 +68,14 @@ ifeq ($(findstring BSD,$(uname_S)),)
         CGIT_LIBS += -ldl
 endif
 
+# glibc 2.1+ offers sendfile which the most common C library on Linux
+ifeq ($(uname_S),Linux)
+        HAVE_LINUX_SENDFILE = YesPlease
+endif
+
+ifdef HAVE_LINUX_SENDFILE
+        CGIT_CFLAGS += -DHAVE_LINUX_SENDFILE
+endif
 
 CGIT_OBJ_NAMES += cgit.o
 CGIT_OBJ_NAMES += cache.o