til_jenkins: add a rudimentary hash function

Presently just for hashing paths and names

3 files changed, 36 insertions, 1 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 692b56e..efb7cc0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,7 +1,7 @@
 SUBDIRS = libs modules
 
 noinst_LTLIBRARIES = libtil.la
-libtil_la_SOURCES = til_args.c til_args.h til_fb.c til_fb.h til_knobs.h til.c til.h til_module_context.c til_module_context.h til_settings.h til_settings.c til_setup.c til_setup.h til_tap.h til_threads.c til_threads.h til_util.c til_util.h
+libtil_la_SOURCES = til_args.c til_args.h til_fb.c til_fb.h til_jenkins.c til_jenkins.h til_knobs.h til.c til.h til_module_context.c til_module_context.h til_settings.h til_settings.c til_setup.c til_setup.h til_tap.h til_threads.c til_threads.h til_util.c til_util.h
 libtil_la_CPPFLAGS = -I@top_srcdir@/src
 libtil_la_LIBADD = modules/blinds/libblinds.la modules/checkers/libcheckers.la modules/compose/libcompose.la modules/drizzle/libdrizzle.la modules/flui2d/libflui2d.la modules/julia/libjulia.la modules/meta2d/libmeta2d.la modules/moire/libmoire.la modules/montage/libmontage.la modules/pixbounce/libpixbounce.la modules/plasma/libplasma.la modules/plato/libplato.la modules/ray/libray.la modules/roto/libroto.la modules/rtv/librtv.la modules/shapes/libshapes.la modules/snow/libsnow.la modules/sparkler/libsparkler.la modules/spiro/libspiro.la modules/stars/libstars.la modules/strobe/libstrobe.la modules/submit/libsubmit.la modules/swab/libswab.la modules/swarm/libswarm.la modules/voronoi/libvoronoi.la libs/grid/libgrid.la libs/puddle/libpuddle.la libs/ray/libray.la libs/sig/libsig.la libs/txt/libtxt.la libs/ascii/libascii.la libs/din/libdin.la
 
diff --git a/src/til_jenkins.c b/src/til_jenkins.c
new file mode 100644
index 0000000..0bc74ba
--- /dev/null
+++ b/src/til_jenkins.c
@@ -0,0 +1,26 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#include "til_jenkins.h"
+
+/* we just need something to hash paths/names, it's not super perf sensitive since
+ * the hashes will be cached @ path/name intialization (they don't change).
+ */
+
+/* simple "one at a time" variant from https://en.wikipedia.org/wiki/Jenkins_hash_function */
+uint32_t til_jenkins(const uint8_t *key, size_t length)
+{
+	uint32_t hash = 0;
+
+	for (size_t i = 0; i < length; i++) {
+		hash += key[i];
+		hash += hash << 10;
+		hash ^= hash >> 6;
+	}
+
+	hash += hash << 3;
+	hash ^= hash >> 11;
+	hash += hash << 15;
+
+	return hash;
+}
diff --git a/src/til_jenkins.h b/src/til_jenkins.h
new file mode 100644
index 0000000..02d5015
--- /dev/null
+++ b/src/til_jenkins.h
@@ -0,0 +1,9 @@
+#ifndef _TIL_JENKINS_H
+#define _TIL_JENKINS_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+uint32_t til_jenkins(const uint8_t *key, size_t length);
+
+#endif