1 files changed, 34 insertions, 0 deletions
diff --git a/src/libdraw/bytesperline.c b/src/libdraw/bytesperline.c
new file mode 100644
index 00000000..08ff7d7f
--- /dev/null
+++ b/src/libdraw/bytesperline.c
@@ -0,0 +1,34 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+
+static
+int
+unitsperline(Rectangle r, int d, int bitsperunit)
+{
+	ulong l, t;
+
+	if(d <= 0 || d > 32)	/* being called wrong.  d is image depth. */
+		abort();
+
+	if(r.min.x >= 0){
+		l = (r.max.x*d+bitsperunit-1)/bitsperunit;
+		l -= (r.min.x*d)/bitsperunit;
+	}else{			/* make positive before divide */
+		t = (-r.min.x*d+bitsperunit-1)/bitsperunit;
+		l = t+(r.max.x*d+bitsperunit-1)/bitsperunit;
+	}
+	return l;
+}
+
+int
+wordsperline(Rectangle r, int d)
+{
+	return unitsperline(r, d, 8*sizeof(ulong));
+}
+
+int
+bytesperline(Rectangle r, int d)
+{
+	return unitsperline(r, d, 8);
+}