1 files changed, 47 insertions, 0 deletions
diff --git a/lpg/libqr/rs-encode.c b/lpg/libqr/rs-encode.c
new file mode 100644
index 0000000..ec99c6b
--- /dev/null
+++ b/lpg/libqr/rs-encode.c
@@ -0,0 +1,47 @@
+#include <assert.h>
+#include <stdlib.h>
+#include "bitstream.h"
+#include "rs.h"
+
+struct bitstream * rs_generate_words(int k, const int * coeff, struct bitstream * data)
+{
+        struct bitstream * ec = 0;
+        unsigned int * b = 0;
+        size_t n, i, dlen;
+
+        dlen = bitstream_size(data);
+        assert(dlen % 8 == 0);
+        dlen /= 8;
+
+        ec = bitstream_create();
+        if (!ec)
+                return 0;
+
+        if (bitstream_resize(ec, k * 8) != 0)
+                goto fail;
+
+        b = calloc(k, sizeof(*b));
+        if (!b)
+                goto fail;
+
+        /* First, prepare the registers (b) with data bits. Note that
+         * the registers are in reverse of the normal order
+         */
+        bitstream_seek(data, 0);
+        for (n = 0; n < dlen; ++n) {
+                unsigned int x = b[0] + bitstream_read(data, 8);
+                for (i = 0; i < k-1; ++i)
+                        b[i] = b[i+1] + coeff[(k-1) - i] * x;
+                b[k-1] = coeff[0] * x;
+        }
+
+        /* Read off the registers */
+        bitstream_pack(ec, b, k, 8);
+
+        free(b);
+        return ec;
+fail:
+        bitstream_destroy(ec);
+        return 0;
+}
+