forgot those

bitstream.c

@@ -0,0 +1,86 @@
+/*
+ *  Bit stream reader
+ *  Copyright (C) 2007 Andreas Öman
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+#include "bitstream.h"
+
+
+void
+init_bits(bitstream_t *bs, uint8_t *data, int bits)
+{
+  bs->data = data;
+  bs->offset = 0;
+  bs->len = bits;
+}
+
+void
+skip_bits(bitstream_t *bs, int num)
+{
+  bs->offset += num;
+}
+
+unsigned int
+read_bits(bitstream_t *bs, int num)
+{
+  int r = 0;
+
+  while(num > 0) {
+    if(bs->offset >= bs->len)
+      return 0;
+
+    num--;
+
+    if(bs->data[bs->offset / 8] & (1 << (7 - (bs->offset & 7))))
+      r |= 1 << num;
+
+    bs->offset++;
+  }
+  return r;
+}
+
+unsigned int
+read_bits1(bitstream_t *bs)
+{
+  return read_bits(bs, 1);
+}
+
+unsigned int
+read_golomb_ue(bitstream_t *bs)
+{
+  int b, lzb = -1;
+
+  for(b = 0; !b; lzb++)
+    b = read_bits1(bs);
+
+  return (1 << lzb) - 1 + read_bits(bs, lzb);
+}
+
+
+signed int
+read_golomb_se(bitstream_t *bs)
+{
+  int v, neg;
+  v = read_golomb_ue(bs);
+  if(v == 0)
+    return 0;
+
+  neg = v & 1;
+  v = (v + 1) >> 1;
+  return neg ? -v : v;
+}

bitstream.h

@@ -0,0 +1,40 @@
+/*
+ *  Bit stream reader
+ *  Copyright (C) 2007 Andreas Öman
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef BITSTREAM_H_
+#define BITSTREAM_H_
+
+typedef struct bitstream {
+  uint8_t *data;
+  int offset;
+  int len;
+} bitstream_t;
+
+void skip_bits(bitstream_t *bs, int num);
+
+void init_bits(bitstream_t *bs, uint8_t *data, int bits);
+
+unsigned int read_bits(bitstream_t *gb, int num);
+
+unsigned int read_bits1(bitstream_t *gb);
+
+unsigned int read_golomb_ue(bitstream_t *gb);
+
+signed int read_golomb_se(bitstream_t *gb);
+
+#endif /* BITSTREAM_H_ */