1 files changed, 89 insertions, 0 deletions
diff --git a/mfx_stub/bitstream.c b/mfx_stub/bitstream.c
new file mode 100644
index 0000000..058cd75
--- /dev/null
+++ b/mfx_stub/bitstream.c
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2024 Mikhail Burakov. This file is part of receiver.
+ *
+ * receiver 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.
+ *
+ * receiver 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 receiver.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "bitstream.h"
+
+#include <string.h>
+
+static uint64_t BitstreamReadBit(struct Bitstream* bitstream) {
+  size_t shift = 7 - (bitstream->offset & 0x7);
+  if (shift == 7) {
+    size_t byte;
+  repeat:
+    byte = bitstream->offset >> 3;
+    if (byte >= bitstream->size) longjmp(bitstream->trap, 1);
+    bitstream->cache = (bitstream->cache << 8) | bitstream->data[byte];
+    if (bitstream->offset >= 24 && (bitstream->cache & 0xffffff) == 3) {
+      bitstream->offset += 8;
+      bitstream->epb_count++;
+      goto repeat;
+    }
+  }
+  bitstream->offset++;
+  return bitstream->cache >> shift & 0x1;
+}
+
+uint64_t BitstreamReadU(struct Bitstream* bitstream, size_t size) {
+  uint64_t result = 0;
+  for (; size; size--) {
+    result = (result << 1) | BitstreamReadBit(bitstream);
+  }
+  return result;
+}
+
+uint64_t BitstreamReadUE(struct Bitstream* bitstream) {
+  size_t size = 0;
+  while (!BitstreamReadBit(bitstream)) size++;
+  return (BitstreamReadU(bitstream, size) | (1 << size)) - 1;
+}
+
+int64_t BitstreamReadSE(struct Bitstream* bitstream) {
+  uint64_t result = BitstreamReadUE(bitstream);
+  int64_t sign = (int64_t)((result & 1) << 1) - 1;
+  return sign * (int64_t)((result + 1) >> 1);
+}
+
+void BitstreamByteAlign(struct Bitstream* bitstream) {
+  bitstream->offset = (bitstream->offset + 7) & ~(size_t)7;
+}
+
+bool BitstreamReadNalu(struct Bitstream* bitstream, struct Bitstream* output) {
+  if (bitstream->offset & 0x7) return false;
+  size_t byte_offset = bitstream->offset >> 3;
+  static const uint8_t kStartCodePrefix[] = {0, 0, 0, 1};
+  if (bitstream->size - byte_offset < sizeof(kStartCodePrefix)) {
+    return false;
+  }
+  const uint8_t* data = bitstream->data + byte_offset;
+  if (memcmp(bitstream->data + byte_offset, kStartCodePrefix,
+             sizeof(kStartCodePrefix))) {
+    return false;
+  }
+  data += sizeof(kStartCodePrefix);
+  byte_offset += sizeof(kStartCodePrefix);
+  size_t max_size = bitstream->size - byte_offset;
+  uint8_t* next =
+      memmem(data, max_size, kStartCodePrefix, sizeof(kStartCodePrefix));
+  size_t size = next ? (size_t)(next - data) : max_size;
+  bitstream->offset = (byte_offset + size) << 3;
+  *output = BitstreamCreate(data, size);
+  return true;
+}
+
+bool BitstreamAvail(const struct Bitstream* bitstream) {
+  return bitstream->offset < (bitstream->size << 3);
+}