(61d00a474) v0.9.7.1

Libraries/webm_mem_playback/libvpx/vpx_dsp/bitreader.c

@@ -0,0 +1,100 @@
+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include <stdlib.h>
+
+#include "./vpx_config.h"
+
+#include "vpx_dsp/bitreader.h"
+#include "vpx_dsp/prob.h"
+#include "vpx_dsp/vpx_dsp_common.h"
+#include "vpx_ports/mem.h"
+#include "vpx_mem/vpx_mem.h"
+#include "vpx_util/endian_inl.h"
+
+int vpx_reader_init(vpx_reader *r, const uint8_t *buffer, size_t size,
+                    vpx_decrypt_cb decrypt_cb, void *decrypt_state) {
+  if (size && !buffer) {
+    return 1;
+  } else {
+    r->buffer_end = buffer + size;
+    r->buffer = buffer;
+    r->value = 0;
+    r->count = -8;
+    r->range = 255;
+    r->decrypt_cb = decrypt_cb;
+    r->decrypt_state = decrypt_state;
+    vpx_reader_fill(r);
+    return vpx_read_bit(r) != 0;  // marker bit
+  }
+}
+
+void vpx_reader_fill(vpx_reader *r) {
+  const uint8_t *const buffer_end = r->buffer_end;
+  const uint8_t *buffer = r->buffer;
+  const uint8_t *buffer_start = buffer;
+  BD_VALUE value = r->value;
+  int count = r->count;
+  const size_t bytes_left = buffer_end - buffer;
+  const size_t bits_left = bytes_left * CHAR_BIT;
+  int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
+
+  if (r->decrypt_cb) {
+    size_t n = VPXMIN(sizeof(r->clear_buffer), bytes_left);
+    r->decrypt_cb(r->decrypt_state, buffer, r->clear_buffer, (int)n);
+    buffer = r->clear_buffer;
+    buffer_start = r->clear_buffer;
+  }
+  if (bits_left > BD_VALUE_SIZE) {
+    const int bits = (shift & 0xfffffff8) + CHAR_BIT;
+    BD_VALUE nv;
+    BD_VALUE big_endian_values;
+    memcpy(&big_endian_values, buffer, sizeof(BD_VALUE));
+#if SIZE_MAX == 0xffffffffffffffffULL
+    big_endian_values = HToBE64(big_endian_values);
+#else
+    big_endian_values = HToBE32(big_endian_values);
+#endif
+    nv = big_endian_values >> (BD_VALUE_SIZE - bits);
+    count += bits;
+    buffer += (bits >> 3);
+    value = r->value | (nv << (shift & 0x7));
+  } else {
+    const int bits_over = (int)(shift + CHAR_BIT - (int)bits_left);
+    int loop_end = 0;
+    if (bits_over >= 0) {
+      count += LOTS_OF_BITS;
+      loop_end = bits_over;
+    }
+
+    if (bits_over < 0 || bits_left) {
+      while (shift >= loop_end) {
+        count += CHAR_BIT;
+        value |= (BD_VALUE)*buffer++ << shift;
+        shift -= CHAR_BIT;
+      }
+    }
+  }
+
+  // NOTE: Variable 'buffer' may not relate to 'r->buffer' after decryption,
+  // so we increase 'r->buffer' by the amount that 'buffer' moved, rather than
+  // assign 'buffer' to 'r->buffer'.
+  r->buffer += buffer - buffer_start;
+  r->value = value;
+  r->count = count;
+}
+
+const uint8_t *vpx_reader_find_end(vpx_reader *r) {
+  // Find the end of the coded buffer
+  while (r->count > CHAR_BIT && r->count < BD_VALUE_SIZE) {
+    r->count -= CHAR_BIT;
+    r->buffer--;
+  }
+  return r->buffer;
+}