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Diff of /src/dvdread/bitreader.c [000000] .. [ea4cd8] Maximize Restore

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+++ b/src/dvdread/bitreader.c
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+/*
+ * Copyright (C) 2000, 2001, 2002, 2003 Hĺkan Hjort <d95hjort@dtek.chalmers.se>
+ *
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+
+#include "bswap.h"
+#include "bitreader.h"
+
+int dvdread_getbits_init(getbits_state_t *state, uint8_t *start) {
+  if ((state == NULL) || (start == NULL)) return 0;
+  state->start = start;
+  state->bit_position = 0;
+  state->byte_position = 0;
+  state->byte = start[0];
+  return 1;
+}
+
+/* Non-optimized getbits. */
+/* This can easily be optimized for particular platforms. */
+uint32_t dvdread_getbits(getbits_state_t *state, uint32_t number_of_bits) {
+  uint32_t result=0;
+  uint8_t byte=0;
+  if (number_of_bits > 32) {
+    printf("Number of bits > 32 in getbits\n");
+    abort();
+  }
+
+  if ((state->bit_position) > 0) {  /* Last getbits left us in the middle of a byte. */
+    if (number_of_bits > (8-state->bit_position)) { /* this getbits will span 2 or more bytes. */
+      byte = state->byte;
+      byte = byte >> (state->bit_position);
+      result = byte;
+      number_of_bits -= (8-state->bit_position);
+      state->bit_position = 0;
+      state->byte_position++;
+      state->byte = state->start[state->byte_position];
+    } else {
+      byte=state->byte;
+      state->byte = state->byte << number_of_bits;
+      byte = byte >> (8 - number_of_bits);
+      result = byte;
+      state->bit_position += number_of_bits; /* Here it is impossible for bit_position > 8 */
+      if (state->bit_position == 8) {
+        state->bit_position = 0;
+        state->byte_position++;
+        state->byte = state->start[state->byte_position];
+      }
+      number_of_bits = 0;
+    }
+  }
+  if ((state->bit_position) == 0) {
+    while (number_of_bits > 7) {
+      result = (result << 8) + state->byte;
+      state->byte_position++;
+      state->byte = state->start[state->byte_position];
+      number_of_bits -= 8;
+    }
+    if (number_of_bits > 0) { /* number_of_bits < 8 */
+      byte = state->byte;
+      state->byte = state->byte << number_of_bits;
+      state->bit_position += number_of_bits; /* Here it is impossible for bit_position > 7 */
+      byte = byte >> (8 - number_of_bits);
+      result = (result << number_of_bits) + byte;
+      number_of_bits = 0;
+    }
+  }
+
+  return result;
+}
+
+#if 0  /* TODO: optimized versions not yet used */
+
+/* WARNING: This function can only be used on a byte boundary.
+            No checks are made that we are in fact on a byte boundary.
+ */
+uint16_t dvdread_get16bits(getbits_state_t *state) {
+  uint16_t result;
+  state->byte_position++;
+  result = (state->byte << 8) + state->start[state->byte_position++];
+  state->byte = state->start[state->byte_position];
+  return result;
+}
+
+/* WARNING: This function can only be used on a byte boundary.
+            No checks are made that we are in fact on a byte boundary.
+ */
+uint32_t dvdread_get32bits(getbits_state_t *state) {
+  uint32_t result;
+  state->byte_position++;
+  result = (state->byte << 8) + state->start[state->byte_position++];
+  result = (result << 8) + state->start[state->byte_position++];
+  result = (result << 8) + state->start[state->byte_position++];
+  state->byte = state->start[state->byte_position];
+  return result;
+}
+
+#endif