git subrepo clone https://github.com/libretro/libretro-common.git deps/libretro-common

[pcsx_rearmed.git] / deps / libretro-common / formats / libchdr / libchdr_bitstream.c

diff --git a/deps/libretro-common/formats/libchdr/libchdr_bitstream.c b/deps/libretro-common/formats/libchdr/libchdr_bitstream.c
new file mode 100644 (file)
index 0000000..1a6cf73
--- /dev/null
+++ b/deps/libretro-common/formats/libchdr/libchdr_bitstream.c
@@ -0,0 +1,119 @@
+/* license:BSD-3-Clause
+ * copyright-holders:Aaron Giles
+***************************************************************************
+
+    bitstream.c
+
+    Helper classes for reading/writing at the bit level.
+
+***************************************************************************/
+
+#include <stdlib.h>
+#include <libchdr/bitstream.h>
+
+/***************************************************************************
+ *  INLINE FUNCTIONS
+ ***************************************************************************
+ */
+
+int bitstream_overflow(struct bitstream* bitstream) { return ((bitstream->doffset - bitstream->bits / 8) > bitstream->dlength); }
+
+/*-------------------------------------------------
+ *  create_bitstream - constructor
+ *-------------------------------------------------
+ */
+
+struct bitstream* create_bitstream(const void *src, uint32_t srclength)
+{
+       struct bitstream* bitstream = (struct bitstream*)malloc(sizeof(struct bitstream));
+       bitstream->buffer = 0;
+       bitstream->bits = 0;
+       bitstream->read = (const uint8_t*)src;
+       bitstream->doffset = 0;
+       bitstream->dlength = srclength;
+       return bitstream;
+}
+
+/*-----------------------------------------------------
+ *  bitstream_peek - fetch the requested number of bits
+ *  but don't advance the input pointer
+ *-----------------------------------------------------
+ */
+
+uint32_t bitstream_peek(struct bitstream* bitstream, int numbits)
+{
+       if (numbits == 0)
+               return 0;
+
+       /* fetch data if we need more */
+       if (numbits > bitstream->bits)
+       {
+               while (bitstream->bits <= 24)
+               {
+                       if (bitstream->doffset < bitstream->dlength)
+                               bitstream->buffer |= bitstream->read[bitstream->doffset] << (24 - bitstream->bits);
+                       bitstream->doffset++;
+                       bitstream->bits += 8;
+               }
+       }
+
+       /* return the data */
+       return bitstream->buffer >> (32 - numbits);
+}
+
+/*-----------------------------------------------------
+ *  bitstream_remove - advance the input pointer by the
+ *  specified number of bits
+ *-----------------------------------------------------
+ */
+
+void bitstream_remove(struct bitstream* bitstream, int numbits)
+{
+       bitstream->buffer <<= numbits;
+       bitstream->bits -= numbits;
+}
+
+/*-----------------------------------------------------
+ *  bitstream_read - fetch the requested number of bits
+ *-----------------------------------------------------
+ */
+
+uint32_t bitstream_read(struct bitstream* bitstream, int numbits)
+{
+       uint32_t result = bitstream_peek(bitstream, numbits);
+       bitstream_remove(bitstream, numbits);
+       return result;
+}
+
+/*-------------------------------------------------
+ *  read_offset - return the current read offset
+ *-------------------------------------------------
+ */
+
+uint32_t bitstream_read_offset(struct bitstream* bitstream)
+{
+       uint32_t result = bitstream->doffset;
+       int bits = bitstream->bits;
+       while (bits >= 8)
+       {
+               result--;
+               bits -= 8;
+       }
+       return result;
+}
+
+/*-------------------------------------------------
+ *  flush - flush to the nearest byte
+ *-------------------------------------------------
+ */
+
+uint32_t bitstream_flush(struct bitstream* bitstream)
+{
+       while (bitstream->bits >= 8)
+       {
+               bitstream->doffset--;
+               bitstream->bits -= 8;
+       }
+       bitstream->bits = bitstream->buffer = 0;
+       return bitstream->doffset;
+}