experimental first implementation of ATRAC encoder

current limitations:
 - only long window
 - naive MDCT (O(n^2))
 - bad table of fixed bit allocation
 - bad usage of CBR
 - time accuracy is not guaranteed
 - dirty, not optimized code

1 files changed, 55 insertions, 0 deletions

diff --git a/src/bitstream/bitstream.cpp b/src/bitstream/bitstream.cpp
new file mode 100644
index 0000000..7de4873
--- /dev/null
+++ b/src/bitstream/bitstream.cpp
@@ -0,0 +1,55 @@
+#include "bitstream.h"
+namespace NBitStream {
+
+union TMix {
+	unsigned long long ull = 0;
+	uint8_t bytes[8];
+};
+
+TBitStream::TBitStream(const char* buf, int size)
+    : Buf(buf, buf+size)
+{}
+TBitStream::TBitStream()
+{}
+
+void TBitStream::Write(unsigned long long val, int n) {
+	if (n > 23 || n < 0)
+		abort();
+    const int bitsLeft = Buf.size() * 8 - BitsUsed;
+    const int bitsReq = n - bitsLeft;
+    const int bytesPos = BitsUsed / 8;
+    const int overlap = BitsUsed % 8;
+
+    if (bitsReq > 0) {
+        Buf.resize(Buf.size() + (bitsReq / 8 + (overlap ? 2 : 1 )), 0);
+    }
+	TMix t;
+    t.ull	= val;
+	t.ull = (t.ull << (64 - n) >> overlap);
+
+	for (int i = 0; i < n/8 + (overlap ? 2 : 1); ++i) {
+		Buf[bytesPos+i] |= t.bytes[7-i];
+	}
+
+    BitsUsed += n;
+}
+unsigned long long TBitStream::Read(int n) {
+	if (n >23 || n < 0)
+		abort();
+    const int bytesPos = ReadPos / 8;
+    const int overlap = ReadPos % 8;
+	TMix t;
+	for (int i = 0; i < n/8 + (overlap ? 2 : 1); ++i) {
+		t.bytes[7-i] = (uint8_t)Buf[bytesPos+i];
+	}
+    
+	t.ull = (t.ull << overlap >> (64 - n));
+	ReadPos += n;
+    return t.ull;
+}
+
+unsigned long long TBitStream::GetSizeInBits() const {
+    return BitsUsed;
+}
+
+}