Support of big endian platforms

Author: dcherednik

src/bitstream/bitstream.cpp

@@ -1,41 +1,24 @@
 #include "bitstream.h"
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define NBITSTREAM__LITTLE_ENDIAN_CPU
+#endif
+
 namespace NBitStream {
 
-union TMix {
-	unsigned long long ull = 0;
-	uint8_t bytes[8];
+union UBytes {
+	uint32_t ui = 0;
+	uint8_t bytes[4];
 };
 
 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 (overlap || 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];
-
-  //      std::cout << "bufPos: "<< bytesPos+i << " buf: " << (int)Buf[bytesPos+i] << std::endl;
-	}
-
-    BitsUsed += n;
-}
-/*
-void TBitStream::Write(unsigned long long val, int n) {
+void TBitStream::Write(uint32_t val, int n) {
     if (n > 23 || n < 0)
         abort();
     const int bitsLeft = Buf.size() * 8 - BitsUsed;
@@ -46,25 +29,38 @@ void TBitStream::Write(unsigned long long val, int n) {
     if (overlap || bitsReq >= 0) {
         Buf.resize(Buf.size() + (bitsReq / 8 + (overlap ? 2 : 1 )), 0);
     }
-    TMix t;
-    t.ull   = (val << (64 - n)) >> overlap;
-    *(unsigned long long*)&Buf[bytesPos-8] |= t.ull;
+    UBytes t;
+    t.ui = (val << (32 - n) >> overlap);
+
+    for (int i = 0; i < n/8 + (overlap ? 2 : 1); ++i) {
+#ifdef NBITSTREAM__LITTLE_ENDIAN_CPU
+        Buf[bytesPos+i] |= t.bytes[3-i];
+#else
+        Buf[bytesPos + i] |= t.bytes[i];
+#endif
+    }
+
     BitsUsed += n;
 }
-*/
-unsigned long long TBitStream::Read(int n) {
-	if (n >23 || n < 0)
-		abort();
+
+uint32_t 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];
-	}
+
+    UBytes t;
+    for (int i = 0; i < n/8 + (overlap ? 2 : 1); ++i) {
+#ifdef NBITSTREAM__LITTLE_ENDIAN_CPU
+        t.bytes[3-i] = (uint8_t)Buf[bytesPos+i];
+#else
+        t.bytes[i] = (uint8_t)Buf[bytesPos+i];
+#endif
+    }
 
-	t.ull = (t.ull << overlap >> (64 - n));
-	ReadPos += n;
-    return t.ull;
+    t.ui = (t.ui << overlap >> (32 - n));
+    ReadPos += n;
+    return t.ui;
 }
 
 unsigned long long TBitStream::GetSizeInBits() const {

src/bitstream/bitstream.h

@@ -18,8 +18,8 @@ class TBitStream {
     public:
         TBitStream(const char* buf, int size);
         TBitStream();
-        void Write(unsigned long long val, int n);
-        unsigned long long Read(int n);
+        void Write(uint32_t val, int n);
+        uint32_t Read(int n);
         unsigned long long GetSizeInBits() const;
         uint32_t GetBufSize() const { return Buf.size(); };
         const std::vector<char>& GetBytes() const {

test/CMakeLists.txt

@@ -14,7 +14,12 @@ endmacro(use_11)
 
 use_11()
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -fsanitize=address -fno-omit-frame-pointer")
+if (CMAKE_SYSTEM_PROCESSOR MATCHES "(x86)|(X86)|(amd64)|(AMD64)")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -fsanitize=address -fno-omit-frame-pointer")
+else ()
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -fno-omit-frame-pointer")
+endif ()
+
 
 include_directories(${gtest_SOURCE_DIR}/include)