Division (#236)

* minor on Bitstream * Minor changes on Bitmask * minor --------- Co-authored-by: Samuel Li <sam@cisl-m121a>
NCAR · Apr 16, 2024 · f6ddfa7 · f6ddfa7
1 parent d87bdd0
commit f6ddfa7
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Showing 2 changed files with 22 additions and 16 deletions.
diff --git a/src/Bitmask.cpp b/src/Bitmask.cpp
@@ -8,7 +8,7 @@ sperr::Bitmask::Bitmask(size_t nbits)
 {
   if (nbits > 0) {
     auto num_longs = nbits / 64;
-    if (nbits % 64 != 0)
+    if (nbits - num_longs * 64 != 0)
       num_longs++;
     m_buf.assign(num_longs, 0);
     m_num_bits = nbits;
@@ -23,7 +23,7 @@ auto sperr::Bitmask::size() const -> size_t
 void sperr::Bitmask::resize(size_t nbits)
 {
   auto num_longs = nbits / 64;
-  if (nbits % 64 != 0)
+  if (nbits - num_longs * 64 != 0)
     num_longs++;
   m_buf.resize(num_longs, 0);
   m_num_bits = nbits;
@@ -36,8 +36,10 @@ auto sperr::Bitmask::rlong(size_t idx) const -> uint64_t
 
 auto sperr::Bitmask::rbit(size_t idx) const -> bool
 {
-  auto word = m_buf[idx / 64];
-  word &= uint64_t{1} << (idx % 64);
+  auto div = idx / 64;
+  auto rem = idx - div * 64;
+  auto word = m_buf[div];
+  word &= uint64_t{1} << rem;
   return (word != 0);
 }
 
@@ -50,7 +52,7 @@ auto sperr::Bitmask::has_true(size_t start, size_t len) const -> int64_t
   // Collect the remaining bits from the start long.
   auto word = m_buf[long_idx];
   auto answer = uint64_t{0};
-  for (auto i = start % 64; i < 64 && processed_bits < len; i++) {
+  for (auto i = start - long_idx * 64; i < 64 && processed_bits < len; i++) {
     answer |= word & (uint64_t{1} << i);
     if constexpr (Position) {
       if (answer != 0)
@@ -133,7 +135,7 @@ void sperr::Bitmask::wlong(size_t idx, uint64_t value)
 void sperr::Bitmask::wbit(size_t idx, bool bit)
 {
   const auto wstart = idx / 64;
-  const auto mask = uint64_t{1} << (idx % 64);
+  const auto mask = uint64_t{1} << (idx - wstart * 64);
 
   auto word = m_buf[wstart];
   if (bit)
@@ -146,7 +148,7 @@ void sperr::Bitmask::wbit(size_t idx, bool bit)
 void sperr::Bitmask::wtrue(size_t idx)
 {
   const auto wstart = idx / 64;
-  const auto mask = uint64_t{1} << (idx % 64);
+  const auto mask = uint64_t{1} << (idx - wstart * 64);
 
   auto word = m_buf[wstart];
   word |= mask;
@@ -156,7 +158,7 @@ void sperr::Bitmask::wtrue(size_t idx)
 void sperr::Bitmask::wfalse(size_t idx)
 {
   const auto wstart = idx / 64;
-  const auto mask = uint64_t{1} << (idx % 64);
+  const auto mask = uint64_t{1} << (idx - wstart * 64);
 
   auto word = m_buf[wstart];
   word &= ~mask;

diff --git a/src/Bitstream.cpp b/src/Bitstream.cpp
@@ -29,7 +29,7 @@ void sperr::Bitstream::reserve(size_t nbits)
   if (nbits > m_buf.size() * 64) {
     // Number of longs that's absolutely needed.
     auto num_longs = nbits / 64;
-    if (nbits % 64 != 0)
+    if (num_longs * 64 < nbits)
       num_longs++;
 
     const auto dist = std::distance(m_buf.begin(), m_itr);
@@ -54,8 +54,9 @@ auto sperr::Bitstream::rtell() const -> size_t
 
 void sperr::Bitstream::rseek(size_t offset)
 {
-  m_itr = m_buf.begin() + offset / 64;
-  const auto rem = offset % 64;
+  size_t div = offset / 64;
+  size_t rem = offset - div * 64;
+  m_itr = m_buf.begin() + div;
   if (rem) {
     m_buffer = *m_itr >> rem;
     ++m_itr;
@@ -90,8 +91,9 @@ auto sperr::Bitstream::wtell() const -> size_t
 
 void sperr::Bitstream::wseek(size_t offset)
 {
-  m_itr = m_buf.begin() + offset / 64;
-  const auto rem = offset % 64;
+  size_t div = offset / 64;
+  size_t rem = offset - div * 64;
+  m_itr = m_buf.begin() + div;
   if (rem) {
     m_buffer = *m_itr;
     m_buffer &= (uint64_t{1} << rem) - 1;
@@ -114,7 +116,7 @@ void sperr::Bitstream::wbit(bool bit)
 #endif
   {
     if (m_itr == m_buf.end()) {  // allocate memory if necessary.
-      const auto dist = m_buf.size();
+      auto dist = m_buf.size();
       m_buf.resize(std::max(size_t{1}, dist) * 2 - dist / 2);  // use a growth factor of 1.5
       m_itr = m_buf.begin() + dist;
     }
@@ -129,7 +131,7 @@ void sperr::Bitstream::flush()
 {
   if (m_bits) {  // only really flush when there are remaining bits.
     if (m_itr == m_buf.end()) {
-      const auto dist = m_buf.size();
+      auto dist = m_buf.size();
       m_buf.resize(std::max(size_t{1}, dist) * 2 - dist / 2);  // use a growth factor of 1.5
       m_itr = m_buf.begin() + dist;
     }
@@ -144,6 +146,7 @@ void sperr::Bitstream::flush()
 void sperr::Bitstream::write_bitstream(void* p, size_t num_bits) const
 {
   assert(num_bits <= m_buf.size() * 64);
+
   const auto num_longs = num_bits / 64;
   auto rem_bytes = num_bits / 8 - num_longs * sizeof(uint64_t);
   if (num_bits % 8 != 0)
@@ -162,8 +165,9 @@ void sperr::Bitstream::write_bitstream(void* p, size_t num_bits) const
 auto sperr::Bitstream::get_bitstream(size_t num_bits) const -> std::vector<std::byte>
 {
   assert(num_bits <= m_buf.size() * 64);
+
   auto num_bytes = num_bits / 8;
-  if (num_bits % 8 != 0)
+  if (num_bits - num_bytes * 8 != 0)
     num_bytes++;
 
   auto tmp = std::vector<std::byte>(num_bytes);