diff --git a/c/ex3.c b/c/ex3.c new file mode 100644 index 0000000..84ff9a3 --- /dev/null +++ b/c/ex3.c @@ -0,0 +1,32 @@ +#include +#include + +static unsigned char reverse_byte(unsigned char c) { + unsigned char res = 0; + for (size_t i = 0; i < CHAR_BIT; ++i) { + unsigned char bit = (c & (1 << i)); + res |= bit << (CHAR_BIT - i - 1); + } + return res; +} + +static void swap_bytes(unsigned char* lhs, unsigned char* rhs) { + unsigned char tmp = *lhs; + *lhs = *rhs; + *rhs = tmp; +} + +void reverse_bytes(unsigned char* buf, size_t n) { + if (!buf || !n) + return; + + // No need to worry about applying reverse_byte twice in the middle by + // mistake if done in a preliminary pass + for (size_t i = 0; i < n; ++i) { + buf[i] = reverse_byte(buf[i]); + } + + for (size_t i = 0; i < ((n + 1) / 2); ++i) { + swap_bytes(&buf[i], &buf[n - 1 - i]); + } +} diff --git a/cpp/ex1.cc b/cpp/ex1.cc new file mode 100644 index 0000000..2882562 --- /dev/null +++ b/cpp/ex1.cc @@ -0,0 +1,28 @@ +#ifdef USE_ATOMIC_N +#include +#endif + +class CountInstances { +public: + CountInstances() { + ++n_instances_; + } + + ~CountInstances() { + --n_instances_; + } + + int nobjs() const { + return n_instances_; // If using atomics, load could use a more relaxed + // memory order, such as memory_order_acquire + } + +private: +#ifdef USE_ATOMIC_N + // Can be used in a multi-thread program + static atomic n_instances_; +#else + // Using a bare int mean races if used in a multi-threaded context + static int n_instances_; +#endif +}; diff --git a/cpp/ex2.cc b/cpp/ex2.cc new file mode 120000 index 0000000..d810e4b --- /dev/null +++ b/cpp/ex2.cc @@ -0,0 +1 @@ +../c/ex1.c \ No newline at end of file