Add build def ZT_NO_TYPE_PUNNING, which when defined disables type punning code that might cause unaligned access errors on architectures that care (e.g. Android/ARM)
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2 changed files with 29 additions and 7 deletions
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@ -39,7 +39,7 @@
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#include "Constants.hpp"
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#include "Utils.hpp"
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#ifdef __GNUC__
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#if defined(__GNUC__) && (!defined(ZT_NO_TYPE_PUNNING))
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#define ZT_VAR_MAY_ALIAS __attribute__((__may_alias__))
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#else
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#define ZT_VAR_MAY_ALIAS
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@ -204,15 +204,19 @@ public:
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{
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if ((i + sizeof(T)) > _l)
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throw std::out_of_range("Buffer: setAt() beyond end of data");
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#ifdef ZT_NO_TYPE_PUNNING
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uint8_t *p = reinterpret_cast<uint8_t *>(_b + i);
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for(unsigned int x=1;x<=sizeof(T);++x)
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*(p++) = (uint8_t)(v >> (8 * (sizeof(T) - x)));
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#else
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T *const ZT_VAR_MAY_ALIAS p = reinterpret_cast<T *>(_b + i);
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*p = Utils::hton(v);
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#endif
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}
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/**
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* Get a primitive integer value at a given position
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*
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* This behaves like set() in reverse.
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*
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* @param i Index to get integer
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* @tparam T Integer type (e.g. uint16_t, int64_t)
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* @return Integer value
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@ -223,8 +227,18 @@ public:
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{
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if ((i + sizeof(T)) > _l)
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throw std::out_of_range("Buffer: at() beyond end of data");
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#ifdef ZT_NO_TYPE_PUNNING
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T v = 0;
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const uint8_t *p = reinterpret_cast<const uint8_t *>(_b + i);
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for(unsigned int x=0;x<sizeof(T);++x) {
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v <<= 8;
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v |= (T)*(p++);
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}
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return v;
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#else
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const T *const ZT_VAR_MAY_ALIAS p = reinterpret_cast<const T *>(_b + i);
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return Utils::ntoh(*p);
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#endif
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}
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/**
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@ -240,8 +254,14 @@ public:
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{
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if ((_l + sizeof(T)) > C)
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throw std::out_of_range("Buffer: append beyond capacity");
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#ifdef ZT_NO_TYPE_PUNNING
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uint8_t *p = reinterpret_cast<uint8_t *>(_b + _l);
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for(unsigned int x=1;x<=sizeof(T);++x)
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*(p++) = (uint8_t)(v >> (8 * (sizeof(T) - x)));
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#else
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T *const ZT_VAR_MAY_ALIAS p = reinterpret_cast<T *>(_b + _l);
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*p = Utils::hton(v);
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#endif
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_l += sizeof(T);
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}
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