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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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This commit is contained in:
Adam Ierymenko 2015-07-08 09:12:51 -07:00
parent 412389ec75
commit a297e4a5bf
2 changed files with 29 additions and 7 deletions
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26
node/Buffer.hpp
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@ -39,7 +39,7 @@
#include "Constants.hpp"
#include "Utils.hpp"
#ifdef __GNUC__
#if defined(__GNUC__) && (!defined(ZT_NO_TYPE_PUNNING))
#define ZT_VAR_MAY_ALIAS __attribute__((__may_alias__))
#else
#define ZT_VAR_MAY_ALIAS
@ -204,15 +204,19 @@ public:
{
if ((i + sizeof(T)) > _l)
throw std::out_of_range("Buffer: setAt() beyond end of data");
#ifdef ZT_NO_TYPE_PUNNING
uint8_t *p = reinterpret_cast<uint8_t *>(_b + i);
for(unsigned int x=1;x<=sizeof(T);++x)
*(p++) = (uint8_t)(v >> (8 * (sizeof(T) - x)));
#else
T *const ZT_VAR_MAY_ALIAS p = reinterpret_cast<T *>(_b + i);
*p = Utils::hton(v);
#endif
}
/**
* Get a primitive integer value at a given position
*
* This behaves like set() in reverse.
*
* @param i Index to get integer
* @tparam T Integer type (e.g. uint16_t, int64_t)
* @return Integer value
@ -223,8 +227,18 @@ public:
{
if ((i + sizeof(T)) > _l)
throw std::out_of_range("Buffer: at() beyond end of data");
#ifdef ZT_NO_TYPE_PUNNING
T v = 0;
const uint8_t *p = reinterpret_cast<const uint8_t *>(_b + i);
for(unsigned int x=0;x<sizeof(T);++x) {
v <<= 8;
v |= (T)*(p++);
}
return v;
#else
const T *const ZT_VAR_MAY_ALIAS p = reinterpret_cast<const T *>(_b + i);
return Utils::ntoh(*p);
#endif
}
/**
@ -240,8 +254,14 @@ public:
{
if ((_l + sizeof(T)) > C)
throw std::out_of_range("Buffer: append beyond capacity");
#ifdef ZT_NO_TYPE_PUNNING
uint8_t *p = reinterpret_cast<uint8_t *>(_b + _l);
for(unsigned int x=1;x<=sizeof(T);++x)
*(p++) = (uint8_t)(v >> (8 * (sizeof(T) - x)));
#else
T *const ZT_VAR_MAY_ALIAS p = reinterpret_cast<T *>(_b + _l);
*p = Utils::hton(v);
#endif
_l += sizeof(T);
}