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Use compiler macros for endianness #2688

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merged 1 commit into from
Jul 12, 2023
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Use compiler macros for endianness #2688

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12 changes: 10 additions & 2 deletions src/image.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -168,8 +168,12 @@ bool Image::isPrintICC(uint16_t type, Exiv2::PrintStructureOption option) {
}

bool Image::isBigEndianPlatform() {
#if defined(__BYTE_ORDER)
#if __BYTE_ORDER == __BIG_ENDIAN
#ifdef __LITTLE_ENDIAN__
return false;
#elif defined(__BIG_ENDIAN__)
return true;
#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__)
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
return true;
#else
return false;
Expand All @@ -184,7 +188,11 @@ bool Image::isBigEndianPlatform() {
#endif
}
bool Image::isLittleEndianPlatform() {
#ifdef __LITTLE_ENDIAN__
return true;
#else
Comment on lines +191 to +193
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Is this macro (__LITTLE_ENDIAN__) sometimes defined when __BYTE_ORDER__ isn't? If so, maybe this logic should be moved to isBigEndianPlatform. I.e. add this to the beginning of isBigEndianPlatform:

#if defined(__BIG_ENDIAN__)
  return true;
#elif defined(__LITTLE_ENDIAN__)
  return false;
#elif ...

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@kmilos kmilos Jul 11, 2023 •
edited
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__LITTLE_ENDIAN__ is our own macro (potentially) defined in config.h.

Everything else comes from the compiler. AFAICT, there is no definition of __BIG_ENDIAN__.

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Is this macro (__LITTLE_ENDIAN__) sometimes defined when __BYTE_ORDER__ isn't?

Potentially on WIN32 and MSVC (which AFAIK does not define __BYTE_ORDER__):

exiv2/include/exiv2/config.h

Line 43 in 50648dd

#if defined(_WIN32) || defined(__CYGWIN__)

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@kmilos kmilos Jul 11, 2023 •
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@kevinbackhouse I'm now leveraging these as well.

return !isBigEndianPlatform();
#endif
}

uint64_t Image::byteSwap(uint64_t value, bool bSwap) {
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