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=head1 LIBECB |
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You suck, we don't(tm) |
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=head2 ABOUT THE HEADER |
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- how to include it |
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- it includes inttypes.h |
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- no .a |
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- whats a bool |
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=head2 GCC ATTRIBUTES |
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blabla where to put, what others |
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=over 4 |
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=item ecb_attribute ((attrs...)) |
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A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and |
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to nothing on other compilers, so the effect is that only GCC sees these. |
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=item ecb_unused |
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Marks a function or a variable as "unused", which simply suppresses a |
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warning by GCC when it detects it as unused. This is useful when you e.g. |
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declare a variable but do not always use it: |
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|
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{ |
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int var ecb_unused; |
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#ifdef SOMECONDITION |
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var = ...; |
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return var; |
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#else |
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return 0; |
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#endif |
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} |
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=item ecb_noinline |
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Prevent a function from being inlined - it might be optimsied away, but |
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not inlined into other functions. This is useful if you know your function |
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is rarely called and large enough for inlining not to be helpful. |
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=item ecb_noreturn |
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=item ecb_const |
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=item ecb_pure |
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=item ecb_hot |
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=item ecb_cold |
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=item ecb_artificial |
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=back |
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=head2 OPTIMISATION HINTS |
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=over 4 |
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=item bool ecb_is_constant(expr) |
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Returns true iff the expression can be deduced to be a compile-time |
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constant, and false otherwise. |
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For example, when you have a C<rndm16> function that returns a 16 bit |
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random number, and you have a function that maps this to a range from |
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0..n-1, then you could use this inline function in a header file: |
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|
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ecb_inline uint32_t |
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rndm (uint32_t n) |
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{ |
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return (n * (uint32_t)rndm16 ()) >> 16; |
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} |
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|
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However, for powers of two, you could use a normal mask, but that is only |
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worth it if, at compile time, you can detect this case. This is the case |
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when the passed number is a constant and also a power of two (C<n & (n - |
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1) == 0>): |
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|
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ecb_inline uint32_t |
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rndm (uint32_t n) |
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{ |
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return is_constant (n) && !(n & (n - 1)) |
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? rndm16 () & (num - 1) |
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: (n * (uint32_t)rndm16 ()) >> 16; |
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} |
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=item bool ecb_expect(expr,value) |
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=item bool ecb_unlikely(bool) |
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=item bool ecb_likely(bool) |
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=item bool ecb_assume(cond) |
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=item bool ecb_unreachable() |
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=item bool ecb_prefetch(addr,rw,locality) |
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=back |
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=head2 BIT FIDDLING / BITSTUFFS |
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=over 4 |
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=item bool ecb_big_endian () |
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=item bool ecb_little_endian () |
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=item int ecb_ctz32 (uint32_t x) |
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=item int ecb_popcount32 (uint32_t x) |
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=item uint32_t ecb_bswap32 (uint32_t x) |
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=item uint32_t ecb_bswap16 (uint32_t x) |
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=item uint32_t ecb_rotr32 (uint32_t x, unsigned int count) |
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=item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
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=back |
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=head2 ARITHMETIC |
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=over 4 |
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=item x = ecb_mod (m, n) [MACRO] |
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=back |
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=head2 UTILITY |
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=over 4 |
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=item ecb_array_length (name) [MACRO] |
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=back |
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