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POBitstream to Float Type Coercion
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  1. POBitstream to Float Type Coercion
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    copied!<p>I'm having trouble getting the following code to work correctly. Using an online IEEE-754 converter, I wrote out (by hand) to the testData.txt file that is read with the bit string that should signify the floating point number 75.5; the actual cout.write does show that the bit string is as I expect as well. However, when I try to coerce the char* into a float using a union (as I have seen is a typical way to accomplish this conversion) the resulting float is not the number I expect.</p> <pre><code>#include&lt;climits&gt; #include&lt;iostream&gt; #include&lt;fstream&gt; #include&lt;bitset&gt; int main( int, char** ) { std::ifstream inputFile( "testData.txt", std::ios_base::in | std::ios_base::binary ); if( !inputFile ) std::cout &lt;&lt; "Failed to open input file!" &lt;&lt; std::endl; char buffer[ CHAR_BIT * sizeof(float) ]; inputFile.read( buffer, CHAR_BIT * sizeof(float) ); std::cout &lt;&lt; "cout.write of input from file = "; std::cout.write( buffer, CHAR_BIT * sizeof(float) ); std::cout &lt;&lt; std::endl; union { float f; char* c; } fToCharStarUnion; fToCharStarUnion.c = buffer; std::bitset&lt; sizeof(float) * CHAR_BIT &gt; bits( std::string( fToCharStarUnion.c ) ); std::cout &lt;&lt; "fToCharStarUnion.f = " &lt;&lt; fToCharStarUnion.f &lt;&lt; " bits = " &lt;&lt; bits &lt;&lt; std::endl; inputFile.close(); return 0; } </code></pre> <p>The return result of running this is:</p> <pre><code>cout.write of input from file = 01000010100101110000000000000000 fToCharStarUnion.f = -1.61821e+38 bits = 01000010100101110000000000000000 </code></pre> <p>Is there something fundamental I am not doing which will make this work correctly?</p>
 

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