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copied!<pre><code>#include <errno.h> #include <stdint.h> /* Insert a bit `idx' positions from the right (lsb). */ uint16_t bit_insert_lsb(uint16_t n, int bit, int idx) { uint16_t lower; if (idx > 15) { errno = ERANGE; return 0U; } /* Get bits 0 to `idx' inclusive. */ lower = n & ((1U << (idx + 1)) - 1); return ((n & ~lower) | ((!!bit) << idx) | (lower >> 1)); } /* Insert a bit `idx' positions from the left (msb). */ uint16_t bit_insert_msb(uint16_t n, int bit, int idx) { uint16_t lower; if (idx > 15) { errno = ERANGE; return 0U; } /* Get bits 0 to `16 - idx' inclusive. */ lower = n & ((1U << (15 - idx + 1)) - 1); return ((n & ~lower) | ((!!bit) << (15 - idx)) | (lower >> 1)); } </code></pre> <p>Bits are typically counted from the right, where the least significant bit (lsb) resides, to the left, where the most significant bit (msb) is located. I allowed for insertion from either side by creating two functions. The one expected, according to the question, is <code>bit_insert_msb</code>.</p> <p>Both functions perform a sanity check, setting <code>errno</code> to <code>ERANGE</code> and returning 0 if the value of <code>idx</code> is too large. I also provided some of C99's <code>_Bool</code> behaviour for the <code>bit</code> parameter in the <code>return</code> statements: 0 is 0 and any other value is 1. If you use a C99 compiler, I'd recommend changing <code>bit</code>'s type to <code>_Bool</code>. You can then replace <code>(!!bit)</code> with <code>bit</code> directly.</p> <p>I'd love to say it could be optimised, but that could very well make it less comprehensible.</p> <p>Happy coding!</p>

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