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| -rw-r--r-- | test/div20.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/test/div20.c b/test/div20.c new file mode 100644 index 0000000..1003ab8 --- /dev/null +++ b/test/div20.c @@ -0,0 +1,60 @@ +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> + + +/* +Page about div +http://bisqwit.iki.fi/story/howto/bitmath/#DivAndModDivisionAndModulo +*/ + +uint8_t div20u8( uint16_t num ) +{ + uint16_t a = num; + uint16_t b = 20; + uint16_t r = 0; + uint16_t m = 1; + while ( b < a ) + { + b = b << 1; + m = m << 1; + } + do + { + if ( a >= b ) + { + a = a - b; + r = r + m; + } + b = b >> 1; + m = m >> 1; + } while ( m != 0 ); + return (uint8_t)r; +} + +int main() +{ + uint32_t a = 10000; + uint32_t b = 5; + uint32_t r = 0; + uint32_t m = 1; + printf("%04x(%d) %04x(%3d) %04x(%3d) %04x(%3d)\n",a,a,b,b,r,r,m,m); + while ( b < a ) + { + b = b << 1; + m = m << 1; + printf("%04x(%3d) %04x(%3d) %04x(%3d) %04x(%3d)\n",a,a,b,b,r,r,m,m); + } + do + { + if ( a >= b ) + { + a = a - b; + r = r + m; + } + b = b >> 1; + m = m >> 1; + printf("%04x(%3d) %04x(%3d) %04x(%3d) %04x(%3d)\n",a,a,b,b,r,r,m,m); + } while ( m != 0 ); + return 0; +}
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