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Diffstat (limited to 'nuttx/lib/fixedmath/lib_rint.c')
-rw-r--r-- | nuttx/lib/fixedmath/lib_rint.c | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/nuttx/lib/fixedmath/lib_rint.c b/nuttx/lib/fixedmath/lib_rint.c new file mode 100644 index 000000000..3a6407b8c --- /dev/null +++ b/nuttx/lib/fixedmath/lib_rint.c @@ -0,0 +1,135 @@ +/************************************************************ + * lib/fixedmath/lib_rint.c + * + * Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ************************************************************/ + +/************************************************************ + * Compilation Switches + ************************************************************/ + +/************************************************************ + * Included Files + ************************************************************/ + +#include <nuttx/config.h> +#include <sys/types.h> +#include <stdlib.h> + +/************************************************************ + * Definitions + ************************************************************/ + +/************************************************************ + * Private Type Declarations + ************************************************************/ + +/************************************************************ + * Private Function Prototypes + ************************************************************/ + +/********************************************************** + * Global Constant Data + **********************************************************/ + +/************************************************************ + * Global Variables + ************************************************************/ + +/********************************************************** + * Private Constant Data + **********************************************************/ + +/************************************************************ + * Private Variables + ************************************************************/ + +double_t rint(double_t x) +{ + double_t ret; + + /* If the current rounding mode rounds toward negative + * infinity, rint() is identical to floor(). If the current + * rounding mode rounds toward positive infinity, rint() is + * identical to ceil(). + */ + +#if defined(CONFIG_FP_ROUND_POSITIVE) && CONFIG_FP_ROUNDING_POSITIVE != 0 + + ret = ceil(x); + +#elif defined(CONFIG_FP_ROUND_NEGATIVE) && CONFIG_FP_ROUNDING_NEGATIVE != 0 + + ret = floor(x); + +#else + + /* In the default rounding mode (round to nearest), rint(x) is the + * integer nearest x with the additional stipulation that if + * |rint(x)-x|=1/2, then rint(x) is even. + */ + + long dwinteger = (long)x; + double_t fremainder = x - (double_t)dwinteger; + + if (x < 0.0) + { + /* fremainder should be in range 0 .. -1 */ + + if (fremainder == -0.5) + { + dwinteger = ((dwinteger+1)&~1); + } + else if (fremainder < -0.5) + { + dwinteger--; + } + } + else + { + /* fremainder should be in range 0 .. 1 */ + + if (fremainder == 0.5) + { + dwinteger = ((dwinteger+1)&~1); + } + else if (fremainder > 0.5) + { + dwinteger++; + } + } + + ret = (double_t)dwinteger; +#endif + + return ret; +} |