diff options
Diffstat (limited to 'arm-wt-22k/lib_src/eas_flog.c')
| -rw-r--r-- | arm-wt-22k/lib_src/eas_flog.c | 168 |
1 files changed, 84 insertions, 84 deletions
diff --git a/arm-wt-22k/lib_src/eas_flog.c b/arm-wt-22k/lib_src/eas_flog.c index 647da2f..16539f5 100644 --- a/arm-wt-22k/lib_src/eas_flog.c +++ b/arm-wt-22k/lib_src/eas_flog.c @@ -1,13 +1,13 @@ -/*----------------------------------------------------------------------------
- *
- * File:
- * eas_flog2.c
- *
- * Contents and purpose:
- * Fixed point square root
- *
- *
- * Copyright (c) 2006 Sonic Network Inc.
+/*---------------------------------------------------------------------------- + * + * File: + * eas_flog2.c + * + * Contents and purpose: + * Fixed point square root + * + * + * Copyright (c) 2006 Sonic Network Inc. * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -20,77 +20,77 @@ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. - *
- *----------------------------------------------------------------------------
- * Revision Control:
- * $Revision$
- * $Date$
- *----------------------------------------------------------------------------
-*/
-
-#include "eas_types.h"
-#include "eas_math.h"
-
-#define MANTISSA_SHIFT 27
-#define MANTISSA_MASK 0x0000000f
-#define MANTISSA_LSB_SHIFT 7
-#define MANTISSA_LSB_MASK 0x000fffff
-#define LOG_EXPONENT_SHIFT 10
-#define INTERPOLATION_SHIFT 20
-#define MAX_NEGATIVE (-2147483647-1)
-
-/* log lookup table */
-static const EAS_U16 eas_log2_table[] =
-{
- 0, 90, 174, 254, 330, 402, 470, 536,
- 599, 659, 717, 773, 827, 879, 929, 977,
- 1024
-};
-
-/*----------------------------------------------------------------------------
- * EAS_flog2()
- *----------------------------------------------------------------------------
- * Purpose:
- * Calculates the log2 of a 32-bit fixed point value
- *
- * Inputs:
- * n = value of interest
- *
- * Outputs:
- * returns the log2 of n
- *
- *----------------------------------------------------------------------------
-*/
-EAS_I32 EAS_flog2 (EAS_U32 n)
-{
- EAS_U32 exp;
- EAS_U32 interp;
-
- /* check for error condition */
- if (n == 0)
- return MAX_NEGATIVE;
-
- /* find exponent */
- for (exp = 31; exp > 0; exp--)
- {
- /* shift until we get a 1 bit in bit 31 */
- if ((n & (EAS_U32) MAX_NEGATIVE) != 0)
- break;
- n <<= 1;
- }
- /*lint -e{701} use shift for performance */
- exp <<= LOG_EXPONENT_SHIFT;
-
- /* get the least significant bits for interpolation */
- interp = (n >> MANTISSA_LSB_SHIFT) & MANTISSA_LSB_MASK;
-
- /* get the most significant bits for mantissa lookup */
- n = (n >> MANTISSA_SHIFT) & MANTISSA_MASK;
-
- /* interpolate mantissa */
- interp = ((eas_log2_table[n+1] - eas_log2_table[n]) * interp) >> INTERPOLATION_SHIFT;
- exp += eas_log2_table[n] + interp;
-
- return (EAS_I32) exp;
-}
-
+ * + *---------------------------------------------------------------------------- + * Revision Control: + * $Revision$ + * $Date$ + *---------------------------------------------------------------------------- +*/ + +#include "eas_types.h" +#include "eas_math.h" + +#define MANTISSA_SHIFT 27 +#define MANTISSA_MASK 0x0000000f +#define MANTISSA_LSB_SHIFT 7 +#define MANTISSA_LSB_MASK 0x000fffff +#define LOG_EXPONENT_SHIFT 10 +#define INTERPOLATION_SHIFT 20 +#define MAX_NEGATIVE (-2147483647-1) + +/* log lookup table */ +static const EAS_U16 eas_log2_table[] = +{ + 0, 90, 174, 254, 330, 402, 470, 536, + 599, 659, 717, 773, 827, 879, 929, 977, + 1024 +}; + +/*---------------------------------------------------------------------------- + * EAS_flog2() + *---------------------------------------------------------------------------- + * Purpose: + * Calculates the log2 of a 32-bit fixed point value + * + * Inputs: + * n = value of interest + * + * Outputs: + * returns the log2 of n + * + *---------------------------------------------------------------------------- +*/ +EAS_I32 EAS_flog2 (EAS_U32 n) +{ + EAS_U32 exp; + EAS_U32 interp; + + /* check for error condition */ + if (n == 0) + return MAX_NEGATIVE; + + /* find exponent */ + for (exp = 31; exp > 0; exp--) + { + /* shift until we get a 1 bit in bit 31 */ + if ((n & (EAS_U32) MAX_NEGATIVE) != 0) + break; + n <<= 1; + } + /*lint -e{701} use shift for performance */ + exp <<= LOG_EXPONENT_SHIFT; + + /* get the least significant bits for interpolation */ + interp = (n >> MANTISSA_LSB_SHIFT) & MANTISSA_LSB_MASK; + + /* get the most significant bits for mantissa lookup */ + n = (n >> MANTISSA_SHIFT) & MANTISSA_MASK; + + /* interpolate mantissa */ + interp = ((eas_log2_table[n+1] - eas_log2_table[n]) * interp) >> INTERPOLATION_SHIFT; + exp += eas_log2_table[n] + interp; + + return (EAS_I32) exp; +} + |