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SwRI can revise these Terms at any time * without notice by updating this posting. * * Trademarks * * The SwRI logo is a trademark of SwRI in the United States and other countries. * */ #ident "@(#) to_sign.c 1.13 05/08/19 SwRI" #include "libbase_idfs.h" /******************************************************************************* * * * IR_TO_SIGN SUBROUTINE * * * * DESCRIPTION * * This routine will take a data value and return its "signed" value. If * * the sign bit is not set, the same value is simply returned. However, if * * the sign bit is set, the signed quantity will be returned. For example, * * if the value were 255, the word was 8 bits long, and the sign bit was not * * set, 255 would be returned. If the sign bit were set, then -1 would be * * returned. * * * * INPUT VARIABLES * * SDDAS_LONG new_val the data value to be examined * * SDDAS_CHAR tdw_len the word length for the data value (in bits)* * * * USAGE * * x = ir_to_sign (new_val, tdw_len) * * * * NECESSARY SUBPROGRAMS * * None * * * * EXTERNAL VARIABLES * * None * * * * INTERNAL VARIABLES * * SDDAS_FLOAT answer the value being returned * * SDDAS_LONG result value used to convert to a signed value * * SDDAS_LONG max_ele the largest possible positive value for this* * word length * * SDDAS_LONG mask masking value to catch the sign bit * * SDDAS_CHAR sgn flag indicating if the sign bit is set * * * * SUBSYSTEM * * Display Level * * * ******************************************************************************/ SDDAS_FLOAT ir_to_sign (SDDAS_LONG new_val, SDDAS_CHAR tdw_len) { SDDAS_FLOAT answer; SDDAS_LONG result, max_ele, mask; SDDAS_CHAR sgn; /***************************************************************************/ /* Since the value that already takes up 4 bytes, simply return, no need */ /* to set sign bit (already set). */ /***************************************************************************/ if (tdw_len == 32) { answer = new_val; return (answer); } /***************************************************************************/ /* Determine the value to use to mask off the sign bit and determine the */ /* largest positive value for this word length. */ /***************************************************************************/ mask = 1 << (tdw_len - 1); max_ele = (1 << tdw_len) - 1; /***************************************************************************/ /* If the sign bit is set, convert to value a signed quantity. */ /***************************************************************************/ sgn = (new_val & mask) >> (tdw_len - 1); if (sgn == 1) { result = -1; answer = (result - max_ele) + new_val; } else answer = new_val; return (answer); }