124 lines
2.9 KiB
C
124 lines
2.9 KiB
C
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/* file: unpack_vax_f.c */
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/*
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**
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** COPYRIGHT (c) 1989 BY
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** DIGITAL EQUIPMENT CORPORATION, MAYNARD, MASSACHUSETTS.
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** ALL RIGHTS RESERVED.
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**
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** THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY BE USED AND COPIED
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** ONLY IN ACCORDANCE WITH THE TERMS OF SUCH LICENSE AND WITH THE
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** INCLUSION OF THE ABOVE COPYRIGHT NOTICE. THIS SOFTWARE OR ANY OTHER
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** COPIES THEREOF MAY NOT BE PROVIDED OR OTHERWISE MADE AVAILABLE TO ANY
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** OTHER PERSON. NO TITLE TO AND OWNERSHIP OF THE SOFTWARE IS HEREBY
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** TRANSFERRED.
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**
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** THE INFORMATION IN THIS SOFTWARE IS SUBJECT TO CHANGE WITHOUT NOTICE
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** AND SHOULD NOT BE CONSTRUED AS A COMMITMENT BY DIGITAL EQUIPMENT
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** CORPORATION.
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**
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** DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE OR RELIABILITY OF ITS
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** SOFTWARE ON EQUIPMENT WHICH IS NOT SUPPLIED BY DIGITAL.
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**
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*/
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/*
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**++
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** Facility:
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**
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** CVT Run-Time Library
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**
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** Abstract:
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**
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** This module contains code to extract information from a VAX
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** f_floating number and to initialize an UNPACKED_REAL structure
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** with those bits.
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**
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** This module is meant to be used as an include file.
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**
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** Author: Math RTL
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**
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** Creation Date: November 24, 1989.
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**
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** Modification History:
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**
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**--
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*/
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/*
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**++
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** Functional Description:
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**
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** This module contains code to extract information from a VAX
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** f_floating number and to initialize an UNPACKED_REAL structure
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** with those bits.
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**
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** See the header files for a description of the UNPACKED_REAL
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** structure.
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**
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** A VAX f_floating number in (16 bit words) looks like:
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**
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** [0]: Sign bit, 8 exp bits (bias 128), 7 fraction bits
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** [1]: 16 more fraction bits
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**
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** 0.5 <= fraction < 1.0, MSB implicit
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**
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**
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** Implicit parameters:
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**
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** input_value: a pointer to the input parameter.
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**
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** r: an UNPACKED_REAL structure
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**
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**--
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*/
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RpcpMemoryCopy(&r[1], input_value, 4);
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/* Initialize FLAGS and perhaps set NEGATIVE bit */
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r[U_R_FLAGS] = (r[1] >> 15) & U_R_NEGATIVE;
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/* Extract VAX biased exponent */
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r[U_R_EXP] = (r[1] >> 7) & 0x000000FFL;
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if (r[U_R_EXP] == 0) {
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if (r[U_R_FLAGS])
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r[U_R_FLAGS] |= U_R_INVALID;
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else
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r[U_R_FLAGS] = U_R_ZERO;
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} else {
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/* Adjust for VAX 16 bit floating format */
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r[1] = ((r[1] << 16) | (r[1] >> 16));
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/* Add unpacked real bias and subtract VAX bias */
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r[U_R_EXP] += (U_R_BIAS - 128);
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/* Set hidden bit */
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r[1] |= 0x00800000L;
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/* Left justify fraction bits */
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r[1] <<= 8;
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/* Clear uninitialized parts for unpacked real */
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r[2] = 0;
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r[3] = 0;
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r[4] = 0;
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}
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