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19025d77ad
Reorganized. Created a new top level include directory that will hold all of Trick's header files. Moved all of the Trick headers to this directory. Created a libexec directory that holds all of the executables that users don't need to execute directly. Changed all of the executables remaining in bin to start with "trick-". In the sim_services directories changed all source files to find the Trick headers in their new location. Since all of the include files are gone in sim_services, removed the src directories as well, moving all of the source files up a level. Moved the makefiles, docs, man, and other architecture independent files into a top level share directory. Renamed lib_${TRICK_HOST_CPU} to lib64 or lib depending on the platform we're currently on.
refs #63
100 lines
4.0 KiB
C
100 lines
4.0 KiB
C
/*
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PURPOSE: (Insert a value into a bitfield.)
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REFERENCE: ((meow) (woof))
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PROGRAMMERS: (((Jane Falgout) (LinCom)) ((Alex Lin) (NASA) (8/00))) */
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#include "trick/bitfield_proto.h"
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unsigned int insert_bitfield_any(unsigned int bitfield, /* In: Bitfiled to insert value into */
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int value, /* In: Value */
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int size, /* In: Declared size of bitfield */
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int start, /* In: Starting bit */
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int bits)
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{ /* In: Number of bits in bitfield */
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unsigned int mask;
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static int numbits = sizeof(unsigned int) * 8;
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union {
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long l;
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char c[sizeof(long)];
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} un;
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un.l = 1; /* Used for Little/Big Endian Detection */
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/* Mask out sign extension bits in case the value is negative */
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value &= (0xFFFFFFFF >> (32 - bits));
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/*
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* Create a mask for the purpose of clearing the previous value of
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* the bit field parameter for which an input was received, while
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* preserving the other values in the underlying memory location
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* shared by other bit field parameters. Do a bitwise AND of this
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* mask with the underlying bit field memory location. The input
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* value has been copied into an unsigned int. Shift the bits of
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* that unsigned int the appropriate number of bits so that the bit
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* position of the input value withing the unsigned int maps to the
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* bit position at which it needs to be stored in the underlying bit
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* field memory location. Do a bitwise OR of the shifted value with
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* the underlying bit field memory location, thus replacing the
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* previous value of the input bit field parameter with the input
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* value while preserving the values of other bit field parameters
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* that share the same underlying memory location.
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* On big endian architectures, the most significant byte (MSB) of an
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* integer is the first byte (i.e, the byte at the starting memory
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* location of the integer). On little endian architectures. the
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* least significant byte (LSB) is the first byte. The manner in
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* which bit fields are packed into a structure is not defined in
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* the ANSI standard, but what has been observed on several
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* platforms is that the bit field values are stored in the order in
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* which they were declared, with the first bit field starting at
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* the first byte. Therefore, the first bit field of a structure
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* on a big endian machine is stored at the high order end of its
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* memory location; on a little endian machine, the first bit field
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* is stored at the low order end of its memory location. These
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* storage differences influence the construction of the bit field
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* mask and the number of bits by which the input value is shifted.
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*
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* Keith says that the comment above might be the longest
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* in Trick source code. I haven't read it. It might even
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* be longer than the sum total of all other comments.
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* When the comments are longer than the code it worries me.
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*/
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if (un.c[sizeof(long) - 1] == 1) {
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/* Big endian */
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if (start == 0)
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mask = 0x00000000;
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else
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mask = 0xFFFFFFFF >> (numbits - start);
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if (start + bits < 32)
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mask |= (0xFFFFFFFF << (start + bits));
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bitfield &= mask;
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bitfield |= (value << start);
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} else {
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/* Little endian */
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/* if bitfield is smaller than 32 bits, adjust start accordingly */
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if (size == sizeof(short)) {
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start += 16;
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} else if (size == sizeof(char)) {
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start += 24;
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}
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if (start == 0)
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mask = 0x00000000;
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else
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mask = 0xFFFFFFFF << (numbits - start);
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if (start + bits < 32)
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mask |= (0xFFFFFFFF >> (start + bits));
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bitfield &= mask;
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bitfield |= (value << (32 - (start + bits)));
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}
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return (bitfield);
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}
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