The Fortress Language Specification - CiteSeerX

40.6 The Trait Fortress.Core.BinaryEndianWord
The type BinaryEndianWordb,bigEndianBytes,bigEndianBits is exactly like BinaryWordb but bears two
kinds of endianness information. A BinaryEndianWord may be split into a sequence of smaller words; the result is of
type BinaryLinearEndianSequence. The flag bigEndianBytes indicates whether subword 0 is the most significant
subword (if bigEndianBytes is true) or least significant subword (if bigEndianBytes is false) of the original binary
word. A BinaryEndianWord may also be subscripted to extract a bit or a bit field; the flag bigEndianBits indicates
whether bit 0 is the most significant bit (if bigEndianBits is true) or least significant bit (if bigEndianBits is false)
of the original binary word. (Yes, it may seem strange for the bit ordering to differ from the subword ordering, but they
do differ on a number of architectures, including SPARC.) Extracting a bit produces a Bit, that is, a BinaryWord0 .
Extracting a bit field of width k produces a BinaryEndianLinearEndianSequence with n = k and b = 0 ; the
endianness of the sequence matches the bit-endianness of the original BinaryEndianWord.
trait BinaryEndianWordnat b,bool bigEndianBytes,bool bigEndianBits
extends { BasicBinaryWordOperationsBinaryEndianWordb,bigEndianBytes,bigEndianBits, b}
comprises {}
where { b ≤ maxBinaryWordBitLog }
coercion int r(x:IntegerStaticr) where { −2 b−1 ≤ r < 2 b }
opr [j: IndexInt] : BinaryEndianWord1,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
opr nat k[j: IntegerStatick] : BinaryEndianWord1,bigEndianBytes,bigEndianBits
where { k < 2 b }
opr nat m[r: RangeOfStaticSizeIndexInt, m] :
BinaryEndianLinearEndianSequence1,bigEndianBytes,bigEndianBits, m,bigEndianBits
throws { IndexOutOfBoundsException }
opr int a,nat m,int c[r:StaticRangea, m, c] :
BinaryEndianLinearEndianSequence1,bigEndianBytes,bigEndianBits, m,bigEndianBits
where { 0 ≤ a < 2 b , 0 ≤ a + m · c < 2 b }
opr [j: IndexInt] := (v: Bit):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
opr nat k[j: IntegerStatick] := (v: Bit):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
where { k < 2 b }
opr nat m[r: RangeOfStaticSizeIndexInt, m] := (v: BinaryLinearSequence1, m):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
opr int a,nat m,int c[r:StaticRangea, m, c] := (v: BinaryLinearSequence1, k):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
where { 0 ≤ a < 2 b , 0 ≤ a + m · c < 2 b }
update(j:IndexInt, v: Bit):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
updatenat k(j: IntegerStatick, v: Bit):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
where { k < 2 b }
updatenat m(r:RangeOfStaticSizeIndexInt, m, v: BinaryLinearSequence1, m):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
updateint a,nat m,int c(r:StaticRangea, m, c, v:BinaryLinearSequence1, m):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
where { 0 ≤ a < 2 b , 0 ≤ a + m · c < 2 b }
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