big: Finish big ZII refactor.

1 files changed, 132 insertions, 0 deletions

diff --git a/core/math/big/common.odin b/core/math/big/common.odin
new file mode 100644
index 000000000..bcbfafaef
--- /dev/null
+++ b/core/math/big/common.odin
@@ -0,0 +1,132 @@
+package big
+
+/*
+	Copyright 2021 Jeroen van Rijn <nom@duclavier.com>.
+	Made available under Odin's BSD-2 license.
+
+	An arbitrary precision mathematics implementation in Odin.
+	For the theoretical underpinnings, see Knuth's The Art of Computer Programming, Volume 2, section 4.3.
+	The code started out as an idiomatic source port of libTomMath, which is in the public domain, with thanks.
+*/
+
+import "core:intrinsics"
+
+/*
+	Tunables
+*/
+_LOW_MEMORY          :: #config(BIGINT_SMALL_MEMORY, false);
+when _LOW_MEMORY {
+	_DEFAULT_DIGIT_COUNT :: 8;
+} else {
+	_DEFAULT_DIGIT_COUNT :: 32;
+}
+
+_MUL_KARATSUBA_CUTOFF :: #config(MUL_KARATSUBA_CUTOFF, _DEFAULT_MUL_KARATSUBA_CUTOFF);
+_SQR_KARATSUBA_CUTOFF :: #config(SQR_KARATSUBA_CUTOFF, _DEFAULT_SQR_KARATSUBA_CUTOFF);
+_MUL_TOOM_CUTOFF      :: #config(MUL_TOOM_CUTOFF,      _DEFAULT_MUL_TOOM_CUTOFF);
+_SQR_TOOM_CUTOFF      :: #config(SQR_TOOM_CUTOFF,      _DEFAULT_SQR_TOOM_CUTOFF);
+
+/*
+	These defaults were tuned on an AMD A8-6600K (64-bit) using libTomMath's `make tune`.
+	TODO(Jeroen): Port this tuning algorithm and tune them for more modern processors.
+*/
+_DEFAULT_MUL_KARATSUBA_CUTOFF ::  80;
+_DEFAULT_SQR_KARATSUBA_CUTOFF :: 120;
+_DEFAULT_MUL_TOOM_CUTOFF      :: 350;
+_DEFAULT_SQR_TOOM_CUTOFF      :: 400;
+
+/*
+	TODO(Jeroen): Decide whether to turn `Sign` into `Flags :: bit_set{Flag; u8}`.
+	This would hold the sign and float class, as appropriate, and would allow us
+	to set an `Int` to +/- Inf, or NaN.
+
+	The operations would need to be updated to propagate these as expected.
+*/
+Sign :: enum u8 {
+	Zero_or_Positive = 0,
+	Negative         = 1,
+};
+
+Int :: struct {
+	used:      int,
+	digit:     [dynamic]DIGIT,
+	sign:      Sign,
+};
+
+/*
+	Errors are a strict superset of runtime.Allocation_Error.
+*/
+Error :: enum byte {
+	None                   = 0,
+	Out_Of_Memory          = 1,
+	Invalid_Pointer        = 2,
+	Invalid_Argument       = 3,
+
+	Unknown_Error          = 4,
+	Max_Iterations_Reached = 5,
+	Buffer_Overflow        = 6,
+	Integer_Overflow       = 7,
+
+	Unimplemented          = 127,
+};
+
+Primality_Flag :: enum u8 {
+	Blum_Blum_Shub = 0,	/* BBS style prime */
+	Safe           = 1,	/* Safe prime (p-1)/2 == prime */
+	Second_MSB_On  = 3,  /* force 2nd MSB to 1 */
+};
+Primality_Flags :: bit_set[Primality_Flag; u8];
+
+/*
+	How do we store the Ints?
+
+	Minimum number of available digits in `Int`, `_DEFAULT_DIGIT_COUNT` >= `_MIN_DIGIT_COUNT`
+	- Must be at least 3 for `_div_school`.
+	- Must be large enough such that `init_integer` can store `u128` in the `Int` without growing.
+ */
+
+_MIN_DIGIT_COUNT :: max(3, ((size_of(u128) + _DIGIT_BITS) - 1) / _DIGIT_BITS);
+#assert(_DEFAULT_DIGIT_COUNT >= _MIN_DIGIT_COUNT);
+
+/*
+	Maximum number of digits.
+	- Must be small enough such that `_bit_count` does not overflow.
+ 	- Must be small enough such that `_radix_size` for base 2 does not overflow.
+	`_radix_size` needs two additional bytes for zero termination and sign.
+*/
+_MAX_BIT_COUNT   :: (max(int) - 2);
+_MAX_DIGIT_COUNT :: _MAX_BIT_COUNT / _DIGIT_BITS;
+
+when size_of(rawptr) == 8 {
+	/*
+		We can use u128 as an intermediary.
+	*/
+	DIGIT        :: distinct(u64);
+	_WORD        :: distinct(u128);
+} else {
+	DIGIT        :: distinct(u32);
+	_WORD        :: distinct(u64);
+}
+#assert(size_of(_WORD) == 2 * size_of(DIGIT));
+
+_DIGIT_TYPE_BITS :: 8 * size_of(DIGIT);
+_WORD_TYPE_BITS  :: 8 * size_of(_WORD);
+
+_DIGIT_BITS      :: _DIGIT_TYPE_BITS - 4;
+_WORD_BITS       :: 2 * _DIGIT_BITS;
+
+_MASK            :: (DIGIT(1) << DIGIT(_DIGIT_BITS)) - DIGIT(1);
+_DIGIT_MAX       :: _MASK;
+_MAX_COMBA       :: 1 <<  (_WORD_TYPE_BITS - (2 * _DIGIT_BITS))     ;
+_WARRAY          :: 1 << ((_WORD_TYPE_BITS - (2 * _DIGIT_BITS)) + 1);
+
+Order :: enum i8 {
+	LSB_First = -1,
+	MSB_First =  1,
+};
+
+Endianness :: enum i8 {
+   Little   = -1,
+   Platform =  0,
+   Big      =  1,
+};
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