setString

Set self from the string representation value.

value must contain only digits <= base and is case insensitive. Base prefixes are not allowed (e.g. 0x43 should simply be 43). Underscores in the input string are ignored and can be used as digit separators.

Asserts there is enough memory for the value in self.limbs. An upper bound on number of limbs can be determined with calcSetStringLimbCount. Asserts the base is in the range [2, 36].

Returns an error if the value has invalid digits for the requested base.

limbs_buffer is used for temporary storage. The size required can be found with calcSetStringLimbsBufferLen.

If allocator is provided, it will be used for temporary storage to improve multiplication performance. error.OutOfMemory is handled with a fallback algorithm.

Function parameters

Parameters

self:*Mutable
base:u8
value:[]const u8
limbs_buffer:[]Limb
allocator:?Allocator

Used to indicate either limit of a 2s-complement integer.

Types

TwosCompIntLimit: Used to indicate either limit of a 2s-complement integer.
Round
Exactness
Mutable: A arbitrary-precision big integer, with a fixed set of mutable limbs.
Const: A arbitrary-precision big integer, with a fixed set of immutable limbs.
Managed: An arbitrary-precision big integer along with an allocator which manages the memory.

Returns the number of limbs needed to store `scalar`, which must be a

Functions

calcLimbLen: Returns the number of limbs needed to store `scalar`, which must be a
calcToStringLimbsBufferLen
calcDivLimbsBufferLen
calcMulLimbsBufferLen
calcMulWrapLimbsBufferLen
calcSetStringLimbsBufferLen
calcSetStringLimbCount: Assumes `string_len` doesn't account for minus signs if the number is negative.
calcPowLimbsBufferLen
calcSqrtLimbsBufferLen
calcNonZeroTwosCompLimbCount: Compute the number of limbs required to store a 2s-complement number of `bit_count` bits.
calcTwosCompLimbCount: Compute the number of limbs required to store a 2s-complement number of `bit_count` bits.
addMulLimbWithCarry: a + b * c + *carry, sets carry to the overflow bits
llcmp: Returns -1, 0, 1 if |a| < |b|, |a| == |b| or |a| > |b| respectively for limbs.

Source

Implementation

pub fn setString(
    self: *Mutable,
    base: u8,
    value: []const u8,
    limbs_buffer: []Limb,
    allocator: ?Allocator,
) error{InvalidCharacter}!void {
    assert(base >= 2);
    assert(base <= 36);

    var i: usize = 0;
    var positive = true;
    if (value.len > 0 and value[0] == '-') {
        positive = false;
        i += 1;
    }

    const ap_base: Const = .{ .limbs = &[_]Limb{base}, .positive = true };
    self.set(0);

    for (value[i..]) |ch| {
        if (ch == '_') {
            continue;
        }
        const d = try std.fmt.charToDigit(ch, base);
        const ap_d: Const = .{ .limbs = &[_]Limb{d}, .positive = true };

        self.mul(self.toConst(), ap_base, limbs_buffer, allocator);
        self.add(self.toConst(), ap_d);
    }
    self.positive = positive;
}