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math.big.int: add calcLimbLen doc comment note

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When trying to allocate memory for functions like `Managed.init` and
`Managed.set` on the stack, a comptime-known allocation size is desired.
The doc comments for these functions indicate that `calcLimbLen` can be
used to determine how many limbs to allocate, but if `value` is not
comptime-known, then neither is `calcLimbLen(value)`.  However, an upper
bound on the allocation size is still computable at comptime in this
case, so this note documents an expression that can be used, rather than
trying to add it to every doc comment that mentions `calcLimbLen`.
This commit is contained in:
Jacob Young 2022-10-12 08:18:47 -04:00
parent 2fe5bdb9ed
commit 38ee512a25
1 changed files with 3 additions and 0 deletions
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lib/std/math/big/int.zig
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@ -21,6 +21,9 @@ const debug_safety = false;
/// Returns the number of limbs needed to store `scalar`, which must be a
/// primitive integer value.
/// Note: A comptime-known upper bound of this value that may be used
/// instead if `scalar` is not already comptime-known is
/// `calcTwosCompLimbCount(@typeInfo(@TypeOf(scalar)).Int.bits)`
pub fn calcLimbLen(scalar: anytype) usize {
if (scalar == 0) {
return 1;