Commit 38ee512a25776976caf787dff53126eed33ff835 | zig

author	Jacob Young <jacobly@ziglang.org> 2022-10-12 08:18:47-04:00
committer	Jacob Young <jacobly@ziglang.org> 2022-10-12 08:18:47-04:00
log	38ee512a25776976caf787dff53126eed33ff835
tree	60ad869a07d0150008d66e4a76875914768c32c9
parent	2fe5bdb9ed4e17c94055a9539092bdf35a55f752

math.big.int: add `calcLimbLen` doc comment note

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`.

1 files changed, 3 insertions(+), 0 deletions(-)

lib
- std
  - math
    big
    int.zig

lib/std/math/big/int.zig+3

 @@ -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;