feat: output overhaul stdlib primitives (chrono format_duration + format left-align)#328
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renders a Duration to a compact ASCII string into a caller buffer with a unit chosen by magnitude (<1ms / Nus / Nms / N.Ns / NmNs). no allocation, no platform branches. covers ns/us/ms/s/m ranges, unit-tested.
extends the hole grammar to '{' [':' ['<'] ['0'] [width] [x|X|c] '}'. a '<'
after ':' (before the optional 0/width) left-aligns: the value is written
first and space-padded on the right. the zero flag is ignored for left-align.
right-align specs ({:N}/{:0N}/{:08x}) stay byte-identical. unit-tested.
This was referenced Jul 2, 2026
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Part of the output-overhaul epic (briar-systems/mach#1773), implementing briar-systems/mach#1774.
Two shared multiplatform stdlib primitives the terminal-output overhaul needs. ASCII-only, no platform branches, no allocation.
1. chrono
format_durationchrono.Durationhad component accessors but no human string. Addsformat_duration(d: Duration, buf: *u8, cap: usize) str— renders a Duration into a caller-provided buffer, returning the null-terminated string (aliasingbuf), ornilifcapis insufficient. A 24-byte buffer holds every i64 duration. Unit chosen by magnitude:0ms<1msNusNmsN.Ns(tenths truncate)NmNsNegative durations carry a leading
-. Minutes is the top band (no hours).2. format
{:<N}left-alignExtends the hole-spec grammar from
'{' [':' ['0'] [width] [x|X|c] '}'to'{' [':' ['<'] ['0'] [width] [x|X|c] '}'. A<immediately after:(before the optional0/width) sets a newSpec.leftflag;emit_field/fmt_str_fieldthen write the value first and space-pad on the right. The zero flag is ignored for left-align (trailing zeros would corrupt the value). Right-align specs ({:N},{:0N},{:08x}) are byte-identical.Tests
mach-std suite green (567 passed, 0 failed). New unit tests:
format_durationacross ns/us/ms/s/m ranges + sign, band boundaries (1s, 1m, >1h), and insufficient-capacity cases.{:<N}left-align for str + int (and hex, negative, zero-flag-ignored, value-over-width), asserting exact padded bytes, with{:N}/{:0N}right-align re-asserted unchanged.Note: the consuming mach repo's
mach.lockbump is coordinated centrally by the epic lead, not in this PR.🤖 Generated with Claude Code