Documentation
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Overview ¶
Package cas holds the atomic content-addressed staging dance used by baseline materialization: build into a sibling temp dir, atomically rename it into the final slot, and — when the rename loses a cross-process race — discard the temp and adopt the winner's already-finalized directory.
What "build" does and how a race is detected are caller-supplied callbacks (baseline writes a git tree and adopts on a finalized directory). The temp-dir lifecycle, the rename, and the discard-on-failure cleanup live here.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
func Stage ¶
func Stage(parent, final, tmpPrefix, finalizePrefix string, build func(staging string) error, adopt func() bool) error
Stage builds final atomically. It creates a sibling temp dir (filepath.Base(final)+".tmp.*") under parent, runs build against that temp dir, then renames it onto final. parent must already exist.
- The MkdirTemp error is wrapped with tmpPrefix ("<tmpPrefix>: %w").
- On a build error the temp dir is removed and the error is returned unwrapped — the build callback owns its own error context.
- On rename success final is the built tree.
- On rename failure the temp dir is removed and adopt is consulted: when adopt reports true a peer already finalized final and we adopt it (no error); otherwise the rename error is wrapped with finalizePrefix ("<finalizePrefix>: %w").
The two prefixes let the caller keep its own error strings intact (baseline passes "baseline staging"/"baseline finalize").
Types ¶
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Source Files