Yichen Jiang
ba37180946
writeFileAtomic: exclusive-create random-suffix temp + rename carrying the caller-stated mode; settings-local persistSection now consumes it. The credentials-local store shares it next.
51 lines
2.1 KiB
TypeScript
51 lines
2.1 KiB
TypeScript
/**
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* Zero-dependency atomic file replacement. `writeFileAtomic` writes a
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* random-suffix sibling with exclusive create and the caller's permission
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* bits, then renames it over the target, so readers observe either the old or
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* the new complete content and a replaced file ends up with exactly the
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* stated mode.
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* @module @deepseek-ai/dsh-atomic-write
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*/
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import { randomBytes } from 'node:crypto'
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import { mkdir, rename, rm, writeFile } from 'node:fs/promises'
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import { dirname } from 'node:path'
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/**
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* Filesystem options for {@link writeFileAtomic}; `mode` is required so the
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* permission decision stays visible at every call site.
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*/
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export interface WriteFileAtomicOptions {
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/**
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* Permission bits stamped on the fresh temp inode and carried through the
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* rename (subject to the process umask, like every fresh inode).
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*/
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mode: number
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}
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/**
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* Replace `filename` with `content` in one atomic step, creating parent
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* directories. The content is first written to a random-suffix sibling opened
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* with exclusive create (`wx`): the open refuses to follow a symlink planted
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* at the temp path, and the fresh inode carries `options.mode` through the
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* rename, so replacing a wider-permission file narrows it without a chmod
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* race. The rename also replaces a symlinked target itself instead of writing
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* through to its referent, and the same-directory sibling keeps the rename on
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* one filesystem. On any failure the temp file is removed and the failure
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* rethrown. Crash durability (fsync) is out of scope.
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* @param filename - final path receiving the content.
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* @param content - complete next file content.
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* @param options - permission bits for the replacement inode.
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*/
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export async function writeFileAtomic(filename: string, content: string, options: WriteFileAtomicOptions): Promise<void> {
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await mkdir(dirname(filename), { recursive: true })
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const temp = `${filename}.${randomBytes(6).toString('hex')}.tmp`
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try {
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await writeFile(temp, content, { mode: options.mode, flag: 'wx' })
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await rename(temp, filename)
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} catch (error) {
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await rm(temp, { force: true })
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throw error
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}
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}
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