49 lines
1.7 KiB
TypeScript
49 lines
1.7 KiB
TypeScript
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/**
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* Filesystem utilities used at configure time.
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*
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* Separate from shell.ts because "quote a shell argument" and "write a
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* file idempotently" share nothing except being utility functions.
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*/
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import { mkdirSync, readFileSync, writeFileSync } from "node:fs";
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/**
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* Write `content` to `path` only if different (or file doesn't exist).
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* Returns whether a write happened.
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*
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* Used throughout the build system for configure-time generated files
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* (PCH wrapper, dep versions header, build.ninja itself). Preserving
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* mtimes on unchanged content is what makes idempotent re-configure
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* actually cheap: ninja sees no changes, does nothing. Without this,
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* every configure touches everything and ninja at minimum re-stats.
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*
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* Synchronous because configure is single-threaded and the files are
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* small. Async would add await noise for no concurrency benefit.
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*/
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export function writeIfChanged(path: string, content: string): boolean {
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try {
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if (readFileSync(path, "utf8") === content) return false;
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} catch {
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// File doesn't exist (or unreadable) — fall through to write.
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}
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writeFileSync(path, content);
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return true;
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}
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/**
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* Create multiple directories (and their parents). Deduplicates so
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* `["a/b/c", "a/b/d"]` only stats/creates `a/b` once.
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*
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* Used at configure time to pre-create all object-file parent dirs —
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* ninja doesn't mkdir, and we don't want N×mkdir syscalls for the same
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* directory when compiling N files that share a parent.
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*/
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export function mkdirAll(dirs: Iterable<string>): void {
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const seen = new Set<string>();
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for (const dir of dirs) {
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if (seen.has(dir)) continue;
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mkdirSync(dir, { recursive: true });
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seen.add(dir);
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}
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}
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