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std/path/posix/relative.ts

Deno standard library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { isPosixPathSeparator } from "./_util.ts";import { resolve } from "./resolve.ts";import { assertArgs } from "../_common/relative.ts";
/** * Return the relative path from `from` to `to` based on current working directory. * * @param from path in current working directory * @param to path in current working directory */export function relative(from: string, to: string): string { assertArgs(from, to);
from = resolve(from); to = resolve(to);
if (from === to) return "";
// Trim any leading backslashes let fromStart = 1; const fromEnd = from.length; for (; fromStart < fromEnd; ++fromStart) { if (!isPosixPathSeparator(from.charCodeAt(fromStart))) break; } const fromLen = fromEnd - fromStart;
// Trim any leading backslashes let toStart = 1; const toEnd = to.length; for (; toStart < toEnd; ++toStart) { if (!isPosixPathSeparator(to.charCodeAt(toStart))) break; } const toLen = toEnd - toStart;
// Compare paths to find the longest common path from root const length = fromLen < toLen ? fromLen : toLen; let lastCommonSep = -1; let i = 0; for (; i <= length; ++i) { if (i === length) { if (toLen > length) { if (isPosixPathSeparator(to.charCodeAt(toStart + i))) { // We get here if `from` is the exact base path for `to`. // For example: from='/foo/bar'; to='/foo/bar/baz' return to.slice(toStart + i + 1); } else if (i === 0) { // We get here if `from` is the root // For example: from='/'; to='/foo' return to.slice(toStart + i); } } else if (fromLen > length) { if (isPosixPathSeparator(from.charCodeAt(fromStart + i))) { // We get here if `to` is the exact base path for `from`. // For example: from='/foo/bar/baz'; to='/foo/bar' lastCommonSep = i; } else if (i === 0) { // We get here if `to` is the root. // For example: from='/foo'; to='/' lastCommonSep = 0; } } break; } const fromCode = from.charCodeAt(fromStart + i); const toCode = to.charCodeAt(toStart + i); if (fromCode !== toCode) break; else if (isPosixPathSeparator(fromCode)) lastCommonSep = i; }
let out = ""; // Generate the relative path based on the path difference between `to` // and `from` for (i = fromStart + lastCommonSep + 1; i <= fromEnd; ++i) { if (i === fromEnd || isPosixPathSeparator(from.charCodeAt(i))) { if (out.length === 0) out += ".."; else out += "/.."; } }
// Lastly, append the rest of the destination (`to`) path that comes after // the common path parts if (out.length > 0) return out + to.slice(toStart + lastCommonSep); else { toStart += lastCommonSep; if (isPosixPathSeparator(to.charCodeAt(toStart))) ++toStart; return to.slice(toStart); }}