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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { assertArg } from "../_common/dirname.ts";import { CHAR_COLON } from "../_common/constants.ts";import { stripTrailingSeparators } from "../_common/strip_trailing_separators.ts";import {  isPathSeparator,  isPosixPathSeparator,  isWindowsDeviceRoot,} from "./_util.ts";
/** * Return the directory path of a `path`. * @param path - path to extract the directory from. */export function dirname(path: string): string {  assertArg(path);
  const len = path.length;  let rootEnd = -1;  let end = -1;  let matchedSlash = true;  let offset = 0;  const code = path.charCodeAt(0);
  // Try to match a root  if (len > 1) {    if (isPathSeparator(code)) {      // Possible UNC root
      rootEnd = offset = 1;
      if (isPathSeparator(path.charCodeAt(1))) {        // Matched double path separator at beginning        let j = 2;        let last = j;        // Match 1 or more non-path separators        for (; j < len; ++j) {          if (isPathSeparator(path.charCodeAt(j))) break;        }        if (j < len && j !== last) {          // Matched!          last = j;          // Match 1 or more path separators          for (; j < len; ++j) {            if (!isPathSeparator(path.charCodeAt(j))) break;          }          if (j < len && j !== last) {            // Matched!            last = j;            // Match 1 or more non-path separators            for (; j < len; ++j) {              if (isPathSeparator(path.charCodeAt(j))) break;            }            if (j === len) {              // We matched a UNC root only              return path;            }            if (j !== last) {              // We matched a UNC root with leftovers
              // Offset by 1 to include the separator after the UNC root to              // treat it as a "normal root" on top of a (UNC) root              rootEnd = offset = j + 1;            }          }        }      }    } else if (isWindowsDeviceRoot(code)) {      // Possible device root
      if (path.charCodeAt(1) === CHAR_COLON) {        rootEnd = offset = 2;        if (len > 2) {          if (isPathSeparator(path.charCodeAt(2))) rootEnd = offset = 3;        }      }    }  } else if (isPathSeparator(code)) {    // `path` contains just a path separator, exit early to avoid    // unnecessary work    return path;  }
  for (let i = len - 1; i >= offset; --i) {    if (isPathSeparator(path.charCodeAt(i))) {      if (!matchedSlash) {        end = i;        break;      }    } else {      // We saw the first non-path separator      matchedSlash = false;    }  }
  if (end === -1) {    if (rootEnd === -1) return ".";    else end = rootEnd;  }  return stripTrailingSeparators(path.slice(0, end), isPosixPathSeparator);}