add hw2

node_modules/bare-path/lib/shared.js

@@ -0,0 +1,67 @@
+const {
+  CHAR_DOT,
+  CHAR_FORWARD_SLASH
+} = require('./constants')
+
+exports.normalizeString = function normalizeString (path, allowAboveRoot, separator, isPathSeparator) {
+  let res = ''
+  let lastSegmentLength = 0
+  let lastSlash = -1
+  let dots = 0
+  let code = 0
+  for (let i = 0; i <= path.length; ++i) {
+    if (i < path.length) {
+      code = path.charCodeAt(i)
+    } else if (isPathSeparator(code)) {
+      break
+    } else {
+      code = CHAR_FORWARD_SLASH
+    }
+
+    if (isPathSeparator(code)) {
+      if (lastSlash === i - 1 || dots === 1) ;
+      else if (dots === 2) {
+        if (res.length < 2 || lastSegmentLength !== 2 || res.charCodeAt(res.length - 1) !== CHAR_DOT || res.charCodeAt(res.length - 2) !== CHAR_DOT) {
+          if (res.length > 2) {
+            const lastSlashIndex = res.lastIndexOf(separator)
+            if (lastSlashIndex === -1) {
+              res = ''
+              lastSegmentLength = 0
+            } else {
+              res = res.substring(0, lastSlashIndex)
+              lastSegmentLength =
+                res.length - 1 - res.lastIndexOf(separator)
+            }
+            lastSlash = i
+            dots = 0
+            continue
+          } else if (res.length !== 0) {
+            res = ''
+            lastSegmentLength = 0
+            lastSlash = i
+            dots = 0
+            continue
+          }
+        }
+        if (allowAboveRoot) {
+          res += res.length > 0 ? `${separator}..` : '..'
+          lastSegmentLength = 2
+        }
+      } else {
+        if (res.length > 0) {
+          res += `${separator}${path.substring(lastSlash + 1, i)}`
+        } else {
+          res = path.substring(lastSlash + 1, i)
+        }
+        lastSegmentLength = i - lastSlash - 1
+      }
+      lastSlash = i
+      dots = 0
+    } else if (code === CHAR_DOT && dots !== -1) {
+      ++dots
+    } else {
+      dots = -1
+    }
+  }
+  return res
+}