first commit

项目合集/校园失物招领/min-backend/utils/aliOss/uploadOssHelper.js

@@ -0,0 +1,46 @@
+const crypto = require("crypto-js");
+
+class uploadOssHelper {
+  constructor(options) {
+    this.accessKeyId = options.accessKeyId;
+    this.accessKeySecret = options.accessKeySecret;
+    // 限制参数的生效时间，单位为小时，默认值为1。
+    this.timeout = options.timeout || 1; 
+    // 限制上传文件的大小，单位为MB，默认值为10。
+    this.maxSize = options.maxSize || 10;
+  }
+
+  createUploadParams() {
+    const policy = this.getPolicyBase64();
+    const signature = this.signature(policy);
+    return {
+      OSSAccessKeyId: this.accessKeyId,
+      policy: policy,
+      signature: signature,
+    };
+  }
+
+  getPolicyBase64() {
+    let date = new Date();
+    // 设置policy过期时间。
+    date.setHours(date.getHours() + this.timeout);
+    let srcT = date.toISOString();
+    const policyText = {
+      expiration: srcT,
+      conditions: [
+        // 限制上传文件大小。
+        ["content-length-range", 0, this.maxSize * 1024 * 1024],
+      ],
+    };
+    const buffer = new Buffer(JSON.stringify(policyText));
+    return buffer.toString("base64");
+  }
+
+  signature(policy) {
+    return crypto.enc.Base64.stringify(
+      crypto.HmacSHA1(policy, this.accessKeySecret)
+    );
+  }
+}
+
+module.exports = uploadOssHelper;