支持生成上传url

README.md

@@ -295,6 +295,41 @@ upyun.upload(File.new('filepath.png'))
 * `sign`: 签名参数，详情见 [sign与non-sign参数说明](http://docs.upyun.com/api/form_api/#note6)
 * 如果在请求中指定了 `ext-param`, 那么返回的结构中也会有 `ext-param` 字段，详情见 [ext-param](http://docs.upyun.com/api/form_api/#note5)
 
+##### 生成上传URL
+客户端可以直接上传文件到upyun(而不先上传自己的主机再传到upyun)。
+
+```ruby
+def upyun_upload_url
+  file_key = SecureRandom.uuid
+  upyun = Upyun::Form.new('form-api-secret', 'bucket')
+  upyun_json = upyun.generate_upload_url('save-key'=> file_key,'content-type'=>'audio/mp3')
+
+  remote_link = 'https://' + bucket + '.b0.upaiyun.com/'+file_key
+  upload_url  = 'https://v0.api.upyun.com/' + bucket
+  render json: { remoteLink: remote_link,
+                 uploadUrl: upload_url,
+                 policy: upyun_json[:policy],
+                 signature: upyun_json[:signature] }
+end
+```
+
+```javascript
+$.get('/user/'+id+'/audio/upyun_upload_url', (function(question, response) {
+    var uploadData = new AudioData();
+    uploadData.append('signature', response.signature);
+    uploadData.append('policy', response.policy);
+    uploadData.append('file', mp3Blob);
+    $.ajax({
+        url: response.uploadUrl,
+        type: 'POST',
+        data: uploadData,
+        contentType: 'audio/mpeg',
+        processData: false
+    });
+}
+```
+
+
 ##### 自定义参数
 可以在上传的时候指定一些策略参数:
 

lib/upyun/form.rb

@@ -42,13 +42,15 @@ def initialize(password, bucket, options={timeout: 60})
       @endpoint = ED_AUTO
     end
 
-    def upload(file, opts={})
-      base_opts = HashWithIndifferentAccess.new({
-        'bucket' => @bucket,
-        'save-key' => '/{year}/{mon}/{day}/{filename}{.suffix}',
-        'expiration' => Time.now.to_i + 600
-      })
+    def generate_upload_url(opts={})
+      payload = {
+        policy: policy(base_opts.merge(opts)),
+        signature: signature,
+        url: "#{base_opts['save-key']}",
+      }
+    end
 
+    def upload(file, opts={})
       payload = {
         policy: policy(base_opts.merge(opts)),
         signature: signature,
@@ -82,6 +84,14 @@ def upload(file, opts={})
     end
 
     private
+      def base_opts
+        HashWithIndifferentAccess.new({
+          'bucket' => @bucket,
+          'save-key' => '/{year}/{mon}/{day}/{filename}{.suffix}',
+          'expiration' => Time.now.to_i + 600
+        })
+      end
+
       def policy(opts)
         @_policy = Base64.strict_encode64(policy_json(opts))
       end