add: gin util: get page and per from query string.

http/gin/page.go

@@ -0,0 +1,33 @@
+package gin
+
+import (
+ "github.com/gin-gonic/gin"
+ "strconv"
+)
+
+// GetPagePerFromQs retrieves the page number and the number of items per page from query string in request.
+// The prerequisite for using this function is that the parameters' name of the page number and the number of items
+// per page in query string must be `page` and `per`, like `example.com?page=2&per=10`.
+//
+// If the page parameter in query string is not a number, the returned page will be 1. And if the per parameter
+// in query string is not a number, the returned per will be defaultPer, if the requested per is larger than
+// maxPer, the returned per will be maxPer.
+func GetPagePerFromQs(c *gin.Context, defaultPer, maxPer int) (page, per int) {
+ pageStr := c.Query("page")
+ perStr := c.Query("per")
+
+ page, err := strconv.Atoi(pageStr)
+ if err != nil {
+ page = 1
+ }
+
+ per, err = strconv.Atoi(perStr)
+ if err != nil {
+ per = defaultPer
+ }
+ if per > maxPer {
+ per = maxPer
+ }
+
+ return
+}