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pagination.go
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/
pagination.go
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// Package pagination contains useful pagination-related helpers.
package pagination
import (
"fmt"
"strconv"
"github.com/pkg/errors"
"github.com/prysmaticlabs/prysm/v4/config/params"
)
// StartAndEndPage takes in the requested page token, wanted page size, total page size.
// It returns start, end page and the next page token.
func StartAndEndPage(pageToken string, pageSize, totalSize int) (int, int, string, error) {
if pageToken == "" {
pageToken = "0"
}
if pageSize < 0 || totalSize < 0 {
return 0, 0, "", errors.Errorf("invalid page and total sizes provided: page size %d , total size %d", pageSize, totalSize)
}
if pageSize == 0 {
pageSize = params.BeaconConfig().DefaultPageSize
}
token, err := strconv.Atoi(pageToken)
if err != nil {
return 0, 0, "", errors.Wrap(err, "could not convert page token")
}
if token < 0 {
return 0, 0, "", errors.Errorf("invalid token value provided: %d", token)
}
// Start page can not be greater than set size.
start := token * pageSize
if start >= totalSize {
return 0, 0, "", fmt.Errorf("page start %d >= list %d", start, totalSize)
}
// End page can not go out of bound.
end := start + pageSize
nextPageToken := strconv.Itoa(token + 1)
if end >= totalSize {
end = totalSize
nextPageToken = "" // Return an empty next page token for the last page of a set
}
return start, end, nextPageToken, nil
}