pikpak: optimize upload by pre-fetching gcid from API

This commit optimizes the PikPak upload process by pre-fetching the Global 
Content Identifier (gcid) from the API server before calculating it locally.

Previously, a gcid required for uploads was calculated locally. This process was 
resource-intensive and time-consuming. By first checking for a cached gcid 
on the server, we can potentially avoid the local calculation entirely. 
This significantly improves upload speed especially for large files.

backend/pikpak/helper.go

@@ -8,13 +8,16 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math/rand"
 	"net/http"
 	"net/url"
 	"os"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/rclone/rclone/backend/pikpak/api"
+	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/lib/rest"
 )
 
@@ -253,6 +256,37 @@ func (f *Fs) requestShare(ctx context.Context, req *api.RequestShare) (info *api
 	return
 }
 
+// getGcid retrieves Gcid cached in API server
+func (f *Fs) getGcid(ctx context.Context, src fs.ObjectInfo) (gcid string, err error) {
+	cid, err := calcCid(ctx, src)
+	if err != nil {
+		return
+	}
+
+	params := url.Values{}
+	params.Set("cid", cid)
+	params.Set("file_size", strconv.FormatInt(src.Size(), 10))
+	opts := rest.Opts{
+		Method:       "GET",
+		Path:         "/drive/v1/resource/cid",
+		Parameters:   params,
+		ExtraHeaders: map[string]string{"x-device-id": f.deviceID},
+	}
+
+	info := struct {
+		Gcid string `json:"gcid,omitempty"`
+	}{}
+	var resp *http.Response
+	err = f.pacer.Call(func() (bool, error) {
+		resp, err = f.rst.CallJSON(ctx, &opts, nil, &info)
+		return f.shouldRetry(ctx, resp, err)
+	})
+	if err != nil {
+		return "", err
+	}
+	return info.Gcid, nil
+}
+
 // Read the gcid of in returning a reader which will read the same contents
 //
 // The cleanup function should be called when out is finished with
@@ -306,6 +340,9 @@ func readGcid(in io.Reader, size, threshold int64) (gcid string, out io.Reader,
 	return
 }
 
+// calcGcid calculates Gcid from reader
+//
+// Gcid is a custom hash to index a file contents
 func calcGcid(r io.Reader, size int64) (string, error) {
 	calcBlockSize := func(j int64) int64 {
 		var psize int64 = 0x40000
@@ -330,3 +367,64 @@ func calcGcid(r io.Reader, size int64) (string, error) {
 	}
 	return hex.EncodeToString(totalHash.Sum(nil)), nil
 }
+
+// calcCid calculates Cid from source
+//
+// Cid is a simplified version of Gcid
+func calcCid(ctx context.Context, src fs.ObjectInfo) (cid string, err error) {
+	srcObj := fs.UnWrapObjectInfo(src)
+	if srcObj == nil {
+		return "", fmt.Errorf("failed to unwrap object from src: %s", src)
+	}
+
+	size := src.Size()
+	hash := sha1.New()
+	var rc io.ReadCloser
+
+	readHash := func(start, length int64) (err error) {
+		end := start + length - 1
+		if rc, err = srcObj.Open(ctx, &fs.RangeOption{Start: start, End: end}); err != nil {
+			return fmt.Errorf("failed to open src with range (%d, %d): %w", start, end, err)
+		}
+		defer fs.CheckClose(rc, &err)
+		_, err = io.Copy(hash, rc)
+		return err
+	}
+
+	if size <= 0xF000 { // 61440 = 60KB
+		err = readHash(0, size)
+	} else { // 20KB from three different parts
+		for _, start := range []int64{0, size / 3, size - 0x5000} {
+			err = readHash(start, 0x5000)
+			if err != nil {
+				break
+			}
+		}
+	}
+	if err != nil {
+		return "", fmt.Errorf("failed to hash: %w", err)
+	}
+	cid = strings.ToUpper(hex.EncodeToString(hash.Sum(nil)))
+	return
+}
+
+// randomly generates device id used for request header 'x-device-id'
+//
+// original javascript implementation
+//
+//	return "xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx".replace(/[xy]/g, (e) => {
+//	    const t = (16 * Math.random()) | 0;
+//	    return ("x" == e ? t : (3 & t) | 8).toString(16);
+//	});
+func genDeviceID() string {
+	base := []byte("xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx")
+	for i, char := range base {
+		switch char {
+		case 'x':
+			base[i] = fmt.Sprintf("%x", rand.Intn(16))[0]
+		case 'y':
+			base[i] = fmt.Sprintf("%x", rand.Intn(16)&3|8)[0]
+		}
+	}
+	return string(base)
+}

backend/pikpak/pikpak.go

@@ -274,6 +274,7 @@ type Fs struct {
 	dirCache     *dircache.DirCache // Map of directory path to directory id
 	pacer        *fs.Pacer          // pacer for API calls
 	rootFolderID string             // the id of the root folder
+	deviceID     string             // device id used for api requests
 	client       *http.Client       // authorized client
 	m            configmap.Mapper
 	tokenMu      *sync.Mutex // when renewing tokens
@@ -489,6 +490,7 @@ func newFs(ctx context.Context, name, path string, m configmap.Mapper) (*Fs, err
 		CanHaveEmptyDirectories: true, // can have empty directories
 		NoMultiThreading:        true, // can't have multiple threads downloading
 	}).Fill(ctx, f)
+	f.deviceID = genDeviceID()
 
 	if err := f.newClientWithPacer(ctx); err != nil {
 		return nil, err
@@ -1694,32 +1696,36 @@ func (o *Object) upload(ctx context.Context, in io.Reader, src fs.ObjectInfo, wi
 	}
 
 	// Calculate gcid; grabbed from package jottacloud
-	var gcid string
-	if srcObj := fs.UnWrapObjectInfo(src); srcObj != nil && srcObj.Fs().Features().IsLocal {
-		// No buffering; directly calculate gcid from source
-		rc, err := srcObj.Open(ctx)
-		if err != nil {
-			return fmt.Errorf("failed to open src: %w", err)
-		}
-		defer fs.CheckClose(rc, &err)
+	gcid, err := o.fs.getGcid(ctx, src)
+	if err != nil || gcid == "" {
+		fs.Debugf(o, "calculating gcid: %v", err)
+		if srcObj := fs.UnWrapObjectInfo(src); srcObj != nil && srcObj.Fs().Features().IsLocal {
+			// No buffering; directly calculate gcid from source
+			rc, err := srcObj.Open(ctx)
+			if err != nil {
+				return fmt.Errorf("failed to open src: %w", err)
+			}
+			defer fs.CheckClose(rc, &err)
 
-		if gcid, err = calcGcid(rc, srcObj.Size()); err != nil {
-			return fmt.Errorf("failed to calculate gcid: %w", err)
+			if gcid, err = calcGcid(rc, srcObj.Size()); err != nil {
+				return fmt.Errorf("failed to calculate gcid: %w", err)
+			}
+		} else {
+			// unwrap the accounting from the input, we use wrap to put it
+			// back on after the buffering
+			var wrap accounting.WrapFn
+			in, wrap = accounting.UnWrap(in)
+			var cleanup func()
+			gcid, in, cleanup, err = readGcid(in, size, int64(o.fs.opt.HashMemoryThreshold))
+			defer cleanup()
+			if err != nil {
+				return fmt.Errorf("failed to calculate gcid: %w", err)
+			}
+			// Wrap the accounting back onto the stream
+			in = wrap(in)
 		}
-	} else {
-		// unwrap the accounting from the input, we use wrap to put it
-		// back on after the buffering
-		var wrap accounting.WrapFn
-		in, wrap = accounting.UnWrap(in)
-		var cleanup func()
-		gcid, in, cleanup, err = readGcid(in, size, int64(o.fs.opt.HashMemoryThreshold))
-		defer cleanup()
-		if err != nil {
-			return fmt.Errorf("failed to calculate gcid: %w", err)
-		}
-		// Wrap the accounting back onto the stream
-		in = wrap(in)
 	}
+	fs.Debugf(o, "gcid = %s", gcid)
 
 	if !withTemp {
 		info, err := o.fs.upload(ctx, in, leaf, dirID, gcid, size, options...)