17574: Speed up manifest parsing.

Previous code spent a lot of time allocating, copying, and GCing
strings. Working with byte slices is much faser.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curii.com>

diff --git a/sdk/go/arvados/collection.go b/sdk/go/arvados/collection.go
index cec20279d1fdc81cb56936ed731dea6c6a4c0e8c..785c18d4a75090a9847be18122b418b392c45474 100644 (file)
--- a/sdk/go/arvados/collection.go
+++ b/sdk/go/arvados/collection.go
@@ -5,11 +5,10 @@
 package arvados
 
 import (
-       "bufio"
+       "bytes"
        "crypto/md5"
        "fmt"
        "regexp"
-       "strings"
        "time"
 
        "git.arvados.org/arvados.git/sdk/go/blockdigest"
@@ -56,40 +55,40 @@ func (c Collection) resourceName() string {
 //
 // Zero-length blocks are not included.
 func (c *Collection) SizedDigests() ([]SizedDigest, error) {
-       manifestText := c.ManifestText
-       if manifestText == "" {
-               manifestText = c.UnsignedManifestText
+       manifestText := []byte(c.ManifestText)
+       if len(manifestText) == 0 {
+               manifestText = []byte(c.UnsignedManifestText)
        }
-       if manifestText == "" && c.PortableDataHash != "d41d8cd98f00b204e9800998ecf8427e+0" {
+       if len(manifestText) == 0 && c.PortableDataHash != "d41d8cd98f00b204e9800998ecf8427e+0" {
                // TODO: Check more subtle forms of corruption, too
                return nil, fmt.Errorf("manifest is missing")
        }
-       var sds []SizedDigest
-       scanner := bufio.NewScanner(strings.NewReader(manifestText))
-       scanner.Buffer(make([]byte, 1048576), len(manifestText))
-       for scanner.Scan() {
-               line := scanner.Text()
-               tokens := strings.Split(line, " ")
+       sds := make([]SizedDigest, 0, len(manifestText)/40)
+       for _, line := range bytes.Split(manifestText, []byte{'\n'}) {
+               if len(line) == 0 {
+                       continue
+               }
+               tokens := bytes.Split(line, []byte{' '})
                if len(tokens) < 3 {
                        return nil, fmt.Errorf("Invalid stream (<3 tokens): %q", line)
                }
                for _, token := range tokens[1:] {
-                       if !blockdigest.LocatorPattern.MatchString(token) {
+                       if !blockdigest.LocatorPattern.Match(token) {
                                // FIXME: ensure it's a file token
                                break
                        }
-                       if strings.HasPrefix(token, "d41d8cd98f00b204e9800998ecf8427e+0") {
+                       if bytes.HasPrefix(token, []byte("d41d8cd98f00b204e9800998ecf8427e+0")) {
                                // Exclude "empty block" placeholder
                                continue
                        }
                        // FIXME: shouldn't assume 32 char hash
-                       if i := strings.IndexRune(token[33:], '+'); i >= 0 {
+                       if i := bytes.IndexRune(token[33:], '+'); i >= 0 {
                                token = token[:33+i]
                        }
-                       sds = append(sds, SizedDigest(token))
+                       sds = append(sds, SizedDigest(string(token)))
                }
        }
-       return sds, scanner.Err()
+       return sds, nil
 }
 
 type CollectionList struct {