Update KOSyncClient

frontend/document/document.lua

@@ -99,7 +99,10 @@ function Document:discardChange()
     self.is_edited = false
 end
 
--- calculate partial digest of the document
+-- calculate partial digest of the document and store in its docsettings to avoid document saving
+-- feature to change its checksum.
+--
+-- To the calculating mechanism itself.
 -- since only PDF documents could be modified by KOReader by appending data
 -- at the end of the files when highlighting, we use a non-even sampling
 -- algorithm which samples with larger weight at file head and much smaller
@@ -109,23 +112,31 @@ end
 -- 1048576, 4194304, 16777216, 67108864, 268435456 or 1073741824, appending data
 -- by highlighting in KOReader may change the digest value.
 function Document:fastDigest()
-    local md5 = require("ffi/MD5")
-    local lshift = bit.lshift
+    if not self.file then return end
     local file = io.open(self.file, 'rb')
     if file then
-        local step, size = 1024, 1024
-        local m = md5.new()
-        for i = -1, 10 do
-            file:seek("set", lshift(step, 2*i))
-            local sample = file:read(size)
-            if sample then
-                m:update(sample)
-            else
-                break
+        local docsettings = require("docsettings"):open(self.file)
+        local result = docsettings:readSetting("partial_md5_checksum")
+        if not result then
+            local md5 = require("ffi/MD5")
+            local lshift = bit.lshift
+            local step, size = 1024, 1024
+            local m = md5.new()
+            for i = -1, 10 do
+                file:seek("set", lshift(step, 2*i))
+                local sample = file:read(size)
+                if sample then
+                    m:update(sample)
+                else
+                    break
+                end
             end
+            result = m:sum()
+            docsettings:saveSetting("partial_md5_checksum", result)
         end
+        docsettings:close()
         file:close()
-        return m:sum()
+        return result
     end
 end