VBScript Requires Chilkat v11.7.0+
Box: Upload a Large File in Parts and Commit the Session

Run the reusable setup once per HttpCurl object, then select names and execute the operation. The setup is repeated here only to make this published example independently runnable. Resolve documents by name, then perform the explicit chunked-upload session, part, and commit loop. Supports 20 MB through 2 GB using int. Saves recovery information and honors bounded commit Retry-After.
See the Box API guide for setup and the complete workflow.
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Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

'  Requires Chilkat 11.7.0 or later and a previously unlocked Chilkat bundle.
'  See Global Unlock Sample.
'  Guide: Box API Guide.

success = 0

'  BEGIN ONE-TIME SETUP
'  This block is repeated so each published example can run on its own.
'  In an application, run the setup example once and pass the SAME curl object
'  to operation code below. Do not recreate it for every operation.
'  See Reusable Box HttpCurl Setup.
set curl = CreateObject("Chilkat.HttpCurl")
curl.SetVar "access_token","BOX_ACCESS_TOKEN"
curl.SetVar "parent_name","/"
'  Box's fixed root ID is an implementation detail; callers supply names.
curl.SetVar "parent_id","0"
set setupCommand = CreateObject("Chilkat.StringBuilder")

'  Register findParent; registration sends no request.
success = setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findParent",setupCommand.GetAsString())
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  Register findFolder; registration sends no request.
success = setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{parent_id}}/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findFolder",setupCommand.GetAsString())
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  Register findFile; registration sends no request.
success = setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{folder_id}}/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findFile",setupCommand.GetAsString())
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  Register findDestination; registration sends no request.
success = setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findDestination",setupCommand.GetAsString())
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  Register getFileDetails; registration sends no request.
success = setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/files/{{file_id}}?fields=id,sha1,file_version"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("getFileDetails",setupCommand.GetAsString())
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  Register getEnterprise; registration sends no request.
success = setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/users/me?fields=enterprise"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("getEnterprise",setupCommand.GetAsString())
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  Register output rules once. Chilkat 11.7.0 evaluates {{name}} variables
'  when extracting each output, using the current value at that time.
success = curl.AddOutput2("findParent","entries","name","{{parent_name}}",1,"id","parent_id")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

success = curl.AddOutput2("findFolder","entries","name","{{folder_name}}",1,"id","folder_id")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

success = curl.AddOutput2("findFile","entries","name","{{file_name}}",1,"id","file_id")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

success = curl.AddOutput2("findDestination","entries","name","{{destination_name}}",1,"id","destination_id")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

success = curl.AddOutput("getFileDetails","file_version.id","file_version_id")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

success = curl.AddOutput("getFileDetails","sha1","file_sha1")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

success = curl.AddOutput("getEnterprise","enterprise.id","enterprise_id")
If (success <> 1) Then
    outFile.WriteLine(curl.LastErrorText)
    WScript.Quit
End If

'  END ONE-TIME SETUP
'  The name lookups below assume each listing fits in one page (1000 items).
'  Parent and destination names select root children; folder_name selects a child
'  of parent_name. "/" selects the root parent. These are not arbitrary paths.

'  BEGIN OPERATION -- keep the configured object when reusing it.
'  Inputs are names. Retain cached IDs when the selected names have not changed.
parentName = "/"
folderName = "documents"
If ((curl.GetVar("parent_name") <> parentName) Or ((parentName = "/") And (curl.VarDefined("parent_id") = 0))) Then
    curl.SetVar "parent_name",parentName
    curl.ClearVar "parent_id"
    curl.ClearVar "folder_id"
    curl.ClearVar "file_id"
    curl.ClearVar "file_version_id"
    curl.ClearVar "file_sha1"
    If (parentName = "/") Then
        curl.SetVar "parent_id","0"
    End If

End If

If (curl.GetVar("folder_name") <> folderName) Then
    curl.SetVar "folder_name",folderName
    curl.ClearVar "folder_id"
    curl.ClearVar "file_id"
    curl.ClearVar "file_version_id"
    curl.ClearVar "file_sha1"
End If

'  Resolve the named destination first. HttpCurl does not expand variables
'  inside multipart -F attributes in the tested build, so this upload is two phases.
curl.ClearTargetOutput "*"
set authorizedCommand1 = CreateObject("Chilkat.StringBuilder")
success = authorizedCommand1.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{folder_id}}?fields=id"" -H ""Authorization: Bearer {{access_token}}""")
headerReplacement1 = authorizedCommand1.Replace("{{access_token}}",curl.GetVar("access_token"))
success = curl.DoYourThing(authorizedCommand1.GetAsString())
If ((success <> 1) Or (curl.StatusCode <> 200)) Then
    outFile.WriteLine("Box request failed. HTTP status: " & curl.StatusCode)
    outFile.WriteLine("Failure reason: " & curl.FailReason)
    outFile.WriteLine(curl.ResponseBodyStr)
    WScript.Quit
End If

'  This example limits size to 2 GB so offsets fit all generated languages' integers.
'  The source must not change during hashing or upload. Create qa_output first.
localPath = "qa_data/large-document.zip"
set file = CreateObject("Chilkat.FileAccess")
'  Check the decimal size before converting so an oversized file cannot overflow int.
sizeString = file.FileSizeStr(localPath)
If (file.LastMethodSuccess <> 1) Then
    outFile.WriteLine(file.LastErrorText)
    WScript.Quit
End If

set sizeText = CreateObject("Chilkat.StringBuilder")
success = sizeText.SetString(sizeString)
set sizeMatch = CreateObject("Chilkat.JsonObject")
If (sizeText.RegexMatch("^([0-9]{1,9}|1[0-9]{9}|2000000000)$",sizeMatch,100) <> 1) Then
    outFile.WriteLine("Choose an input between 20 MB and 2 GB for this example.")
    WScript.Quit
End If

fileSize = CLng(sizeString)
If (fileSize < 20971520) Then
    outFile.WriteLine("Choose an input between 20 MB and 2 GB for this example.")
    WScript.Quit
End If

set http = CreateObject("Chilkat.Http")
http.AuthToken = curl.GetVar("access_token")
set response = CreateObject("Chilkat.HttpResponse")
set request = CreateObject("Chilkat.JsonObject")
success = request.UpdateString("folder_id",curl.GetVar("folder_id"))
success = request.UpdateString("file_name","large-document.zip")
success = request.UpdateInt("file_size",fileSize)
success = http.HttpJson("POST","https://upload.box.com/api/2.0/files/upload_sessions",request,"application/json",response)
If (success <> 1) Then
    outFile.WriteLine(http.LastErrorText)
    WScript.Quit
End If

If (response.StatusCode <> 201) Then
    outFile.WriteLine(response.BodyStr)
    WScript.Quit
End If

set session = CreateObject("Chilkat.JsonObject")
success = session.Load(response.BodyStr)
If (success <> 1) Then
    outFile.WriteLine(session.LastErrorText)
    WScript.Quit
End If

success = session.WriteFile("qa_output/box_upload_session.json")
If (success <> 1) Then
    outFile.WriteLine(session.LastErrorText)
    WScript.Quit
End If

partSize = session.IntOf("part_size")
uploadUrl = session.StringOf("session_endpoints.upload_part")
commitUrl = session.StringOf("session_endpoints.commit")
If ((partSize <= 0) Or (uploadUrl = "") Or (commitUrl = "")) Then
    outFile.WriteLine("Invalid session response.")
    WScript.Quit
End If

set hash = CreateObject("Chilkat.Crypt2")
hash.HashAlgorithm = "sha1"
hash.EncodingMode = "base64"
fileDigest = hash.HashFileENC(localPath)
If (hash.LastMethodSuccess <> 1) Then
    outFile.WriteLine(hash.LastErrorText)
    WScript.Quit
End If

success = file.FileOpen(localPath,2147483648,1,3,0)
If (success <> 1) Then
    outFile.WriteLine(file.LastErrorText)
    WScript.Quit
End If

set commit = CreateObject("Chilkat.JsonObject")
set partResponse = CreateObject("Chilkat.JsonObject")
set chunk = CreateObject("Chilkat.BinData")
set range = CreateObject("Chilkat.StringBuilder")
set digestHeader = CreateObject("Chilkat.StringBuilder")
offset = 0
partIndex = 0

Do While offset < fileSize
    success = chunk.Clear()
    success = file.FileReadBd(partSize,chunk)
    If (success <> 1) Then
        outFile.WriteLine(file.LastErrorText)
        file.FileClose 
        WScript.Quit
    End If

    partLength = chunk.NumBytes
    If (partLength <= 0) Then
        outFile.WriteLine("Unexpected end of file.")
        file.FileClose 
        WScript.Quit
    End If

    lastByte = offset + (partLength - 1)
    range.Clear 
    success = range.Append("bytes ")
    success = range.AppendInt(offset)
    success = range.Append("-")
    success = range.AppendInt(lastByte)
    success = range.Append("/")
    success = range.AppendInt(fileSize)
    partDigest = hash.HashBdENC(chunk)
    If (hash.LastMethodSuccess <> 1) Then
        outFile.WriteLine(hash.LastErrorText)
        file.FileClose 
        WScript.Quit
    End If

    success = digestHeader.SetString("sha=")
    success = digestHeader.Append(partDigest)
    http.SetRequestHeader "Digest",digestHeader.GetAsString()
    http.SetRequestHeader "Content-Range",range.GetAsString()
    success = http.HttpBd("PUT",uploadUrl,chunk,"application/octet-stream",response)
    If ((success <> 1) Or (response.StatusCode <> 200)) Then
        outFile.WriteLine("Part failed. HTTP status: " & response.StatusCode)
        outFile.WriteLine(response.BodyStr)
        outFile.WriteLine("Inspect the saved session and server list_parts before retrying this part.")
        file.FileClose 
        WScript.Quit
    End If

    success = partResponse.Load(response.BodyStr)
    If (success <> 1) Then
        file.FileClose 
        WScript.Quit
    End If

    commit.I = partIndex
    '  Copy the server's acknowledged part fields into the commit manifest.
    success = commit.UpdateString("parts[i].part_id",partResponse.StringOf("part.part_id"))
    success = commit.UpdateInt("parts[i].offset",partResponse.IntOf("part.offset"))
    success = commit.UpdateInt("parts[i].size",partResponse.IntOf("part.size"))
    success = commit.UpdateString("parts[i].sha1",partResponse.StringOf("part.sha1"))
    success = commit.WriteFile("qa_output/box_upload_parts.json")
    If (success <> 1) Then
        outFile.WriteLine(commit.LastErrorText)
        file.FileClose 
        WScript.Quit
    End If

    offset = offset + partLength
    partIndex = partIndex + 1
Loop
file.FileClose 
http.RemoveRequestHeader "Content-Range"
success = digestHeader.SetString("sha=")
success = digestHeader.Append(fileDigest)
http.SetRequestHeader "Digest",digestHeader.GetAsString()
attempts = 0

set retryHeader = CreateObject("Chilkat.StringBuilder")
set retryMatch = CreateObject("Chilkat.JsonObject")
completed = 0
Do While (attempts < 10) And (completed = 0)
    success = http.HttpJson("POST",commitUrl,commit,"application/json",response)
    If (success <> 1) Then
        outFile.WriteLine("Commit failed: " & response.StatusCode)
        outFile.WriteLine(response.BodyStr)
        WScript.Quit
    End If

    If (response.StatusCode = 201) Then
        completed = 1
    Else
        If (response.StatusCode <> 202) Then
            outFile.WriteLine("Unexpected commit status: " & response.StatusCode)
            WScript.Quit
        End If

        '  Box's asynchronous commit response supplies Retry-After in seconds.
        success = retryHeader.SetString(response.GetHeaderField("Retry-After"))
        If (retryHeader.RegexMatch("^[0-9]{1,2}$",retryMatch,100) <> 1) Then
            outFile.WriteLine("Commit pending. Preserve the session and inspect Retry-After before resuming: " & retryHeader.GetAsString())
            WScript.Quit
        End If

        waitSeconds = CLng(retryHeader.GetAsString())
        If ((waitSeconds < 1) Or (waitSeconds > 60)) Then
            outFile.WriteLine("Commit pending. Resume commit after Retry-After: " & response.GetHeaderField("Retry-After"))
            WScript.Quit
        End If

        http.SleepMs waitSeconds * 1000
    End If

    attempts = attempts + 1
Loop
If (completed = 0) Then
    outFile.WriteLine("Commit still pending; retain session and part manifests to resume commit later.")
    WScript.Quit
End If

outFile.WriteLine("Upload committed: " & response.BodyStr)

outFile.Close