Function PlanDownload

internal/sessions/transfer.go:148–177

PlanDownload decides the transfer strategy and chunk count for a download. fileSize should be obtained from a probe command; if 0 or negative the plan assumes chunked shell transfer with a single probe-then-decide chunk.

(fileSize int, userAgent string)

// fileSize should be obtained from a probe command; if 0 or negative the plan
// assumes chunked shell transfer with a single probe-then-decide chunk.
func PlanDownload(fileSize int, userAgent string) TransferPlan {
	profile := MatchAgentProfile(userAgent)

	plan := TransferPlan{
		TotalSize: fileSize,
		AgentName: profile.Name,
	}

	if fileSize > 0 && fileSize <= smallFileThreshold {
		plan.Strategy = StrategyDirectTool
		plan.NumChunks = 1
		return plan
	}

	plan.Strategy = StrategyShellBase64
	plan.ChunkSize = profile.ChunkSizeBytes

	if fileSize <= 0 {
		// Unknown size; caller should probe first.
		plan.NumChunks = 0
		return plan
	}

	if fileSize <= profile.ChunkSizeBytes {
		plan.NumChunks = 1
	} else {
		plan.NumChunks = int(math.Ceil(float64(fileSize) / float64(profile.ChunkSizeBytes)))
	}
	return plan
}

// ---------------------------------------------------------------------------
// Chunk generation