Function appendLogDataWithCap

riverlog/river_log.go:240–267

(metadataBytes, newLogEntryBytes []byte, maxTotalBytes int)

}

func appendLogDataWithCap(metadataBytes, newLogEntryBytes []byte, maxTotalBytes int) ([]byte, int, error) {
	existingLogData := gjson.GetBytes(metadataBytes, metadataKey)
	var existingLogArrayBytes []byte
	switch {
	case !existingLogData.Exists():
		existingLogArrayBytes = []byte("[]")
	case existingLogData.IsArray():
		// Slice raw JSON straight from metadata bytes to avoid an extra copy.
		existingLogArrayBytes = metadataBytes[existingLogData.Index : existingLogData.Index+len(existingLogData.Raw)]
	default:
		return nil, 0, fmt.Errorf("%q value is not an array", metadataKey)
	}

	existingElementBounds, err := getArrayElementBounds(existingLogArrayBytes)
	if err != nil {
		return nil, 0, err
	}

	// Determine the smallest suffix to keep that still fits with the new entry.
	// This keeps pruning oldest-first while avoiding repeated full rewrites.
	keepStart := getKeepStart(existingElementBounds, len(newLogEntryBytes), maxTotalBytes)

	// Build the final array once from the kept suffix plus the new entry.
	appendedLogDataBytes := buildAppendedArray(existingLogArrayBytes, existingElementBounds, keepStart, newLogEntryBytes)
	numDroppedEntries := min(keepStart, len(existingElementBounds))

	return appendedLogDataBytes, numDroppedEntries, nil
}

type arrayElementBounds struct {
	Start int