StorageFactory/interface/IOTypes.h

0001 #ifndef STORAGE_FACTORY_IO_TYPES_H
0002 #define STORAGE_FACTORY_IO_TYPES_H
0003
0004 #include <cstdint>
0005 #include <cstdlib>
0006
0007 namespace edm::storage {
0008   /** Invalid channel descriptor constant.  */
0009   constexpr int EDM_IOFD_INVALID = -1;
0010
0011   /** Type for buffer sizes in I/O operations.  It measures units in
0012     memory: buffer sizes, amounts to read and write, etc., and is
0013     unsigned.  Never use IOSize to measure file offsets, as it is
0014     most likely smaller than the file offset type on your system!  */
0015   typedef size_t IOSize;
0016
0017   /** Type for file offsets for I/O operations, including file sizes.
0018     This type is always compatible with large files (64-bit offsets)
0019     whether the system supports them or not.  This type is signed.  */
0020   typedef int64_t IOOffset;
0021
0022   /** Type the system uses for channel descriptors.  */
0023   typedef int IOFD;
0024
0025   /** I/O operation mask.  */
0026   enum IOMask {
0027     IORead = 0x01,    //< Read
0028     IOWrite = 0x02,   //< Write
0029     IOUrgent = 0x04,  //< Exceptional or urgent condition
0030     IOAccept = 0x08,  //< Socket accept
0031     IOConnect = 0x10  //< Socket connect
0032   };
0033
0034   /** Safely convert IOOffset @a n into a #IOSize quantity.  If @a n is
0035     larger than what #IOSize can hold, it is truncated to maximum
0036     value that can be held in #IOSize.  */
0037   inline IOSize IOSized(IOOffset n) {
0038     // If IOSize and IOOffset are the same size, largest positive value
0039     // is half of maximum IOSize.  Otherwise all bits of IOSize work.
0040     IOOffset largest = (sizeof(IOOffset) == sizeof(IOSize) ? ~IOSize(0) / 2 : ~IOSize(0));
0041     return IOSize(n > largest ? largest : n);
0042   }
0043 }  // namespace edm::storage
0044 #endif  // STORAGE_FACTORY_IO_TYPES_H