Prof Brian Ripley wrote: > When I originally implemented connections in R 1.2.0, I followed the model > in the 'Green Book' closely. There were a number of features that forced > a particular implementation, and one was getConnection() that allows one > to recreate a connection object from a number. [...] > Another issue is that the current connection objects can be saved and > restored but refer to a global table that is session-specific so they lose > their meaning (and perhaps gain an unintended one). > > What I suspect is that very few users are aware of the Green Book > description and so we have freedom to make some substantial changes > to the implementation. Both issues suggest that connection objects should > be based on external pointers (which did not exist way back in 1.2.0).
Sounds great! I would also like to see the following interface (all or in parts) added for working with connections from C. This is an update to the patch I created here: http://wiki.r-project.org/rwiki/doku.php?id=developers:r_connections_api /* Acting upon a connection */ void R_CloseConnection(SEXP); int R_VfprintfConnection(SEXP, const char *format, va_list ap); int R_FgetcConnection(SEXP); double R_SeekConnection(SEXP, double where, int origin, int rw); void R_TruncateConnection(SEXP); int R_FlushConnection(SEXP); size_t R_ReadConnection(SEXP, void *buf, size_t size, size_t n); size_t R_WriteConnection(SEXP, const void *buf, size_t size, size_t n); /* Querying a connection */ Rboolean R_ConnectionIsText(SEXP); Rboolean R_ConnectionIsOpen(SEXP); Rboolean R_ConnectionCanRead(SEXP); Rboolean R_ConnectionCanWrite(SEXP); Rboolean R_ConnectionCanSeek(SEXP); Rboolean R_ConnectionIsBlocking(SEXP); /* Prototypes for new connections created in C */ typedef Rboolean (*Rc_open)(void *private); typedef void (*Rc_close)(void *private); typedef void (*Rc_destroy)(void *private); /* when closing connection */ typedef int (*Rc_vfprintf)(void *private, const char *, va_list); typedef int (*Rc_fgetc)(void *private); typedef double (*Rc_seek)(void *private, double, int, int); typedef void (*Rc_truncate)(void *private); typedef int (*Rc_fflush)(void *private); typedef size_t (*Rc_read)(void *, size_t, size_t, void *private); typedef size_t (*Rc_write)(const void *, size_t, size_t, void *private); /* Create a Connection */ SEXP R_NewConnection(char *class, char *description, char *mode, Rboolean blocking, Rc_open, Rc_close, Rc_destroy, Rc_vfprintf, Rc_fgetc, Rc_seek, Rc_truncate, Rc_fflush, Rc_read, Rc_write, void *private); /* Swap out the standard C streams. More exotic, but it may clean up the messy R_ConsoleFile, R_Outputfile, WriteConsole(), WriteConsoleEx(), etc... confusion. */ Rboolean R_RegisterStdinConnection(SEXP scon); Rboolean R_RegisterStdoutConnection(SEXP scon); Rboolean R_RegisterStderrConnection(SEXP scon); Jeff -- http://biostat.mc.vanderbilt.edu/JeffreyHorner ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
