diff options
Diffstat (limited to 'libbutl/fdstream.hxx')
| -rw-r--r-- | libbutl/fdstream.hxx | 50 |
1 files changed, 49 insertions, 1 deletions
diff --git a/libbutl/fdstream.hxx b/libbutl/fdstream.hxx index 730d4dd..1a8f9a6 100644 --- a/libbutl/fdstream.hxx +++ b/libbutl/fdstream.hxx @@ -652,6 +652,54 @@ namespace butl LIBBUTL_SYMEXPORT ifdstream& getline (ifdstream&, std::string&, char delim = '\n'); + // The non-blocking getline() version that reads the line in potentially + // multiple calls. Key differences compared to getline(): + // + // - Stream must be in the non-blocking mode and exception mask must have + // at least badbit. + // + // - Return type is bool instead of stream. Return true if the line has been + // read or false if it should be called again once the stream has more + // data to read. Also return true on failure. + // + // - The string must be empty on the first call. + // + // - There could still be data to read in the stream's buffer (as opposed to + // file descriptor) after this function returns true and you should be + // careful not to block on fdselect() in this case. In fact, the + // recommended pattern is to call this function first and only call + // fdselect() if it returns false. + // + // The typical usage in combination with the eof() helper: + // + // fdselect_set fds {is.fd (), ...}; + // fdselect_state& ist (fds[0]); + // fdselect_state& ...; + // + // for (string l; ist.fd != nullfd || ...; ) + // { + // if (ist.fd != nullfd && getline_non_blocking (is, l)) + // { + // if (eof (is)) + // ist.fd = nullfd; + // else + // { + // // Consume line. + // + // l.clear (); + // } + // + // continue; + // } + // + // ifdselect (fds); + // + // // Handle other ready fds. + // } + // + LIBBUTL_SYMEXPORT bool + getline_non_blocking (ifdstream&, std::string&, char delim = '\n'); + // Open a file returning an auto_fd that holds its file descriptor on // success and throwing ios::failure otherwise. // @@ -858,7 +906,7 @@ namespace butl // underlying OS error. // // Note that the function clears all the previously-ready entries on each - // call. Entries with nullfd are ignored. + // call. Entries with nullfd are ignored (but cleared). // // On Windows only pipes and only their input (read) ends are supported. // |