TIFFERROR(3tiff)

NAME
TIFFError - library error handling interface

SYNOPSIS

        #include <tiffio.h>
        #include <stdarg.h>

    void TIFFError(const char *module, const char *fmt, ...)

    void TIFFErrorExt(thandle_t fd, const char *module, const char *fmt, ...)

    void TIFFErrorExtR(TIFF *tif, const char *module, const char *fmt, ...)

    typedef void (*TIFFErrorHandler)(const char *module, const char *fmt, va_list ap)

    typedef void (*TIFFErrorHandlerExt)(thandle_t fd, const char *module, const char *fmt, va_list ap)

    typedef int (*TIFFErrorHandlerExtR)(TIFF *tif, void *user_data, const char *module, const char *fmt, va_list ap)

    TIFFErrorHandler TIFFSetErrorHandler(TIFFErrorHandler handler)

    TIFFErrorHandlerExt TIFFSetErrorHandlerExt(TIFFErrorHandlerExt handler)

DESCRIPTION

TIFFError() invokes the library-wide error handler function to (normally) write an error message to stderr. The fmt parameter is a printf() format string, and any number arguments can be supplied. The module parameter is interpreted as a string that, if non-zero, should be printed before the message; it typically is used to identify the software module in which an error is detected.

Applications that desire to capture control in the event of an error should use TIFFSetErrorHandler() to override the default error handler. A NULL (0) error handler function may be installed to suppress error messages.

Two more application-specific error handler callbacks are available, each with different call parameters and passing parameters to the handler. Each handler is also linked with an error message function, i.e. TIFFErrorExt() and TIFFErrorExtR() if the application intends to call the handler with those extended parameters.

TIFFErrorExt() provides a file handle as parameter. Within libtiff TIFFErrorExt() is called passing tif->tif_clientdata as fd, which represents the TIFF file handle (file descriptor). The application-specific and library-wide handler for TIFFErrorExt() is setup with TIFFSetErrorHandlerExt().

TIFFErrorExtR() (introduced with libtiff 4.5) is called with its TIFF handle and thus provides access to a per-TIFF handle (re-entrant) error handler. That means for different TIFF handles, different error handlers can be setup. This application-specific handler can be setup when a TIFF file is opened with one of the following functions: TIFFOpenExt(), TIFFOpenWExt(), TIFFFdOpenExt() or TIFFClientOpenExt(). Furthermore, a custom defined data structure user_data for the error handler can be given along.

NOTE

Both functions TIFFError() and TIFFErrorExt() each attempt to call both handler functions if they are defined. First TIFFErrorHandler() is called and then TIFFErrorHandlerExt(). However, TIFFError() passes a “0” as a file handle to TIFFErrorHandlerExt().

TIFFErrorExtR() tries first to call the per-TIFF handle defined error handler. If TIFFErrorHandlerExtR() is not defined or returns 0, TIFFErrorHandler() and then TIFFErrorHandlerExt() are called. From libtiff 4.5 onwards TIFFErrorExtR() is used within the libtiff library where the TIFF handle is available. Otherwise, TIFFErrorExt() is used!

RETURN VALUES

TIFFSetErrorHandler() and TIFFSetErrorHandlerExt() returns a reference to the previous error handler function.

TIFFErrorHandlerExtR() returns an integer as “stop” to control the call of further error handler functions within TIFFErrorExtR():

            •   0: both functions TIFFErrorHandler() and TIFFErrorHandlerExt() are called.

            •   non-zero: no further error message function is called.

SEE ALSO

TIFFWarning (3tiff), TIFFOpen (3tiff), libtiff (3tiff), printf (3)

AUTHOR
LibTIFF contributors

COPYRIGHT
1988-2022, LibTIFF contributors