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70 lines
3.6 KiB
Plaintext
70 lines
3.6 KiB
Plaintext
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Hpux:
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=====
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The use of a timeout does not affect any pending timers set up by alarm(), ualarm(), or setitimer().
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On successful completion, the object pointed to by the timeout argument may be modified.
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The FD_SETSIZE is used in the definition of fd_set structure. It is set to a value of 2048 to
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accommodate 2048 file descriptors. Any user code that uses FD_SETSIZE or the structure fd_set
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should redefine FD_SETSIZE to a smaller value (greater than or equal to the number of open files the
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process will have) in order to save space. Similarly, any user code that wants to test more than 2048
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file descriptors should redefine FD_SETSIZE to the required higher value.
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Solaris:
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========
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The default value for FD_SETSIZE (currently 1024) is larger
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than the default limit on the number of open files. To
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accommodate 32-bit applications that wish to use a larger
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number of open files with select(), it is possible to
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increase this size at compile time by providing a larger
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definition of FD_SETSIZE before the inclusion of
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<sys/types.h>. The maximum supported size for FD_SETSIZE is
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65536. The default value is already 65536 for 64-bit appli-
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cations.
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Windows:
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========
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Four macros are defined in the header file Winsock.h for manipulating and checking the
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descriptor sets. The variable FD_SETSIZE determines the maximum number of descriptors in a
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set. (The default value of FD_SETSIZE is 64, which can be modified by defining FD_SETSIZE to
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another value before including Winsock.h.) Internally, socket handles in an FD_SET structure are
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not represented as bit flags as in Berkeley Unix. Their data representation is opaque. Use of
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these macros will maintain software portability between different socket environments. The
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macros to manipulate and check FD_SET contents are:
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Aix:
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====
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Although the provision of getdtablesize(2SEQ) was intended to allow user programs to be written independently of the kernel limit on the number of open
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files, the dimension of a sufficiently large bit field for select remains a problem. The default size FD_SETSIZE (currently 8192) is somewhat larger than the
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current kernel limit to the number of open files. However, in order to accommodate programs which might potentially use a larger number of open files with
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select, it is possible to increase this size within a program by providing a larger definition of FD_SETSIZE before the inclusion of <sys/select.h>.
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select() should probably return the time remaining from the original timeout, if any, by modifying the time value in place. This may be implemented in future
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versions of the system. Thus, it is unwise to assume that the timeout value will be unmodified by the select() call.
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Tru 64:
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=======
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3.This step is required only for applications that use select(), fd_set, FD_CLR, FD_ISSET, FD_SET, or FD_ZERO. Choose one of the following:
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Override the default value (4k) for FD_SETSIZE in <sys/select.h> by specifying the new maximum (65536). You must do this before
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including the <sys/time.h> header file, which includes <sys/select.h>:
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#define FD_SETSIZE 65536
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#include <sys/time.h>
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This setting is not inherited by child processes; therefore, FD_SETSIZE must be set explicitly in the code of a child process that requires 64k file
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descriptor support.
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Linux:
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======
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No documented way of overriding the variable.
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/* One element in the file descriptor mask array. */
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typedef unsigned long int __fd_mask;
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/* Number of descriptors that can fit in an `fd_set'. */
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#define __FD_SETSIZE 1024
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