Class LibCUtil
off_t because it is dependent upon features
 selected at compile-time. This class provides helper methods that safely
 avoid these types by using 64-bit mappings when available.- 
Method SummaryModifier and TypeMethodDescriptionstatic intftruncate(int fd, long length) Causes the regular file referenced byfdto be truncated to a size of preciselylengthbytes.static PointerCreates a new mapping in the virtual address space of the calling process.static voidrequire32Bit(long val, String value) Test that a value is 32-bit, throwing a custom exception otherwise
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Method Details- 
mmapCreates a new mapping in the virtual address space of the calling process.- Parameters:
- addr- The starting address for the new mapping.- If - addris NULL, then the kernel chooses the (page-aligned) address at which to create the mapping; this is the most portable method of creating a new mapping. If- addris not NULL, then the kernel takes it as a hint about where to place the mapping; on Linux, the kernel will pick a nearby page boundary (but always above or equal to the value specified by- /proc/sys/vm/mmap_min_addr) and attempt to create the mapping there. If another mapping already exists there, the kernel picks a new address that may or may not depend on the hint. The address of the new mapping is returned as the result of the call.
- length- Specifies the length of the mapping (which must be greater than 0).
- prot- describes the desired memory protection of the mapping (and must not conflict with the open mode of the file). It is either- PROT_NONEor the bitwise OR of one or more of- PROT_READ,- PROT_WRITE, or- PROT_EXEC.
- flags- determines whether updates to the mapping are visible to other processes mapping the same region, and whether updates are carried through to the underlying file. This behavior is determined by including exactly one of- MAP_SHARED,- MAP_SHARED_VALIDATE, or- MAP_PRIVATE. In addition, 0 or more additional flags can be ORed in- flags.
- fd- The file descriptor for the object to be mapped. After the- mmap()call has returned, the file descriptor can be closed immediately without invalidating the mapping.
- offset- The contents of a file mapping (as opposed to an anonymous mapping), are initialized using- lengthbytes starting at offset- offsetin the file (or other object) referred to by the file descriptor,- fd.- offsetmust be a multiple of the page size as returned by- sysconf(_SC_PAGE_SIZE).
- Returns:
- On success, returns a pointer to the mapped area. On error, the value
         MAP_FAILED(that is, (void *) -1) is returned, anderrnois set to indicate the cause of the error.
 
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ftruncatepublic static int ftruncate(int fd, long length) Causes the regular file referenced byfdto be truncated to a size of preciselylengthbytes.If the file previously was larger than this size, the extra data is lost. If the file previously was shorter, it is extended, and the extended part reads as null bytes ('\0'). The file must be open for writing - Parameters:
- fd- a file descriptor
- length- the number of bytes to truncate or extend the file to
- Returns:
- On success, zero is returned. On error, -1 is returned, and
         errnois set appropriately.
 
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require32BitTest that a value is 32-bit, throwing a custom exception otherwise- Parameters:
- val- The value to test
- value- The name of the value, to be inserted in the exception message if not 32-bit
- Throws:
- IllegalArgumentException- if- valis not 32-bit
 
 
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