HP-UX Reference (11i v1 05/09) - 2 System Calls (vol 5)

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mmap(2) mmap(2)

[EINVAL] The mapping already exists in 32-bit address space, but the application performing the

current mmap() request has been compiled as a 64-bit executable and did not specify

MAP_ADDR32 in the ﬂags argument.

[EMFILE] The number of mapped regions would exceed an implementation-dependent limit (per

process or per system).

[ENODEV] The ﬁldes argument refers to a ﬁle whose type is not supported by

mmap().

[ENOMEM]

MAP_FIXED was speciﬁed, and the range [addr, addr+len] exceeds that allowed for the

address space of a process; or if

MAP_FIXED was not speciﬁed and there is insufﬁcient

room in the address space to effect the mapping.

[ENXIO] Addresses in the range [off, off+len] are invalid for ﬁldes.

APPLICATION USAGE

Use of

mmap() may reduce the amount of memory available to other memory allocation functions.

Use of MAP_FIXED may result in unspeciﬁed behavior in further use of

brk(), sbrk(), malloc(),

and

shmat(). The use of MAP_FIXED

is discouraged, as it may prevent an implementation from making

the most effective use of resources.

The application must ensure correct synchronization when using

mmap() in conjunction with any other ﬁle

access method, such as

read() and write(), standard input/output, and

shmat().

The

mmap() function allows access to resources via address space manipulations, instead of

read()/write(). Once a ﬁle is mapped, all a process has to do to access it is use the data at the

address to which the ﬁle was mapped. So, using pseudo-code to illustrate the way in which an existing pro-

gram might be changed to use mmap(), the following:

fildes = open(...)

lseek(fildes, some_offset)

read(fildes, buf, len)

/* use data in buf */

becomes:

fildes = open(...)

address = mmap(0, len, PROT_READ, MAP_PRIVATE, fildes, some_offset)

/* use data at address */