array_allocate(3) [debian man page]
array_allocate(3) Library Functions Manual array_allocate(3) NAME
array_allocate - make sure array has at least n elements allocated SYNTAX
#include <array.h> void* array_allocate(array* x, uint64 membersize, int64 pos); array x; int64 pos; t* p = array_allocate(&x,sizeof(t),pos); DESCRIPTION
array_allocate makes sure that enough bytes are allocated in x for at least pos+1 objects of type t. (The size of t must be positive; oth- erwise the effects are undefined.) If not enough bytes are allocated (or x is unallocated), array_allocate allocates more bytes, moving the dynamically allocated region if necessary. array_allocate often allocates somewhat more bytes than necessary, to save time later. array_allocate then makes sure that the number of bytes initialized covers at least those pos+1 objects. If not enough bytes are initial- ized, array_allocate initializes more bytes (setting them to 0), up to exactly the end of the pos+1st object. array_allocate then returns a pointer to the pos+1st object; i.e., object number pos, with objects numbered starting at 0. This pointer can be used to change or inspect the object. The pointer can continue to be used through subsequent calls to array_get, array_start, array_length, and array_bytes, but it must not be used after any other operations on this array. If something goes wrong, array_allocate returns 0, setting errno appropriately, without touching x. In particular, array_allocate returns 0 if o x has failed, or o pos is negative, or o not enough memory is available. array_allocate does not change x to have failed; if you want to do that, use array_fail. SEE ALSO
array_get(3), array_start(3), array_fail(3) array_allocate(3)
Check Out this Related Man Page
lseek(2) System Calls Manual lseek(2) Name lseek, tell - move read or write pointer Syntax #include <sys/types.h> #include <unistd.h> pos = lseek(d, offset, whence) off_t pos; int d, whence; off_t offset; pos = tell(d) off_t pos; int d; Description The system call moves the file pointer associated with a file or device open for reading or writing. The descriptor d refers to a file or device open for reading or writing. The system call sets the file pointer of d as follows: o If whence is SEEK_SET, the pointer is set to offset bytes. o If whence is SEEK_CUR the pointer is set to its current location plus offset. o If whence is SEEK_END, the pointer is set to the size of the file plus offset. Seeking beyond the end of a file and then writing to the file creates a gap or hole that does not occupy physical space and reads as zeros. The system call returns the offset of the current byte relative to the beginning of the file associated with the file descriptor. Environment System Five If you compile a program in the System Five environment, an invalid whence argument causes SIGSYS to be sent. This complies with the behavior described in the System V Interface Definition (SVID), Issue 1. Return Values Upon successful completion, a long integer (the current file pointer value) is returned. This pointer is measured in bytes from the begin- ning of the file, where the first byte is byte 0. (Note that some devices are incapable of seeking. The value of the pointer associated with such a device is undefined.) If a value of -1 is returned, errno is set to indicate the error. Diagnostics The system call fails and the file pointer remains unchanged under the following conditions: [EBADF] The fildes is not an open file descriptor. [EINVAL] The whence is not a proper value. [ESPIPE] The fildes is associated with a pipe or a socket. See Also dup(2), open(2) lseek(2)