vrb_read_min3

Usage

Library

-lvrb

Overview

vrb_read_min reads a minimum amount of data from a specified open file descriptor using read(2) into the specified virtual ring buffer until the specified maximum length has been read, the buffer is full, or end-of-file, or an error is returned (including EAGAIN or EWOULDBLOCK for a non-blocking descriptor). If there is insufficient space in the buffer to read the minimum amount, then read(2) will not be called.

Arguments

vrb_p vrb
specifies which virtual ring buffer.

int fd
specifies the open file descriptor to read from

size_t maxsize
specifies the maximum length to read, or ~0 for unlimited.

size_t minsize
specifies the minimum length to read.

Return value

size_t
If successful, the actual length of data read into the buffer is returned. If the minimum amount of space was not available to read into, 0 is returned. If end-of-file occurs, the return value is ~0 and errno is 0. If an error occurs from read(2), the return value is ~0 and errno is set by read(2).

Errors

If an error is returned, then errno will have one of the following values:

0

An end-of-file has occurred. Note that this is a different way of returning an end-of-file condition than read(2) uses.

EINVAL

An invalid virtual ring buffer pointer was specified.