sousa-gecko/docs/nspr/reference/pr_writev.md

PR_Writev

Writes data to a socket from multiple buffers.

Syntax

#include <prio.h>

PRInt32 PR_Writev(
  PRFileDesc *fd,
  PRIOVec *iov,
  PRInt32 size,
  PRIntervalTime timeout);

#define PR_MAX_IOVECTOR_SIZE 16

Parameters

The function has the following parameters:

fd

A pointer to a {ref}PRFileDesc object for a socket.

iov

An array of PRIOVec structures that describe the buffers to write from.

size

Number of PRIOVec structures in the iov array. The value of this parameter must not be greater than PR_MAX_IOVECTOR_SIZE. If it is, the function will fail and the error will be set to PR_BUFFER_OVERFLOW_ERROR.

timeout

A value of type {ref}PRIntervalTime describing the time limit for completion of the entire write operation.

Returns

One of the following values:

• A positive number indicates the number of bytes successfully written.
• The value -1 indicates that the operation failed. The reason for the failure can be obtained by calling {ref}PR_GetError.

Description

The thread calling {ref}PR_Writev blocks until all the data is written or the write operation fails. Therefore, the return value is equal to either the sum of all the buffer lengths (on success) or -1 (on failure). Note that if {ref}PR_Writev returns -1, part of the data may have been written before an error occurred. If the timeout parameter is not PR_INTERVAL_NO_TIMEOUT and all the data cannot be written in the specified interval, {ref}PR_Writev returns -1 with the error code PR_IO_TIMEOUT_ERROR.

This is the type definition for PRIOVec:

typedef struct PRIOVec {
  char *iov_base;
  int iov_len;
} PRIOVec;

The PRIOVec structure has the following fields:

iov_base

A pointer to the beginning of the buffer.

iov_len

The size of the buffer.