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| | // SPDX-License-Identifier: GPL-2.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* lineread.c - Allocation free line-by-line buffered file input
*
* Copyright Red Hat
* Author: David Gibson <david@gibson.dropbear.id.au>
*/
#include <stddef.h>
#include <fcntl.h>
#include <string.h>
#include <stdbool.h>
#include <unistd.h>
#include "lineread.h"
#include "util.h"
/**
* lineread_init() - Prepare for line by line file reading without allocation
* @lr: Line reader state structure to initialize
* @fd: File descriptor to read lines from
*/
void lineread_init(struct lineread *lr, int fd)
{
lr->fd = fd;
lr->next_line = lr->count = 0;
}
/**
* peek_line() - Find and NULL-terminate next line in buffer
* @lr: Line reader state structure
* @eof: Caller indicates end-of-file was already found by read()
*
* Return: length of line in bytes, -1 if no line was found
*/
static int peek_line(struct lineread *lr, bool eof)
{
char *nl;
/* Sanity checks (which also document invariants) */
ASSERT(lr->count >= 0);
ASSERT(lr->next_line >= 0);
ASSERT(lr->next_line + lr->count >= lr->next_line);
ASSERT(lr->next_line + lr->count <= LINEREAD_BUFFER_SIZE);
nl = memchr(lr->buf + lr->next_line, '\n', lr->count);
if (nl) {
*nl = '\0';
return nl - lr->buf - lr->next_line + 1;
}
if (eof) {
lr->buf[lr->next_line + lr->count] = '\0';
/* No trailing newline, so treat all remaining bytes
* as the last line
*/
return lr->count;
}
return -1;
}
/**
* lineread_get() - Read a single line from file (no allocation)
* @lr: Line reader state structure
* @line: Place a pointer to the next line in this variable
*
* Return: Length of line read on success, 0 on EOF, negative on error
*/
int lineread_get(struct lineread *lr, char **line)
{
bool eof = false;
int line_len;
while ((line_len = peek_line(lr, eof)) < 0) {
int rc;
if ((lr->next_line + lr->count) == LINEREAD_BUFFER_SIZE) {
/* No space at end */
if (lr->next_line == 0) {
/* Buffer is full, which means we've
* hit a line too long for us to
* process. FIXME: report error
* better
*/
return -1;
}
memmove(lr->buf, lr->buf + lr->next_line, lr->count);
lr->next_line = 0;
}
/* Read more data into the end of buffer */
rc = read(lr->fd, lr->buf + lr->next_line + lr->count,
LINEREAD_BUFFER_SIZE - lr->next_line - lr->count);
if (rc < 0)
return rc;
if (rc == 0)
eof = true;
else
lr->count += rc;
}
*line = lr->buf + lr->next_line;
lr->next_line += line_len;
lr->count -= line_len;
return line_len;
}
|