/*
 * Copyright (c) Alex Holden <alex@linuxhacker.org> 2000, 2001.
 *
 * This code is public domain; you can do whatever you want with it, though I
 * would prefer you to contribute any bug fixes back to me if possible.
 * This software comes with NO WARRANTY WHATSOEVER, not even the implied
 * warranties of merchantability and fitness for a particular purpose.
 *
 * lineget.c: Reads data a line at a time from a file descriptor.
 *
 * Modelled after getline(), but with no dependency on the stdio library.
 *
 * ssize_t lineget(char **line, size_t *size, long *pos, long *ex, int fd);
 *
 * line is the address of the line buffer pointer. size is the address of a
 * value describing the length of the buffer. pos is the address of a value
 * describing the position after the current line in the buffer (it should be
 * set to 0 to start with). ex is the address of a value describing the
 * number of bytes following the current line which have already been read.
 * fd is the file descriptor to read from. lineget reads from fd into *line
 * until it reaches a \n character, and then returns either the number of
 * characters read or -1 on error. The returned string includes the \n
 * character, and is not null terminated (in fact, there may be null characters
 * within the string). If the line buffer is not big enough, lineget will
 * automatically reallocate it to a larger size and update the line and size
 * variables. If *line is NULL and *size is zero (for example on the first
 * call), the buffer will be newly allocated.
 */

#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include "arch.h"
#include "util.h"
#include "lineget.h"

ssize_t lineget(char **line, size_t *size, long *pos, long *ex, int fd)
{
	char *p;
	ssize_t i;

	/* Move the extra text to the start of the line */
	if(*pos) {
		if(*ex) memmove(*line, *line + *pos, *ex);
		*pos = 0;
	}

	/* Start off with the buffer one block in size */
	if(*size != LINEGET_BUF_SIZE) {
		*size = LINEGET_BUF_SIZE;
		*line = realloc(*line, *size);
	}

	/* Make sure there is some data in the buffer to start with */
	if(!*ex) {
		if((i = safe_read(fd, *line, *size)) == -1) return -1;
		else if(!i) return 0;
		else *ex = i;
	}

	while(1) {
		/* Search for end of line until we run out of data */
		p = *line;
		while((*ex)--) if(p[(*pos)++] == '\n') return(*pos);

		/* If we're at the end of the buffer, grow it */
		if(*pos >= *size) {
			*size += LINEGET_INC_SIZE;
			*line = realloc(*line, *size);
		}

		/* Refill the buffer */
		if((i = safe_read(fd, *line + *pos, *size - *pos)) == -1)
			return -1;
		else if(!i) return *pos;
		else *ex = i;
	}

	/* Not reached */
	return -1;
}