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dab2c6ee1f
Two places in passt need to read files line by line (one parsing resolv.conf, the other parsing /proc/net/*. They can't use fgets() because in glibc that can allocate memory. Instead they use an implementation line_read() in util.c. This has some problems: * It has two completely separate modes of operation, one buffering and one not, the relation between these and how they're activated is subtle and confusing * At least in non-buffered mode, it will mishandle an empty line, folding them onto the start of the next non-empty line * In non-buffered mode it will use lseek() which prevents using this on non-regular files (we don't need that at present, but it's a surprising limitation) * It has a lot of difficult to read pointer mangling Add a new cleaner implementation of allocation-free line-by-line reading in lineread.c. This one always buffers, using a state structure to keep track of what we need. This is larger than I'd like, but it turns out handling all the edge cases of line-by-line reading in C is surprisingly hard. This just adds the code, subsequent patches will change the existing users of line_read() to the new implementation. Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
32 lines
803 B
C
32 lines
803 B
C
/* SPDX-License-Identifier: AGPL-3.0-or-later
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* Copyright Red Hat
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* Author: David Gibson <david@gibson.dropbear.id.au>
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*/
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#ifndef LINEREAD_H
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#define LINEREAD_H
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#define LINEREAD_BUFFER_SIZE 8192
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/**
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* struct lineread - Line reader state
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* @fd: File descriptor lines are read from
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* @next_line: Offset in @buf of the start of the first line not yet
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* returned by lineread_get()
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* @count: Number of bytes in @buf read from the file, but not yet
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* returned by lineread_get()
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* @buf: Buffer storing data read from file.
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*/
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struct lineread {
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int fd; int next_line;
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int count;
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/* One extra byte for possible trailing \0 */
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char buf[LINEREAD_BUFFER_SIZE+1];
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};
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void lineread_init(struct lineread *lr, int fd);
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int lineread_get(struct lineread *lr, char **line);
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#endif /* _LINEREAD_H */
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