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/* dctrl-tools - Debian control file inspection tools
Copyright © 2003, 2005, 2012 Antti-Juhani Kaijanaho
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef FSAF_H
#define FSAF_H
#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
/* FAST (MOSTLY) SEQUENTIAL-ACCESS FILE LAYER */
struct fsaf_private {
char *fname;
int fd;
char * buf;
size_t buf_capacity;
size_t buf_offset;
size_t buf_size;
size_t invalid_mark;
size_t eof_mark; /* can be (size_t)(-1) if not reached yet */
};
typedef struct fsaf_private FSAF;
/* Open a FSAF for the given fd. Only read access is supported for
* now. The whole file is initially valid. */
FSAF * fsaf_fdopen(int fd, char const *fname);
/* Close the given FSAF. This DOES NOT close the underlying fd. */
void fsaf_close(FSAF *);
/* Return a pointer to a buffer containing len bytes from the FSAF
* starting at offset. Note that if offset is below the invalid mark,
* we return b = NULL. This is a CHEAP operation, if the full range
* has already been accessed. The buffer may be invalidated by any
* subsequent call to this function. */
struct fsaf_read_rv {
char const * b;
size_t len;
};
static inline
struct fsaf_read_rv fsaf_read(FSAF * fp, size_t offset, size_t len)
{
void fsaf_slurp(FSAF * fp, size_t len);
/* Reading nothing - since offset can be bogus in this
* situation, this could foul up our assumptions later, so
* return already here. */
if (len == 0) {
return (struct fsaf_read_rv){ .b = "", .len = 0 };
}
/* Make sure we don't read past the EOF mark. */
if (offset + len > fp->eof_mark) len = fp->eof_mark - offset;
/* Ensure that we have enough data in the buffer. */
assert(offset >= fp->buf_offset);
if (offset - fp->buf_offset + len > fp->buf_size) {
fsaf_slurp(fp, offset - fp->buf_offset + len - fp->buf_size);
if (offset - fp->buf_offset + len > fp->buf_size) {
len = fp->buf_size - (offset - fp->buf_offset);
}
}
assert(offset - fp->buf_offset + len <= fp->buf_size);
assert(offset + len <= fp->eof_mark);
return (struct fsaf_read_rv){
.b = fp->buf + (offset - fp->buf_offset),
.len = len
};
}
/* Behaves like fsaf_read except that the result is put in a malloc'd
* zero-terminated buffer. NULL return value indicates either memory
* allocation failure or that the read was below the invalid mark. */
static inline
char * fsaf_getas(FSAF * fp, size_t offset, size_t len)
{
struct fsaf_read_rv r = fsaf_read(fp, offset, len);
if (r.b == 0) return 0;
char * rv = malloc(r.len+1);
if (rv == 0) return 0;
memcpy(rv, r.b, r.len);
rv[r.len] = 0;
return rv;
}
static inline
int fsaf_getc(FSAF * fp, size_t offset)
{
if (offset >= fp->eof_mark) return -1;
struct fsaf_read_rv r = fsaf_read(fp, offset, 1);
if (offset >= fp->eof_mark) return -1;
assert(r.len == 1);
return (unsigned char)r.b[0];
}
/* Invalidate all bytes in FSAF up to and excluding offset. */
void fsaf_invalidate(FSAF *, size_t offset);
/* Return an upper bound for the end of file, either the smallest
* offset beyond eof or (size_t)(-1). */
static inline
size_t fsaf_eof(FSAF * fp) { return fp->eof_mark; }
#endif /* FSAF_H */
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