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/*
* libdpkg - Debian packaging suite library routines
* meminfo.c - system memory information functions
*
* Copyright © 2021 Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
* Copyright © 2021-2022 Guillem Jover <guillem@debian.org>
*
* This 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 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, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <compat.h>
#include <sys/stat.h>
#include <errno.h>
#include <inttypes.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <dpkg/dpkg.h>
#include <dpkg/fdio.h>
#include <dpkg/meminfo.h>
/*
* An estimate of how much memory is available. Swap will not be used, the
* page cache may be purged, not everything will be reclaimed that might be
* reclaimed, watermarks are considered.
*/
struct meminfo_field {
const char *name;
ssize_t len;
int tag;
uint64_t value;
};
#define MEMINFO_FIELD(name, tag) name, sizeof(name) - 1, tag, 0
static struct meminfo_field *
meminfo_find_field(struct meminfo_field *fields, const size_t nfields,
const char *fieldname, const ssize_t fieldlen)
{
size_t f;
for (f = 0; f < nfields; f++) {
if (fieldlen != fields[f].len)
continue;
if (strncmp(fieldname, fields[f].name, fields[f].len) != 0)
continue;
return &fields[f];
}
return NULL;
}
static uint64_t
meminfo_sum_fields(const struct meminfo_field *fields, const size_t nfields)
{
uint64_t sum = 0;
size_t f;
for (f = 0; f < nfields; f++)
sum += fields[f].value;
return sum;
}
enum meminfo_error_code
meminfo_get_available_from_file(const char *filename, uint64_t *val)
{
char buf[4096];
char *str;
ssize_t bytes;
int fd;
struct meminfo_field fields[] = {
{ MEMINFO_FIELD("MemFree", DPKG_BIT(0)) },
{ MEMINFO_FIELD("Buffers", DPKG_BIT(1)) },
{ MEMINFO_FIELD("Cached", DPKG_BIT(2)) },
};
const int want_tags = DPKG_BIT(array_count(fields)) - 1;
int seen_tags = 0;
*val = 0;
fd = open(filename, O_RDONLY);
if (fd < 0)
return MEMINFO_NO_FILE;
bytes = fd_read(fd, buf, sizeof(buf));
close(fd);
if (bytes <= 0)
return MEMINFO_NO_DATA;
buf[bytes] = '\0';
str = buf;
while (1) {
struct meminfo_field *field;
char *end;
end = strchr(str, ':');
if (end == 0)
break;
field = meminfo_find_field(fields, array_count(fields),
str, end - str);
if (field) {
intmax_t num;
str = end + 1;
errno = 0;
num = strtoimax(str, &end, 10);
if (num <= 0)
return MEMINFO_INT_NEG;
if ((num == INTMAX_MAX) && errno == ERANGE)
return MEMINFO_INT_MAX;
/* It should end with ' kB\n'. */
if (end[0] != ' ' || end[1] != 'k' || end[2] != 'B')
return MEMINFO_NO_UNIT;
/* This should not overflow, but just in case. */
if (num < (INTMAX_MAX / 1024))
num *= 1024;
field->value = num;
seen_tags |= field->tag;
}
if (seen_tags == want_tags)
break;
end = strchr(end + 1, '\n');
if (end == 0)
break;
str = end + 1;
}
if (seen_tags != want_tags)
return MEMINFO_NO_INFO;
*val = meminfo_sum_fields(fields, array_count(fields));
return MEMINFO_OK;
}
enum meminfo_error_code
meminfo_get_available(uint64_t *val)
{
#ifdef __linux__
return meminfo_get_available_from_file("/proc/meminfo", val);
#else
return MEMINFO_NO_FILE;
#endif
}
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