diff options
Diffstat (limited to 'lib/dpkg/meminfo.c')
| -rw-r--r-- | lib/dpkg/meminfo.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/lib/dpkg/meminfo.c b/lib/dpkg/meminfo.c new file mode 100644 index 0000000..998f65c --- /dev/null +++ b/lib/dpkg/meminfo.c @@ -0,0 +1,168 @@ +/* + * 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 != ' ' || *(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 +} |