[git commit] libpwdgrp: store getXXnam result in a single malloc block
Denys Vlasenko
vda.linux at googlemail.com
Sat Jan 3 19:47:47 UTC 2015
commit: http://git.busybox.net/busybox/commit/?id=134c53098bdcbf7a0c34b60b97c46280d86eb48f
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master
This saves a bit of memory but more importantly, allows to create
xmalloc_getpwnam() API where result can be deleted simply using free().
function old new delta
getXXnam 134 173 +39
parse_common 188 212 +24
convert_to_struct 277 290 +13
get_S 90 88 -2
tokenize 129 126 -3
bb_internal_getpwent_r 175 172 -3
getXXnam_r 208 198 -10
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/4 up/down: 76/-18) Total: 58 bytes
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
libpwdgrp/pwd_grp.c | 58 ++++++++++++++++++++++++++++----------------------
1 files changed, 32 insertions(+), 26 deletions(-)
diff --git a/libpwdgrp/pwd_grp.c b/libpwdgrp/pwd_grp.c
index 1b2418a..4b61b61 100644
--- a/libpwdgrp/pwd_grp.c
+++ b/libpwdgrp/pwd_grp.c
@@ -34,24 +34,21 @@
struct const_passdb {
const char *filename;
- const char def[9];
- const uint8_t off[9];
+ const char def[7 + 2*ENABLE_USE_BB_SHADOW];
+ const uint8_t off[7 + 2*ENABLE_USE_BB_SHADOW];
uint8_t numfields;
+ uint8_t size_of;
};
struct passdb {
const char *filename;
- const char def[9];
- const uint8_t off[9];
+ const char def[7 + 2*ENABLE_USE_BB_SHADOW];
+ const uint8_t off[7 + 2*ENABLE_USE_BB_SHADOW];
uint8_t numfields;
+ uint8_t size_of;
FILE *fp;
char *malloced;
- char struct_result[
- /* Should be max(sizeof passwd,group,spwd), but this will do: */
- IF_NOT_USE_BB_SHADOW(sizeof(struct passwd))
- IF_USE_BB_SHADOW(sizeof(struct spwd))
- ];
};
-/* Note: for shadow db, def[9] will not contain terminating NUL,
+/* Note: for shadow db, def[] will not contain terminating NUL,
* but convert_to_struct() logic detects def[] end by "less than SP?",
* not by "is it NUL?" condition; and off[0] happens to be zero
* for every db anyway, so there _is_ in fact a terminating NUL there.
@@ -76,7 +73,7 @@ static const struct const_passdb const_pw_db = {
offsetof(struct passwd, pw_dir), /* 5 S */
offsetof(struct passwd, pw_shell) /* 6 S */
},
- sizeof(PW_DEF)-1
+ sizeof(PW_DEF)-1, sizeof(struct passwd)
};
static const struct const_passdb const_gr_db = {
_PATH_GROUP, GR_DEF,
@@ -86,7 +83,7 @@ static const struct const_passdb const_gr_db = {
offsetof(struct group, gr_gid), /* 2 I */
offsetof(struct group, gr_mem) /* 3 m (char **) */
},
- sizeof(GR_DEF)-1
+ sizeof(GR_DEF)-1, sizeof(struct group)
};
#if ENABLE_USE_BB_SHADOW
static const struct const_passdb const_sp_db = {
@@ -102,19 +99,20 @@ static const struct const_passdb const_sp_db = {
offsetof(struct spwd, sp_expire), /* 7 l */
offsetof(struct spwd, sp_flag) /* 8 r Reserved */
},
- sizeof(SP_DEF)-1
+ sizeof(SP_DEF)-1, sizeof(struct spwd)
};
#endif
/* We avoid having big global data. */
struct statics {
- /* It's ok to use same buffer (db[0].struct_result) for getpwuid and getpwnam.
+ /* It's ok to use same buffer (db[0].malloced) for getpwuid and getpwnam.
* Manpage says:
* "The return value may point to a static area, and may be overwritten
* by subsequent calls to getpwent(), getpwnam(), or getpwuid()."
*/
struct passdb db[2 + ENABLE_USE_BB_SHADOW];
char *tokenize_end;
+ unsigned string_size;
};
static struct statics *ptr_to_statics;
@@ -205,21 +203,21 @@ static char *parse_common(FILE *fp, const char *filename,
bb_error_msg("bad record at %s:%u", filename, count);
goto free_and_next;
}
+ S.string_size = S.tokenize_end - buf;
-/* Ugly hack: group db requires aqdditional buffer space
+/* Ugly hack: group db requires additional buffer space
* for members[] array. If there is only one group, we need space
* for 3 pointers: alignment padding, group name, NULL.
* +1 for every additional group.
*/
if (n_fields == sizeof(GR_DEF)-1) { /* if we read group file */
- int resize = 3;
+ int cnt = 3;
char *p = buf;
while (*p)
if (*p++ == ',')
- resize++;
- resize *= sizeof(char**);
- resize += S.tokenize_end - buf;
- buf = xrealloc(buf, resize);
+ cnt++;
+ S.string_size += cnt * sizeof(char*);
+ buf = xrealloc(buf, S.string_size);
}
if (!key) {
@@ -258,8 +256,8 @@ static void *convert_to_struct(struct passdb *db,
const char *def = db->def;
const uint8_t *off = db->off;
-/* TODO? for consistency, zero out all fields */
-/* memset(result, 0, size_of_result);*/
+ /* For consistency, zero out all fields */
+ memset(result, 0, db->size_of);
for (;;) {
void *member = (char*)result + (*off++);
@@ -305,7 +303,7 @@ static void *convert_to_struct(struct passdb *db,
/* def "r" does nothing */
def++;
- if ((unsigned char)*def < (unsigned char)' ')
+ if ((unsigned char)*def <= (unsigned char)' ')
break;
buffer += strlen(buffer) + 1;
}
@@ -328,7 +326,9 @@ static int FAST_FUNC getXXnam_r(const char *name, uintptr_t db_and_field_pos,
db = &S.db[db_and_field_pos >> 2];
*(void**)result = NULL;
- buf = parse_file(db->filename, db->numfields, name, db_and_field_pos & 3);
+ buf = parse_file(db->filename, db->numfields, name, 0 /*db_and_field_pos & 3*/);
+ /* "db_and_field_pos & 3" is commented out since so far we don't implement
+ * getXXXid_r() functions which would use that to pass 2 here */
if (buf) {
size_t size = S.tokenize_end - buf;
if (size > buflen) {
@@ -433,8 +433,14 @@ static void* FAST_FUNC getXXnam(const char *name, unsigned db_and_field_pos)
buf = parse_common(db->fp, db->filename, db->numfields, name, db_and_field_pos & 3);
if (buf) {
free(db->malloced);
- db->malloced = buf;
- result = convert_to_struct(db, buf, db->struct_result);
+ /* We enlarge buf and move string data up, freeing space
+ * for struct passwd/group/spwd at the beginning. This way,
+ * entire result of getXXnam is in a single malloced block.
+ * This enables easy creation of xmalloc_getpwnam() API.
+ */
+ db->malloced = buf = xrealloc(buf, db->size_of + S.string_size);
+ memmove(buf + db->size_of, buf, S.string_size);
+ result = convert_to_struct(db, buf + db->size_of, buf);
}
return result;
}
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