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libpwdgrp: store getXXnam result in a single malloc block

Browse Source 
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@googlemail.com>
This commit is contained in:
Denys Vlasenko 2015-01-03 20:47:47 +01:00
parent 20c0a16334
commit 134c53098b
1 changed files with 32 additions and 26 deletions
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58
libpwdgrp/pwd_grp.c
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@ -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;
}