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util-lib: add ether_addr_from_string()

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This isn't quite symmetrical to in_addr_from_string() because it also returns
an offset indicating how much of the string was consumed by the matched
pattern.  This offset reporting is needed for either of the following use
cases:

 * verifying the lack of trailing garbage after such an address
 * parsing subsequent data from the same string
This commit is contained in:
Daniel Kahn Gillmor 2016-05-17 11:00:29 -04:00
parent 1a7906ae91
commit dd4d201ab1
2 changed files with 71 additions and 0 deletions
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69
src/basic/ether-addr-util.c
View File

@ -23,6 +23,7 @@
#include "ether-addr-util.h"
#include "macro.h"
#include "string-util.h"
char* ether_addr_to_string(const struct ether_addr *addr, char buffer[ETHER_ADDR_TO_STRING_MAX]) {
assert(addr);
@ -54,3 +55,71 @@ bool ether_addr_equal(const struct ether_addr *a, const struct ether_addr *b) {
a->ether_addr_octet[4] == b->ether_addr_octet[4] &&
a->ether_addr_octet[5] == b->ether_addr_octet[5];
}
int ether_addr_from_string(const char *s, struct ether_addr *ret, size_t *offset) {
size_t pos = 0, n, field;
char sep = '\0';
const char *hex = HEXDIGITS, *hexoff;
size_t x;
bool touched;
#define parse_fields(v) \
for (field = 0; field < ELEMENTSOF(v); field++) { \
touched = false; \
for (n = 0; n < (2 * sizeof(v[0])); n++) { \
if (s[pos] == '\0') \
break; \
hexoff = strchr(hex, s[pos]); \
if (hexoff == NULL) \
break; \
assert(hexoff >= hex); \
x = hexoff - hex; \
if (x >= 16) \
x -= 6; /* A-F */ \
assert(x < 16); \
touched = true; \
v[field] <<= 4; \
v[field] += x; \
pos++; \
} \
if (!touched) \
return -EINVAL; \
if (field < (ELEMENTSOF(v)-1)) { \
if (s[pos] != sep) \
return -EINVAL; \
else \
pos++; \
} \
}
assert(s);
assert(ret);
sep = s[strspn(s, hex)];
if (sep == '\n')
return -EINVAL;
if (strchr(":.-", sep) == NULL)
return -EINVAL;
if (sep == '.') {
uint16_t shorts[3] = { 0 };
parse_fields(shorts);
for (n = 0; n < ELEMENTSOF(shorts); n++) {
ret->ether_addr_octet[2*n] = ((shorts[n] & (uint16_t)0xff00) >> 8);
ret->ether_addr_octet[2*n + 1] = (shorts[n] & (uint16_t)0x00ff);
}
} else {
struct ether_addr out = { .ether_addr_octet = { 0 } };
parse_fields(out.ether_addr_octet);
for (n = 0; n < ELEMENTSOF(out.ether_addr_octet); n++)
ret->ether_addr_octet[n] = out.ether_addr_octet[n];
}
if (offset)
*offset = pos;
return 0;
}

2
src/basic/ether-addr-util.h
View File

@ -35,3 +35,5 @@ bool ether_addr_equal(const struct ether_addr *a, const struct ether_addr *b);
static inline bool ether_addr_is_null(const struct ether_addr *addr) {
return ether_addr_equal(addr, &ETHER_ADDR_NULL);
}
int ether_addr_from_string(const char *s, struct ether_addr *ret, size_t *offset);