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#include "cobs.h"
int cobs_encode_usart(int (*output)(void*, char), void *userdata, char *src, size_t srclen) {
if (srclen > 254)
return -1;
size_t p = 0;
while (p <= srclen) {
char val;
if (p != 0 && src[p-1] != 0) {
val = src[p-1];
} else {
size_t q = p;
while (q < srclen && src[q] != 0)
q++;
val = (char)q-p+1;
}
int rv = output(userdata, val);
if (rv)
return rv;
p++;
}
int rv = output(userdata, 0);
if (rv)
return rv;
return 0;
}
/*@ requires \valid(dst + (0..dstlen-1));
@ requires \valid_read(src + (0..srclen-1));
@ requires \separated(dst + (0..dstlen-1), src + (0..srclen-1));
@
@ behavior maybe_valid_frame:
@ assumes 1 <= srclen <= dstlen <= 65535;
@ assumes \exists integer j; j > 0 && \forall integer i; 0 <= i < j ==> src[i] != 0;
@ assumes \exists integer i; 0 <= i < srclen && src[i] == 0;
@ assigns dst[0..dstlen-1];
@ ensures \result >= 0 || \result == -3;
@ ensures \result >= 0 ==> src[\result+1] == 0;
@ ensures \result >= 0 ==> (\forall integer i; 0 <= i < \result ==> src[i] != 0);
@
@ behavior invalid_frame:
@ assumes 1 <= srclen <= dstlen <= 65535;
@ assumes src[0] == 0 || \forall integer i; 0 <= i < srclen ==> src[i] != 0;
@ assigns dst[0..dstlen-1];
@ ensures \result == -2;
@
@ behavior invalid_buffers:
@ assumes dstlen < 0 || dstlen > 65535
@ || srclen < 1 || srclen > 65535
@ || dstlen < srclen;
@ assigns \nothing;
@ ensures \result == -1;
@
@ complete behaviors;
@ disjoint behaviors;
@*/
ssize_t cobs_decode(char *dst, size_t dstlen, char *src, size_t srclen) {
if (dstlen > 65535 || srclen > 65535)
return -1;
if (srclen < 1)
return -1;
if (dstlen < srclen)
return -1;
size_t p = 1;
size_t c = (unsigned char)src[0];
//@ assert 0 <= c < 256;
//@ assert 0 <= c;
//@ assert c < 256;
if (c == 0)
return -2; /* invalid framing. An empty frame would be [...] 00 01 00, not [...] 00 00 */
//@ assert c >= 0;
//@ assert c != 0;
//@ assert c <= 257;
//@ assert c > 0;
//@ assert c >= 0 && c != 0 ==> c > 0;
/*@ //loop invariant \forall integer i; 0 <= i <= p ==> (i == srclen || src[i] != 0);
@ loop invariant \forall integer i; 1 <= i < p ==> src[i] != 0;
@ loop invariant c > 0;
@ loop invariant 1 <= p <= srclen <= dstlen <= 65535;
@ loop invariant \separated(dst + (0..dstlen-1), src + (0..srclen-1));
@ loop invariant \valid_read(src + (0..srclen-1));
@ loop invariant \forall integer i; 1 <= i <= srclen ==> \valid(dst + i - 1);
@ loop assigns dst[0..dstlen-1], p, c;
@ loop variant srclen-p;
@*/
while (p < srclen && src[p]) {
char val;
c--;
//@ assert src[p] != 0;
if (c == 0) {
c = (unsigned char)src[p];
val = 0;
} else {
val = src[p];
}
//@ assert 0 <= p-1 <= dstlen-1;
dst[p-1] = val;
p++;
}
if (p == srclen)
return -2; /* Invalid framing. The terminating null byte should always be present in the input buffer. */
if (c != 1)
return -3; /* Invalid framing. The skip counter does not hit the end of the frame. */
//@ assert 0 < p <= srclen <= 65535;
//@ assert src[p] == 0;
//@ assert \forall integer i; 1 <= i < p ==> src[i] != 0;
return p-1;
}
void cobs_decode_incremental_initialize(struct cobs_decode_state *state) {
state->p = 0;
state->c = 0;
}
int cobs_decode_incremental(struct cobs_decode_state *state, char *dst, size_t dstlen, char src) {
if (state->p == 0) {
if (src == 0)
goto empty_errout; /* invalid framing. An empty frame would be [...] 00 01 00, not [...] 00 00 */
state->c = (unsigned char)src;
state->p++;
return -1;
}
if (!src) {
if (state->c != 1)
goto errout; /* Invalid framing. The skip counter does not hit the end of the frame. */
int rv = state->p-1;
cobs_decode_incremental_initialize(state);
return rv;
}
char val;
state->c--;
if (state->c == 0) {
state->c = (unsigned char)src;
val = 0;
} else {
val = src;
}
size_t pos = state->p-1;
if (pos >= dstlen)
return -4; /* output buffer too small */
dst[pos] = val;
state->p++;
return -1;
errout:
cobs_decode_incremental_initialize(state);
return -2;
empty_errout:
cobs_decode_incremental_initialize(state);
return -3;
}
#ifdef VALIDATION
/*@
@ requires 0 <= d < 256;
@ assigns \nothing;
@*/
size_t test(char foo, unsigned int d) {
unsigned int c = (unsigned char)foo;
if (c != 0) {
//@ assert c < 256;
//@ assert c >= 0;
//@ assert c != 0;
//@ assert c > 0;
}
if (d != 0) {
//@ assert d >= 0;
//@ assert d != 0;
//@ assert d > 0;
}
return c + d;
}
#include <__fc_builtin.h>
void main(void) {
char inbuf[254];
char cobsbuf[256];
char outbuf[256];
size_t range = Frama_C_interval(0, sizeof(inbuf));
Frama_C_make_unknown((char *)inbuf, range);
cobs_encode(cobsbuf, sizeof(cobsbuf), inbuf, sizeof(inbuf));
cobs_decode(outbuf, sizeof(outbuf), cobsbuf, sizeof(cobsbuf));
//@ assert \forall integer i; 0 <= i < sizeof(inbuf) ==> outbuf[i] == inbuf[i];
}
#endif//VALIDATION
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